**Cruise Report**

**CLIVAR A16S 2005**

**R/V *Ronald H. Brown*, RB0501b**

**11 January 2005 - 24 February 2005**

**Punta Arenas, Chile - Fortaleza, Brazil**

**Co-Chief Scientists:**

**Dr. Rik Wanninkhof**

**National Oceanic and Atmospheric Administration**

**Atlantic Oceanographic and Meteorological Laboratory**

**Dr. Scott Doney**

**Woods Hole Oceanographic Institution**

![](media/image1.png){width="3.8354166666666667in" height="3.975in"}

**Preliminary Cruise Report**

**(last modified 2 November 2005)**

Table of Contents

Summary 1

Acknowledgments 1

Introduction 2

Description of Measurement Techniques 4

1\. CTD/Hydrographic Measurements Program 4

1.1. Water Sampling Package 5

1.2. Underwater Electronics Packages 7

1.3. Navigation and Bathymetry Data Acquisition 7

1.4. Real-Time CTD Data Acquisition System 8

1.5. Shipboard CTD Data Processing 9

1.6. CTD Laboratory Calibration 10

1.7. Shipboard CTD Calibration Procedures 10

*1.7.1. CTD Pressure* 11

*1.7.2. CTD Temperature* 11

*1.7.3. CTD Conductivity* 12

*1.7.4. CTD Dissolved Oxygen* 14

1.8. Final CTD Data Processing 16

1.9. Final CTD Calibration Procedures 18

*1.9.1 CTD Pressure* 18

*1.9.2 CTD Temperature* 18

*1.9.3 CTD Conductivity* 18

*1.9.4 CTD Dissolved Oxygen* 19

1.10. Particulate Optical Sensors on CTD Package 22

1.11. Lowered Acoustic-Doppler Current Profiler (LADCP) 24

2\. Bottle Sampling 30

2.1. Bottle Sampling Procedures 30

2.2. Bottle Data Processing 30

2.3. Sampling and Analyses of Bottle Data 31

2.4. Tests Performed on Bullister Bottles to Determine Sample Integrity
of

CFC, Salts, and O~2~ 32

2.5. Discussion of Bottle Sampling for Samples Preserved for Shore-Side
Analysis. 38

*2.5.1. Helium and Tritium Sampling* 38

*2.5.2. Particulate Sampling* 39

*2.5.3. DOC Sampling* 40

*2.5.4. C-DOM Sampling* 40

*2.5.5. ^14^C Sampling* 41

*2.5.6. Oxygen, Nitrogen, and Argon (ONAR) Sampling* 41

2.6. Parameters Sampled and Analyzed on the Cruise 42

*2.6.1. Chlorofluorocarbon (CFC) Measurements* 42

*2.6.2. Dissolved Oxygen Analyses* 46

*2.6.3. Discrete Halocarbon/Alkyl Nitrate Analyses* 51

*2.6.4. Discrete pCO~2~ Analyses* 55

*2.6.5. Total Dissolved Inorganic Carbon (DIC) Analyses* 59

*2.6.6. Discrete pH Analyses* 64

*2.6.7. Total Alkalinity Analyses* 68

*2.6.8. Salinity Analysis* 72

*2.6.9. Inorganic Nutrients (Phosphate, Nitrate, Nitrite, and Silicate)*
74

2.7. Underway Measurements 77

*2.7.1 Shipboard Computing System (SCS)* 77

*2.7.2 Underway pCO~2~ (fCO~2~) Measurements* 78

*2.7.3 SAMI Underway pCO~2~ Measurement System* 83

*2.7.4 Underway Spectrophotometric Measurements of pCO~2~, TCO~2~, and
pH* 86

2.8. Aerosol Sampling 90

**List of Figures**

Figure 1.0. Sample distribution, stations 1-34 4

Figure 1.1. Sample distribution, stations 32-62 4

Figure 1.2. Sample distribution, stations 60-92 5

Figure 1.3. Sample distribution, stations 88-121 5

Figure 1.4. T1-T2 by station, p \> 500 db 11

Figure 1.5. T1-T2 by pressure, station/casts 5/2-50/1 11

Figure 1.6. Uncorrected C1-C2 by station, p \> 500 db 12

Figure 1.7. Uncorrected bottle C-C1 by station, p \> 500 db 12

Figure 1.8. Corrected bottle C-C1 by station, all pressures 13

Figure 1.9. Corrected bottle C-C1 by pressure, all pressures 13

Figure 1.10. Corrected bottle C-C1 by station, p \> 500 db 13

Figure 1.11. Salinity residual by station, p \> 500 db 14

Figure 1.12. O~2~ residuals by station, all pressures 14

Figure 1.13. O~2~ residuals by pressure, all pressures 15

Figure 1.14. O~2~ residuals by station number, p \> 500 db 15

Figure 1.15. Calibrated CTD-bottle conductivity differences plotted
against station number 19

Figure 1.16. Calibrated CTD-bottle conductivity differences plotted
against pressure 19

Figure 1.17. Calibrated CTD-bottle oxygen differences plotted against
station number 20

Figure 1.18. Calibrated CTD-bottle oxygen differences plotted against
pressure 21

Figure 1.19. Preliminary observations of (a) zonal velocity, (b)
meridional

velocity, (c) velocity standard error, and (d) acoustic backscatter 27

Figure 1.20. Preliminary shaded estimates of eddy diffusivity and
log-scale

eddy diffusivity uncertainty from cruise-processed LADCP data 29

Figure 2.1. Control plot of the reagent blanks over the cruise 47

Figure 2.2. Control plot of thiosulfate concentration changes over the
cruise 48

Figure 2.3. Difference between photometrically and amperometrically
determined

oxygen concentration versus photometric oxygen concentration 49

Figure 2.4. Schematic of the automated purge and trap GCMS system 52

Figure 2.5. Comparison of the results from the two SAMIs and the
underway

pCO~2~ system 84

**List of Tables**

Table 1.1. Scientific personnel, A16S 2005 2

Table 1.2. Principal programs of A16S 2005 3

Table 1.3. A16S 2005 rosette underwater electronics 8

Table 1.4. A16S 2005 CTD sensor calibration dates 10

Table 1.5. A16S 2005 CTD sensor configurations 10

Table 1.6. Final oxygen calibration coefficients 20

Table 1.7. Initial configuration and instrument and command changes 25

Table 2.1. Water requirements for the different parameters drawn on the

Bullister bottles 31

Table 2.2. Results for station 88 storage tests 33

Table 2.3. Results for station 102 storage tests 34

Table 2.4. Results for station 112 storage tests 34

Table 2.5. Changes in concentrations for station 112 storage test 35

Table 2.6. Summary of CFC changes for the storage tests 35

Table 2.7. Bottle blanks for Bullister bottles 36

Table 2.8. Summary of bottle tests for station 121 37

Table 2.9. Comparison of oxygen concentrations determined by photometric

and amperometric point detection methods at station 106 49

Table 2.10. Calibration standard tanks used for discrete pCO~2~ 56

Table 2.11. Duplicate discrete pCO~2~ samples 57

Table 2.12. Test results of different sample bottle sizes for DIC 62

Table 2.13. Summary of number of nutrient samples taken and estimated
precision 76

Table 2.14. Hourly sampling cycle for the underway pCO~2~ system
(version 2.5) 79

Table 2.15. Wavelengths used for spectrophotometric determination of
inorganic

carbon species 87

Summary

A hydrographic survey consisting of a meridional LADCP/CTD/rosette
section in the western South Atlantic was carried out in
January-February 2005. The R/V *Ronald H. Brown* departed Punta Arenas,
Chile on 11 January 2005. A total of 121 LADCP/CTD/Rosette stations were
occupied, and 12 Argos floats and 11 drifters were deployed from 17
January-21 February. Water samples (up to 36), LADCP, CTD and
bio-optical data were collected on each cast to within 20 m of the
bottom. Salinity, dissolved oxygen, and nutrient samples were analyzed
from every bottle sampled on the rosette. Other parameters from the
bottles were sampled at a lower density. The cruise ended in Fortaleza,
Brazil on 24 February 2005. This report describes the participants and
details of sampling and analytical methodologies of all projects.
Further information, pictures, graphics, and data can be found on the
A16S 2005 cruise website at <http://sts.ucsd.edu/>cruise/a16s/hydro/.
The data are also posted at <http://ushydro.ucsd.edu/>

Acknowledgments

The successful completion of the cruise relied on dedicated assistance
from many individuals on shore and on the NOAA ship *Ronald H. Brown*.
Funded investigators in the project and members of the Repeat
Hydrography Oversight Committee, with Lynne Talley and Richard Feely as
co-chairs, were instrumental in planning and executing the cruise. The
participants in the cruise showed dedication and camaraderie during
their 45 days at sea. Officers and crew of the *Ronald H. Brown*
exhibited a high degree of professionalism and assistance to accomplish
the mission and to make us feel at home during the long voyage*.*

The U.S. CLIVAR/CO~2~ Repeat Hydrography Program is jointly sponsored by
the National Science Foundation's Physical and Chemical Oceanography
Programs, and NOAA's Office of Climate Observation, with contributions
from the National Aeronautics and Space Administration and the
Department of Energy. In particular, we wish to thank program managers
Eric Itsweire (NSF/OCE), Don Rice (NSF/OCE), Mike Johnson (NOAA/OCO),
and Kathy Tedesco (NOAA/OGP) for their moral and financial support in
the effort. Editorial assistance in producing this report by Gail Derr
of AOML was greatly appreciated.

**Introduction**

A sea-going science team from 12 oceanographic institutions in the U.S.
participated on the cruise. Several other science programs were
supported with no dedicated cruise participant. The science party and
their responsibilities are listed in Tables 1.1 and 1.2.

  ---------------------------- --------------------- ---------------------
  **Table 1.1. Scientific                            
  personnel, A16S 2005.**                            

  **Duties**                   **Name**              **Affiliation\***

  Co-Chief Scientist           Rik Wanninkhof        AOML

  Co-Chief Scientist           Scott Doney           WHOI

  Data Manager                 Frank Delahoyde       SIO

  CTD Processing               Kristy McTaggart      PMEL

  Watch Stander                Naomi Levine          MIT/WHOI

  Watch Stander                Carlos Fonseca        CIMAS-U. Miami

  LADCP/Electronics Technician Doug Anderson         AOML

  LADCP/Electronics Technician Philip Orton          LDEO

  Salinity                     David Wisegarver      PMEL

  O~2~                         Chris Langdon         RSMAS-U. Miami

  O~2~                         George Berberian      CIMAS-U. Miami

  Nutrients                    Charlie Fischer       AOML

  Nutrients                    Calvin Mordy          UW

  CFCs                         Mark Warner           UW

  CFCs                         John Bullister        PMEL

  CFCs                         Eric Wisegarver       PMEL

  Helium/Tritium               Andrew Mutter         LDEO

  HCFCs                        Shari Yvon-Lewis      TAMU

  HCFCs                        Benjamin Kates        AOML

  Alkalinity/pH                William Hiscock       RSMAS-U. Miami

  Alkalinity/pH                John Michael Trapp    RSMAS-U. Miami

  Alkalinity/pH                Mareva Chanson        RSMAS-U. Miami

  Alkalinity/pH                Taylor Graham         RSMAS-U. Miami

  DIC                          Esa Peltola           AOML

  DIC                          Robert Castle         AOML

  DOM                          Wenhao Chen           RSMAS-U. Miami

  POC/PIC                      Alexandra Thompson    LBNL

  CO~2~ Development            Zhaohui Aleck Wang    USF

  CO~2~ Development            Brittany Doupnik      USF

  SAMI/pCO~2~                  Stacy Smith           U. Montana

  Aerosols                     Matt Lenington        CWU
  ---------------------------- --------------------- ---------------------

**\*[Affiliations]{.underline}:**

AOML NOAA-Atlantic Oceanographic and Meteorological Laboratory

CIMAS Cooperative Institute for Marine and Atmospheric Studies

CWU Central Washington University

LBNL Lawrence-Berkeley National Laboratory

LDEO Lamont-Doherty Earth Observatory, Columbia University

MIT Massachusetts Institute of Technology

PMEL NOAA-Pacific Marine Environmental Laboratory

RSMAS Rosenstiel School of Marine and Atmospheric Sciences

SIO Scripps Institution of Oceanography, University California, San
Diego

TAMU Texas A&M University

U. Hawaii University of Hawaii

U. Miami University of Miami

U. Montana University of Montana

UCSB University of California at Santa Barbara

USF University of South Florida

UW University of Washington

WHOI Woods Hole Oceanographic Institution

  ------------------ -------------------- -------------------------------
  **Table 1.2.                            
  Principal programs                      
  of A16S 2005.**                         

  **Analysis**       **Institution**      **Principal Investigator**

  CTD                PMEL/AOML            Greg Johnson/Molly Baringer

  Salinity           PMEL                 Greg Johnson

  CFCs               UW/PMEL              Mark Warner/John Bullister

  HCFCs              TAMU                 Shari Yvon-Lewis

  DIC                AOML/PMEL            Rik Wanninkhof/Dick Feely

  Discrete pCO~2~    AOML                 Rik Wanninkhof

  Dissolved O~2~     RSMAS-U. Miami       Chris Langdon

  Nutrients          UW/AOML              Calvin Mordy/Jia-Zhong Zhang

  Helium/Tritium     LDEO                 Peter Schlosser

  CO~2~-Alkalinity   RSMAS-U. Miami       Frank Millero

  CO~2~-pH           RSMAS-U. Miami       Frank Millero

  PIC/POC            LBNL                 Jim Bishop

  DOC                RSMAS-U. Miami       Dennis Hansell

  CDOM               UCSB                 Norm Nelson/Craig Carlson

  Underway pCO~2~    AOML                 Rik Wanninkhof

  ^13^C/^14^C        WHOI                 Ann McNichol

  ADCP/LADCP         U. Hawaii/LDEO       Eric Firing/Andreas Thurnherr

  Aerosols           CWU                  Anne Johansen

  SAMI/CO~2~         U. Montana           Mike DeGrandpre

  CO~2~ System       USF                  Robert Byrne
  Develop.                                
  ------------------ -------------------- -------------------------------

Description of Measurement Techniques

1\. CTD/Hydrographic Measurements Program

![](media/image2.png){width="4.8in" height="2.9027777777777777in"}The
basic CTD/hydrographic measurements consisted of salinity, dissolved
oxygen, and nutrient measurements made from water samples taken on
CTD/rosette casts, plus pressure, temperature, salinity, dissolved
oxygen, and transmissometer from CTD profiles. A total of 125
CTD/rosette casts were made, usually to within 20 m of the bottom. No
major problems were encountered during the operation. The distribution
of samples is illustrated in Figures 1.0-1.3.

**Figure 1.0.** Sample distribution, stations 1-34.

![](media/image3.png){width="4.809722222222222in"
height="2.917361111111111in"}

**Figure 1.1.** Sample distribution, stations 32-62.

![](media/image4.png){width="4.791666666666667in"
height="2.888888888888889in"}

**Figure 1.2.** Sample distribution, stations 60-92.

![](media/image5.png){width="4.791666666666667in"
height="2.888888888888889in"}

**Figure 1.3.** Sample distribution, stations 88-121.

1.1. Water Sampling Package

LADCP/CTD/rosette casts were performed with a package consisting of a
36-place, 12-liter rosette frame (PMEL), a 36-place pylon (SBE32) and
36, 12-liter Bullister bottles. This package was deployed on
station/casts 5/2-121/1. A smaller 24-place 3-liter foul weather rosette
package was deployed on station/casts 1/1-5/1. Underwater electronic
components consisted of a Sea-Bird Electronics (SBE) 9 plus CTD with
dual pumps and the following sensors: dual temperature (SBE3), dual
conductivity (SBE4), dissolved oxygen (SBE43), transmissometer (Wetlabs
SeaStar), turbidity (Seapoint Sensors), and PIC (Wetlabs). The other
Underwater electronic components consisted of RDI LADCPs, a Simrad or
Benthos altimeter, an AM Cells load cell, and a Benthos pinger.

The CTD was mounted vertically in an SBE CTD cage attached to the bottom
center of the rosette frame. All SBE4 conductivity and SBE3 temperature
sensors and their respective pumps were mounted vertically as
recommended by SBE. Pump exhausts were attached to outside corners of
the CTD cage and directed downward. The altimeter was mounted on the
inside of a support strut adjacent to the bottom frame ring. The
transmissometer, turbidity and PIC sensors were mounted horizontally on
a fiberglass grid attached off center to the rosette frame adjacent to
the CTD. The LADCPs were vertically mounted inside the bottle rings with
one set of transducers pointing down, the other up.

The rosette system was suspended from a UNOLS-standard three-conductor
0.322\" electro-mechanical sea cable.

The R/V *Brown's* forward CTD winch was used with the 24-place 3-liter
rosette for station/casts 1/1-5/1. The aft CTD winch was used with the
36-place 12-liter rosette for the remaining station/casts (5/2-121/2).

A single Sea cable termination for each winch served the entire leg.
Station/cast 5/1 was aborted due to problems with the forward winch that
required lowering the package back to the bottom (\~1000 m) after
bottles had been tripped. The decision was made to switch to the aft
winch, the 36-place12-liter package and CTD #315 for station/cast 5/2.
Station/cast 51/1 was aborted when the CTD signal was abruptly lost at
1274 decibars on the down cast. The problem was later traced to the
turbidity sensor, which was shorting out the CTD #315 auxiliary power
supply. Station/cast 51/2 was made with CTD #209 (installed in the
36-place rosette) which was used for all subsequent casts.

The deck watch prepared the rosette within 40 minutes prior to each
cast. All valves, vents, and lanyards were checked for proper
orientation. The bottles were cocked and all hardware and connections
rechecked. Once stopped on station, the LADCP was turned on and syringes
were removed from the CTD sensor intake ports. As directed by the deck
watch leader, the CTD was powered-up and the data acquisition system
started. Two stabilizing taglines were threaded through rings on the
rosette frame. The deck watch leader directed the winch operator to
raise the package, the squirt boom and rosette were extended outboard,
and the package quickly lowered into the water. The tag lines were
removed and the package was lowered to 10 m. The CTD console operator
waited for the CTD sensor pumps to turn on, waited an additional 60
seconds for sensors to stabilize, then directed the winch operator to
bring the package close to the surface, pause for typically 10 seconds,
and begin the descent.

Descent speeds were 30 m/min to 50m, 45 m/min to 200m, and 60 m/min
beyond 200m. Each rosette cast was usually lowered to within 20 m of the
bottom, using the altimeter and pinger to determine a safe distance.

On the up cast, the winch operator was directed to stop at each bottle
trip depth. The CTD console operator waited 30 seconds before tripping a
bottle, then an additional 10 seconds after receiving the trip
confirmation before directing the winch to proceed to the next bottle
stop.

Standard sampling depths were used throughout A16S 2005, depending on
the overall water depth. The standard depths were staggered every other
pair of stations.

Recovering the package at the end of the deployment was essentially the
reverse of launching, with the additional use of poles and snap-hooks to
attach tag lines for added safety and stability. The rosette was left on
deck for sampling. The bottles and rosette were examined before samples
were taken, and anything unusual noted on the sample log.

Each bottle on the rosette had a unique serial number. This bottle
identification was maintained independently of the bottle position on
the rosette, which was used for sample identification. Nine bottles were
replaced on this leg, and parts of others were replaced or repaired.

Routine CTD maintenance included soaking the conductivity and DO sensors
in a solution of Triton-X as recommended by Sea-Bird between casts to
maintain sensor stability. Rosette maintenance was performed on a
regular basis. O-rings were changed as necessary and bottle maintenance
was performed each day to insure proper closure and sealing. Valves were
inspected for leaks and repaired or replaced as needed.

1.2. Underwater Electronics Packages

CTD data were collected with SBE9plus CTDs (PMEL #315 and #209). These
instruments provided pressure, dual temperature (SBE3), dual
conductivity (SBE4), dissolved oxygen (SBE43), transmissometer (Wetlabs
SeaStar), turbidity (Seapoint Sensors), PIC (Wetlabs), load cell (AM
Cells), and altimeter (Benthos/Simrad 807) channels (Table 1.3). The
CTDs supplied a standard Sea-Bird format data stream at a data rate of
24 frames/second.

The CTD was outfitted with dual pumps. Primary temperature,
conductivity, and dissolved oxygen were plumbed on one pump circuit and
secondary temperature and conductivity on the other. The sensors were
deployed vertically. The primary temperature and conductivity sensors
(T1 #4193, C1 #2882 sation/casts 1/1-5/1, 51/2-120/1; T1 #4341, C1 #2887
station/casts 5/2-51/1; and T1 #4193, C1 #0354 station/casts 121/1) were
used for reported CTD temperatures and conductivities on all casts. The
secondary temperature and conductivity sensors were used for calibration
checks.

The SBE9plus CTD was connected to the SBE32 36-place pylon providing for
single-conductor sea cable operation. Power to the SBE9plus CTD (and
sensors), SBE32 pylon, auxiliary sensors, and altimeter was provided
through the sea cable from the SBE11plus deck unit in the computer lab.

1.3. Navigation and Bathymetry Data Acquisition

Navigation data were acquired by the database workstation at 1-second
intervals from the ship's Trimble PCODE GPS receiver beginning January
11. Although the ship had a Seabeam multibeam system functioning during
the cruise and displaying center beam depth, the data were not available
to other computers on the ship. The A16S bathymetry data were
synthesized from ETOPO~2~ data along the cruise track and used for
preliminary vertical sections, maps and estimated bottom depths.

  -------------------------------------- --------------------------------
  **Table 1.3. A16S 2005 rosette         
  underwater electronics.**              

  **Item**                               **Serial Number (station/cast
                                         used)**

  Sea-Bird SBE32 36-place Carousel Water 
  Sampler                                

  Sea-Bird SBE9plus CTD                  PMEL #315

  Sea-Bird SBE9plus CTD                  PMEL #209

  Paroscientific Digiquartz Pressure     S/N 53960 (5/2-51/1)
  Sensor                                 

  Paroscientific Digiquartz Pressure     S/N 53586 (1/1-5/1, 51/2-121/1)
  Sensor                                 

  Sea-Bird SBE3plus Temperature Sensor   S/N 03P-4193 (Primary 1/1-5/1,
                                         51/2-121/1)

  Sea-Bird SBE3plus Temperature Sensor   S/N 03P-4335 (Secondary
                                         1/1-5/1,51/2-121/1)

  Sea-Bird SBE3plus Temperature Sensor   S/N 03P-4341 (Primary 5/2-51/1)

  Sea-Bird SBE3plus Temperature Sensor   S/N 03P-1370 (Secondary
                                         5/2-51/1)

  Sea-Bird SBE4C Conductivity Sensor     S/N 04-2882 (Primary 1/1-5/1,
                                         51/2-120/1)

  Sea-Bird SBE4C Conductivity Sensor     S/N 04-2882 (Secondary 121/1)

  Sea-Bird SBE4C Conductivity Sensor     S/N 04-1434 (Secondary 1/1-5/1,
                                         51/2-58/1)

  Sea-Bird SBE4C Conductivity Sensor     S/N 04-2887 (Primary 5/2-51/1)

  Sea-Bird SBE4C Conductivity Sensor     S/N 04-0354 (Secondary 5/2-51/1,
                                         59/1-120/1)

  Sea-Bird SBE4C Conductivity Sensor     S/N 04-0354 (Primary 121/1)

  Sea-Bird SBE43 DO Sensor               S/N 43-0312 (1/1-5/1,
                                         51/2-121/1)

  Sea-Bird SBE43 DO Sensor               S/N 43-0664 (5/2-51/1)

  Wetlabs SeaStar Transmissometer        S/N CST-391DR

  Seapoint Sensors OBS Turbidity Sensor  S/N 10366

  Wetlabs PIC Sensor                     S/N PIC001

  Benthos Altimeter                      S/N 1035

  Simrad 807 Altimeter                   S/N 92010101 (AOML)

  AM Cell (Load Cell)                    S/N 1109

  RDI LADCP                              S/N 299 (5/1-10/1, 36/1-63/1,
                                         82/1)

  RDI LADCP                              S/N 149 (10/1-35/1, 64/1-81/1,
                                         83/1-121/1)

  LADCP Battery Pack                     
  -------------------------------------- --------------------------------

1.4. Real-Time CTD Data Acquisition System

The CTD data acquisition system consisted of an SBE-11plus (V1) deck
unit and a networked generic PC workstation running Windows 2000. SBE
Seasave software was used for data acquisition and to close bottles on
the rosette.

CTD deployments were initiated by the console watch after the ship
stopped on station. The watch maintained a console operations log
containing a description of each deployment, a record of every attempt
to close a bottle and any pertinent comments.

Once the deck watch had deployed the rosette, the winch operator would
lower it to 10 m. The CTD sensor pumps were configured with a 60 second
startup delay. The console operator checked the CTD data for proper
sensor operation, waited an additional 60 seconds for sensors to
stabilize, then instructed the winch operator to bring the package to
the surface, pause for 10 seconds, and descend to a target depth. The
profiling rate was no more than 30 m/min to 50 m, no more than 45 m/min
to 200 m, and no more than 60 m/min deeper than 200 m depending on sea
cable tension and the sea state.

The console watch monitored the progress of the deployment and quality
of the CTD data through interactive graphics and operational displays.
Additionally, the watch created a sample log for the deployment which
would be later used to record the correspondence between rosette bottles
and analytical samples taken. The altimeter channel, CTD pressure,
wire-out and bathymetric depth were all monitored to determine the
distance of the package from the bottom, usually allowing a safe
approach to within 20 m.

Bottles were closed on the up cast by operating a "point and click"
graphical trip button. The data acquisition system responded with trip
confirmation messages and the corresponding CTD data in a rosette bottle
trip window on the display. All tripping attempts were noted on the
console log. The console watch then directed the winch operator to raise
the package up to the next bottle trip location.

After the last bottle was tripped, the console watch directed the deck
watch to bring the rosette on deck. Once on deck, the console watch
terminated the data acquisition, turned off the deck unit, and assisted
with rosette sampling.

1.5. Shipboard CTD Data Processing

Shipboard CTD data processing was performed automatically at the end of
each deployment using SIO/ODF CTD processing software. The raw CTD data
and bottle trips acquired by SBE Seasave on the Windows 2000 workstation
were copied onto the Linux database and webserver workstation, then
processed to a 0.5 second time series. Bottle trip values were extracted
and a 2-decibar (dbar) down cast pressure series created. This pressure
series was used by the web service for interactive plots, sections, and
CTD data distribution (the 0.5 second time series was also available for
distribution). During and after the deployment the data were redundantly
backed up to another Linux workstation and a Windows workstation.

CTD data were examined at the completion of each deployment for clean
corrected sensor response and any calibration shifts. As bottle salinity
and oxygen results became available, they were used to refine shipboard
conductivity and oxygen sensor calibrations.

A total of 125 casts were made (including 1 test cast and 2 aborted
casts). The 24-place 3-liter rosette and CTD #209 was used on
station/casts 1/1-5/1, the 36-place 12-liter rosette and CTD #315 was
used on station/casts 5/2-51/1, and the 36-place 12-liter rosette and
CTD #209 was used on station/casts 51/2-121/1.

1.6. CTD Laboratory Calibration

Laboratory calibrations of the CTD pressure, temperature, and
conductivity sensors were all performed at SBE. The calibration dates
are listed in Table 1.4.

+-------------------------+--------------+-------------+--------------+
| **Table 1.4. A16S 2005  |              |             |              |
| CTD sensor calibration  |              |             |              |
| dates.**                |              |             |              |
+-------------------------+--------------+-------------+--------------+
| **Sensor**              | **Serial     | **P         | **P          |
|                         | Number**     | re-Cruise** | ost-Cruise** |
|                         |              |             |              |
|                         |              | **          | *            |
|                         |              | Calibration | *Calibration |
|                         |              | Date**      | Date**       |
+-------------------------+--------------+-------------+--------------+
| Paroscientific          | 53960        | 23-Sep-03   | 25-May-05    |
| Digiquartz Pressure     |              |             |              |
+-------------------------+--------------+-------------+--------------+
| Paroscientific          | 53586        | 17-Aug-00   | Not          |
| Digiquartz Pressure     |              |             | calibrated   |
+-------------------------+--------------+-------------+--------------+
| Sea-Bird SBE3plus       | 03P-4193     | 30-Nov-04   | 13-Apr-05    |
| Temperature             |              |             |              |
+-------------------------+--------------+-------------+--------------+
| Sea-Bird SBE3plus       | 03P-4335     | 30-Nov-04   | 13-Apr-05    |
| Temperature             |              |             |              |
+-------------------------+--------------+-------------+--------------+
| Sea-Bird SBE3plus       | 03P-4341     | 30-Nov-04   | 13-Apr-05    |
| Temperature             |              |             |              |
+-------------------------+--------------+-------------+--------------+
| Sea-Bird SBE3           | 03-1370      | 23-Jul-04   | 13-Apr-05    |
| Temperature             |              |             |              |
+-------------------------+--------------+-------------+--------------+
| Sea-Bird SBE4C          | 04-2882      | 15-Dec-04   | 12-Apr-05    |
| Conductivity            |              |             |              |
+-------------------------+--------------+-------------+--------------+
| Sea-Bird SBE4C          | 04-1434      | 30-Nov-04   | Not          |
| Conductivity            |              |             | calibrated   |
+-------------------------+--------------+-------------+--------------+
| Sea-Bird SBE4C          | 04-2887      | 30-Nov-04   | 12-Apr-05    |
| Conductivity            |              |             |              |
+-------------------------+--------------+-------------+--------------+
| Sea-Bird SBE4C          | 04-0354      | 30-Nov-04   | 12-Apr-05    |
| Conductivity            |              |             |              |
+-------------------------+--------------+-------------+--------------+

1.7. Shipboard CTD Calibration Procedures

Two CTDs (PMEL #315 and #209) were used on this leg, for a total of four
distinct pressure, temperature and conductivity sensor configurations
(Table 1.5).

  ------------------- ----------- -------- -------- -------- -------- ------------------
  **Table 1.5. A16S                                                   
  2005 sensor                                                         
  configurations.**                                                   

  **Configuration**   **CTD**     **T1**   **C1**   **T2**   **C2**   **Station/Cast**

  1                   0209        4193     2882     4335     1434     1/1-5/1, 51/2-58/1

  2                   0315        4341     2887     1370     0354     5/2-51/1

  3                   0209        4193     2882     4335     0354     59/1-120/1

  4                   0209        4193     0354     4335     2882     121/1
  ------------------- ----------- -------- -------- -------- -------- ------------------

Each CTD was deployed with all sensors and pumps aligned vertically, as
recommended by SBE. CTD #209 was initially configured in the small
24-place 3-liter rosette and was used for the first five stations
because of sea conditions. CTD #315 was configured in the 36-place
12-liter rosette and was used on station/casts 5/2-51/1. CTD #209 was
installed in the 36-place rosette prior to 51/2 and was used for all
subsequent station/casts (51/2-121/1). Secondary temperature and
conductivity (T2 and C2) sensors served as calibration checks for the
reported primary temperature and conductivity (T1 and C1) on all casts.
In-situ salinity and dissolved O~2~ check samples collected during each
cast were used to calibrate the conductivity and dissolved O~2~ sensors.

### 1.7.1. CTD Pressure

Pressure sensor calibration coefficients derived from the pre-cruise
calibrations were applied to raw pressure data during each cast.
Residual pressure offsets (the difference between the first and last
submerged pressures) were examined to check for calibration shifts. All
were \<0.5 db, and both sensors exhibited \<0.5 db offset shift over
their periods of use. No additional adjustments were made to the
calculated pressures.

### 1.7.2. CTD Temperature

Temperature sensor calibration coefficients derived from the pre-cruise
calibrations were applied to raw primary and secondary temperature data
during each cast.

![](media/image6.png){width="3.9402777777777778in"
height="2.2215277777777778in"}Calibration accuracy was examined by
tabulating T1-T2 over a range of pressures (bottle trip locations) for
each cast. These comparisons are summarized in Figure 1.4.

**Figure 1.4.** T1-T2 by station, p \> 500 db.

![](media/image7.png){width="3.920138888888889in"
height="2.1381944444444443in"}CTD configurations 1, 3, and 4 (CTD #209,
station/casts 1/1-5/1,51/2-121/1) exhibit a deep relative calibration
error of 0.0008°C at station/cast 59/1, drifting to 0.0002°C by
station/cast 85/1 and stabilizing. CTD configuration #2 (CTD #315,
station/casts 5/2-50/1) exhibits a relative error of -0.0008°C at
station/cast 20/1 and drifts to +0.0004°C by station/cast 50/1.
Configuration #2 also shows a T1-T2 pressure response of ‑2.7e‑7°C/db as
shown in Figure 1.5.

**Figure 1.5.** T1-T2 by pressure, station/casts 5/2-50/1.

It is likely that all three temperature sensors used on A16S 2005
exhibited some calibration drift. Although the mean deep T1-T2 for the
leg is close to 0, it should not be interpreted as a reliable metric of
temperature calibration accuracy.

### 1.7.3. CTD Conductivity

Conductivity sensor calibration coefficients derived from the pre-cruise
calibrations were applied to raw primary and secondary conductivities.

Comparisons between the primary and secondary sensors and between each
of the sensors to check sample conductivities (conductivity calculated
from bottle salinities) were used to derive conductivity corrections.
These corrections were determined for three distinct groupings of
station/casts, corresponding to the T1/C1 sensor pair used. Although
1/1-5/1 used the same T1/C1 as 51/2-120/1, it was treated as a separate
grouping because of the amount of time between 5/1 and 51/2. 121/1 was a
1-cast grouping in which C1 and C2 were swapped (T1C2, T2C1) in an
attempt to resolve the source of a .0007 salinity offset in T1/C1
observed between the down and up casts.

Uncorrected C1-C2 and bottle C-C1 were first examined to identify sensor
drift (Figures 1.6 and 1.7).

![](media/image8.png){width="3.9298611111111112in"
height="2.1083333333333334in"}**Figure 1.6.** Uncorrected C1-C2 by
station, p \> 500db.

**Figure 1.7.** Uncorrected bottle C-C1 by station, p \> 500db.

C1 offset corrections were determined to account for drift over time.
After applying the drift corrections, the residuals were examined to
determine conductivity slope and pressure response corrections. Figures
1.8-1.11 show the residuals after applying all corrections.

![](media/image10.png){width="4.020833333333333in"
height="2.1458333333333335in"}**Figure 1.8.** Corrected bottle C-C1 by
station, all pressures.

![](media/image11.png){width="3.9479166666666665in"
height="2.1354166666666665in"}

**Figure 1.9.** Corrected bottle C-C1 by pressure, all pressures.

![](media/image12.png){width="3.8958333333333335in"
height="2.1458333333333335in"}

**Figure 1.10.** Corrected bottle C-C1 by station, p \> 500 db.

![](media/image13.png){width="3.9902777777777776in"
height="2.151388888888889in"}**Figure 1.11.** Salinity residual by
station, p \> 500 db.

Figure 1.11 represents an estimate of the salinity accuracy on A16S
2005. The 95% confidence limit is ±0.0015.

### 1.7.4. CTD Dissolved Oxygen

Two SBE43 dissolved O~2~ (DO) sensors were used on this leg; S/N 43-0312
on station/casts 1/1-5/1, 51/2-121/1 and S/N 43-0664 on 5/2-50/1. Both
sensors behaved well, the only problems occurring on station/casts
105/1-107/1 when some particulate material clogged the primary pump
circuit relief valve. This problem affected the top 50 db of the down
casts.

The DO sensors were calibrated to dissolved O~2~ check samples by
matching the up cast bottle trips to down cast CTD data along isopycnal
surfaces, calculating CTD dissolved O~2~, and then minimizing the
residuals using a non-linear least-squares fitting procedure. The
fitting determined calibration coefficients for the sensor model
conversion equation and proceeded in a series of steps. Each sensor was
fit in a separate sequence. The first step was to determine the time
constants for the exponential terms in the model. These time constants
are sensor-specific but applicable to an entire cruise. Once the time
constants had been determined, casts were fit individually to O~2~ check
sample data. The resulting calibration coefficients were then smoothed
and held constant during a refit to determine sensor slope and offset.
The residuals are shown in Figures 1.12-1.14.

![](media/image14.png){width="3.920138888888889in"
height="2.1083333333333334in"}**Figure 1.12.** O~2~ residuals by
station, all pressures.

![](media/image15.png){width="4.0in"
height="2.1666666666666665in"}**Figure 1.13.** O~2~ residuals by
pressure, all pressures.

![](media/image16.png){width="3.9444444444444446in"
height="2.111111111111111in"}**Figure 1.14.** O~2~ residuals by station
number, p \> 500 db.

The standard deviations of 1.14 µM/kg for all oxygens and 0.81 µM/kg for
deep oxygens are presented as metrics of variability between up cast and
down cast dissolved O~2~. We make no claims regarding the precision or
accuracy of CTD dissolved O~2~ data.

The general form of the SIO/ODF O~2~ conversion equation for Clark cells
follows Brown and Morrison (1978) Millard (1982), and Owens and Millard
(1985). ODF models membrane and sensor temperatures with lagged CTD
temperatures and a lagged thermal gradient. In-situ pressure and
temperature are filtered to match the sensor response. Time-constants
for the pressure response, Taup, two temperature responses, TauTs and
TauTf, and thermal gradient response, TaudT, are fitting parameters. The
thermal gradient term is derived by low-pass filtering the difference
between the fast response (Tf) and slow response (Ts) temperatures. This
term is SBE43-specific and corrects a non- linearity introduced by
analog thermal compensation in the sensor. The Oc gradient, dOc/dt, is
approximated by low-pass filtering first-order Oc differences. This
gradient term attempts to correct for reduction of species other than
O~2~ at the sensor cathode. The time-constant for this filter, Tauog, is
a fitting parameter. The dissolved O~2~ concentration is then
calculated:

O~2~ ml/l =
\[c1\*Oc+c2~.~\]\*fsat(S,T,P)\*e\*\*(c3\*Pl+c4\*Tf+c5\*Ts+c6\*dOc/dt(1.7.4.0)

where:

O~2~ ml/l = Dissolved O~2~ concentration in ml/l;

Oc = Sensor current (uamps);

fsat (S,T,P) = O~2~ saturation concentration at S,T,P (ml/l);

S = Salinity at O~2~ response-time (PSUs);

T = Temperature at O~2~ response-time (°C);

P = Pressure at O~2~ response-time (decibars);

Pl = Low-pass filtered pressure (decibars);

Tf = Fast low-pass filtered temperature (°C);

Ts = Slow low-pass filtered temperature (°C);

dOc/dt = Sensor current gradient (uamps/secs);

dT = low-pass filtered thermal gradient (Tf - Ts).

1.8. Final CTD Data Processing

The reduction of profile data began with a standard suite of processing
modules using Sea-Bird Data Processing Win32 version 5.32 software in
the following order:

DATCNV converts raw data into engineering units and creates a .ROS
bottle file. Both down and up casts were processed for scan, elapsed
time(s), pressure, t0, t1, c0, c1, and oxygen voltage. Optical sensor
data were not carried through the processing stream. MARKSCAN was used
to determine the number of scans acquired on deck and while priming the
system to exclude these scans from processing.

ALIGNCTD aligns temperature, conductivity, and oxygen measurements in
time relative to pressure to ensure that derived parameters are made
using measurements from the same parcel of water. Primary conductivity
is automatically advanced in the deck unit by 0.073 seconds. No
additional alignment was necessary for either of the primary
conductivity sensors. As for the secondary conductivity sensors used
during this cruise, s/n 354 associated with CTD 315 was advanced 0.068
seconds in ALIGNCTD, and s/n 1434 associated with CTD 209 was advanced
0.056 seconds. It was not necessary to align temperature or oxygen.

ROSSUM averages bottle data over an 8-second interval and derives
salinity, theta, sigma-theta, and oxygen (µmol/kg). Averaging began at
the bottle confirm bit for casts 0011-0251, and from 4 seconds before
the confirm bit to 4 seconds after the confirm bit for casts 0261-1211.

WILDEDIT computes the standard deviation of 100 point bins, and then
makes two passes through the data. The first pass flags points that
differ from the mean by more than 2 standard deviations. A new standard
deviation is computed excluding the flagged points and the second pass
marks bad values greater than 20 standard deviations from the mean. For
this data set, data were kept within a distance of 100 of the mean
(i.e., all data).

FILTER applies a low pass filter to pressure with a time constant of
0.15 seconds. In order to produce zero phase (no time shift), the filter
is first run forward through the file and then run backwards through the
file.

CELLTM uses a recursive filter to remove conductivity cell thermal mass
effects from measured conductivity. In areas with steep temperature
gradients the thermal mass correction is on the order of 0.005 PSS-78.
In other areas the correction is negligible. The value used for the
thermal anomaly amplitude (alpha) was 0.03°C. The value used for the
thermal anomaly time constant (1/beta) was 7.0°C.

LOOPEDIT removes scans associated with pressure slowdowns and reversals.
If the CTD velocity is less than 0.25 m/s or the pressure is not greater
than the previous maximum scan, the scan is omitted.

BINAVG averages the data into 1 dbar bins. Each bin is centered on an
integer pressure value, e.g., the 1 dbar bin averages scans where
pressure is between 0.5 dbar and 1.5 dbar. There is no surface bin. The
number of points averaged in each bin is included in the data file.

DERIVE uses 1 dbar averaged pressure, temperature, and conductivity to
compute primary and secondary salinities.

TRANS converts the binary data file into ASCII format.

Package slowdowns and reversals owing to ship roll can move mixed water
in tow to in front of the CTD sensors and create artificial density
inversions and other artifacts. In addition to Seasoft module LOOPEDIT,
a PMEL program computes values of density locally referenced between
every 1 dbar of pressure to compute N^2^ and linearly interpolates
temperature, conductivity, and oxygen voltage over those records where
N^2^ is less than or equal to -1 10^-5^ per s^2^. During this cruise it
was noted that 19 profiles failed the criteria in the top 10 meters.
These data were retained but flagged as questionable in the final WOCE
formatted files.

Final calibrations are applied to delooped data files. ITS-90
temperature, salinity, and oxygen are computed, and WOCE quality flags
are created. ASCII files are converted WOCE format for submission to the
CLIVAR and Carbon Hydrographic Data Office (CCHDO).

During casts 105/1-107/1, the air-bleed hole in the plumbing of the
primary sensors was blocked, resulting in low surface salinities and
oxygen spikes as deep as 53 dbar. Low salinities were flagged as bad and
slightly low salinities were flagged as questionable.

1.9. Final CTD Calibration Procedures

*1.9.1. CTD Pressure*

Pressure calibrations for both CTD instruments used during this cruise
are pre-cruise. On deck pressure readings prior to each cast were
examined and remained within 1 dbar of calibration. Differences between
first and last submerged pressures for each cast were also examined and
the residuals for both sensors shifted \<0.5 dbar over their periods of
use. So no additional adjustments were applied.

*1.9.2. CTD Temperature*

Using pre- and post-cruise laboratory calibrations, a linearly
interpolated drift correction at the midpoint of the cruise was applied
to each sensor. For temperature sensor s/n 4193 used for station/casts
1/1-5/1 and 51/2-120/1, this correction is 0.00024°C. For temperature
sensor s/n 4341 used for station/casts 5/2-51/1, this correction is
0.00038°C. And for temperature sensor s/n 4335 used for cast 121/1, this
correction is 0.00032°C. Also, a uniform correction was applied to all
sensors for heating of the thermistor owing to viscous effects.
Thermistors are biased high by this effect and were adjusted down by
0.0006°C. This adjustment results in errors of no more than ±0.00015°C
from this effect for the full range of oceanographic temperature and
salinity.

*1.9.3. CTD Conductivity*

CTD conductivity are calibrated against bottle salinity data assuming a
constant additive correction (bias), a station-dependent multiplicative
correction (slope), and where needed, a linear pressure-dependent term.
PMEL FORTRAN programs combine individual ROSSUM bottle files into one
listing for each conductivity sensor. Sample salinities flagged as
"good" are matched to CTD salinities by station/sample number. MATLAB
functions CALCOSn are used to determine the best fit of CTD and bottle
data, where n is the order of the station-dependent linear or polynomial
fit. CALCOSn recursively throws out data greater than 2.8 standard
deviations. CALCOSn returns a single conductivity bias and a
conductivity slope for each station. A station-dependent slope
coefficient best models the gradual shift in the conductivity sensor
with time. CALCOPn additionally returns a linear pressure term (modified
beta) that is multiplied by CTD pressure and added to conductivity.

For conductivity sensor s/n 2882 used for station/casts 1/1-5/1 and
51/2-121/1, the best results are an overall, second-order,
station-dependent fit with a linear pressure correction. About 82% of
the 2509 points (2052 points) used in the fit produced a standard
deviation of 0.0010 PSS-78. The bias is 0.0018644 mS/cm, the pressure
correction is -3.4731617 10^-8^ mS/cm/dbar, and the slope coefficients
range from 1.0000184-1.0002895. For conductivity sensor s/n 2887 used
for station/cast 5/2-051/1, the best results are an overall, linear,
station-dependent fit with a linear pressure correction. About 85% of
the 1525 points (1302 points) used in the fit produce a standard
deviation of 0.0008 PSS-78. The bias is 0.0071032 mS/cm, the pressure
correction is -3.3595083 10^-7^ mS/cm/dbar, and the slope coefficients
range from 0.9998770-1.0000159.

![](media/image17.png){width="2.683333333333333in"
height="2.2243055555555555in"}CTD-bottle conductivity differences
plotted against station number and pressure (Figures 1.15-1.16) are used
to verify the success of the fit parameters. Matlab routines apply
post-cruise calibrations to temperature and conductivity, and compute
final salinity values.

![](media/image18.png){width="2.673611111111111in"
height="2.214583333333333in"}**Figure 1.15.** Calibrated CTD-bottle
conductivity differences plotted against station number.

**Figure 1.16.** Calibrated CTD-bottle conductivity differences plotted
against pressure.

*1.9.4. CTD Dissolved Oxygen*

CTD oxygen sensors are modeled following the essential form of Owens and
Millard (1985). Here, the equation

O~2~ = (slope\*Oc+bias+lag\*dOc/dt)\*O~2sat~(S,T)\*exp(Tcor\*T+Pcor\*P)

is used where O~2~ is the calibrated CTD oxygen value, Oc is the
reported oxygen current, dOc/dt is its time derivative (smoothed with a
15-dbar hanning filter), and O~2sat~ is the oxygen saturation (Benson
and Krause, 1984). CTD temperature, pressure, and salinity are used for
T, P, and S. The parameters of slope, bias, lag, Tcor, and Pcor are
solved by nonlinear least squares regression of matched bottle oxygen
and CTD downcast data, recursively discarding 2.8 standard deviation
outliers.

Significant hysteresis between the down and up oxygen profiles at deep
stations warrant using the downcast oxygen data for calibration. PMEL
FORTRAN programs combine individual ROSSUM bottle files into one listing
for each oxygen sensor. Sample oxygen flagged as good (2 or 6) are
matched to CTD oxygen by station/sample number. Upcast bottle data are
matched to downcast profile data by locally referenced potential
densities using MATLAB routine MATCH_SG_N_nnn, where nnn is the oxygen
sensor serial number. If interpolated bottle pressures were more than 50
dbar from matched downcast pressures, then matching was redone using
pressure instead of density in MATCH_SG_N_nnn. Calibration coefficients
are determined using function RUN_OXYGEN_CAL_1. The best results are
from a least-squares fit with a linear station-dependent slope (Table
1.6).

  ----------------- --------------- ---------- --------- ---------- ---------- ----------- --------
  **Table 1.6.                                                                             
  Final oxygen                                                                             
  calibration                                                                              
  coefficients.**                                                                          

  **Station**       **Slope Range** **Bias**   **Lag**   **Tcor**   **Pcor**   **Points    **Std
                                                                               Used**      Dev**

  1-4               0.3477-0.3481   -0.5814    8.2167    -0.0001    0.0001     85 88.2%    0.7401

  5-20              0.4350-0.4375   -0.5047    4.3258    0.0015     0.0001     464 80.17%  0.8677

  21-34             0.4373-0.4426   -0.5016    3.8727    0.0008     0.0001     489 85.5%   1.1244

  35-50             0.4423-0.4434   -0.5036    4.3414    0.0007     0.0001     566 86.4%   0.6828

  51-65             0.3423-0.3440   -0.5718    7.2016    0.0015     0.0001     535 92.0%   0.6009

  66-89             0.3467-0.3499   -0.5787    7.5763    0.0013     0.0001     843 97.0%   0.7276

  90-99             0.3517-0.3521   -0.5841    7.1488    0.0011     0.0001     359 93.6%   0.5822

  100-121           0.3518-0.3521   -0.5777    5.5720    0.0010     0.0001     774 88.4%   0.6449
  ----------------- --------------- ---------- --------- ---------- ---------- ----------- --------

![](media/image19.png){width="2.745138888888889in"
height="2.214583333333333in"}CTD-bottle oxygen differences plotted
against station number and pressure show the stability of the calibrated
CTD oxygens relative to the bottle oxygens (Figures 1.17-1.18). Matlab
routines apply oxygen calibration coefficients to profile and bottle
data and compute final oxygen values in µmol/kg.

**Figure 1.17.** Calibrated CTD-bottle oxygen differences plotted
against station number.

![](media/image20.png){width="2.754861111111111in"
height="2.2243055555555555in"}**Figure 1.18.** Calibrated CTD-bottle
oxygen differences plotted against pressure.

References

Benson, B.B., and D. Krause, 1984: The concentration and isotopic
fractionation of oxygen dissolved in freshwater and seawater in
equilibrium with the atmosphere. *Limnol. Oceanogr.*, v. 29, pp.
620-632.

Brown, N.L., and G.K. Morrison, 1978: WHOI/Brown conductivity,
temperature, and depth microprofiler. Woods Hole Oceanographic
Institution, Technical Report No. 78-23.

Joyce, T., and C. Corry (eds.), 1994: Requirements for WOCE Hydrographic
Programme data reporting. WOCE Hydrographic Programme Office, Woods
Hole, MA, USA (May 1994, Rev. 2), Report WHPO 90-1, WOCE Report No.
67/91, pp. 52-55.

Millard, R.C., Jr., 1982: CTD calibration and data processing techniques
at WHOI using the practical salinity scale. *Proceedings, International
STD Conference and Workshop,* Marine Technical Society, La Jolla, CA, p.
19.

Owens, W.B., and R.C. Millard, 1985: A new algorithm for CTD oxygen
calibration. *J. Phys. Oceanogr.,* v. 15, no. 5, pp. 621-631.

1.10. Particulate Optical Sensors on CTD Package

**Principal Investigator:** Jim Bishop, LBNL, JKBishop@lbl.gov

**On board personnel:** Alexandra Thompson, LBNL,
alex@nature.berkeley.edu

**Equipment:**

1.  Seastar transmissometer (Wetlabs SN: CST-391DR): Detects mainly
    particulate organic carbon

2.  PIC equipped with open flow cell (Wetlabs SN: PIC-001): Detects
    particulate inorganic carbon

3.  Seapoint (Seapoint): Measures turbidity

**Data Collection:**

1\. The Seastar collected data every cast apart from:

-   Stations 1-5/1: due to deployment of small CTD

-   Stations 52-57: due to CTD failure and until problem identified

-   Total casts: 112 (including test cast)

-   Seawater data not available for station 101 when deployed with beam
    blocked for calibration.

2\. The PIC collected data every cast apart from:

-   Stations 1-5/1: due to deployment of small CTD

-   Stations 52-57: due to CTD failure and until problem identified

-   Stations 84-104: due to inconsistent calibration caused by faulty
    filter holder and then because cabling issues delayed its
    redeployment.

-   Total casts: 91 (including test cast)

-   Seawater data not available for station 111 when deployed with beam
    blocked, and stations 117 and 121 when deployed with filtered beam
    (4.3 OD) for calibration.

3\. The Seapoint collected data on the following casts:

-   Stations: Test, 4 (up only), 6 - 20, 21 (up only), 22 - 24, 25 (down
    only).

-   Total casts: 18 (up and down), 3 (up or down)

**Calibration:**

The Seastar and PIC sensors were calibrated 20 times over the course of
the cruise, and the Seapoint 7 times. Calibrations were carried out in
air while mounted on the CTD and in the lab using an alternate power
supply. The Seastar and Seapoint sensors were calibrated using end
points: the signal in air and with a blocked beam. The PIC sensor is
calibrated by determining the signal when the beam is subjected to a
series of optical density (OD) filters (4.3 OD, 4.6 OD, 4.9 OD, and 5.2
OD, flow cell removed) and when it is completely blocked. The signal
through the flow cell in air was also recorded. These calibrations were
carried out from 0°C to 25°C.

In order to probe in-situ temperature dependence and response times
during casts, the Seastar and PIC were deployed on casts with the beam
blocked and, in the case of the PIC, with a 4.3 OD filter in the beam.

**Problems:**

1.  The Seapoint began to show an erratic behavior on the downcast of
    station 21 at \>3600 db. The signal returned to normal until the
    upcast of station 25 when again the sensor produced unreasonable
    signals and continued to do so until failing completely at
    station 27. The failure coincides with the first deployments to
    pressures above \~5000 db. The Seapoint was not removed from the CTD
    package until the CTD failed at station 52.

2.  The flow cell of the PIC at cold temperatures can be subject to
    torque. Torturing results in increased signals, and due to warming
    delays, at times significant hysteresis between up and down cast
    data. This problem was solved by increasing the amount of allowable
    movement of the flow cell. To determine optimal "give," movement of
    the cell was probed over the duration of the cruise: i.e., allowing
    varying amounts of movement in each of three dimensions at the laser
    or detector end of the cell. Eventually this thermal hysteresis was
    removed by filing away the inside of both cell mounts and loosening
    holding screws/adding others to allow \~2 mm up/down and in/out
    movement at the detector end, less at the laser end, and no movement
    back and forth between the laser and detector windows.

3.  In order to determine the in-situ temperature dependence of the PIC
    sensor, a special apparatus was built on the ship to hold three
    optical density filters in place perpendicular to the beam over the
    detector window during a cast while the instrument was on the CTD.
    However, the middle (and unseen) filter was not positioned correctly
    or robustly, giving inconsistent calibrations and increasingly
    erratic signals. This resulted in the PIC sensor being removed from
    the CTD for 21 stations (stations 84-104). A second filter holder
    was made and deployed successfully in stations 117 and 121.

4.  In order to redeploy the PIC sensor on the CTD package at station
    105, cabling modifications needed to be made because a spare port
    was not available following the replacement of the altimeter on the
    CTD package. To have both the PIC sensor and the Seastar on the CTD
    package simultaneously, a Y-cable was spliced so that both sensor
    ends were four point (as opposed to one 4 and one 6 point). During
    the casts at station 105 and 106, the PIC signal dropped out for
    short periods and recovered. Before station 107, the cable ends were
    swapped between the PIC sensor and the Seastar. There were no more
    dropouts of PIC data. The Seastar had data dropouts on stations 115
    and 119-121, indicating that this problem may have been in the
    Y-cable.

1.11. Lowered Acoustic-Doppler Current Profiler (LADCP)

**Principal Investigator:** Andreas Thurnherr

> Lamont-Doherty Earth Observatory of Columbia
>
> University (LDEO), <ant@ldeo.columbia.edu>

**Onboard Personnel:** (primary) Philip Orton, LDEO,
<orton@ldeo.columbia.edu>

> Douglas Anderson, NOAA-AOML

**Additional Personnel:** Bruce Huber, LDEO

**Summary:**

Paired upward and downward LADCPs on the CTD rosette frame collected
data at every station where the primary CTD rosette frame was used
(stations 5-121); no LADCP data was collected stations 1-4, where the
smaller 24-bottle weather rosette was used due to high wind/sea-state
conditions. Preliminary processing was completed during the cruise,
using LDEO-LADCP software. A noteworthy highlight is that strong
velocities associated with the Antarctic Circumpolar Current were
captured very well by the LADCP system. Velocity uncertainties were low
relative to resolved velocities in the southern 40% of the section but
increased rapidly afterward due to low backscatter levels; the acoustic
measurements of velocity rely on the presence of particles in the water
column. Uncertainty levels decreased somewhat over the final ten
stations, as we approached the equator. Final processing will likely
lead to a slight improvement in the data quality, due primarily to the
incorporation of shipboard ADCP data that helps constrain the best-fit
velocity profile solution. Additional useful data from the LADCP system
includes acoustic backscatter and estimates of eddy diffusivity.

**Equipment:**

One Workhorse Monitor broadband 300 kHz RDI Acoustic Doppler Current
Profiler (ADCP) was directed upward and one directed downward on the
rosette frame. Both instruments were equipped with RDI's LADCP firmware
upgrade that expands the list of available user commands. The
instruments shared one battery pack, which held a stack of 36 alkaline
D-cells, and batteries were changed every 5-10 stations. On-deck
communication with the ADCPs was facilitated through RS-232
communications with a laptop, via a long cable leading into the main
lab. Both instruments were hooked up to a 4-port RS-232 to USB
converter, feeding into a Dell laptop running Linux. Communication
software written by Andreas Thurnherr (utilizing bbabble and expect
scripts) allowed data to be downloaded from both instruments
simultaneously at full nominal speed (115 kbps).

Instruments swapouts and command-file changes are summarized in Table
1.7. The first instrument change (station 10) was motivated by perceived
failure of a quality control test -- the attempted matching of the
down-looking instrument only solution with the up-looking instrument
only solution. Later, it was discovered that the test was being executed
incorrectly, and the instrument was giving comparable data to the 150
kHz shipboard ADCP (SADCP). The next instrument change (station 36) was
made due to a "broken beam" warning in the LADCP software (described
below), which indicates that power on the beam is low. The beam was
still collecting data, and the profile appears to have been of
reasonably good quality, however. The station 62 and 64 instrument
changes occurred when we tested a high-power LADCP for two stations. The
instrument performed poorly on the first cast, and on the second cast
reported a broken beam. In this case, the beam collected almost no data,
severely reducing the quality of station 63 velocity estimates. The
final instrument changes occurred at stations 82-83. There, the up
looking and down looking ADCPs were switched to test whether the data
quality improved. The result was an apparent decrease in performance --
a "bad beam" warning on ADCP S/N 299, which is less severe than a broken
beam warning. The ADCPs were switched back again for the next station
and no further bad beam warnings were received the rest of the cruise.

  --------------- ------------ ----------- ----------- -------------------- ------------------
  **Table 1.7.                                                              
  Initial                                                                   
  configuration                                                             
  (started at                                                               
  station 5) and                                                            
  instrument and                                                            
  command                                                                   
  changes.**                                                                

  **Station**     **Master**   **Slave**   **Nbins**   **Transformation to  **3-Beam
                                                       Earth Coordinates**  Solutions**

  Initial         299          754         25          ADCP                 ADP

  10              149                                                       

  34                           150                                          

  36              299                                                       

  49                                       20          Laptop               None\*

  62              5089                                                      

  64              149                                                       

  82              299          149                                          

  83              149                                                       

  101                                                  ADCP                 ADCP

  \*No 3-beam                                                               
  solutions are                                                             
  currently                                                                 
  computed by the                                                           
  software. By                                                              
  including                                                                 
  3-beam                                                                    
  solutions, one                                                            
  could increase                                                            
  the number of                                                             
  samples per                                                               
  depth interval                                                            
  and possibly                                                              
  the data                                                                  
  quality.                                                                  
  --------------- ------------ ----------- ----------- -------------------- ------------------

Calibration drift is not a serious problem with ADCPs, and the
instruments are generally only serviced (calibrated and tank-tested)
when wear and tear causes equipment malfunctions. Three of the five
ADCPs utilized were serviced in recent months and the other two were
likely serviced about two years ago.

**Sampling:**

Stations have the same numbering system as with the CTD data collection,
and progress from 5 (58ºS latitude) through 121 (2º20´S). Command files
were uploaded to the instruments at each station, \~10 minutes prior to
rosette deployment. Sampling parameters included: bin size of 10 m,
ambiguity velocity of 250 cm s^-1^, 0 m blanking distance (but
discarding the first bin of data), 1.5 seconds per 1-ping ensemble, and
synchronization of the down-looking (master) and up-looking (slave)
units. As shown in Table 1.6, the initial configuration called for the
transformation from beam coordinates to earth coordinates within the
ADCP, with 3-beam solutions enabled. This was changed at station 49,
because we were examining the impact of 3-beam solutions on the
frequency of warnings of velocities over 3 m s^-1^. We found that the
warnings persisted. At this point, the number of bins was also reduced
from 25 to 20 because the range was never over 20 bins. The coordinate
transformation and 3-beam solutions was re-enabled at station 101,
because there were few scatterers in the water column and it was felt
that 3-beam solutions might improve the data.

**Preliminary Processing:**

Data were processed using the LDEO LADCP Software, Version 8b, written
in Matlab by Martin Visbeck and modified by Andreas Thurnherr. This
software implements an inversion for the best possible velocity profiles
estimates (Visbeck, 2002), and enables the user to incorporate two
ADCPs, bottom track estimates from water pings, CTD/GPS data, SADCP
data, and a frame/cable drag model, if so desired. LADCP profiles for
stations 5-45 were processed with 10 m bins, while those thereafter were
processed with 20 m bins in an attempt to combat poor data quality
resulting from low backscatter levels (data was collected using 10 m
bins, however). Although it is possible with the LDEO software, we did
not utilize the "small shear" (i.e., low-mode solution) constraint or
the drag model.

In the final post-cruise processing, two steps remain that could improve
the data quality. First, the ship based ADCP data will be incorporated
into the inversion. Second, 3-beam solutions are not possible with the
software, so were not incorporated for the casts that did not have
internal ADCP coordinate transformations (49-100). Code may be written
that computes these velocity estimates.

**Data Quality, Uncertainty and Preliminary Results:**

[Velocity]{.underline}

Preliminary velocity data are presented in Figures 1.19a-b, with
uncertainty estimates in Figure 1.19c. Between 50 and 45ºS latitude, we
appear to have observed the well-documented Antarctic Circumpolar
Current flow along the Sub-Antarctic and Polar Fronts (Rintoul *et al*.,
2001). Maximum currents in both fronts were 50 cm s^-1^ at 300-350 m
depth and were at least 15 cm s^-1^ through most of the water column.

Velocity uncertainty was low in the southern 40% of the section, but
increased rapidly afterwards due to low backscatter levels (Figure
1.19d); the acoustic measurements of velocity rely on particles in the
water column. Uncertainty decreased somewhat as we approached the
equator. The estimated standard error was generally below 5 cm s^-1^
between 57º30´ and 35ºS, then 10-30+ cm s^-1^ between 35 and 7ºS, and
finally back to 5-15 cm s^-1^ from 7º to 2º20´S. These confidence
intervals are conservative; they not only incorporate observed
single-ping noise but are also automatically increased when solution
consistency checks are not passed. These checks include comparisons of
downcast-only versus upcast-only solutions, and shear method versus the
inversion solutions. If any of these solutions disagree substantially,
the error is amplified.

**Figure 1.19.** Preliminary observations of (a) zonal velocity, (b)
meridional velocity, (c) velocity standard error, and (d) acoustic
backscatter. All panels include logarithmically-spaced contours of
density anomaly σ~4~ (kg m^-3^) to identify density structure and black
bathymetry shading interpolated along the ship-track from a
satellite-derived global dataset. Velocity data have been omitted
(white) where acoustic backscatter was low, generally indicating low
data quality. For brief discussions of these preliminary data, their
quality, and uncertainty, see the section titled *Data Quality,
Uncertainty, and Preliminary Results*.

![](media/image21.jpeg){width="6.5in"
height="4.0208661417322835in"}![](media/image22.jpeg){width="6.208267716535433in"
height="1.8543307086614174in"}![](media/image23.jpeg){width="6.069291338582677in"
height="1.8751968503937009in"}

A preliminary test of data quality was possible using the SADCP data.
The range of the SADCP was from 0-450 m in the first 40% of the cruise,
due to good backscatter levels, and about 0-230 m for the remainder of
the cruise. Frequent approximate comparisons between the LADCP and SADCP
during the cruise generally showed good agreement. The incorporation of
SADCP data, as well as 3-beam solutions for stations 49-100, will likely
improve the data quality somewhat. Apart from a few regions with
anomalously high backscatter and strong currents (e.g., bottom boundary
layers), it is unlikely that uncertainty levels from stations 63-110
below roughly 1000 m can be reduced to be below velocity estimates.

[Acoustic Backscatter]{.underline}

Acoustic backscatter (ABS) data (Figure 1.19d) has not been
range-normalized, but it would not be difficult to make this alteration
if there is interest in more quantitative analyses. Fortunately, the
data collection procedure approximately normalizes ABS, because the
LADCPs measure backscatter at a given depth from many distances. Depths
a few tens of meters above or below rosette stops are likely to have a
bias toward high backscatter (the top few hundred meters and the bottom
50 m), but this bias should be constant from station-to-station
throughout the cruise. Acoustic pings at 300 kHz dominantly scatter off
particles of sizes above roughly 1 mm, and high backscatter is likely
due to zooplankton, marine snow, or higher-density falling detritus.
There is a clear diurnal periodic signal in the surface 100 m between
stations 44 and 80, with high near-surface backscatter at night likely
resulting from vertical zooplankton migrations. Also note the elevated
backscatter levels at roughly 500 m between stations 50 and 80,
particularly in the core of the station 77 eddy.

[Eddy Diffusivity]{.underline}

Philip Orton developed a separate Matlab toolbox during the cruise, for
LADCP/CTD ocean mixing research. Of four published methods the toolbox
uses for determining eddy diffusivity, the most promising utilizes
vertical strain (nonlinearity in dρ/dz) and velocity shear, following
methods of Polzin *et al*. (2002) as modified by Naveira Garabato *et
al*. (2004). Preliminary results (Figure 1.20) indicate that typical
diffusivities were roughly 10^-4^ m^2^ s^-1^ in the ACC, often higher in
the bottom 1000 m, and 10^-4^ to 10^-6^ m^2^ s^-1^ in other regions.
Note that uncertainties for this method, when applied to individual
profiles, are estimated to be close to plus or minus one order of
magnitude (±10x). This could be reduced with spatial averaging, as was
done in Naveira-Garabato *et al.* (2004), but this would require major
modifications to the toolbox (*e.g.,* to work with the velocity data
from the entire transect instead of profile-by-profile).

**Files and Directories:**

The LADCP datasets should contain the following directories, which
contain everything that is needed in order to re-process the LADCP data:

-   Raw data, instrument-setup command files, communication logfiles

-   CTD time series and profiles used for LADCP processing

-   Shipboard ADCP data used for LADCP processing

-   Processed data files and processing figures

![](media/image24.jpeg){width="6.0in" height="4.6930555555555555in"}

**Figure 1.20.** Preliminary shaded estimates of (top) eddy diffusivity
and (bottom) log-scale eddy diffusivity uncertainty (± log~10~ std.
err.) from cruise-processed LADCP data. As with Figure 1, each panel
includes logarithmically-spaced contours of density anomaly σ~4~ (kg
m^-3^) to identify density structure, and black bathymetry shading
interpolated along the ship-track from a satellite-derived global
dataset. Data have been omitted (white) where the lower error bar on the
estimate was zero.

References

Naveira Garabato, A.C., K.L. Polzin, B.A. King, K.J. Heywood, and M.
Visbeck, 2004: Widespread intense turbulent mixing in the Southern
Ocean. *Science,* v. 303, pp. 210-213.

Polzin, K., E. Kunze, J. Hummon, and E. Firing, 2002: The fine-scale
response of lowered ADCP velocity profiles. *J. Atmos. Oceanic Tech.*,
v. 19, pp. 205-224.

Rintoul, S.R., C.W. Hughes, and D. Olbers, 2001: The Antarctic
Circumpolar Current system. In *Ocean Circulation and Climate: Observing
and Modeling the Global Ocean*, G. Siedler, J. Church, and J. Gould
(eds.). Academic Press, pp. 271-302.

Visbeck, M., 2002: Deep velocity profiling using lowered acoustic
Doppler current profilers: Bottom track and inverse solutions. *J.
Atmos. Oceanic Tech.*, v. 19, pp. 795-807.

2\. Bottle Sampling

2.1. Bottle Sampling Procedures

At the end of each rosette deployment, water samples were drawn from the
bottles in the following order listed below. The correspondence between
individual sample containers and the rosette bottle from which the
sample was drawn was recorded on the sample log for the cast. This log
also included any comments or anomalous conditions noted about the
rosette and bottles. One member of the sampling team was designated the
"sample cop," whose responsibility was to maintain this log and insure
that sampling progressed in the proper drawing order.

Normal sampling practice included opening the drain valve and then the
air vent on the bottle, indicating an air leak if water escaped. This
observation, together with other diagnostic comments (e.g., "lanyard
caught in lid," "valve left open") that might later prove useful in
determining sample integrity, were routinely noted on the sample log.
Drawing oxygen samples also involved taking the sample draw temperature
from the bottle. The temperature was noted on the sample log and was
sometimes useful in determining leaking or mis-tripped bottles.

Once individual samples had been drawn and properly prepared, they were
distributed for analysis. Oxygen, nutrient, and salinity analyses were
performed on computer-assisted (PC) analytical equipment networked to
the data processing computer for centralized data management.

2.2. Bottle Data Processing

Water samples collected and properties analyzed shipboard were managed
centrally in a relational database (PostgreSQL-7.4.6) run on a Linux
workstation. A web service (OpenAcs-5.1.3 and AOL Server-4.0.9)
front-end provided ship-wide access to CTD and water sample data through
web pages. Web-based facilities included on-demand arbitrary
property-property plots and vertical sections, as well as data uploads
and downloads.

The sample log (and any diagnostic comments) was entered into the
database once sampling was completed. WOCE/CLIVAR quality flags
associated with sampled properties were set to indicate that the
property had been sampled, and sample container identifications were
noted where appropriate (e.g., oxygen flask number).

The results of individual shipboard analyses were then uploaded through
the website as results became available. These results included a
quality code associated with each measured value and followed the coding
scheme developed for the World Ocean Circulation Experiment (WOCE)
Hydrographic Programme (WHP) (Joyce, 1994).

Various consistency checks and detailed examination of the data
continued throughout the cruise.

2.3. Sampling and Analyses of Bottle Data

Samples for chlorofluorocarbons (CFCs), helium isotopes (^3^He), oxygen
(O~2~), hydrochlorofluorocarbon (HCFCs), partial pressure of CO~2~
(pCO~2~), dissolved inorganic carbon (DIC), hydrogen ion activities
(pH), total alkalinity (TAlk), radiocarbon (DI^14^C), tritium, dissolved
organic carbon (DOC), chromophoric dissolved organic matter (CDOM),
particulate inorganic/organic carbon (PIC/POC), salinity, and nutrients
were drawn in this sequence from a CTD sampling package containing 36,
12-l Bullister bottles. Sampling of the 36 bottles on the package took
about 1.5 hours. The samples analyzed for gases were sampled first and
usually drawn within an hour. The deepest bottle was sampled first and
bottles were sampled sequentially to the surface bottle. Care was taken
to coordinate the sampling to minimize the time between the initial
opening of each bottle and the completion of sample drawing. In most
cases, CFCs, ^3^He, dissolved oxygen, and HCFC samples were collected
within several minutes of the initial opening of each bottle.

Oxygen, nutrient, and salinity samples were taken from all bottles.
Oxygen draw temperature readings were commenced after station 25. For
the other parameters, not all stations or all bottles were sampled. The
stations at full degrees of latitude (odd numbered stations) were
generally completely sampled for CFCs, DIC, pH, and TAlk, with partial
sampling for DOC and CDOM. The half-degree stations were partially
sampled for HCFC, PIC/POC, CFCs, DIC, pH, and TAlk. Discrete pCO~2~
profiles were obtained at every two degrees. ^3^He, DI^14^C, and tritium
were sampled at different intervals (primarily at full-latitude
stations) as noted below. For casts where many parameters were sampled,
water levels in the Bullister bottles were very low when the salinity
and nutrients were drawn. This was particularly true for the bottom two
bottles and top two bottles that were often used for duplicate sampling
for parameters with large water requirements such as DIC and TAlk.
Estimated water requirements for the samples are listed in the Table
2.1.

  --------------------------------------------------- -------------------
  **Table 2.1. Water requirements (including bottle   
  rinses and sample) for the different parameters     
  drawn on the Bullister bottles.**                   

  **Parameter**                                       **Volume (l)**

  Chlorofluorocarbons (CFCs)                          0.5

  Helium isotopes (^3^He)                             0.5

  Oxygen (O~2~)                                       0.5

  Hydrochlorofluorocarbons (HCFCs)                    0.5

  Partial pressure of CO~2~ (pCO~2~)                  1.2

  Dissolved inorganic carbon (DIC)                    1.5

  Hydrogen ion activities (pH)                        0.3

  Total alkalinity (TAlk)                             1.5

  Radiocarbon (DI^14^C)                               0.8

  Tritium                                             1.2

  Dissolved organic carbon (DOC)                      0.2

  Chromophoric dissolved organic matter (CDOM)        0.2

  Particulate inorganic/organic carbon (PIC/POC)      1.5

  Salinity                                            0.3

  Nutrients                                           0.3
  --------------------------------------------------- -------------------

Most samples were analyzed on board with the exception of ^3^He,
DI^14^C, tritium, DOC, CDOM, and PIC/POC that were sampled and preserved
for shore-based analysis. Below are the descriptions of sampling and
analysis procedures for each parameter, as well as the relevant
statistics on data quantity and quality.

2.4. Tests Performed on Bullister Bottles to Determine Sample Integrity
of CFCs, Salts, and O~2~

Two types of tests were performed on the 12-liter Bullister bottles
("12-B Bottles") used on A16S cruise:

1\. Test Type 1 was designed to estimate the rate of change of dissolved
CFCs (CFC-11, CFC-12, CFC-113 and carbon tetrachloride (CCl~4~))
concentrations in seawater held inside closed bottles.

2\. Test Type 2 was designed to determine the rate of change of
dissolved CFCs, CCl~4~, oxygen, and salinity in seawater remaining
inside a bottle after the bottle had been opened and other seawater
samples withdrawn.

**Background:**

Once a bottle is closed in the water column during a hydrocast, the
concentrations of dissolved CFCs in the water inside may increase slowly
due to release of trace amounts of CFCs present in the bottle walls,
O-rings, and other materials. The release of these contaminants
contributes to the non-zero CFC concentrations ("bottle blank")
typically observed even in regions of the deep ocean thought to be
essentially CFC-free.

The extent of this contamination is thought to be a function of:

-   the materials used in constructing the bottles

-   the exposure of these materials to CFCs in the atmosphere prior to
    the cast

-   the length of time the water remains in the bottle before transfer

-   the temperature

Once a bottle is opened on deck and water withdrawn for sampling, gas
exchange between the air in the headspace and water in the bottle begins
and can alter the dissolved gas concentrations and salinity in the
remaining water. The unbuffered gases, e.g., He, CFCs, HCFCs and O~2,~
are believed to be most susceptible to these changes. These changes can
be especially significant when large gradients in partial pressures are
present between the gases in the water and in the headspace, for
example, when a deep sample containing near-zero concentrations of
dissolved CFC is exposed to a headspace of marine air.

**Bottle Tests:**

***Test Type 1: Changes in CFC Concentration in Closed 12-B Bottles***

The following tests were performed to estimate the rates at which
dissolved CFCs increase in water stored in closed 12-B Bottles. In each
test, replicate sets of bottles were closed at a depth with low CFC
concentrations to allow small changes to be more easily detected. Some
replicate deep bottles were allowed to warm on deck before sampling,
while others were kept cold in a walk-in refrigerator before sampling.

Bottle temperatures ("O~2~ Draw Temp") were recorded as each oxygen
sample was drawn using a thermistor inserted into the oxygen flask,
following the same procedure used for standard oxygen draw temperatures.
These tests were performed at stations 88, 102, and 112.

**Station 88:** five 12-liter bottles (9-13) were closed at \~3100 m
depth (Table 2.2):

-   Bottle 9 was sampled normally in sequence (about 32 minutes after
    arrival on deck);

-   Bottles 10 and 12 were left closed on the rosette frame and sampled
    before the next cast;

-   Bottles 11 and 13 were removed from the rosette and placed on a
    spare frame in the shade on deck to allow for longer storage times.

<table>
<colgroup>
<col style="width: 5%" />
<col style="width: 9%" />
<col style="width: 8%" />
<col style="width: 9%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="12"><strong>Table 2.2. Results for station 88 storage
tests.</strong></td>
</tr>
<tr class="even">
<td><strong>Bot.</strong></td>
<td><p><strong>CFC</strong></p>
<p><strong>Syringe</strong></p></td>
<td><p><strong>HCFC</strong></p>
<p><strong>Flask</strong></p></td>
<td><p><strong>Oxygen</strong></p>
<p><strong>Flask</strong></p></td>
<td><p><strong>O<sub>2</sub></strong></p>
<p><strong>Draw</strong></p>
<p><strong>Temp<sup>1</sup></strong></p>
<p><strong>(°C)</strong></p></td>
<td><p><strong>Salt</strong></p>
<p><strong>Bottle</strong></p></td>
<td><p><strong>Sample</strong></p>
<p><strong>Time<sup>2</sup></strong></p>
<p><strong>(Z)</strong></p></td>
<td><p><strong>CFC-12</strong></p>
<p><strong>(pmol kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>CFC-11</strong></p>
<p><strong>(pmol kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>CFC-13</strong></p>
<p><strong>(pmol</strong></p>
<p><strong>kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>CC1<sub>4</sub></strong></p>
<p><strong>(pmol</strong></p>
<p><strong>kg<sup>-1</sup>)</strong></p></td>
<td><strong>Salinity</strong></td>
</tr>
<tr class="odd">
<td>9</td>
<td>5573</td>
<td>4</td>
<td>161</td>
<td>7.3</td>
<td>209</td>
<td>00:30</td>
<td>0.011</td>
<td>0.021</td>
<td>0</td>
<td>0.082</td>
<td>34.9137</td>
</tr>
<tr class="even">
<td>9</td>
<td>7692</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>00:31</td>
<td>0.013</td>
<td>0.024</td>
<td>0</td>
<td>0.089</td>
<td></td>
</tr>
<tr class="odd">
<td>10</td>
<td>5564</td>
<td>4</td>
<td>40</td>
<td>13.2</td>
<td>210</td>
<td>01:40</td>
<td>0.012</td>
<td>0.027</td>
<td>0</td>
<td>0.084</td>
<td>34.9153</td>
</tr>
<tr class="even">
<td>12</td>
<td>7674</td>
<td>4</td>
<td></td>
<td>17.9</td>
<td>212</td>
<td>03:05</td>
<td>0.014</td>
<td>0.022</td>
<td>0</td>
<td>0.088</td>
<td>34.9151</td>
</tr>
<tr class="odd">
<td>11</td>
<td>7735</td>
<td>5</td>
<td></td>
<td>23.4</td>
<td>211</td>
<td>07:45</td>
<td>0.017</td>
<td>0.027</td>
<td>0</td>
<td>0.090</td>
<td>34.9148</td>
</tr>
<tr class="even">
<td>13</td>
<td>9888</td>
<td>4</td>
<td>40</td>
<td>26.5</td>
<td>213</td>
<td>15:05</td>
<td>0.024</td>
<td>0.050</td>
<td>0</td>
<td>0.089</td>
<td>34.9155</td>
</tr>
<tr class="odd">
<td colspan="12"><p>Cast on deck 11 Feb 2005 at ~23:58Z.</p>
<p><sup>1</sup>Initial (potential) temperature for seawater samples was
~2.430°C.</p>
<p><sup>2</sup>Date: 12 Feb 2005; all times are UTC.</p></td>
</tr>
</tbody>
</table>

**Station 102**: five bottles (6-10) closed at \~2950 m (Table 2.3):

-   Bottle 6 was sampled normally (about 32 minutes after arrival on
    deck);

-   Bottles 6 and 10 were left closed on frame and sampled before the
    next cast;

-   Bottles 7 and 9 were removed from the rosette frame after about 1
    hour on deck and placed in walk in cooler at \~4°C Substantial
    warming occurred during the period on deck, and subsequent cooling
    may have caused air to be drawn into the bottles. Sounds were
    detected when bottle 9 was inverted, indicating the presence of an
    air pocket in this bottle. Consequently, samples from bottle 9 were
    not drawn, and the data from bottle 7 are considered suspect.

<table>
<colgroup>
<col style="width: 5%" />
<col style="width: 9%" />
<col style="width: 8%" />
<col style="width: 9%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="12"><strong>Table 2.3. Results for station 102 storage
tests.</strong></td>
</tr>
<tr class="even">
<td><strong>Bot.</strong></td>
<td><p><strong>CFC</strong></p>
<p><strong>Syringe</strong></p></td>
<td><p><strong>HCFC</strong></p>
<p><strong>Flask</strong></p></td>
<td><p><strong>Oxygen</strong></p>
<p><strong>Flask</strong></p></td>
<td><p><strong>O<sub>2</sub></strong></p>
<p><strong>Draw</strong></p>
<p><strong>Temp<sup>1</sup></strong></p>
<p><strong>(°C)</strong></p></td>
<td><p><strong>Salt</strong></p>
<p><strong>Bottle</strong></p></td>
<td><p><strong>Sample</strong></p>
<p><strong>Time<sup>2</sup></strong></p>
<p><strong>(Z)</strong></p></td>
<td><p><strong>CFC-12</strong></p>
<p><strong>(pmol kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>CFC-11</strong></p>
<p><strong>(pmol kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>CFC-13</strong></p>
<p><strong>(pmol</strong></p>
<p><strong>kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>CC1<sub>4</sub></strong></p>
<p><strong>(pmol</strong></p>
<p><strong>kg<sup>-1</sup>)</strong></p></td>
<td><strong>Salinity</strong></td>
</tr>
<tr class="odd">
<td>6</td>
<td>629</td>
<td>3</td>
<td>6</td>
<td>6.4</td>
<td>606</td>
<td>05:00</td>
<td>0.016</td>
<td>0.030</td>
<td>0</td>
<td>0.100</td>
<td>34.9173</td>
</tr>
<tr class="even">
<td>6</td>
<td>7695A</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>05:01</td>
<td>0.020</td>
<td>0.031</td>
<td>0</td>
<td>0.102</td>
<td></td>
</tr>
<tr class="odd">
<td>8</td>
<td>7638</td>
<td>16</td>
<td></td>
<td>14.7</td>
<td>608</td>
<td>06:10</td>
<td>0.018</td>
<td>0.043</td>
<td>0</td>
<td>0.104</td>
<td>34.9175</td>
</tr>
<tr class="even">
<td>10</td>
<td>367</td>
<td>17</td>
<td></td>
<td>16.9</td>
<td>610</td>
<td>07:10</td>
<td>0.022</td>
<td>0.048</td>
<td>0.005</td>
<td>0.102</td>
<td>34.9189</td>
</tr>
<tr class="odd">
<td>7<sup>3</sup></td>
<td>7701</td>
<td>18</td>
<td></td>
<td>5.5</td>
<td>607</td>
<td>19:10</td>
<td>0.035</td>
<td>0.061</td>
<td>0</td>
<td>0.110</td>
<td>34.9189</td>
</tr>
<tr class="even">
<td colspan="12"><p>Cast on deck 16 Feb 2005 at ~04:18Z.</p>
<p><sup>1</sup>Potential temperature for seawater samples was
~2.507°C.</p>
<p><sup>2</sup>Date: 16 Feb 2005; all times are UTC.</p>
<p><sup>3</sup>Bottle 7 likely contaminated with air.</p></td>
</tr>
</tbody>
</table>

**Station 112**: five bottles (10-14) closed at \~3000 m (Table 2.4):

-   Bottle 10 was sampled normally (about 11 minutes after arrival on
    deck);

-   Bottles 12 and 14 were left closed on frame and sampled before the
    next cast;

-   Bottles 11 and 13 were removed immediately after arrival on deck and
    placed in walk in cooler at \~4°C;

-   No oxygen samples were drawn on bottles 11-14.

<table>
<colgroup>
<col style="width: 5%" />
<col style="width: 9%" />
<col style="width: 8%" />
<col style="width: 9%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="12"><strong>Table 2.4. Results for station 112 storage
tests.</strong></td>
</tr>
<tr class="even">
<td><strong>Bot.</strong></td>
<td><p><strong>CFC</strong></p>
<p><strong>Syringe</strong></p></td>
<td><p><strong>HCFC</strong></p>
<p><strong>Flask</strong></p></td>
<td><p><strong>Oxygen</strong></p>
<p><strong>Flask</strong></p></td>
<td><p><strong>O<sub>2</sub></strong></p>
<p><strong>Draw</strong></p>
<p><strong>Temp<sup>1</sup></strong></p>
<p><strong>(°C)</strong></p></td>
<td><p><strong>Salt</strong></p>
<p><strong>Bottle</strong></p></td>
<td><p><strong>Sample</strong></p>
<p><strong>Time<sup>2</sup></strong></p>
<p><strong>(Z)</strong></p></td>
<td><p><strong>CFC-12</strong></p>
<p><strong>(pmol kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>CFC-11</strong></p>
<p><strong>(pmol kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>CFC-13</strong></p>
<p><strong>(pmol</strong></p>
<p><strong>kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>CC1<sub>4</sub></strong></p>
<p><strong>(pmol</strong></p>
<p><strong>kg<sup>-1</sup>)</strong></p></td>
<td><strong>Salinity</strong></td>
</tr>
<tr class="odd">
<td>10</td>
<td>7628</td>
<td>4</td>
<td>10</td>
<td>6.7</td>
<td>110</td>
<td>03:45</td>
<td>0.011</td>
<td>0.022</td>
<td>0.003</td>
<td>0.084</td>
<td>34.9173</td>
</tr>
<tr class="even">
<td>12</td>
<td>5567A</td>
<td>1</td>
<td></td>
<td>13.0</td>
<td>112</td>
<td>05:10</td>
<td>0.018</td>
<td>0.023</td>
<td>0</td>
<td>0.087</td>
<td>34.9179</td>
</tr>
<tr class="odd">
<td>14</td>
<td>674</td>
<td>17</td>
<td></td>
<td>18.2</td>
<td>114</td>
<td>06:35</td>
<td>0.017</td>
<td>0.024</td>
<td>0</td>
<td>0.087</td>
<td>34.9170</td>
</tr>
<tr class="even">
<td>11</td>
<td><p>7674</p>
<p>7692A</p></td>
<td>17, 18</td>
<td></td>
<td>5.1</td>
<td>111</td>
<td>19:20</td>
<td>0.019</td>
<td>0.029</td>
<td>0</td>
<td>0.086</td>
<td>34.9181</td>
</tr>
<tr class="odd">
<td>13</td>
<td>9833</td>
<td>1, 2</td>
<td></td>
<td>4.4</td>
<td>113</td>
<td>20:40<strong><sup>3</sup></strong></td>
<td>0.015</td>
<td>0.031</td>
<td>0</td>
<td>0.086</td>
<td>34.9159</td>
</tr>
<tr class="even">
<td colspan="12"><p>Cast on deck 19 Feb 2005 at ~03:36Z.</p>
<p><sup>1</sup>Potential temperature for seawater samples was
~2.439°C.</p>
<p><sup>2</sup>Date: 19 Feb 2005; all times are UTC.</p>
<p><sup>3</sup>Date: 20 Feb 2005.</p></td>
</tr>
</tbody>
</table>

**Discussion of Results from Test Type 1:**

During hydrocasts on the A16S cruise, the deep bottles were closed
earlier than shallower bottles; however, the deep bottles were sampled
first on deck. Hence, for deep hydrocasts on A16S, the mean time that
seawater typically remained inside bottles before opening was roughly
the same (about 2 hours) for both deep and shallow bottles.

At high latitudes during the A16S cruise, there was typically little
warming of the water on deck before sampling. In mid and low latitudes,
mid-depth and deep water samples underwent warming (as determined by the
difference between the potential temperature and oxygen draw
temperature) during their transit through the thermocline, mixed layer,
and while on deck before sampling. The amount of warming was determined
by temperature measurements made during the oxygen sampling process, and
was typically several degrees.

The station 112 experiment examined the CFC changes in bottles where
seawater was stored inside at cold temperatures (\~5^o^C) for an
extended period of time. The changes in the cold bottles (relative to
the initially sampled bottle) are denoted in Table 2.5.

<table style="width:100%;">
<colgroup>
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 9%" />
<col style="width: 7%" />
<col style="width: 9%" />
<col style="width: 15%" />
<col style="width: 7%" />
<col style="width: 15%" />
<col style="width: 7%" />
<col style="width: 14%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="10"><strong>Table 2.5. Changes in concentrations for
station 112 storage test.</strong></td>
</tr>
<tr class="even">
<td><strong>Sta.</strong></td>
<td><strong>Bot.</strong></td>
<td><p><strong>Time</strong></p>
<p><strong>(Hours)</strong></p></td>
<td><p><strong>O<sub>2</sub></strong></p>
<p><strong>Draw</strong></p>
<p><strong>Temp</strong></p>
<p><strong>(°C)</strong></p></td>
<td><p><strong>CFC-12</strong></p>
<p><strong>(pmol</strong></p>
<p><strong>kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>dCFC-12/dt</strong></p>
<p><strong>(pmol kg<sup>-1</sup> hr<sup>-1</sup>)</strong></p></td>
<td><p><strong>CFC-11</strong></p>
<p><strong>(pmol</strong></p>
<p><strong>kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>dCFC-11/dt</strong></p>
<p><strong>(pmol kg<sup>-1</sup> hr<sup>-1</sup>)</strong></p></td>
<td><p><strong>CC1<sub>4</sub></strong></p>
<p><strong>(pmol</strong></p>
<p><strong>kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>dCCl<sub>4</sub>/dt</strong></p>
<p><strong>(pmol kg<sup>-1</sup> hr<sup>-1</sup>)</strong></p></td>
</tr>
<tr class="odd">
<td>112</td>
<td>11</td>
<td>15.58</td>
<td>5.1</td>
<td>0.008</td>
<td>0.00051</td>
<td>0.007</td>
<td>0.00045</td>
<td>0.002</td>
<td>0.00013</td>
</tr>
<tr class="even">
<td>112</td>
<td>13</td>
<td>40.91</td>
<td>4.4</td>
<td>0.004</td>
<td>0.00010</td>
<td>0.009</td>
<td>0.00022</td>
<td>0.002</td>
<td>0.00005</td>
</tr>
<tr class="odd">
<td></td>
<td></td>
<td></td>
<td></td>
<td colspan="2"><p>mean = 0.00031</p>
<p>sd = ±0.00029</p></td>
<td colspan="2"><p>mean = 0.00033</p>
<p>sd = ±0.00016</p></td>
<td colspan="2"><p>mean = 0.00009</p>
<p>sd = ±0.00006</p></td>
</tr>
</tbody>
</table>

The scatter in the derived rates in Table 2.5 is likely due to the fact
that the observed concentration changes in Table 2.5 are close to
detection limits for these compounds (roughly \~0.002-0.004 pmol
kg^-1^). These results do indicate that in regions where there is little
warming before sampling (e.g., high latitudes) the rate of increase of
CFCs in the 12-B bottles during the 2 hours between closing and sampling
is small. CFC-113 showed no consistent pattern of increase (see Table
2.4). CFC-11, CFC-12 and CCl~4~ showed very small increases (Table 2.5)
of \<0.001 pmol kg^-1^ hr^-1^.

The station 88, 102, and 112 experiments examined the CFC changes in
bottles where seawater inside was allowed to warm on deck for various
periods of time. The changes in the bottles (relative to the initially
sampled bottle) are listed in Table 2.6.

<table style="width:100%;">
<colgroup>
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 9%" />
<col style="width: 7%" />
<col style="width: 9%" />
<col style="width: 15%" />
<col style="width: 7%" />
<col style="width: 15%" />
<col style="width: 7%" />
<col style="width: 14%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="10"><strong>Table 2.6. Summary of CFC changes for the
storage tests.</strong></td>
</tr>
<tr class="even">
<td><strong>Sta.</strong></td>
<td><strong>Bot.</strong></td>
<td><p><strong>Time</strong></p>
<p><strong>(Hours)</strong></p></td>
<td><p><strong>O<sub>2</sub></strong></p>
<p><strong>Draw</strong></p>
<p><strong>Temp</strong></p>
<p><strong>(°C)</strong></p></td>
<td><p><strong>CFC-12</strong></p>
<p><strong>(pmol</strong></p>
<p><strong>kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>dCFC-12/dt</strong></p>
<p><strong>(pmol kg<sup>-1</sup> hr<sup>-1</sup>)</strong></p></td>
<td><p><strong>CFC-11</strong></p>
<p><strong>(pmol</strong></p>
<p><strong>kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>dCFC-11/dt</strong></p>
<p><strong>(pmol kg<sup>-1</sup> hr<sup>-1</sup>)</strong></p></td>
<td><p><strong>CC1<sub>4</sub></strong></p>
<p><strong>(pmol</strong></p>
<p><strong>kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>dCCl<sub>4</sub>/dt</strong></p>
<p><strong>(pmol kg<sup>-1</sup> hr<sup>-1</sup>)</strong></p></td>
</tr>
<tr class="odd">
<td>88</td>
<td>10</td>
<td>1.17</td>
<td>13.2</td>
<td>0.000</td>
<td>0</td>
<td>0.004</td>
<td>0.00384</td>
<td>-0.0014</td>
<td>-0.00120</td>
</tr>
<tr class="even">
<td>88</td>
<td>12</td>
<td>2.58</td>
<td>17.9</td>
<td>0.002</td>
<td>0.00078</td>
<td>-0.001</td>
<td>-0.00039</td>
<td>0.0026</td>
<td>0.00101</td>
</tr>
<tr class="odd">
<td>88</td>
<td>11</td>
<td>7.25</td>
<td>23.4</td>
<td>0.005</td>
<td>0.00069</td>
<td>0.004</td>
<td>0.00062</td>
<td>0.0046</td>
<td>0.00063</td>
</tr>
<tr class="even">
<td>88</td>
<td>13</td>
<td>14.58</td>
<td>26.5</td>
<td>0.012</td>
<td>0.00082</td>
<td>0.027</td>
<td>0.00189</td>
<td>0.0036</td>
<td>0.00025</td>
</tr>
<tr class="odd">
<td>102</td>
<td>8</td>
<td>1.17</td>
<td>14.7</td>
<td>0.000</td>
<td>0</td>
<td>0.013</td>
<td>0.01068</td>
<td>0.003</td>
<td>0.00256</td>
</tr>
<tr class="even">
<td>102</td>
<td>10</td>
<td>2.17</td>
<td>16.9</td>
<td>0.004</td>
<td>0.00184</td>
<td>0.018</td>
<td>0.00806</td>
<td>0.001</td>
<td>0.00046</td>
</tr>
<tr class="odd">
<td>112</td>
<td>12</td>
<td>1.41</td>
<td>13.0</td>
<td>0.007</td>
<td>0.00496</td>
<td>0.001</td>
<td>0.00071</td>
<td>0.003</td>
<td>0.00213</td>
</tr>
<tr class="even">
<td>112</td>
<td>14</td>
<td>2.83</td>
<td>18.2</td>
<td>0.006</td>
<td>0.00212</td>
<td>0.002</td>
<td>0.00071</td>
<td>0.003</td>
<td>0.00106</td>
</tr>
<tr class="odd">
<td></td>
<td></td>
<td></td>
<td></td>
<td colspan="2"><p>mean = 0.00140</p>
<p>sd = ±0.00163</p></td>
<td colspan="2"><p>mean = 0.00327</p>
<p>sd = ±0.00403</p></td>
<td colspan="2"><p>mean = 0.00086</p>
<p>sd = ±0.00116</p></td>
</tr>
</tbody>
</table>

As in the cold experiment in Table 2.5, since the observed concentration
changes were often near the minimum detection limits for the compounds,
there is considerable scatter in the rates of CFC increase derived in
Table 2.6.

As in the cold tests, CFC-113 showed no consistent pattern of increase
(see Tables 2.2 and 2.3) in the warming bottles. CFC-12 and CCl~4~
showed small mean increases (Table 2.6) of \~0.0014 and \~0.0011 pmol
kg^-1^ hr^-1^, respectively. The mean rate of increase in CFC-11
(\~0.0033 pmol kg^-1^ hr^-1^) was somewhat larger.

The results from Table 2.5 indicate that in cold regions, blanks for
seawater stored for 2 hours in the 12-B bottles are \<0.001 pmol kg^-1^
for all four compounds.

An estimate of the deep bottle blanks in warm regions can be made from
Table 2.6, assuming that for the typical 2 hours that water is held
inside the bottles, significant warming occurs only during the last hour
as the bottle passed though the thermocline and were stored on deck.

From Tables 2.5 and 2.6, rough estimates of the bottle blanks are
denoted in Table 2.7.

+---------------+-------------------------+---------------------------+
| **Table 2.7.  |                         |                           |
| Bottle blanks |                         |                           |
| for Bullister |                         |                           |
| bottles.**    |                         |                           |
+---------------+-------------------------+---------------------------+
|               | **Cold Regions**        | **Warm Regions**          |
|               |                         |                           |
|               | **(pmol kg^-1^)**       | **(pmol kg^-1^)**         |
+---------------+-------------------------+---------------------------+
| CFC-12        | 0                       | 0.002                     |
+---------------+-------------------------+---------------------------+
| CFC-11        | 0                       | 0.004                     |
+---------------+-------------------------+---------------------------+
| CFC-113       | 0                       | 0                         |
+---------------+-------------------------+---------------------------+
| CC1~4~        | 0                       | 0.001                     |
+---------------+-------------------------+---------------------------+

***Test Type 2: A16S Bottle Time Series***

At station 121, three 12-B bottles (19, 20, 21) were closed at the same
depth (1000 m) near the oxygen minimum zone and in a region of low CFCs.
This depth was chosen to maximize the gradient in partial pressures of
these gases between the water and air present in the bottle headspace
once the bottles were opened. The goal of this test was to determine
possible changes in dissolved CFCs, oxygen, and salinity as a function
of time and of the volume of water drained from a 12-B bottle after the
bottle was initially opened. Table 2.8 depicts a summary of the bottle
tests for station 121.

**Procedure:**

-   Bottle 20 was sampled normally, approximately 20 minutes after the
    cast was on deck.

-   Bottle 19 was sampled for salinity, CFCs, and oxygen \~5 minutes
    after the cast was on deck and then resampled for these parameters
    as rapidly as possible four additional times. The total sampling
    time for the five sets of samples from bottle 19 was \~17 minutes.

-   Bottle 21 was sampled for salinity, CFCs, and oxygen \~6 minutes
    after the cast came on deck, and then resampled for these parameters
    four more times at \~30 minute intervals over a period of 2.5 hrs.

Samples in bottles 19 and 21 were drawn in the order: salinity,
salinity, CFC, oxygen. For bottles 19 and 21, a total of about 2 l of
water was used to draw each set of samples, so at the completion of the
fifth set, about 2 l of water remained in the bottles.

Bottle temperatures ("O~2~ Draw Temp") were recorded as each oxygen
sample was drawn using a thermistor inserted into the oxygen flask,
following the same procedure used for standard oxygen draw temperatures.

<table style="width:100%;">
<colgroup>
<col style="width: 5%" />
<col style="width: 7%" />
<col style="width: 6%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 7%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 2%" />
<col style="width: 6%" />
<col style="width: 9%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="13"><strong>Table 2.8. Summary of bottle tests for station
121.</strong></td>
</tr>
<tr class="even">
<td><strong>Bot</strong></td>
<td><p><strong>Sample</strong></p>
<p><strong>Time<sup>1</sup></strong></p></td>
<td><p><strong>Salt</strong></p>
<p><strong>Bottle</strong></p></td>
<td><p><strong>CFC</strong></p>
<p><strong>syringe</strong></p></td>
<td><p><strong>Oxygen</strong></p>
<p><strong>Flask</strong></p></td>
<td><p><strong>O<sub>2</sub></strong></p>
<p><strong>Draw</strong></p>
<p><strong>Temp<sup>2</sup></strong></p>
<p><strong>(<sup>o</sup>C)</strong></p></td>
<td><p><strong>CFC-12</strong></p>
<p><strong>(pmol kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>CFC-11</strong></p>
<p><strong>(pmol kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>CFC-113</strong></p>
<p><strong>(pmol kg<sup>-1</sup>)</strong></p></td>
<td><p><strong>CCl<sub>4</sub></strong></p>
<p><strong>(pmol kg<sup>-1</sup>)</strong></p></td>
<td colspan="2"><p><strong>Oxygen<sup>3</sup></strong></p>
<p><strong>(umol l<sup>-1</sup>)</strong></p></td>
<td><strong>Salinity</strong></td>
</tr>
<tr class="odd">
<td>20</td>
<td>17:55</td>
<td>820</td>
<td>984</td>
<td>168</td>
<td>9.0</td>
<td>0.030</td>
<td>0.077</td>
<td>0</td>
<td>0.155</td>
<td colspan="2"></td>
<td>34.5782</td>
</tr>
<tr class="even">
<td>19</td>
<td>17:40</td>
<td><p>1001</p>
<p>1002</p></td>
<td>7692A</td>
<td>41</td>
<td>6.7</td>
<td>0.036</td>
<td>0.077</td>
<td>0</td>
<td>0.156</td>
<td colspan="2">165.2</td>
<td><p>34.5795</p>
<p>34.5781</p></td>
</tr>
<tr class="odd">
<td></td>
<td>17:43</td>
<td><p>1003</p>
<p>1004</p></td>
<td>9837</td>
<td>42</td>
<td>7.7</td>
<td>0.034</td>
<td>0.077</td>
<td>0</td>
<td>0.147</td>
<td colspan="2">165.</td>
<td><p>34.5778</p>
<p>34.5775</p></td>
</tr>
<tr class="even">
<td></td>
<td>17:48</td>
<td><p>1005</p>
<p>1006</p></td>
<td>7701</td>
<td>43</td>
<td>8.4</td>
<td>0.038</td>
<td>0.077</td>
<td>0</td>
<td>0.154</td>
<td colspan="2">165.4</td>
<td><p>34.5775</p>
<p>34.5778</p></td>
</tr>
<tr class="odd">
<td></td>
<td>17:52</td>
<td><p>1007</p>
<p>1008</p></td>
<td>lost</td>
<td>44</td>
<td>9.5</td>
<td>---</td>
<td>---</td>
<td>---</td>
<td>---</td>
<td colspan="2">166.4</td>
<td><p>34.5779</p>
<p>34.5779</p></td>
</tr>
<tr class="even">
<td></td>
<td>17:57</td>
<td><p>1009</p>
<p>1010</p></td>
<td>9825</td>
<td>45</td>
<td>11.4</td>
<td>0.056</td>
<td>0.118</td>
<td>0</td>
<td>0.183</td>
<td colspan="2">167.0</td>
<td><p>34.5777</p>
<p>34.5770</p></td>
</tr>
<tr class="odd">
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td colspan="3"><p>mean salinity =</p>
<p>sd =</p></td>
<td><p>34.5787</p>
<p>0.0006</p></td>
</tr>
<tr class="even">
<td>21</td>
<td>17:40</td>
<td><p>1011</p>
<p>1012</p></td>
<td>18<strong><sup>4</sup></strong></td>
<td>46</td>
<td>7.0</td>
<td>0.052</td>
<td>0.076</td>
<td>0</td>
<td colspan="2">0.151</td>
<td>165.3</td>
<td><p>34.5771</p>
<p>34.5762</p></td>
</tr>
<tr class="odd">
<td></td>
<td>18:10</td>
<td><p>1013</p>
<p>1014</p></td>
<td>7674</td>
<td>47</td>
<td>10.2</td>
<td>0.047</td>
<td>0.103</td>
<td>0</td>
<td colspan="2">0.177</td>
<td>165.9</td>
<td><p>34.5763</p>
<p>34.5766</p></td>
</tr>
<tr class="even">
<td></td>
<td>18:40</td>
<td><p>1015</p>
<p>1016</p></td>
<td>17<strong><sup>4</sup></strong></td>
<td>48</td>
<td>13.3</td>
<td>0.074</td>
<td>0.095</td>
<td>0</td>
<td colspan="2">0.169</td>
<td>166.0</td>
<td><p>34.5762</p>
<p>34.5756</p></td>
</tr>
<tr class="odd">
<td></td>
<td>19:10</td>
<td><p>1017</p>
<p>1018</p></td>
<td>9833</td>
<td>49</td>
<td>16.2</td>
<td>0.054</td>
<td>0.106</td>
<td>0.005</td>
<td colspan="2">0.178</td>
<td>167.3</td>
<td><p>34.5769</p>
<p>34.5769</p></td>
</tr>
<tr class="even">
<td></td>
<td>19:40</td>
<td><p>1019</p>
<p>1020</p></td>
<td>7638</td>
<td>167</td>
<td>18.7</td>
<td>0.078</td>
<td>0.148</td>
<td>0.008</td>
<td colspan="2">0.221</td>
<td>169.9</td>
<td><p>34.5756</p>
<p>34.5759</p></td>
</tr>
<tr class="odd">
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td colspan="3"><p>mean salinity =</p>
<p>sd =</p></td>
<td><p>34.5763</p>
<p>0.0005</p></td>
</tr>
<tr class="even">
<td colspan="13"><p>Cast on deck 21 Feb 2005 ~17:29; all times are
UTC.</p>
<p><strong><sup>1</sup></strong>21 Feb 2005.</p>
<p><strong><sup>2</sup></strong>Potential temperature for seawater
samples was ~4.274°C.</p>
<p><strong><sup>3</sup></strong>Oxygen values are preliminary and in
umol l<sup>-1</sup>.</p>
<p><strong><sup>4</sup></strong>Indicates syringe borrowed from HCFC
group, CFC values may be suspect.</p>
<p><strong>Notes on Test 2</strong>: Ship was underway during this
period--little ship roll. Bottles were in shade, relative wind ~10
knots; relative humidity, 84%; air temp, 27.6°C. After sampling,
approximately 2 liters remained of original 12 liters--each sampling
cycle is estimated to have used ~2 liters of water.</p></td>
</tr>
</tbody>
</table>

**Discussion of Test Type 2:**

From the very small data set in this test, changes in dissolved CFC
concentrations appear to be functions of the time after the bottle is
opened and of the volume of water removed prior to drawing the samples.
For bottle 19, the changes in measured CFCs and dissolved oxygen within
the first 8 minutes of sampling (and after two sets of samples have been
removed previously) were very small and are within the analytical
precision of the analyses. These results indicate that under some
conditions a short delay in sampling for CFC and oxygen after a bottle
is opened (and after a few liters of water are withdrawn) may not cause
measurable changes in the resulting CFC and oxygen concentration
measurements. It is important to note that these tests were performed
using 12-liter bottles on a large, stable research vessel under calm
conditions. The rate of change of dissolved CFC and oxygen inside opened
bottles may be significantly greater under other conditions.

Significant increases in CFC and oxygen concentrations did occur within
17 minutes in bottle 19, after four sets of samples (\~8 liters of
water) had been withdrawn. The rate on change of CFCs and oxygen in
bottle 21 during the first hour is slower than the rate in bottle 19
during the first 18 minutes, perhaps because of less water draw down
(\~4 liters vs. \~8 liters) up to that point. Changes in Bottle 21 are
large at the end of the 2-hour period, where 8 liters of water had been
drawn previously.

There was no significant change in salinity during the drawdown tests,
although there was substantial warming of the bottles during the
sampling period (see Table 2.8). Changes in salinity observed in some
heavily sampled bottles during the A16S cruise may be due water vapor
exchange between the water inside the bottle and the air introduced into
the headspace. Since the vapor pressure of water is strongly dependent
on temperature, this effect may be increased when the bottle undergoes
warming on deck, and may also depend on the temperature and humidity of
air entering the headspace. These effects may become more pronounced as
the volume of water remaining in the bottle decreases during sampling.

**2.5. Discussion of Bottle Sampling for Samples Preserved for
Shore-Side Analysis**

### 2.5.1. Helium and Tritium Sampling

**Principal Investigator:** Peter Schlosser, Lamont-Doherty Earth
Observatory

Palisades NY 10964

schlosser@ldeo.columbia.edu

**Sampler:** Andrew Mutter, LDEO, amutter@ldeo.columbia.edu

Sampling of helium isotope (^3^He) and tritium samples for Peter
Schlosser of LDEO was carried out by Andrew Mutter
(amutter@ldeo.columbia.edu). A total of 26 stations were sampled with an
average of 20 samples taken per cast, for both ^3^He and tritium. The
total number of samples obtained is 508 ^3^He samples and 570 tritium
samples. No duplicates were taken.

Sampling involved separate containers for ^3^He and tritium. Seawater
for ^3^He analysis was sampled into re-useable stainless steel tubes of
90-ml in volume. Tritium was sampled into 1 liter brown glass bottles.
The ^3^He samples were taken first and care was made to rid the vessel
of air bubbles by hitting them with a stick and opening and closing the
two valves at each end of the tube. Tritium was sampled by rinsing the
bottles twice and filling with water up to the curve at the top of the
bottle to allow room to allow for thermal expansion.

The He extraction was done on ship. Eight filled tubes were pumped down
on a vacuum extraction system supplied by WHOI (W. Jenkins and D. Lott).
The tube was pumped down in two-step processes. First, by a mechanical
pump the pressure was taken down to below 10^-3^ torr (approximately 10
min). Second, the pressure was pumped to mid 10^-6^ to high 10^-7^ torr
pressure by a diffusion pump (approximately 1 hr). The water was then
allowed out of the container and into a lower metal container where it
was heated to 90-100°C. The gas was collected in a glass bulb cooled in
ice water. After 10 minutes, the bulbs were flame sealed and stored for
on-shore analyses.

One tritium sample was lost (dropped on deck). Two to three ^3^He
samples were lost due to bad seals and one to operator error of the
extraction vacuum system, which called for dismantling and cleaning of
equipment.

### 2.5.2. Particulate Sampling

**Principal Investigator:** Jim Bishop, LBNL, JKBishop@lbl.gov

**Onboard Personnel:** Alexandra Thompson, LBNL,
alex@nature.berkeley.edu

Particulate matter sampling was performed in support of the optics
program on the CTD. ICP-MS phosphorus gives us a cross-check on
estimating POC, and ICP-MS calcium gives us a calibration/verification
of the PIC sensor.

**Sampling:**

Seawater samples were collected from casts from every even numbered
station, excluding stations 60 and 102. From each sampled cast, 7-18
samples were collected from the rosette, chosen with a focus on the
first 200 m and either the top 2000 m or bottom 3000 m. The 1-liter
samples were collected in plastic bottles and, in most cases, filtering
began within 30 minutes. The seawater was filtered under vacuum
(0.25-0.5 atm) through polycarbonate 0.4 Micron 47mm filters (Osmonics
Cat #K04CP04700) in filter holders equipped with PreSep mesh spacers
(Osmonics Cat #C32WP04200). Filtration was carried out in a flow bench
(Airclean 600 PCR Workstation) and took between 10 minutes to 5 hours
for each sample. After exposure, each filter was rinsed with 0.5 ml MQ
water and the filter transferred to 100 ml Nalgene bottles, capped, and
stored at room temperature for transport to LBNL. After use all bottles,
caps, and filter holders were rinsed in MQ water.

Total number of samples: 921

Number of blanks: 39

Number of repeats: 41

Number of casts sampled: 59

**Problems:**

The only problems encountered were minor and included leaky bottles and
occasional air bubbles causing the filtration to stall.

## **Shore-Side Analysis:**

At LBNL, the filters will be analyzed using ICP-MS for 20 elements,
including P, C, Ca, Fe, Ba, and Sr.

### 2.5.3. DOC Sampling

**Principal Investigator:** Dennis Hansell, U. Miami, RSMAS, 4600
Rickenbacker

Causeway, Miami, FL 33149, dhansell@rsmas.miami.edu

**Sampler:** Wenhao Chen, U. Miami, RSMAS

wenchen@rsmas.miami.edu

Seawater samples were taken directly from the Niskin Bottles into the 60
ml precleaned bottles for deeper than 200 m. Samples from the up 200 m
were collected by in-line filtration through a GF/F filter. All samples
were kept in frozen before analysis.

Total number of samples: 1630

Total number of duplicates: 12

Total number of stations: 60

### 2.5.4. C-DOM Sampling

**Principal Investigator:** Norm Nelson, UCSB

**Sampler:** Wenhao Chen, U. Miami, RSMAS

wenchen@rsmas.miami.edu

Seawater was taken directly from the Niskin bottles into a 120-ml dark
glass bottle and then filtered through a 0.2 um Nucleopore filter by
vacuum filtration within 2 hours. Filtrates were collected in 40 ml dark
glass vials and kept refrigerated before analysis.

Total number of samples: 540

Total number of duplicates: 4

Total number of stations: 36

### 2.5.5. ^14^C Sampling

**Principal Investigator:** Ann McNichol, WHOI

**Samplers:** Wenhao Chen, U. Miami, RSMAS

wenchen@rsmas.miami.edu

Matt Lenington, CWU, leningtm@cwu.edu

Seawater was drawn directly from the Niskin bottles into 500-ml glass
bottles after about 250 ml overflow of the water. Samples were then
poisoned with 100 µl saturated HgCl~2~ solution and sealed by greased
stoppers. Bottles with samples are kept in cases for shipping back to
WHOI.

Reference: *Measuring ^14^C in Seawater TCO~2~ by Accelerator Mass
Spectrometry,* WHOI in WHP Operation and Methods-July, 2003.

Total number of samples: 496

Total number of duplicates: 16

Total number of stations: 29

### 2.5.6. Oxygen, Nitrogen, and Argon (ONAR) Sampling

**Principal Investigator:** Steven Emerson, University of Washington

> emerson@u.washington.edu

**Samplers:** Mark Warner, University of Washington

warner@u.washington.edu

Samples were collected for analyses of dissolved oxygen, nitrogen, and
argon (ONAR) at three stations during the A16S repeat hydrography
section. At each station, duplicate samples (\~100 ml) from six
different depths were collected into evacuated glass flasks for analyses
in the laboratory of Dr. Steven Emerson at the University of Washington.
The samples were collected from the 12-l bottle immediately after the
dissolved oxygen sample was drawn. In the shipboard laboratory, the
headspace in the neck of the flask was flushed with CO~2~ gas and capped
for transport back to the laboratory.

The goal of this ancillary project is to determine the saturations of
these gases in water masses formed in the northern (NADW) and southern
(AABW, AAIW) high latitudes. The differences in saturation values should
provide useful information on the relative importance of bubbles in
mediating the gas exchange, thus setting the surface ocean boundary
conditions, in the formation regions of these water masses.

Total number of samples: 36

Total number of duplicates: 18

Total number of stations: 3

**2.6. Parameters Sampled and Analyzed on the Cruise**

### 2.6.1. Chlorofluorocarbon (CFC) Measurements

**Principal Investigators:** Mark J. Warner, University of Washington

warner@u.washington.edu

John L. Bullister, NOAA-PMEL

John.L.Bullister@noaa.gov

**Samplers and Analysts:** Mark J. Warner, University of Washington

John L. Bullister, NOAA-PMEL

Eric Wisegarver, University of Washington

esw@u.washington.edu

Samples for the analysis of dissolved CFC-11, CFC-12, CFC-113, and
carbon tetrachloride (CCl~4~) were drawn from 2378 of the 4192 water
samples collected during the expedition. Specially-designed 12-liter
Bullister sample bottles were used on the cruise to reduce CFC
contamination. These bottles have the same outer diameter as standard 10
liter Niskin bottles, but use a modified end-cap design to minimize the
contact of the water sample with the end-cap O-rings after closing. The
O-rings used in these water sample bottles were vacuum-baked prior to
the first station. Stainless steel springs covered with a nylon powder
coat were substituted for the internal elastic tubing provided with
standard Niskin bottles. When taken, water samples for CFC and carbon
tetrachloride analysis were the first samples drawn from the 12-liter
bottles. Care was taken to coordinate the sampling of CFCs with other
samples to minimize the time between the initial opening of each bottle
and the completion of sample drawing. In most cases, dissolved oxygen,
^3^He, and HCFC samples were collected within several minutes of the
initial opening of each bottle. To minimize contact with air, the CFC
samples were drawn directly through the stopcocks of the 12-liter
bottles into 100 ml precision glass syringes equipped with two-way metal
stopcocks. The syringes were immersed in a holding tank of clean surface
seawater until analyzed.

For air sampling, a \~100 m length of 3/8\" OD Dekaron tubing was run
from the main laboratory to the bow of the ship. A flow of air was drawn
through this line into the main laboratory using a KNF Neuburger pump.
The air was compressed in the pump, with the downstream pressure held at
\~1.5 atm. using a backpressure regulator. A tee allowed a flow (100 ml
min^-1^) of the compressed air to be directed to the gas sample valves
of the CFC and HCFC analytical systems, while the bulk flow of the air
(\>7 l min^-1^) was vented through the backpressure regulator. Air
samples were only analyzed when the relative wind direction was within
60 degrees of the bow of the ship to reduce the possibility of shipboard
contamination. The pump was run continuously to insure that the air
inlet lines and pump were thoroughly flushed. Analysis of bow air was
performed at 26 locations along the cruise track. At each location, five
measurements were made to increase the precision.

Concentrations of CFC-11 and CFC-12, CFC-113, and carbon tetrachloride
in air samples, seawater, and gas standards were measured by shipboard
electron capture gas chromatography (EC-GC) using techniques modified
from those described by Bullister and Weiss (1988). For seawater
analyses, water was transferred from a glass syringe to a fixed volume
chamber (\~30 ml). The contents of the chamber were then injected into a
glass-sparging chamber. The dissolved gases in the seawater sample were
extracted by passing a supply of CFC-free purge gas through the sparging
chamber for a period of 4 minutes at 70 ml min^-1^. Water vapor was
removed from the purge gas during passage through an 18 cm long, 3/8"
diameter glass tube packed with the desiccant magnesium perchlorate. The
sample gases were concentrated on a cold-trap consisting of a 1/8" OD
stainless steel tube with a \~10 cm section packed tightly with Porapak
N (60-80 mesh). A vortex cooler, using compressed air at 100 psi, was
used to cool the trap, to approximately -20°C. After 4 minutes of
purging, the trap was isolated, and the trap was heated electrically to
\~100^o^C. The sample gases held in the trap were then injected onto a
precolumn (\~25 cm of 1/8" O.D. stainless steel tubing packed with
80-100 mesh Porasil C, held at 70°C) for the initial separation of
CFC-12, CFC-11, and CFC-113 from carbon tetrachloride. After the CFCs
had passed from the pre-column into the main analytical column (\~183 cm
of 1/8" OD stainless steel tubing packed with Carbograph 1AC, 80-100
mesh, held at 70°C) of GC1 (a HP 5890 Series II gas chromatograph with
ECD), a valve was used to direct the precolumn flow (and more slowly
eluting carbon tetrachloride peak) to a second gas chromatograph
(Shimadzu Mini II GC with ECD). For the first 52 stations, the
chromatographic column in the Shimadzu GC was 1 m of 1/8" OD stainless
steel tubing packed with 80/100 mesh Porasil C.

The apparent supersaturation of dissolved CCl~4~ observed in the near
surface waters of these stations was attributed to an unidentified
compound present in near surface waters that co-eluted with CCl~4~. The
Porasil C column was replaced with a Carbograph 1AC 80-100 mesh column
(183 cm of 1/8' OD SS tubing), resulting in the separation of the CCl~4~
peak from this interfering peak. In both cases the column was maintained
at 90°C.

Both of the analytical systems were calibrated frequently, with
frequency listed below, using a standard gas of known CFC composition.
Gas sample loops of known volume were thoroughly flushed with standard
gas and injected into the system. The temperature and pressure was
recorded so that the amount of gas injected could be calculated. The
procedures used to transfer the standard gas to the trap, precolumn,
main chromatographic column, and EC detector were similar to those used
for analyzing water samples. Two sizes of gas sample loops were used.
Multiple injections of these loop volumes could be made to allow the
system to be calibrated over a relatively wide range of concentrations.
Air samples and system blanks (injections of loops of CFC-free gas) were
injected and analyzed in a similar manner. The typical analysis time for
seawater, air, standard or blank samples was \~11 minutes.

Concentrations of the CFCs and CCl~4~ in air, seawater samples, and gas
standards are reported relative to the SIO98 calibration scale (Cunnold
*et. al.*, 2000). Concentrations in air and standard gas are reported in
units of mole fraction CFC in dry gas, and are typically in the parts
per trillion (ppt) range. Dissolved CFC and CCl~4~ concentrations are
given in units of picomoles per kilogram seawater (pmol kg^-1^). CFC and
CCl~4~ concentrations in air and seawater samples were determined by
fitting their chromatographic peak areas to multi-point calibration
curves, generated by injecting multiple sample loops of gas from a
working standard (PMEL cylinder 45191 for CFC-11, CFC-12, CFC-113, and
CCl~4~) into the analytical instrument. The response of the detector to
the range of moles of CFC passing through the detector remained
relatively constant during the cruise. Full-range calibration curves
were run at intervals of 14 days during the cruise. These were
supplemented with occasional injections of multiple aliquots of the
standard gas at more frequent time intervals. Single injections of a
fixed volume of standard gas at one atmosphere were run much more
frequently (at intervals of \~90 minutes) to monitor short-term changes
in detector sensitivity. The CFC-113 peak was often on a small bump on
the baseline, resulting in a large dependence of the peak area on the
choice of endpoints for integration. The height of the peak was instead
used to provide better precision. The precisions of measurements of the
standard gas in the fixed volume (n = 690) were ± 0.67% for CFC-12,
0.59% for CFC-11, 2.6% for CFC-113, and 1.8% for CCl~4~.

Although the CCl~4~ calibration and precision are of high quality over
most of the cruise, there appears to be a problem with the preliminary
calibration of the working standard. The calculated atmospheric
concentrations, relative to this standard, are approximately 70 part per
trillion (ppt). The values reported by the AGAGE network are
approximately 20 ppt higher. This would also explain the
undersaturations in the surface waters calculated using the AGAGE
concentrations. The working standard will be recalibrated at PMEL when
returned at the end of the expedition.

The efficiency of the purging process was evaluated periodically by
re-stripping high concentration surface water samples and comparing the
residual concentrations to initial values. These re-strip values ranged
from approximately 1% for CFC-11 and CFC-12, 3% for CFC-113, and 4% for
CCl~4~ in cold waters to values of \<1% for all four compounds in warm
waters. A fit of the re-strip efficiency as a function of temperature
will be applied to the final data set. The cold-water values have been
applied to all values in the preliminary data set.

There were very few measurements of CFC-11 and CFC-12 concentrations
less than 0.005 pmol kg^-1^ along this section. CFC-113, on the other
hand, was extremely low throughout the section. There were also no
measurements of CCl~4~-free waters. Several tests of the 12-l sampling
bottles were performed to estimate the possible desorption of CFCs and
CCl~4~ from the walls into the seawater sample and the changes in CFCs,
CCl~4~, dissolved oxygen, and salinity in bottles as a function of time
after opening. The results are discussed above under the subsection
"Bullister Bottle Tests."

On this expedition, based on the analysis of 100 duplicate samples, we
estimate precisions (1 standard deviation) of 0.45% or 0.003 pmol kg^-1^
(whichever is greater) for dissolved CFC-11, 0.78% or 0.004 pmol kg^-1^
for CFC-12 measurements, 2.6% or 0.004 pmol kg^-1^ for CFC-113, and 1.1%
or 0.005 pmol kg^-1^ for CCl~4~ measurements.

A very small number of water samples had anomalously high CFC or CCl~4~
concentrations relative to adjacent samples. These samples occurred
sporadically during the cruise and were not clearly associated with
other features in the water column (e.g., anomalous dissolved oxygen,
salinity, or temperature features). This suggests that these samples
were probably contaminated with CFCs or CCl~4~ during the sampling or
analysis processes. Measured concentrations for these anomalous samples
are included in the preliminary data, but are given a quality flag value
of either 3 (questionable measurement) or 4 (bad measurement). A quality
flag of 5 was assigned to samples which were drawn from the rosette but
never analyzed due to a variety of reasons (e.g., leaking stopcock,
plunger jammed in syringe barrel). A total of 13 analyses of CFC-11, 16
analyses of CFC-12, 10 analyses of CFC-113, and 145 analyses of CCl~4~
were assigned a quality flag of 3. A total of 4 analyses of CFC-11, 6
analyses of CFC-12, 7 analyses of CFC-113, and 6 of CCl~4~ were assigned
a quality flag of 4. A total of 13 samples were given a flag of 5
(sampled but not analyzed).

References

Bullister, J.L., and R.F. Weiss, 1988: Determination of CC1~3~F and
CC1~2~F~2~ seawater and air. *Deep-Sea Res.,* v. 25, pp. 839-853.

Prinn, R.G., R.F. Weiss, P.J. Fraser, P.G. Simmonds, D.M. Cunnold, F.N.
Alyea, S. O\'Doherty, P. Salameh, B.R. Miller, J. Huang, R.H.J. Wang,
D.E. Hartley, C. Harth, L.P. Steele, G. Sturrock, P.M. Midgley, and A.
McCulloch, 2000: A history of chemically and radiatively important gases
in air deduced from ALE/GAGE/ AGAGE. *J. Geophys. Res.,* v. 105, pp.
17,751-17,792.

***2.6.2. Dissolved Oxygen Analyses***

**Principal Investigator:** Chris Langdon, U. Miami, RSMAS, 4600
Rickenbacker

Causeway, Miami FL 33149

clangdon@rsmas.miami.edu

**Samplers:** Chris Langdon (12 midnight-12 noon)

George Berberian, NOAA-AOML (12 noon-12 midnight)

George.Berberian@noaa.gov

**Analysts:** Chris Langdon (12 midnight-12 noon)

George Berberian (12 noon-12 midnight)

**Data Reduction:** Chris Langdon

Frank Delahoyde, SIO

**Sampling:**

Samples were drawn from 12-l Bullister bottles into calibrated 140 ml
iodine titration flasks using Tygon tubing with a Silicone adapters that
fit over the petcock to avoid contamination of DOC samples. Bottles were
rinsed twice and filled from the bottom, overflowing three volumes while
taking care not to entrain any bubbles. One-ml of MnCl~2~ and one-ml of
NaOH/NaI were added, the flask stoppered, and shaken. DIW was added to
the neck of each flask to create a water seal. The flasks were stored in
the lab in plastic totes at room temperature for 1-2 hours before
analysis.

Thirty-six samples were drawn from most stations (exceptions for shallow
stations where fewer bottles tripped or for bottles with visible
problems during sampling, e.g., leaking, open vent cap, etc.) for a
total of 121 stations. Two to three duplicates were drawn at each
station. In addition, samples were drawn in duplicate from the underway
seawater line at 6-hour intervals between Punta Arenas and the start of
the line at 60°S, 31°W which are not included in the tally below.

Total number of samples: 4659

Total number of samples flagged after initial shipboard reduction of
quality control:

Questionable (QC=3): 37

Bad (QC=4): 4

Not reported (QC=5): 3

Sampling for dissolved oxygen began within minutes of the rosette being
brought on deck. Using a Tygon and silicone drawing tube, nominal 125 ml
volume-calibrated iodine flasks were rinsed 3 times, then filled and
allowed to overflow for at least 3 flask volumes. From station 33 onward
(46.6 ˚S, 31.8 ˚W, 1/25/05) sample draw temperature was measured with a
platinum resistance thermometer placed in the flask while the flask was
overflowing. These temperatures were used to calculate μmol kg^-1^
concentrations and a diagnostic check of bottle integrity. For station
1-32 the CTD temperature at trip depth was used. Reagents were added to
fix the oxygen before stoppering. The flasks were shaken until
thoroughly mixed, once immediately after drawing, and then again after
about 20 minutes. Samples were analyzed within 1-4 hours of collection,
and uploaded into the cruise database.

**Analyzer Description:**

Dissolved oxygen analyses were performed with a MBARI-designed automated
oxygen titrator using photometric end-point detection based on the
absorption of 365 nm wavelength ultra-violet light. The titration of the
samples and the data logging were controlled by a 386 PC running the
Oxygen program written by Gernot Friedrich (Friederich, 1984).
Thiosulfate was dispensed by a Dosimat 665 fitted with a 5.0 ml burette.
The whole-bottle titration technique of Carpenter (1965) with
modifications by Culberson *et al.* (1991), but with a more dilute
solution of thiosulfate (10 g l^-1^). The autotitrator and Dosimat
generally performed well.

**Standardization:**

Standard curves were run at the beginning and end of each 1-l batch of
thiosulfate, typically 2-3 days. The reagent blank was taken to be the
intercept of the standard curve. The titrant for the photometric
titrator was standardized via the standard curve method where standards
are prepared by dispensing 2, 4, 6, 8, and 10 ml of the 0.0100 N KIO~3~
standard solutions. Thiosulfate molarities were calculated from each
standard curve and corrected to 20ºC. The 20ºC molarities were plotted
versus time and were reviewed for possible problems. Blank volumes and
thiosulfate molarities were smoothed (linear fits) at the end of the
cruise and the oxygen values recalculated (see Figures 2.1 and 2.2).

![](media/image25.png){width="4.843055555555556in"
height="3.341666666666667in"}Two to three sets of duplicates were drawn
at each station for a total of 265 duplicates. The average standard
deviation was 0.25 μmol kg^-1^.

**Figure 2.1.** Control plot of the reagent blanks over the cruise.

![](media/image26.png){width="4.972222222222222in"
height="3.301388888888889in"}**Figure 2.2.** Control plot of thiosulfate
concentration changes over the cruise.

**Comparison of Photometric and Amperometric End Point Titrators:**

A comparison was conducted between the photometric end point titrator
and a titrator that detected the end point amperometrically.
Standardization of the thiosulfate titrant and determination of the
reagent blank for the amperometric titrator were done as described in
Culberson *et al.* (1991). The oxygen concentration in the seawater
sample was calculated as described by Culberson *et al.* (1991). Sets of
duplicate or quadruplicate flasks were drawn from the same rosette
bottle and then analyzed by the two systems. The systems used different
burettes (photometric 5 ml and amperometric 2 ml) and different molarity
thiosulfate solutions (photometric 0.040 M and amperometric 0.14 M).
Blanks and standards for both systems were prepared using the same
standard solution and the same dispenser. The reagent blank was assumed
to be equal to the intercept of the plot of thiosulfate titer versus ml
of standard solution. Standardization of the thiosulfate titrant and
determination of the reagent blank for the amperometric titrator were
done as described in Culberson *et al.* (1991). The oxygen concentration
in the seawater sample was calculated as described by Culberson *et al.*
(1991). Data are summarized in Table 2.9. Each method was found to have
a similar precision, i.e., 0.11 and 0.14 μmol l^-1^. There was a small
but significant bias for the amperometric result to be smaller than the
photometric result by 0.47 μmol l^-1^. This was investigated further by
comparing sets of duplicates from station 106 (9º30'S, 25ºW) where the
oxygen concentration spanned a very wide range (Table 2.9). It was found
that the difference between the two methods was not randomly distributed
with respect to oxygen concentration (Figure 2.3). The cause for the
systematic bias requires further investigation back at the shore-based
laboratory.

  ---------------- ------------ ----------------- ---------- -------- ------------------ ---------- -------- ------------------
  **Table 2.9:                                                                                               
  Comparison of                                                                                              
  oxygen                                                                                                     
  concentrations                                                                                             
  determined by                                                                                              
  photometric and                                                                                            
  amperometric                                                                                               
  point detection                                                                                            
  methods at                                                                                                 
  station 106.**                                                                                             

                                **Photometric**                       **Amperometric**                       

                                **(µmoles                             **(µmoles l^-1^)**                     
                                l^-1^)**                                                                     

  **CTD**          **Niskin**   **\[O~2~\]**      **Mean**   **SD**   **\[O~2~\]**       **Mean**   **SD**   **Photo-Ampero**

  106              8            259.50            259.45     0.05     259.70             259.65     0.05     -0.2

  106              8            259.40                                259.60                                 

  106              20           175.20            175.20     0.00     175.80             175.80     0.00     -0.6

  106              20           175.20                                175.80                                 

  106              27           98.30             98.15      0.15     98.90              98.80      0.10     -0.7

  106              27           98.00                                 98.70                                  

  106              27                                                 98.80                                  

  106              33           218.30            218.45     0.15     218.70             218.75     0.05     -0.3

  106              33           218.60                                218.80                                 

                                                                                                             
  ---------------- ------------ ----------------- ---------- -------- ------------------ ---------- -------- ------------------

![](media/image27.png){width="5.282638888888889in"
height="3.609722222222222in"}**Figure 2.3.** Difference between
photometrically and amperometrically determined oxygen concentration
versus photometric oxygen concentration.

**Volumetric Calibration:**

Oxygen flask volumes were determined gravimetrically with degassed
deionized water to determine flask volumes at AOML. The Dosimat and
Wheaton positive displacement dispenser used for dispensing the KIO~3~
were calibrated in the same way.

**Standards:**

Liquid potassium iodate standard solution with a normality of 0.0100 was
prepared and bottled at AOML prior to the cruise. A single batch was
used during the cruise.

References

Carpenter, J.H., 1965: The Chesapeake Bay Institute technique for the
Winkler dissolved oxygen method. *Limnol. Oceanogr.*, v. 10, pp.
141-143.

Culberson, C.H., and S. Huang, 1987: Automated amperometric oxygen
titration. *Deep-Sea Res.*, v. 34, pp. 875-880.

Culberson, C.H., G. Knapp, M. Stalcup, R.T. Williams, and F. Zemlyak,
1991: A comparison of methods for the determination of dissolved oxygen
in seawater.

Friederich, G.E., P. Sherman, and L.A. Codispoti, 1984: A high precision
automated Winkler titration system based on a HP-85 computer: A simple
colorimeter and an inexpensive electromechanical buret. Bigelow Lab.,
Technical Report 42, 24 pp.

***2.6.3. Discrete Halocarbon/Alkyl Nitrate Analyses***

**Principal Investigators:** Shari Yvon-Lewis, Dept. of Oceanography,
Texas A&M

University, 3146 TAMU, College Station, TX 77845

syvon-lewis@ocean.tamu.edu

Eric Saltzman, Earth System Science, 3325 Croul Hall

> University of California-Irvine, Irvine, CA 92697
>
> esaltzma@uci.edu

**Samplers:** Ben Kates (12 midnight-12 noon), Ben.Kates@noaa.gov

Shari Yvon-Lewis (12 noon-2 midnight)

**Analysts:** Ben Kates (12 midnight-12 noon)

Shari Yvon-Lewis (12 noon-12 midnight)

**Data Reduction:** Shari Yvon-Lewis

**Sampling:**

Samples were drawn from 12-l Bullister bottles into 100 ml ground glass
syringes. The syringes have nickel-plated Luer tipped stopcocks. The
Luer tips are inserted directly into the petcocks. The syringes are
rinsed twice with full 100 ml volumes of water. Bubbles are carefully
flushed out, and the third fill is the final sample. The syringes are
wrapped with a stiff rubber band to maintain pressure on the plunger and
sample reducing the potential for outgassing in the syringes. Storage of
the samples is kept to a minimum (\<3 hours). They are stored vertically
in buckets in the climate controlled cold-room (\~4^o^C). The cold
temperature is used to minimize the chemical degradation of some of the
species being measured. Fifteen to 17 samples were drawn from the even
numbered stations. This represents 1^o^ latitude spacing on the half
degree for a total of 60 stations.

Total number of samples: 893

Each sample was analyzed for 21 chemical species (HCFC-22, CFC-12,
HCFC-142b, Halon-1211, CFC-11, HCFC-141b, CFC-113, CH~3~CCl~3~, CCl~4~,
C~2~Cl~4~ (PCE), CH~3~Cl, CH~3~Br, CH~3~I, CH~2~Cl~2~, CH~2~Br~2~,
CHCl~3~, CHBr~3~, CH~2~ONO~2~, C~2~H~4~ONO~2~, i‑C~3~H~6~ONO~2~,
n-C~3~H~6~ONO~2~). The total number of samples flagged after preliminary
shipboard data reduction and quality control, varied by compound:

Questionable (QC=3): \~3

Bad (QC=4): \~21

Not Reported (QC=5): \~22

**Analyzer Description:**

The halocarbon measurement system was described in Yvon-Lewis *et al.*
(2004). There have been a couple of modifications since to facilitate
analysis of alkyl nitrates and to improve performance. The measurements
were made with a laboratory-built, automated purge and trap system
coupled to a gas chromatograph (GC, HP5890 series II) with mass
spectrometer (MS, HP5973) (Figure 2.4). The autosampler allows us to
load all of the depth profile samples directly into gas tight glass
bulbs (each with a measured volume including tubing of \~70 ml) kept in
a temperature-controlled cooler at approximately 5ºC. The entire 100+ ml
of seawater in the syringe is flushed through the bulb and tubing.

![](media/image28.jpeg){width="6.0in" height="4.5in"}

**Figure 2.4.** Schematic of the automated purge and trap GCMS system.
There are 16 calibrated sample bulbs attached to PV2; however, to reduce
clutter in the diagram, only calibrated sample bulb #3 is shown.

The computer switches purge valve #2 (PV2), a Valco loop selection valve
(VICI Metronics, TX) with 34 ports and 16 positions, from bulb to bulb
allowing the humidified helium purge gas stream to push each sample from
the bulb into the temperature-controlled (50ºC) sparger. The purge gas
passes through the bulb on its way to the sparger and will pick up any
trace amounts of the gases left in water along the walls and any of the
trace gases that may have undergone some degassing while sitting in the
bulb prior to sampling. In this way, we maximize sample recovery and
preconcentration on the first cryotrap. The dried (Nafion PD-100T-24SS,
PermaPure Inc.) sparger effluent passes over a Unibeads 1S packed trap
(3.175 mm OD, 1.6 mm ID) at -80ºC and into a calibrated, evacuated
stainless steel flask. The change in flask pressure and the flask
temperature are recorded electronically. For a calibration run, the
pressure in the flask is used to determine the exact volume of the whole
air standard that passed over the cryotrap. GC valve #1 (GCV1) is
switched from load to transfer, and the primary trap is then flash
heated (200ºC, 3 min.). The sample is focused on a second Unibeads 1S
packed trap (1.59 mm OD, 0.5 mm ID) at -80ºC. GC valve #2 (GCV2) is
switched from backflush to inject, the focusing trap is flash heated
(200ºC, 3 min.) and the sample is injected onto the analytical column
(0.25 mm ID  5m pre- and 55m main, DB-VRX; J&W). The pre-column is
backflushed at 10 min. after injection to prevent accumulation of the
heavier compounds on the column between runs. The GC is temperature
programmed to start at 30ºC and end at 210ºC.

**Parameters Sampled on the Cruise:**

Each sample, blank, and standard is analyzed simultaneously for all of
the compounds, HCFC-22, CFC-12, HCFC-142b, CFC-11, HCFC-141b, CFC-113,
CH~3~CCl~3~, CCl~4~, PCE, CH~3~Cl, CH~3~Br, CH~3~I, CH~2~Cl~2~,
CH~2~Br~2~, CHCl~3~, CHBr~3~, methyl nitrate, ethyl nitrate, isopropyl
nitrate, and n-propyl nitrate. The mass spectrometer is programmed to
record signals from specific sets of masses over predetermined intervals
(i.e., single ion monitoring, SIM). In this way, the mass spectrometer
is extremely selective and can detect only the compound of interest at
any given time, reducing the potential for co-elution contamination of
the signal.

**Calibration:**

Purge valve #1 (PV1) is used to switch between the humidified purge
helium and the calibration gas streams before they enter the rest of the
purge system. The calibration gases are from secondary standard
cylinders filled with coastal Miami air. These whole air standards (two
dry acculife treated cylinders and one wet electropolished 6-l flask)
have been calibrated using NOAA/CMDL halocarbon standards and alkyl
nitrate standards from the lab of Dr. Eric Saltzman (University of
California, Irvine). During a calibration run, the calibration gas
follows the same path as the humidified purge helium does during a
normal sample run; however, PV2 is kept in the position of the last
sample, which has already been analyzed so the sample bulb is empty. The
number of moles of gas that pass over the trap is calculated from the
known volume of the flask and the recorded temperature and pressure of
the flask. The dry mole fractions of the halocarbons and alkyl nitrates
in the calibration gas are used to determine the number of moles of each
compound in each calibration run, sample, and blank. After a calibration
run and before the next sample run, the entire flow path is flushed with
the humidified helium. Blanks are run in the same way as calibration
runs except that PV1 is in position to allow the humidified helium to
flow through the system not the calibration gas. Every seventh injection
is a standard. This allows for tracking drift in the detector's response
for each compound.

**Data Processing:**

As mentioned above, every seventh injection is a calibration gas
standard. The three standards were swapped periodically during the
cruise. The standard or reference gases are used to determine the
response factors (response per mole of analyte) for the mass
spectrometer for each compound. Any drift or degradation in signal over
time is corrected by interpolating the response factors between
reference runs. The interpolated response factor is then used with the
observed sample response (blank corrected) to determine the moles of
analyte present in that sample. Blanks are run every seventh injection
just prior to the reference run. The blank response for a specific
compound in any given sample is determined by interpolating between
blanks. The three reference gas tanks will be recalibrated after the
cruise to determine if there was any drift in their concentrations over
time.

**Ancillary Measurements:**

Approximately once per day, for a total of 40 samples, a calibration run
was substituted with an air sample. A 3/8" O.D. Decabon line was run
from the aft section of the main lab to the jackstaff on the bow of the
ship. A pump (KNF Neuburger with a Viton diaphragm) with a back pressure
regulator maintained a 6 l min^-1^ flow through the Decabon with a back
pressure of \~6 psi in sampling line that could be attached to the purge
and trap instrument. When an air sample was collected, the calibration
gas line was swapped with the sample line from the air pump, and the air
sample was collected and analyzed instead of a calibration gas sample.
The air data will be reported in the final report after post-cruise
calibrations are done.

**Problems:**

The HCFC-22 concentrations measured in the water samples were
excessively high at the beginning of the cruise. There were leaks in the
ship refrigerator compressor, and apparently not too long before this
cruise a large amount of HCFC-22 was lost in a leak in the engine room
and permeated the entire ship. Later in the cruise, the HCFC-22
background appeared to decrease. Some of the HCFC-22 data may be
recoverable after some post-cruise analysis. However, at the time of
this preliminary data report, all of the HCFC-22 data has been flagged
as bad (QC=4).

During the last week of the cruise a possible problem with calibrated
volume #1 was observed. Steps were taken to avoid a loss of data after
the possible problem was identified. There was not enough time left in
the cruise to attempt to fix the problem. Post-cruise analysis will
determine the full extent of the data that may have been compromised.

References

Yvon-Lewis, S.A., D.B. King, R. Tokarczyk, K.D. Goodwin, E.S. Saltzman,
and J.H. Butler, 2004: Methyl bromide and methyl chloride in the
Southern Ocean. *J. Geophys Res.*, v. 109, C02008,
doi:10.1029/2003JC001809.

***2.6.4. Discrete pCO~2~ Analyses***

**Principal Investigator:** Rik Wanninkhof, NOAA/AOML, 4301 Rickenbacker

Causeway Miami Fl 33149

Rik.Wanninkhof@noaa.gov

**Samplers:** Naomi Levine (12 midnight-12 noon), nlevine@whoi.edu

Rik Wanninkhof (12 noon-12 midnight)

**Analysts:** Robert Castle (12 midnight-12 noon)

<Robert.Castle@noaa.gov>

> Rik Wanninkhof (12 noon-12 midnight)
>
> Stacey Smith (day time through station 43)
>
> Stacy.Smith@mso.umt.edu

**Data Reduction:** Robert Castle, Robert.Castle@noaa.gov

**Sampling:**

Samples were drawn from 12-l Bullister bottles into 500 ml Pyrex™
volumetric flasks using Tygon™ tubing with a Silicone adapter that fit
over the petcock to avoid contamination of DOM samples. Bottles were
rinsed twice and filled from the bottom, overflowing half a volume while
taking care not to entrain any bubbles. About 5 ml of water was
withdrawn by removing the pinched off sampling tube from the neck of the
flask to create a small expansion volume. 0.2 ml of saturated mercuric
chloride (HgCl2 ) solution was added as a preservative. The sample
bottles were sealed with a screw cap containing a polyethylene liner.
The samples were stored upside down in coolers at room temperature for a
maximum of 10 hours.

Thirty samples were drawn every fourth station (@ 2 degree intervals)
for a total of 29 stations. In addition, samples were drawn in duplicate
from the underway seawater line at 6-hour intervals between Punta Arenas
and the start of the line at 60°S, 31°W. These samples are not included
in the tally below.

Total number of samples: 847

Total number of samples flagged after initial shipboard data reduction
of quality control:

Questionable (QC=3): 9

Bad (QC=4): 1

Not reported (QC=5) (tests): 5

Duplicates (QC=6): 9

# **Analyzer Description:**

The discrete pCO~2~ system is patterned after the setup described in
Chipman *et al.* (1993) and is discussed in detail in Wanninkhof and
Thoning (1993) and Chen *et al.* (1995). The major difference between
the system of Chipman and ours is that our setup uses a LI-COR™ (model
6262) non-dispersive infrared analyzer, while the system of Chipman *et
al.* (1993) utilizes a gas chromatograph with a flame ionization
detector and a methanizer that quantitatively converts CO~2~ into CH~4~
for analysis.

Samples collected in the 500-ml volumetric flasks are brought to a
temperature of 20.00 ± 0.02°C by first inserting the flasks upside down
in a pre-bath at ≈21°C and subsequently in a Neslab™ (model RT-220)
controlled temperature bath for equilibration and analysis. A 60-ml
headspace is created in the sample flask by displacing the water using a
compressed standard gas with a CO~2~ mixing ratio close to the
anticipated pCO~2~ of the water. The headspace is circulated in a closed
loop through the infrared analyzer that measures CO~2~ and water vapor
levels in the sample cell. The headspaces of two flasks are equilibrated
simultaneously in two channels. While headspace from the flask in the
first channel goes through the IR analyzer, the headspace of the flask
in second channel is recirculated in a closed loop. After the first
sample is analyzed, a valve is switched to put the second channel in
line with the analyzer. The samples are equilibrated until the running
mean of 20 consecutive 1-second readings from the analyzer differ by
less than 0.1 ppm (parts per million by volume), which on average takes
about 10 minutes. An expandable volume in the circulation loop near the
flasks consisting of a small deflated balloon keeps the content of
flasks at room pressure.

**Standardization:**

In order to account for instrument drift and to maintain measurement
precision, a set of six gas standards is run through the system before
and after every eight seawater samples. The standards were obtained from
Scott-Marin and referenced against primary standards purchased from C.D.
Keeling in 1991. The primary standards are on the WMO-78 scale (Table
2.10).

  ---------------------- ---------------------- -------------------------
  **Table 2.10.                                 
  Calibration standard                          
  tanks used for                                
  discrete pCO~2~.**                            

  **Standard sequence**  **Tank number**        **CO~2~ concentration
                                                (ppm)**

  1                      CA05989                378.71

  2                      CA05980                792.51

  3                      CA05984                1036.92

  4                      CA05940                1533.7

  5                      CA05988                593.64

  6                      CA05998                205.07
  ---------------------- ---------------------- -------------------------

These concentrations bracket the pCO~2~ at 20°C (pCO~2~(20)) values
observed during the South Atlantic A16S 2005 cruise.

**Data Processing:**

The determination of pCO~2~(20) in water from the headspace measurement
involves several steps. The IR detector response for the standards is
normalized for temperature. The IR analyzer raw output of derived dry
mole fraction of CO~2~ (XCO~2~) for samples are normalized to 1 atm
pressure. The sample values are converted to the true mixing ratio based
on a second-order polynomial fit between the instrument XCO~2~ readout
and the values of the three nearest concentrations compressed gas
standards. The mixing ratio in the headspace is converted to a partial
pressure assuming 100% humidity and corrected to partial pressure of
CO~2~ in the water sample prior to equilibration by accounting for
change in total CO~2~ in water during the equilibration process (for
details see Wanninkhof and Thoning, 1993). The change in pCO~2~(20)
caused by the change in DIC is calculated using the constraint that TAlk
remains constant during exchange of CO~2~ gas between the headspace and
the water. The calculation is outlined in the appendix of Peng *et al.*
(1987).

Uncertainty based on duplicate sampling of the same Bullister bottle for
pCO2 analysis was determined on select stations of the cruise. The
comparisons are presented In Table 2.11.

+------------+----------------+------------+----------+---------------+
| **Table    |                |            |          |               |
| 2.11.      |                |            |          |               |
| Duplicate  |                |            |          |               |
| discrete   |                |            |          |               |
| pCO~2~     |                |            |          |               |
| samples.** |                |            |          |               |
+------------+----------------+------------+----------+---------------+
| *          | **Sample No.** | **         | **∆      | **%           |
| *Station** |                | pCO~2av~** | pCO~2~** | difference**  |
+------------+----------------+------------+----------+---------------+
| 5          | 203            | 1093.8     | 3\.      | 0.3           |
+------------+----------------+------------+----------+---------------+
| 5          | 209            | 1089       | 2.3      | 0.2           |
+------------+----------------+------------+----------+---------------+
| 9          | 103            | 1087.3     | 1.5      | 0.1           |
+------------+----------------+------------+----------+---------------+
| 9          | 105            | 1088.8     | 2.4      | 0.2           |
+------------+----------------+------------+----------+---------------+
| 9          | 109            | 1081.6     | 2.7      | 0.2           |
+------------+----------------+------------+----------+---------------+
| 21         | 135            | 572.7      | 0.4      | 0.07          |
+------------+----------------+------------+----------+---------------+
| 49         | 121            | 838\.      | 0.4      | 0.05          |
+------------+----------------+------------+----------+---------------+
| 65         | 121            | 756.1      | 5.6      | 0.7           |
+------------+----------------+------------+----------+---------------+
| 93         | 124            | 1040.3     | 2.3      | 0.2           |
+------------+----------------+------------+----------+---------------+
| pCO~2av~ = |                |            |          |               |
| average of |                |            |          |               |
| the        |                |            |          |               |
| duplicate  |                |            |          |               |
| samples.   |                |            |          |               |
|            |                |            |          |               |
| ∆pCO~2~ =  |                |            |          |               |
| absolute   |                |            |          |               |
| difference |                |            |          |               |
| between    |                |            |          |               |
| the        |                |            |          |               |
| duplicates |                |            |          |               |
|            |                |            |          |               |
| \%         |                |            |          |               |
| difference |                |            |          |               |
| =          |                |            |          |               |
| ∆pCO~2     |                |            |          |               |
| ~/pCO~2av~ |                |            |          |               |
| \* 100     |                |            |          |               |
+------------+----------------+------------+----------+---------------+

**Problems:**

The instrument performed very well during the cruise despite its age and
outdated DOS GW Basic instrument control software. At the start of the
cruise it was noticed that the standard values drifted during the
30-second read sequence. It was determined that diffusion out of the
line leading from the IR cell to the internal barometer was the cause.
The internal barometer was placed in this unit in the spring of 2003.
This problem was remedied by placing a capillary tube in the 1/4" OD
tube to decrease its internal volume and decrease exchange. In addition,
the read sequence was shortened to 10 readings from the original 30
readings for standards and samples.

One solenoid failed and was replaced without discernable downtime. Three
sampling bottles were broken; two because of thermal expansion of the
water without adequate headspace and one was dropped on deck during
sampling.

References

Chen, H., R. Wanninkhof, R.A. Feely, and D. Greeley, 1995: Measurement
of fugacity of carbon dioxide in sub-surface water: An evaluation of a
method based on infrared analysis. NOAA Technical Memorandum, ERL
AOML-85, 54 pp.

Chipman, D.W., J. Marra, and T. Takahashi, 1993: Primary production at
47°N and 20°W in the North Atlantic Ocean: A comparison between the 14C
incubation method and mixed layer carbon budget observations. *Deep-Sea
Res., II,* v. 40, pp. 151-169.

Peng, T.-H., T. Takahashi, W.S. Broecker, and J. Olafsson, 1987:
Seasonal variability of carbon dioxide, nutrients, and oxygen in the
northern North Atlantic surface water: Observations and a model.
*Tellus,* v. 39B, pp. 439-458.

Wanninkhof, R., and K. Thoning, 1993: Measurement of fugacity of CO~2~
in surface water using continuous and discrete sampling methods. *Mar.
Chem.*, v. 44, no. 2-4, pp. 189-205.

***2.6.5. Total Dissolved Inorganic Carbon (DIC) Analyses (updated
7/27/05)***

**Principal Investigator:** Rik Wanninkhof, NOAA/AOML, 4301 Rickenbacker

Causeway, Miami, FL 33149

Rik.Wanninkhof@noaa.gov

**Samplers:** Robert Castle (12 midnight-12 noon)

Robert.Castle@noaa.gov

Esa Peltola (12 noon-12 midnight), Esa.Peltola@noaa.gov

**Analysts:** Robert Castle (12 midnight-12 noon)

Robert.Castle@noaa.gov

Esa Peltola (12 noon-12 midnight), Esa.Peltola@noaa.gov

**Data Reduction:** Robert Castle, Robert.Castle@noaa.gov

Esa Peltola, Esa.Peltola@noaa.gov

**Sampling:**

Samples were drawn according to procedures outlined in the Handbook of
Methods for CO~2~ Analysis (DOE, 1994) from 12-l Bullister bottles into
cleaned 540-ml Pyrex bottles using Tygon tubing with a silicone adapter
on the petcock to avoid contamination of DOC samples. Bottles were
rinsed and filled from the bottom, leaving 5 ml of headspace. Care was
taken not to entrain any bubbles. 0.2 ml of saturated HgCl~2~ solution
was added as a preservative. The sample bottles were sealed with glass
stoppers lightly covered with Apiezon-L grease and were stored at room
temperature for a maximum of 12 hours prior to analysis.

DIC samples were collected at every degree from 36 depths with three
replicate samples. Some samples were also collected at every
half-degree. The replicate seawater samples were taken from the surface,
1000 m, and bottom Bullister bottles and run at different times during
the cell. The first replicate of the bottom water was used at the start
of the cell with fresh coulometer solution, the first one of the 1000 m
replicates was run in the middle of the cell after about 12 mg of C were
titrated. The second one of the bottom replicates was run at the end of
the cell after about 25 mg of C were titrated. A new coulometer cell was
started with the second one of the 1000 m replicate and the first one of
the surface replicate samples. In the middle of this cell the second one
of the surface replicates was run and the first one of the surface
duplicates of a partial station. The second one of the duplicates of the
partial station was run at the end of this cell. No systematic
difference between the replicates was observed. There was no systematic
dependency of results with an amount of carbon titrated for a particular
cell.

Total number of samples analyzed: 2482

Total number of samples flagged after initial shipboard data reduction
of quality control:

Good (QC=2): 2245

Duplicates (QC=6): 180

Questionable (QC=3): 31

Bad (QC=4): 20

Not Reported (QC=5): 6

**Analyzer Description:**

The DIC analytical equipment was set up in a seagoing laboratory van.
The analysis was done by coulometry with two analytical systems (AOML-1
and AOML-2) used simultaneously on the cruise. Each system consisted of
a coulometer (UIC, Inc.) coupled with a SOMMA (Single Operator
Multi-parameter Metabolic Analyzer) inlet system developed by Kenneth
Johnson (Johnson *et al.*, 1985, 1987, 1993; Johnson, 1992) formerly of
Brookhaven National Laboratory (BNL). In the coulometric analysis of
DIC, all carbonate species are converted to CO~2~ (gas) by addition of
excess hydrogen ion (acid) to the seawater sample, and the evolved CO~2~
gas is swept into the titration cell of the coulometer with pure air or
compressed nitrogen, where it reacts quantitatively in with a
proprietary reagent based on ethanolamine to generate hydrogen ions. In
this process the color changes from blue to colorless, which triggers a
current through the cell and causes coulometrical generation of OH^--^
ions at the anode. The OH^--^ ions react with the H^+^, and the color of
the solution turn back to blue. A lightbeam shines through the solution
and a photometric detector at the opposite side of the cell senses the
change in transmission. Once the percent transmission reaches its
original value, the coulometric titration is stopped and the amount of
CO~2~ that enters the cell is determined by integrating the total charge
during the titration.

**Standardization:**

The coulometers were calibrated by injecting aliquots of pure CO~2~
(99.995%) by means of an 8-port valve outfitted with two sample loops
with known gas volumes (AOML-1: 1.9951 ml @ 25.05°C and 0.9807 ml @
25.10°C; AOML-2: 2.0018 ml @ 25.09°C and 0.9949 ml @ 25.06°C) bracketing
the amount of CO~2~ extracted from the water samples for the two AOML
systems.

The stability of each coulometer cell solution was confirmed three
different ways: the Certified Reference Material (CRM, **Batch 66**,
supplied by Dr. A. Dickson of Scripps Institution of Oceanography, SIO)
was measured at the beginning and the middle, gas loops in the beginning
and at the end, and the duplicate samples in the beginning, middle and
at the end of each cell solution. The coulometer cell solution was
replaced after 25 mg of carbon was titrated, typically after 9-12 hours
of continuous use.

The pipette volume was determined by taking aliquots at known
temperature of distilled water from the volumes. The weights with the
appropriate densities were used to determine the volume of the pipettes
(AOML1: 28.716 ml @ 20.00°C, AOML2: 22.547 ml @ 20.00°C).

**Data Processing:**

Calculation of the amount of CO~2~ injected was according to the
Department of Energy (DOE) CO~2~ handbook (DOE, 1994). The concentration
of CO~2~ (\[CO~2~\]) in the samples was determined according to:

$$\lbrack\text{CO}_{2}\rbrack\text{  =  Cal}\text{.}\text{ factor * }\frac{(\text{Counts-Blank*Run Time})\text{*K }m\text{mol/count}}{\text{pipette volume*density of sample}}\text{         }$$

where \"Cal. Factor\" is the calibration factor, "Counts" is the
instrument reading at the end of the analysis, "Blank" is the
counts/minute determined from blank runs performed at least once for
each cell solution, "Run Time" is the length of coulometric titration
(in minutes), and K is the conversion factor from counts to µmol.

The instrument has a salinity sensor, but all DIC values were
recalculated to a molar weight (µmol kg^-1^) using density obtained from
the CTD's salinity sensor. The DIC values were corrected for dilution by
0.2 ml of HgCl~2~ used for sample preservation. The total water volume
of the sample bottles was 540 ml. The correction factor used for
dilution was 1.00037. A correction was also applied for the offset from
the CRM. This correction was applied for each cell using the CRM value
obtained in the beginning of the cell. The results underwent initial
quality control on the ship using property plots: DIC-Depth,
DIC-Potential Temperature, DIC-AOU, DIC-NO~3~; DIC-SiO~3~, DIC-PO~4~,
DIC-TAlk, and DIC-pH. Also DIC-LAT-Depth contour plots were used to
analyze the quality of the data.

**Problems:**

The overall performance of the instruments was good during the cruise.
The air purifier supplying carrier and pneumatic gas malfunctioned
during station 24. Compressed tanks of ultra-high purity nitrogen gas
were used thereon. At the same time, soda lime traps used to scrub any
CO~2~ from the carrier gas were removed from the air/N~2~ line, since
they developed cracks over time and also they appeared to release CO~2~
in pulses into the carrier. A coulometer was replaced during the test
cast runs. It did not find an endpoint and did not stop counting. A
number of pinch valves failed and they were replaced. Also some cell
caps started leaking and leads of electrodes broke. The Orbo tubes
(filled with silica gel to absorb possible acid vapors) tended to break
and leak and they were not used after station 109 on either system.

**Tests of Different Size Sampling Bottles:**

Because of concerns about the large amount of water used for a DIC
sample and use of grease on the stoppers that could contaminate samples
for DOM, comparison tests were performed with samples drawn in 250 ml
borosilicate bottles with ground glass stoppers stored under cold water
with the regular sampling procedures outlined above. The results are
shown in Table 2.12.

+---------+--------+------+----------+----------+---------+----------+
| **Table |        |      |          |          |         |          |
| 2.12.   |        |      |          |          |         |          |
| Test    |        |      |          |          |         |          |
| results |        |      |          |          |         |          |
| of      |        |      |          |          |         |          |
| di      |        |      |          |          |         |          |
| fferent |        |      |          |          |         |          |
| sample  |        |      |          |          |         |          |
| bottle  |        |      |          |          |         |          |
| sizes   |        |      |          |          |         |          |
| for     |        |      |          |          |         |          |
| DIC.**  |        |      |          |          |         |          |
+---------+--------+------+----------+----------+---------+----------+
| *       | **Bo   | **   | **DIC**  | **Bul    | **V     | **A      |
| *Type** | ttle** | RT** |          | lister** | olume** | verage** |
|         |        |      |          |          |         |          |
|         |        |      |          | **       | *       |          |
|         |        |      |          | Bottle** | *(ml)** |          |
+---------+--------+------+----------+----------+---------+----------+
| CRM     | 213    | 14   | 1971.11  |          |         |          |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | A9     | 13   | 2122.29  | 9        | 500     |          |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | C9     | 13   | 2121.10  | 9        | 500     | 2121.69  |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | S76    | 10   | 2119.95  | 9        | 250     |          |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | S77    | 12   | 2120.01  | 9        | 250     | 2119.98  |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | S78    | 12   | 2120.28  | 10       | 250     |          |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | S79    | 11   | 2120.89  | 10       | 250     | 2120.58  |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | A10    | 13   | 2121.04  | 10       | 500     |          |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | C10    | 12   | 2122.5   | 10       | 500     | 2121.77  |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | A11    | 12   | 2121.37  | 11       | 500     |          |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | C11    | 14   | 2123.05  | 11       | 500     | 2122.21  |
+---------+--------+------+----------+----------+---------+----------+
| CRM     | 213    | 15   | 1972.10  |          |         |          |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | S80    | 13   | 2120.74  | 11       | 250     |          |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | S81    | 19   | 2121.09  | 11       | 250     | 2120.915 |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | S82    | 11   | 2120.51  | 12       | 250     |          |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | S83    | 17   | 2121.03  | 12       | 250     | 2120.77  |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | A12    | 20   | 2126.01  | 12       | 500     |          |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | C12    | 20   | 2125.5   | 12       | 500     |          |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | A13    | 20   | 2128.34  | 13       | 500     |          |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | C13    | 17   | 2122.12  | 13       | 500     | 2122.12  |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | S84    | 11   | 2120.61  | 13       | 250     |          |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | S85    | 11   | 2119.34  | 13       | 250     | 2119.97  |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | S86    | 9    | 2119.26  | 14       | 250     |          |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | S87    | 9    | 2119.41  | 14       | 250     | 2119.33  |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | A14    | 9    | 2120.74  | 14       | 500     |          |
+---------+--------+------+----------+----------+---------+----------+
| bottle  | C14    | 9    | 2121.61  | 14       | 500     | 2121.17  |
+---------+--------+------+----------+----------+---------+----------+
| CRM     |        |      |          |          |         |          |
| Ce      |        |      |          |          |         |          |
| rtified |        |      |          |          |         |          |
| Value   |        |      |          |          |         |          |
| 1       |        |      |          |          |         |          |
| 969.57. |        |      |          |          |         |          |
|         |        |      |          |          |         |          |
| **Le    |        |      |          |          |         |          |
| gend:** |        |      |          |          |         |          |
|         |        |      |          |          |         |          |
| Type:   |        |      |          |          |         |          |
| CRM =   |        |      |          |          |         |          |
| ce      |        |      |          |          |         |          |
| rtified |        |      |          |          |         |          |
| re      |        |      |          |          |         |          |
| ference |        |      |          |          |         |          |
| ma      |        |      |          |          |         |          |
| terial; |        |      |          |          |         |          |
| bottle  |        |      |          |          |         |          |
| =       |        |      |          |          |         |          |
| sample  |        |      |          |          |         |          |
| bottle. |        |      |          |          |         |          |
|         |        |      |          |          |         |          |
| Bottle: |        |      |          |          |         |          |
| bottles |        |      |          |          |         |          |
| with    |        |      |          |          |         |          |
| prefix  |        |      |          |          |         |          |
| "S" are |        |      |          |          |         |          |
| the 250 |        |      |          |          |         |          |
| ml      |        |      |          |          |         |          |
| bottle, |        |      |          |          |         |          |
| the     |        |      |          |          |         |          |
| others  |        |      |          |          |         |          |
| are the |        |      |          |          |         |          |
| 540 ml  |        |      |          |          |         |          |
| bottles |        |      |          |          |         |          |
| used    |        |      |          |          |         |          |
| during  |        |      |          |          |         |          |
| the     |        |      |          |          |         |          |
| cruise. |        |      |          |          |         |          |
|         |        |      |          |          |         |          |
| RT: run |        |      |          |          |         |          |
| time of |        |      |          |          |         |          |
| the     |        |      |          |          |         |          |
| sample  |        |      |          |          |         |          |
| on the  |        |      |          |          |         |          |
| cou     |        |      |          |          |         |          |
| lometer |        |      |          |          |         |          |
| in      |        |      |          |          |         |          |
| m       |        |      |          |          |         |          |
| inutes. |        |      |          |          |         |          |
|         |        |      |          |          |         |          |
| DIC:    |        |      |          |          |         |          |
| results |        |      |          |          |         |          |
| of the  |        |      |          |          |         |          |
| a       |        |      |          |          |         |          |
| nalyses |        |      |          |          |         |          |
| in µmol |        |      |          |          |         |          |
| kg^-1^  |        |      |          |          |         |          |
|         |        |      |          |          |         |          |
| Bu      |        |      |          |          |         |          |
| llister |        |      |          |          |         |          |
| Bottle: |        |      |          |          |         |          |
| Bu      |        |      |          |          |         |          |
| llister |        |      |          |          |         |          |
| bottle  |        |      |          |          |         |          |
| number. |        |      |          |          |         |          |
|         |        |      |          |          |         |          |
| Volume: |        |      |          |          |         |          |
| nominal |        |      |          |          |         |          |
| sample  |        |      |          |          |         |          |
| bottle  |        |      |          |          |         |          |
| volume. |        |      |          |          |         |          |
|         |        |      |          |          |         |          |
| A       |        |      |          |          |         |          |
| verage: |        |      |          |          |         |          |
| Average |        |      |          |          |         |          |
| of      |        |      |          |          |         |          |
| du      |        |      |          |          |         |          |
| plicate |        |      |          |          |         |          |
| large   |        |      |          |          |         |          |
| or      |        |      |          |          |         |          |
| du      |        |      |          |          |         |          |
| plicate |        |      |          |          |         |          |
| small   |        |      |          |          |         |          |
| bottles |        |      |          |          |         |          |
| taken   |        |      |          |          |         |          |
| from a  |        |      |          |          |         |          |
| par     |        |      |          |          |         |          |
| ticular |        |      |          |          |         |          |
| Bu      |        |      |          |          |         |          |
| llister |        |      |          |          |         |          |
| bottle. |        |      |          |          |         |          |
+---------+--------+------+----------+----------+---------+----------+

**Statistics:**

[Large]{.underline} [Small]{.underline}

Average: 2121.79 2120.26

St. Dev.: 0.37 0.55

These test and more ad-hoc tests at the beginning of the cruise showed a
small but systematic difference between the small and large sample
bottles. The cause of the artifact is not clear, but the tests led to
our decision to use the 500-ml greased stopper bottles for the entire
cruise.

References

DOE, 1994: Handbook of methods for the analysis of the various
parameters of the carbon dioxide system in sea water. Version 2, A.G.
Dickson and C. Goyet (eds.), ORNL/CDIAC-74.

Johnson, K.M., K.D. Wills, D.B. Butler, W.K. Johnson, and C.S. Wong,
1993: Coulometric total carbon dioxide analysis for marine studies:
Maximizing the performance of an automated continuous gas extraction
system and coulometric detector. *Mar. Chem.,* v. 44, pp. 167-189.

Johnson, K.M., 1992: Operator's manual: Single operator multiparameter
metabolic analyzer (SOMMA) for total carbon dioxide (CT) with
coulometric detection. Brookhaven National Laboratory, Brookhaven, NY,
70 pp.

Johnson, K.M., P.J. Williams, L. Brandstrom, and J. McN. Sieburth, 1987:
Coulometric total carbon analysis for marine studies: Automation and
calibration. *Mar. Chem.*, v. 21, pp. 117-133.

Johnson, K.M., A.E. King, and J. McN. Sieburth, 1985. Coulometric DIC
analyses for marine studies: An introduction. *Mar. Chem.,* v*.* 16, pp.
61-82.

***2.6.6. Discrete pH Analyses***

**Principal Investigators:** Frank J. Millero, U. Miami, RSMAS

4600 Rickenbacker Causeway, Miami, FL 33149

fmillero@rsmas.miami.edu

**Samplers:** William T. Hiscock (12 noon-12 midnight)

whiscock@rsmas.miami.edu

John M. Trapp (12 midnight-12 noon)

jtrapp@rsmas.miami.edu

**Analysts:** William T. Hiscock (12 noon-12 midnight)

whiscock@rsmas.miami.edu

John M. Trapp (12 midnight-12 noon)

jtrapp@rsmas.miami.edu

**Data Reduction:** William T. Hiscock, whiscock@rsmas.miami.edu

**Sampling:**

Samples were drawn from 12-l Bullister bottles into 50 ml glass syringes
using polycarbonate Luer-lock valves that fit in the petcock. Syringes
were rinsed a minimum of three times and filled while taking care not to
entrain any bubbles. A rubber band ensured positive pressure on the
barrel of the syringe. The samples were stored at room temperature for a
maximum of 7 hours. Thirty-six samples and three duplicates were drawn
on odd numbered stations (at 1 degree intervals) for a total of 60 full
stations. At even number stations, surface water and a duplicate were
always taken; in addition, five to 20 other depths were also sampled,
for a total of 59 half stations. Typically, nine depths were sampled
with a duplicate at the surface for the half-stations. Underway samples
were drawn in duplicate from the underway seawater line at 6-hour
intervals between Punta Arenas, Chile and the start of the line at 60°S,
31°W which are not included in the tally below.

Total number of samples: 2811

Questionable (QC=3): 44

Bad (QC=4): 64

Not Reported (QC=5): 51

**Analyzer Description:**

Measurements of the pH of seawater on the total hydrogen ion
concentration pH scale (pH~t~) were made using the multi-wavelength
spectrophotometric techniques of Clayton and Byrne (1993). Determination
of the absorbance at several wavelengths eliminates the need to know the
concentrations of indicator in the sample. Sulphonphthalein indicators
such as m-cresol purple (mCP), thymol blue, and cresol red are suitable
for the determination of pH. The system is patterned after the standard
operating procedure developed by the U.S. Department of Energy (DOE)
(1994) and utilizes mCP. This fully automated system performs discrete
analysis of pH samples approximately every 12 minutes on a sample volume
of 25 ml. A microprocessor controlled syringe and sampling valve
aspirates and injects the seawater sample into the 10 cm optical cell at
a precisely controlled rate. The syringe rinses and primes the optical
cell with 20 ml of sample and the software permits five minutes for
temperature stabilization. A refrigerated circulating temperature bath
(Neslab, model RTE-17) regulates the temperature of the sample at 25 ±
0.01ºC. An Agilent 8453 UV/VIS spectrophotometer measures background
absorbance of the sample. The automated syringe and sampling valves
aspirates 4.90 ml seawater and 0.008 ml of indicator and injects the
mixture into the cell. After the software permits five minutes for
temperature stabilization, a Guildline 9540 digital platinum resistance
thermometer measures the temperature and the spectrophotometer acquires
the absorbance at 434, 578 and 730 nm.

**Reagents:**

A concentrated solution, 2.0 mM, of mCP (C21H18O3S) dye solution of
known pH~t ~= 7.91 and R = 1.625 at 25ºC.

**Standardization:**

A precision of better than 0.001 pH units is possible with care,
specifically with regard to temperature equilibration and sample
handling. Measurements made on duplicate samples, TRIS buffers and
Certified Reference Material, Batch 59 (Dr. Andrew Dickson, Marine
Physical Laboratory, La Jolla, California) provide validation of the
precision and accuracy. Duplicate analyses provide additional quality
assurance and were taken from same Bullister bottle. The pH~sws~ for the
Certified Reference Material was determined by spectrophotometric
methods independently in the laboratory at RMSAS, University of Miami:

Batch #59: pH~sws~ @ 25°C 7.9048 ± 0.0007 (n = 19)

Salinity 33.316

**Data Processing:**

The pH~t~ of the sample is perturbed by the addition of the indicator.
The magnitude of this perturbation is a function of the difference
between the seawater and indicator acidity. A correction factor applied
for each batch of dye adjusts for this perturbation. For a 4.90 ml
sample of seawater, 0.008 ml of mCP is added and the absorbance ratio
measured. From a second addition of mCP and a second absorbance ratio
measurement, a change in the absorbance ratio per ml of added indicator
(DR) is calculated. The value of the absorbance ratio (R~m~) measured
subsequent to the initial addition of the indicator was used to
calculate R from:

R = R~m~ + (0.00095 - 0.00133 R~m~) V~ind~ (1)

where V~ind~ is the volume of mCP used. Clayton and Byrne (1993)
calibrated the mCP indicator using TRIS buffers (Ramette *et al*., 1977)
and the equations of Dickson (1993). These equations are used to
calculate pH~t~, the total scale in units of moles per kilogram of
solution. The conversion of the pH~t~ (mol/kg~H2O~) to the seawater
scale (mol/kg~sol~) can be made using equations of Dickson and Millero
(1987), Dickson and Riley (1979), and Dickson (1990).

CRM

Total number of Sets: 136

Number of Sets Used: 124

CRM Batch #59: 7.9050 ± 0.0024 (pH~sws~ @ 25°C)

TRIS Buffer

Total number of Sets: 296

Number of Sets Used: 264

TRIS Buffer (0.04 m): 8.0935 ± 0.0019 (pH~t~ @ 25°C)

Duplicates

Total number of Sets: 291

Number of Sets Used: 214

Standard Deviation: ± 0.0019 (pHsws @ 25°C)

Note: The instrumental software automatically runs a duplicate analysis
when the baseline absorbance at 730 nm is beyond a set threshold, thus a
large number of omitted duplicate results. Duplicate samples whose
difference was three times larger than the standard deviation were
omitted from the analyses. The number omitted is the difference between
the total number of sets and the sets used.

**Problems:**

At the start of the cruise, the outflow from the optical cell leaked
into the thermostated water jacket; this was repaired by replacing the
tubing. Sporadically, samples drawn from the syringe entrained an air
bubble because the valve was improperly opened, tubing was pinched, or
the syringe plunger was dry and became stuck in the barrel. Some
syringes suffered from fatigue at the metal Luer-lock and resulted in
the sample being lost or a failed analysis. Occasionally the software
would lose communication with the microprocessor-controlled syringe
pumps and pause analysis; the problem was resolved by following the
steps outlined in the software to reestablish communication.

References

Clayton, T.D., and R.H. Byrne, 1993: Spectrophotometric seawater pH
measurements: Total hydrogen ion concentration scale calibration of
m-cresol purple and at-sea results. *Deep-Sea Res.,* v. 40, pp.
2315-2329.

Dickson, A.G., 1990: Thermodynamics of the dissociation of boric acid in
synthetic seawater from 273.15 to 318.15 K. *Deep-Sea Res., Part A,* v.
37, no. 5, pp. 755-766.

Dickson, A.G., 1993: The measurement of seawater. *Mar. Chem.,* v. 44,
no. 2-4, pp. 131-142.

Dickson, A.G., and F.J. Millero, 1987: A comparison of the equilibrium
constants for the dissociation of carbonic acid in seawater media.
*Deep-Sea Res., Part A,* v. 34, no. 10, pp. 1733-1743.

Dickson, A.G., and J.P. Riley, 1979: The estimation of acid dissociation
constants in seawater media from potentiometric titration with strong
base, 1: The ionic product of water-KSUS-w. *Mar. Chem*., v. 7, no. 2,
pp. 89-99.

DOE, 1994: Handbook of methods for the analysis of the various
parameters of the carbon dioxide system in sea water. Version 2, A.G.
Dickson and C. Goyet (eds.), ORNL/CDIAC-74.

Ramette, R.W., C.H. Culberson, and R.G. Bates, 1977: Acid-base
properties of Tris(hydroxymethyl)aminomethane (Tris) buffers in seawater
from 5 to 40°C. *Anal. Chem*., v. 49, pp.867-870.

***2.6.7. Total Alkalinity Analyses***

**Principal Investigator:** Frank J. Millero, U. Miami, RSMAS

4600 Rickenbacker Causeway, Miami, FL 33149

fmillero@rsmas.miami.edu

**Samplers:** Taylor B. Graham (12 noon-12 midnight)

tgraham@rsmas.miami.edu

Mareva Chanson (12 midnight-12 noon)

mchanson@rsmas.miami.edu

**Analysts:** Taylor B. Graham (12 noon-12 midnight)

tgraham@rsmas.miami.edu

Mareva Chanson (12 midnight-12 noon)

mchanson@rsmas.miami.edu

**Data Reduction:** William T. Hiscock, whiscock@rsmas.miami.edu

**Sampling:**

Samples were drawn from 12-l Bullister bottles into 500 ml borosilicate
flasks using Silicone tubing that fit over the petcock to avoid
contamination of DOC samples. Bottles were rinsed a minimum of two times
and filled from the bottom, overflowing a quarter of a volume while
taking care not to entrain any bubbles. Approximately 15 ml of water was
withdrawn from the flask by arresting the sample flow and removing the
sampling tube, thus creating a small expansion volume and a reproducible
headspace. The sample bottles were sealed at a ground glass joint with a
glass stopper. The samples were stored at room temperature for a maximum
of 7 hours. Thirty-six samples and three duplicates were drawn on odd
number stations (at 1 degree intervals) for a total of 61 full stations.
Typically, nine depths were sampled with a duplicate at the surface at
the 60 "half stations." Periodically, multiple duplicate samples were
drawn with a specific focus on photic zone and region of high dissolved
organic carbon (DOC). The purpose was to determine the difference in
Total Alkalinity after filtration with a 0.45 µm nylon membrane filter.
Additional underway samples were drawn in duplicate from the underway
seawater line at 6-hour intervals between Punta Arenas, Chile and the
start of the line at 60°S, 31°W, which are not included in the tally
below.

Total number of samples: 2784

Questionable (QC=3): 64

Bad (QC=4): 42

Not Reported (QC=5): 51

**Analyzer Description:**

The total alkalinity of seawater (TAlk) was evaluated from the proton
balance at the alkalinity equivalence point, pH~equiv~ = 4.5 at 25ºC and
zero ionic strength in one kilogram of sample. The method utilizes a
multi-point hydrochloric acid titration of seawater according to the
definition of total alkalinity (Dickson, 1981).

The titration system used consists of a Metrohm 665 Dosimat titrator, an
Orion 720A pH meter and a custom designed plastic water-jacketed
titration cell (Millero *et al*., 1993b). Both the seawater sample and
acid titrant are temperature equilibrated to a constant temperature of
25 ± 0.1ºC with a water bath (Neslab, model RTE-17). The plastic
water-jacketed cell is similar to the cells used by Bradshaw and Brewer
(1988) except a larger volume (\~200 ml) is employed to increase the
precision. Each cell has a fill and drain valve which increases the
reproducibility of the volume of sample contained in the cell. The
titration acidified seawater past the carbonic acid endpoint by adding
HCl stepwise through an injection tip into the cell. A typical titration
recorded the EMF after the readings became stable (deviation less than
0.09 mV) and then enough acid was added to change the voltage a
pre-assigned increment (13 mV). A full titration (\~25 points) takes
about 20 minutes. The electrodes used to measure the EMF of the sample
during a titration consisted of a ROSS glass pH electrode (Orion, model
810100) and a double junction Ag, AgCl reference electrode (Orion, model
900200).

**Reagents:**

A single 50-l batch of \~0.25 m HCl acid was prepared in 0.45 m NaCl by
dilution of concentrated HCl, AR Select‚ Mallinckrodt, to yield a total
ionic strength similar to seawater of salinity 35.0 (I ≈ 0.7 M). The
acid was standardized by a coulometric technique (Marinenko and Taylor,
1968; Taylor and Smith, 1959) and verified with alkalinity titrations on
seawater of known alkalinity. Furthermore, Andrew Dickson's laboratory
performed an independent determination of the acid molality on
sub-samples. The calibrated molality of the acid used was 0.2434 ±
0.0001 m HCl. The acid was stored in 500-ml glass bottles sealed with
Apiezon® L grease for use in the field.

**Standardization:**

The volumes of the cells used were determined to ± 0.03 ml in the
laboratory by multiple titrations using seawater of known total
alkalinity and CRM. Calibrations of the burette of the Dosimat with
water at 25ºC indicate that the systems deliver 3.000 ml (the
approximate value for a titration of seawater) to a precision of ±
0.0004 ml, resulting in an error of ± 0.3 µmol·kg^-1^ in TAlk and DIC.
The reproducibility and precision of measurements are checked using low
nutrient surface seawater and Certified Reference Material (Dr. Andrew
Dickson, Marine Physical Laboratory, La Jolla, California), Batch 59 and
66. CRM were utilized in order to account for instrument drift and to
maintain measurement precision. Duplicate analyses provide additional
quality assurance and were taken from same Bullister bottle.

The assigned values of the Certified Reference Material provided by A.
Dickson of SIO are:

Batch #59: Total Alkalinity: 2220.98 ± 0.58 µmol·kg^-1^ Salinity: 33.316

Batch #66: Total Alkalinity: 2193.27 ± 0.60 µmol·kg^-1^ Salinity: 32.962

**Data Processing:**

An integrated program controls the titration, data collection, and the
calculation of the carbonate parameters (TAlk, pH, and DIC ) (Millero
*et al.*, 1993a). The program is patterned after those developed by
Dickson (1981), Johansson and Wedborg (1982), and U.S. Department of
Energy (DOE) (1994). The program uses a Levenberg-Marquardt nonlinear
least-squares algorithm to calculate the TAlk, DIC, and from the
potentiometric titration data.

[CRM]{.underline} [Instrument 1]{.underline} [Instrument 2]{.underline}

Total number of sets: 56 52

Number of sets used: 48 46

Standard deviation: ±3.5 µmol·kg^-1^ ±2.7 µmol·kg^-1^

[Duplicates]{.underline} [Between Systems]{.underline} [Instrument
1]{.underline} [Instrument 2]{.underline}

Total number of sets: 143 31 42

Number of sets used: 130 25 35

Standard deviation: ±2.9 µmol·kg^-1^ ±1.6 µmol·kg^-1^ ±1.3 µmol.kg^-1^

Note: Duplicate samples whose difference was three times larger than
standard deviation were omitted from the analyses. The number omitted is
the difference between the total number of set and the sets used.

**Problems:**

At the start of the cruise a titration cell was swapped out for a spare
cell because of a combination of instability in the electrodes and an
air bubble consistently being trapped. One valve and a proximity switch
were replaced without discernible downtime. Sporadically, a solenoid
valve at the bottom of the titration cell would fail to engage or
disengage, resulting in the loss of the sample or a failed titration due
to a poor rinse or an air bubble. The titration cell on system one
showed some drift in CRM values on February 4, 2005; the titration cells
recalibration values were used to correct this. Communication problems
between the software and the components of the TAlk system were remedied
with replacement of cables and/or components. A Metrohm 665 Dosimat
titrator and Orion 720A pH meter were replaced. Computer instability
resulted in the loss of one sample.

References

Bradshaw, A.L., and P.G. Brewer, 1988: High precision measurements of
alkalinity and total carbon dioxide in seawater by potentiometric
titration, 1: Presence of unknown protolyte(s)? *Mar. Chem.,* v. 23, pp.
69-86.

Dickson, A.G., 1981: An exact definition of total alkalinity and a
procedure for the estimation of alkalinity and total CO~2~ from
titration data. *Deep-Sea Res., Part A,* v. 28, pp. 609-623.

DOE, 1994: Handbook of methods for the analysis of the various
parameters of the carbon dioxide system in sea water. Version 2, A.G.
Dickson and C. Goyet (eds.), ORNL/CDIAC-74.

Johansson, O., and M. Wedborg, 1982: On the evaluation of potentiometric
titrations of seawater with hydrochloric acid. *Oceanologica Acta,* v.
5, pp. 209-218.

Marinenko, G., and J.K. Taylor, 1968: Electrochemical equivalents of
benzoic and oxalic acid. *Anal. Chem.*, v. 40, pp. 1645-1651.

Millero, F.J., R.H. Byrne, R. Wanninkhof, R. Feely, T. Clayton, P.
Murphy, and M.F. Lamb, 1993a: The internal consistency of CO~2~
measurements in the equatorial Pacific. *Mar. Chem.,* v. 44, pp.
269-280.

Millero, F.J., J.-Z. Zhang, K, Lee, and D.M. Campbell, 1993b: Titration
alkalinity of seawater. *Mar. Chem.*, v. 44, pp. 153-165.

Taylor, J.K., and S.W. Smith, 1959: Precise coulometric titration of
acids and bases. *J. Res. Natl. Bur. Stds.,* v. 63, pp. 153-159.

***2.6.8. Salinity Analysis***

**Principal Investigators:** Gregory C. Johnson, NOAA/PMEL

**Analyst:** Dave Wisegarver, NOAA/PMEL

**Samplers:** Dave Wisegarver (primary from 4 a.m.-4 p.m.)

Scott Doney, Rik Wanninkhof, Bill Hiscock, Wenhau Chen

Samples were run on a Guildline 8400B Laboratory Salinometer, serial
number 60843. The salinometer had been last calibrated at Guildline in
January of 2004. IAPSO Standard Seawater was used to standardize the
instrument. The standard water was from batch:

P143, 26-Feb-2003, K15 = 0.99989, Salinity 34.996.

The instrument was located in a small temperature controlled room, off
the hydro lab. A recording temperature sensor was placed near the
salinometer to monitor the temperature during analyses. For the most
part, the temperature logged by this sensor was 22-24°C; however, there
were several deviations, one as high as 25.3°C and one as low as 21.7°C.
On one occasion, analysis was halted for about half an hour, while the
room cooled.

Samples were drawn from the Bullister bottles into 250-ml Kimax
borosilicate bottles. The bottles were rinsed at least three times
before filling to approximately 220 ml. A plastic insert and Nalgene cap
were used to seal the sample in the bottle. At the conclusion of
sampling, the time was noted and samples were placed into the
salinometer lab so they could equilibrate to the room temperature.
Samples were analyzed after a period of at least 10 hours and typically
not more than 24 hours from the time of sampling. With the exception of
a few shallow casts, an IAPSO standard seawater bottle was analyzed
before and after each station.

The software used (ASALW) was developed at Scripps Institution of
Oceanography. As per the instructions provided in the software, the cell
was rinsed at least two times with sample at a relatively fast flow
rate; the flow was adjusted to a slower rate for the final fill, and a
reading was taken. The cell was drained and slowly filled for a second
reading. If the two readings agreed within 0.00005, the values were
accepted; otherwise, an additional reading was required. PSS-78 salinity
(UNESCO, 1981) was calculated. Corrections were applied to the data for
differences between beginning and ending standards.

A total of 4174 salinity samples were taken, of which 127 were flagged
as questionable, 3 as bad, and 2 were lost during analysis. A number of
samples could not be drawn during heavily sampled casts, due to a lack
of water. This occurred most frequently when using the small 3-liter
bottles in the first few stations.

References

UNESCO, 1981: Background papers and supporting data on the practical
salinity scale., 1978. *UNESCO Technical Papers in Marine Science*, No.
37, p. 144.

***2.6.9. Inorganic Nutrients (Phosphate, Nitrate, Nitrite, and
Silicate)***

**Principal Investigators:** Dr. Calvin Mordy, NOAA/PMEL

Dr. Jia-Zhong Zhang, NOAA/AOML

**Samplers and Analysts:** Charlie Fischer, NOAA/AOML (12 noon-12
midnight)

Calvin Mordy, UW (12 midnight-12 noon)

**Data Reduction:** Calvin Mordy

**Equipment and Techniques:**

Dissolved nutrients (phosphate, silicic acid, nitrate and nitrite) were
measured using automated continuous flow analysis with a segmented flow
and colorimetric detection. The four-channel autoanalyzer was customized
using components from various systems. The major components were an
Alpkem 301 sampler, two 24 channel Ismatek peristaltic pumps, four
ThermoSeparation monochrometers, and custom software for digitally
logging and processing the chromatographs. Glass coils and tubing from
the Technicon Autoanalyzer II were used for analysis of phosphate, and
micro-coils from Alpkem were used for the other three analyses.

The detailed methods were described by Gordon *et al.* (1992). Because
pump tubing destined for the cruise was lost in transit, some of the
pump tube sizes suggested in the manual had to be modified. Pump tubes
were changed four times during the expedition.

Silicic acid was analyzed using a modification of Armstrong *et al*.
(1967). An acidic solution of ammonium molybdate was added to a seawater
sample to produce silicomolybic acid. Oxalic acid was added to inhibit a
secondary reaction with phosphate. Finally, the reduction with ascorbic
acid formed the blue compound silicomolybdous acid. The color formation
was detected using a 6 mm flowcell at 660 nm. The use of oxalic acid and
ascorbic acid (instead of tartaric acid and stannous chloride as
suggested by Gordon *et al.*) was to reduce the toxicity of our waste
stream.

Nitrate and nitrite analyses were also modified from Armstrong *et al*.
(1967). Nitrate was reduced to nitrite in a cadmium column, formed into
a red azo dye by complexing nitrite with sulfanilamide and
N-1-naphthylethylenediamine, and the color formation was detected using
a 6 mm flowcell at 540 nm. The same technique was used to measure
nitrite (excluding the reduction step), but the color formation was
detected using a 10 mm flowcell at 540 nm.

Phosphate analysis was based on the technique of Bernhardt and Wilhelms
(1967). An acidic solution of ammonium molybdate was added to the sample
to produce phosphomolybdic acid, and this was reduced to the blue
compound phosphomolybdous acid following the addition of hydrazine
sulfate. The reaction was heated to 55°C to bring the reaction to
completion, and color formation was detected using a 10 mm flowcell at
815 nm.

**Sampling and Standards:**

Nutrient samples were drawn in 40 ml HDPE Boston Round sample bottles
that had been stored in 10% HCl and rinsed four to five times with
sample before filling. A replicate was always drawn from the deep bottle
for analysis on the subsequent station. All samples were brought to room
temperature prior to analysis. A separate analytical run was conducted
at each station (except for the most shallow stations). An analytical
run consisted of blanks and working standards, old working standard,
deep water from the previous station, samples analyzed from deep to
surface, replicate analysis of the four deep samples and any problem
samples, and finally the working standards and blanks. The blanks were
deionized water, and the standards were simply a "zero" standard in Low
Nutrient Seawater (LNSW), and a high standard. Linearity of the
autoanalyzer was checked every ten days, and corrections for
non-linearity will be applied during final data reduction.

The high standard was made from the addition of 1 ml of primary nitrite
standard and 20 ml of a secondary mixed standard (containing silicic
acid, nitrate, and phosphate) in 500 ml of LNSW. A new high standard was
prepared for each analytical run. Calibrated Eppendorf pipettes normally
used for dispensing the primary and secondary standards were not
delivered to the ship, so a calibrated Rainin electronic digital pipette
was used.

Dry standards were pre-weighed at PMEL and dissolved to prepare primary
standards at sea. Silicic acid (Na~2~SiF~6~, \>98%) and nitrate (KNO~3~,
99.99%) were from Aldrich, phosphate (KH~2~PO~4~, 99.99%), and nitrite
(NaNO~2~, 98.2%) were from Baker. The mixed standard was prepared by
additions of the nitrate and phosphate primary standards during
preparation of the silicic acid primary standard.

After each run, the electronic chromatograph was scrutinized to ensure
proper selection of individual peak heights. The peak information was
inserted into Microsoft Excel and the concentrations were calculated
after factoring the baseline drift, carryover corrections, refractive
index, and standard drift. Quality control plots were maintained of the
baseline, matrix, carryover, standard factor, old standard, and
station-to-station variability of the deep water replicate.

Nutrient concentrations were reported to the shipboard data manager in
micromole per liter. The laboratory temperature during analysis was also
reported to facilitate unit conversion to a micromole per kg basis. The
nutrient concentration as shown in µmol kg‑^1^ units presented in the
bottle data files.

**Problems:**

During the cruise, several detectors and a sampler had to be replaced,
but no data were compromised due to these equipment failures. During the
first two stations, the phosphate heater was not functioning, and these
data were considered suspect.

**Number of Samples, Replicates, and Precision:**

A replicate sample was almost always drawn from the deepest bottle, and
replicate analyses were almost always conducted on the four deepest
bottles. A few replicate analyses were conducted for samples in the
upper water, and the precision of nitrate was determined from those
samples with concentrations \>0.05 μM. The precision of phosphate,
silicic acid and nitrate was within 2% of full scale (Table 2.13).

  ---------------------------- --------------- ----------- ------------- -------------
  **Table 2.13. Summary of                                               
  number of nutrient samples                                             
  taken and estimated                                                    
  precision.**                                                           

                               **Phosphate**   **Silicic   **Nitrate**   **Nitrite**
                                               Acid**                    

  Number of samples            4286            4286        4243          4286

  Number of replicates         755             759         680           19\*

  Average standard deviation   0.01            0.4         0.08          0.005
  (µM)                                                                   

  Percent deviation            0.8%            1.7%        1.4%          2%

  \*Samples with nitrate                                                 
  concentrations higher that                                             
  0.05 μM.                                                               
  ---------------------------- --------------- ----------- ------------- -------------

References

Armstrong, F.A.J., C.R. Stearns, and J.D.H. Strickland, 1967: The
measurement of upwelling and subsequent biological processes by means of
the Technicon AutoAnalyzer and associated equipment. *Deep-Sea Res.,* v.
14, pp. 381-389.

Bernhardt, H., and A. Whihelms, 1967: The continuous determination of
low level iron, soluble phosphate, and total phosphate with the
AutoAnalyzer. Technicon Symposia, I., pp. 385-389.

Gordon, L.I., J.C. Jennings Jr., A.A. Ross, and J.M. Krest, 1993: A
suggested protocol for continuous automated analysis of seawater
nutrients (phosphate, nitrate, nitrite, and silicic acid) in the WOCE
Hydrographic program and the Joint Global Ocean Fluxes Study, WOCE
Operations Manual, Vol. 3: The Observational Programme, Section 3.2:
WOCE Hydrographic Programme, Part 3.1.3: WHP Operations and Methods. WHP
Office Report WHPO 91-1; WOCE Report No. 68/91. November, 1994, Revision
1, Woods Hole, Mass., USA, 52 pp.

2.7. Underway Measurements

Several groups measured carbon system parameters from the uncontaminated
seawater line. All systems but one were located in the hydrolab where
the seawater stream was diverted to the different instruments. A total
of about 25 l/min of water was used, while an additional 10-15 l/min was
discharged overboard aft of the hydrolab. This decreased the transit
time from the intake at 5-m depth at the bow through the 100-m 2\"
Teflon lined stainless steel tube. Transit time from the bow to the
hydrolab was about 2.5 minutes. An EnviroTech nutrient monitor (NAS-2E)
was set up at an outlet in the main lab but did not function properly
throughout the cruise.

Underway systems that were used on the cruise included an underway
pCO~2~ system that is installed on a permanent basis from AOML, two SAMI
pCO~2~ systems from the University of Montana, and a multi-inorganic
carbon species analyzer from the University of South Florida. A Seabird
thermosalinograph (SBE-45) was situated in the sink of the hydrolab and
logged in the datastream from the underway pCO~2~ system. In addition,
there was an uncalibrated fluorometer in the hydrolab and a
thermosalinograph at the bow of the ship approximately 5 m from the
intake. The fluorometer and thermosalinograph data are logged on the
shipboard computing system (SCS).

The underway data was not submitted to the data manager while at sea as
further quality control of the full data set is to be performed on
shore. The data will be submitted to the data manager, Frank Delahoyd at
SIO, and placed on the A16S website. The data will include the
appropriate time and location stamps such that the datasets can be
compared with each other and surface bottle data from the CTD casts. The
bottle data taken from the underway sample line for a surface survey
between Punta Arenas and the start of the CTD section at 60ºS, 32˚W is
provided as a separate file.

***2.7.1. Shipboard Computing System (SCS)***

The shipboard computing system logs all data routinely acquired by the
permanent shipboard sensors including TSG, rain, meteorological
parameters, and speed and course. The data are logged at 30-second
intervals and are available from the chief scientist (RW).

***2.7.2. Underway pCO~2~ (fCO~2~) Measurements***

**Principal Investigator:** Rik Wanninkhof, NOAA/AOML

4301 Rickenbacker Causeway, Miami FL 33149

Rik.Wanninkhof@noaa.gov

**Shipboard Analyst:** Jonathan Shannahoff, Chief Survey Technician

R/V *Ronald H. Brown*

Jonathan.Shannahoff@noaa.gov

**Data Reduction:** Robert Castle, NOAA/AOML

4301 Rickenbacker Causeway, Miami FL 33149

Robert.Castle@noaa.gov

**Equipment and Analytical Techniques: Underway pCO~2~ System (Version
2.5) AOML:**

The shipboard automated underway pCO2 system is situated in the
hydrolab. It runs on an hourly cycle during which three gas standards,
eight headspace samples from the equilibrator, and three ambient air
samples are analyzed. The system consists of an equilibrator where
surface seawater from the bow intake is equilibrated with headspace, a
valve box that contains the infrared analyzer, and an electronics box
with a computer and interface boards that control valves and log
sensors.

The equilibrator, designed by R. Weiss of SIO, is made from a 58 cm H X
23 cm ID cylindrical Plexiglas™ chamber. Surface seawater flows through
a showerhead in the top at a rate of 10-13 l/min. The water spray
through the 16-l headspace and the turbulence of the water streams
impinging on the surface of 8 l of water cause the gases in water and
headspace to equilibrate. Excess water flows through an outlet 20 cm
from the bottom of the equilibrator into an over-the-side drain. Two
vents in the top of the equilibrator insure that the headspace remains
at the measured laboratory pressure. Headspace gas circulates in a
closed loop driven by a KNF pump at 200 ml/min. From the equilibrator
the gas passes through a condensor, a column of magnesium perchlorate, a
mass flow meter (MFM), the 12 ml sample cell of a Licor™ Model 6251
non-dispersive infrared analyzer (IR), and back into the equilibrator
headspace.

A second KNF pump draws marine air from an intake on the bow mast
through 100 m of 0.95 cm (= 3/8\") OD Dekoron™ tubing at a rate of 6-8
l/min. A filter of glass wool at the intake prevents particles from
entering the gas stream. At designated times, the program diverts 250
ml/min of air from this line into the Licor sample cell for analysis.
Excess marine air and the two vent lines from the equilibrator empty
through an endcap into an open ended PVC tube. This means that any air
drawn into the equilibrator is marine air rather than lab air with
elevated and variable CO~2~ concentration.

Both sample streams (equilibrator headspace and marine air) are analyzed
bone dry. They pass first through a cold trap (condensor) at 5^o^C and
then through a column of magnesium perchlorate. Standard gases also run
through the magnesium perchlorate.

A custom developed program run under LabView controls the system and
graphically displays air and water XCO~2~ readings. The program logs the
voltage and temperature of the infrared analyzer, water flow, gas flows,
equilibrator temperature, and barometric pressure. It also logs
temperature and salinity from a Seabird MicroTSG unit connected to the
seawater line near the equilibrator. An RS-422 feed from the shipboard
computing system (SCS) provides additional data including time,
latitude, longitude, temperature and salinity in the sea chest near the
seawater intake, relative and absolute wind speed and direction, and
fluorometer readings. The program writes all of this data to disk at the
end of each measurement phase.

The details of instrumental design can be found in Wanninkhof and
Thoning (1993), Ho *et al*. (1995), and Feely *et al.* (1998).

**Sampling Cycle:**

The system runs on an hourly cycle during which three standard gases,
three marine air samples, and eight surface water samples (from the
equilibrator headspace) are analyzed on the schedule listed below (Table
2.14). A Valco multi-port valve selects the gas to be analyzed. Each
measurement phase starts by flowing either standard (@\~50ml/min),
equilibrator headspace (@\~200ml/min), or marine air (@\~250ml/min)
through the Licor. Fifteen seconds before the end of each phase, a
solenoid valve stops the gas flow. Ten seconds later, the program logs
all sensors and writes the data to disk.

+------------------------------+---------------------------------------+
| **Table 2.14. Hourly         |                                       |
| sampling cycle for the       |                                       |
| underway pCO~2~ system**     |                                       |
|                              |                                       |
| **(version 2.5).**           |                                       |
+------------------------------+---------------------------------------+
| **Minutes after the Hour**   | **Sample**                            |
+------------------------------+---------------------------------------+
| 4                            | Low standard                          |
+------------------------------+---------------------------------------+
| 8                            | Mid standard                          |
+------------------------------+---------------------------------------+
| 12                           | High standard                         |
+------------------------------+---------------------------------------+
| 16.5                         | Water (= headspace of equilibrator)   |
+------------------------------+---------------------------------------+
| 21                           | Water                                 |
+------------------------------+---------------------------------------+
| 25.5                         | Water                                 |
+------------------------------+---------------------------------------+
| 30                           | Water                                 |
+------------------------------+---------------------------------------+
| 34                           | Air (marine air from the bow line)    |
+------------------------------+---------------------------------------+
| 38                           | Air                                   |
+------------------------------+---------------------------------------+
| 42                           | Air                                   |
+------------------------------+---------------------------------------+
| 46.5                         | Water                                 |
+------------------------------+---------------------------------------+
| 51                           | Water                                 |
+------------------------------+---------------------------------------+
| 55.5                         | Water                                 |
+------------------------------+---------------------------------------+
| 60                           | Water                                 |
+------------------------------+---------------------------------------+

The headspace equilibration time, as determined by return to equilibrium
after perturbation by adding nitrogen to the headspace, is approximately
2.5 minutes. The transit time of water from the bow to the equilibrator
was determined in 1998 by injecting a slug of dye into the intake and
measuring the response on a fluorometer that is located in the hydrolab,
close to the equilibrator. The response time, defined as the time
elapsed between peak concentration and the half peak level, t~1/2~, is
1.45 minutes. This short time suggests little dispersion of the water
during transit through the tubing.

**Standards:**

The unit is standardized every hour with three compressed air standards
containing known amounts of CO~2~ gas in (natural) air. The standard
gases are purchased from NOAA/CMDL in Boulder and are directly traceable
to the WMO scale.

The standards used on the cruise are:

Mole Fraction

[Tank \#]{.underline} [CO~2~ (ppm) (= XCO~2~)]{.underline}

CC 71588 531.98

CA05344 411.42

CA05395 315.25

**Units:**

All XCO~2~ values are reported in parts per million (ppm), and fCO~2~
values are reported in micro atmospheres (µatm).

**Data Processing:**

The mixing ratios of ambient air and equilibrated headspace air are
calculated by fitting a second-order polynomial through the
hourly-averaged response of the detector versus mixing ratios of the
standards preceding and following the air and water samples. Mixing
ratios of dried equilibrated headspace and air are converted to fugacity
of CO~2~ in surface seawater (fCO~2~) and water saturated air. For
ambient air (a) and equilibrator headspace (eq), the fCO~2a~, or
fCO~2eq~, are calculated assuming 100% water vapor content:

fCO~2a/eq~ = xCO~2a/eq~(P-pH~2~O) exp((B~11~+2d~12~)P/RT)

where fCO~2a/eq~ is the fugacity in ambient air or equilibrator, pH~2~O
is the water vapor pressure at the sea surface temperature, P is the
atmospheric pressure (in atm), T is the SST or equilibrator temperature
(in K), and R is the ideal gas constant (82.057 ml atm deg^-1^ mol^-1^).
The exponential term is the fugacity correction where B~11~ is the
second virial coefficient of pure CO~2~:

B~11~ = -1636.75 + 12.0408 T - 0.032795T^2^ + 3.16528E-5 T^3^

and

d~12~ = 57.7 - 0.118 T

where d~12~ is the correction for an air-CO~2~ mixture in units of ml
mol^-1^ (Weiss, 1974).

The calculation for the fugacity at SST as measured by the
thermosalinograph involves a temperature correction term for the
increase of fCO~2~ due to heating of the water from passing through the
pump and through 5 cm ID Teflon sleeved stainless steel tubing within
the ship. The water in the equilibrator is typically 0.2 to 0.3°C warmer
than sea surface temperature. At the Southern end of the transect when
SST ≈ 2-5 ˚C the difference was as much as 1 ˚C. The empirical
temperature correction from equilibrator temperature to SST is outlined
in Weiss *et al.* (1982).

dln(fCO~2~)=(t~eq~-SST)(0.03107-2.7851 10^-4^ t~eq~ - 1.839 10^-3^
ln(fCO~2eq~))

where dln(fCO~2~) is the difference between the natural logarithm of the
fugacity at t~eq~ and SST, and t~eq~ is the equilibrator temperature in
˚C.

The precision of the measurements is estimated at 0.2 ppm based on
repetitive measurements of marine air. The accuracy of the air values is
believed to be better than 0.5 ppm based on comparisons with flask
samples on tests performed in 1995. Equilibrator headspace values are
believed to be accurate to within 2 µatm. The greater uncertainty is
attributed to the equilibration efficiency. Outside the calibration
range of the standards, an accuracy of 5 ppm (µatm) is assigned based on
laboratory tests where the calibrated IR output is compared with
standards of known concentration outside the calibration range.

**Problems:**

At the start of the cruise, from 1/14/05 17:04 (UTC) until 1/16/05 15:50
(UTC), Problems with the electrical power caused the program to run out
of sync and the equilibrator thermistor to give bad readings. Connecting
the instrument to an uninterruptible power supply (UPS) eliminated the
problem. A similar problem surfaced in the spring of 2004 at the end of
a cruise when the USF group removed their equipment. We suspect that
some electrical interference is caused by the USF instrumentation,
although our system was on the ship's UPS and their water bath was on a
different ("dirty power") outlet.

References

DOE, 1994: Handbook of methods for the analysis of the various
parameters of the carbon dioxide system in sea water. Version 2, A.G.
Dickson and C. Goyet (eds.), ORNL/CDIAC-74.

Feely, R.A., R. Wanninkhof, H.B. Milburn, C.E. Cosca, M. Stapp, and P.P.
Murphy, 1998: A new automated underway system for making high precision
pCO~2~ measurements onboard research ships. *Analytica Chim. Acta,* v.
377, pp. 185-191.

Ho, D.T., R. Wanninkhof, J. Masters, R.A. Feely, and C.E. Cosca, 1997:
Measurement of underway fCO~2~ in the eastern equatorial Pacific on NOAA
ships *Baldrige* and *Discoverer*. NOAA Data Report, ERL AOML-30, 52 pp.

Masters, J., R. Wanninkhof, D. Ho, M. Steckley, R. Feely, and C. Cosca,
1997: Continuous air and surface seawater measurements of fCO~2~ on
board the NOAA ship *Malcolm Baldrige* around the world cruise in 1995.
NOAA Data Report, ERL AOML-31, 80 pp.

Wanninkhof, R., and K. Thoning, 1993: Measurement of fugacity of CO~2~
in surface water using continuous and discrete sampling methods. *Mar.
Chem.*, v. 44, no. 2-4, pp. 189-205.

Weiss, R.F., 1970: The solubility of nitrogen, oxygen, and argon in
water and seawater. *Deep-Sea Res.,* v. 17, pp. 721-735.

Weiss, R.F., 1974: Carbon dioxide in water and seawater: The solubility
of a non-ideal gas. *Mar. Chem.,* v. 2, pp. 203-215.

Weiss, R.F., R.A. Jahnke, and C.D. Keeling, 1982: Seasonal effects of
temperature and salinity on the partial pressure of CO~2~ in seawater.
*Nature,* v. 300, pp. 511-513.

***2.7.3. SAMI Underway pCO~2~ Measurement System***

**Principal Investigator:** Michael DeGrandpre, Chemistry Department

University of Montana, Missoula, MT 59812

Michael.DeGrandpre@umontana.edu

(NOAA grant NA04OAR4310092)

**Shipboard analyst:** Stacy Smith, Chemistry Department

University of Montana, Missoula, MT 59812

Stacy.Smith@mso.umt.edu

**Equipment: SAMI-CO~2~ System (Submersible Autonomous Moored Instrument
for CO~2~):**

The SAMI is a chemical sensor designed to measure *p*CO~2~; the
technology is based upon CO~2~ equilibration with a pH sensitive
indicator (DeGrandpre *et al.,* 1999, 2000). The instrument is
commercially available from Sunburst Sensors (Missoula, MT). SAMI's
components include the indicator, pump, valve, membrane equilibrator,
optical cell and detector.

Briefly, 50 µl of the indicator bromothymol blue (BTB) is pumped through
a coiled CO~2~-permeable silicone rubber membrane into a custom-made
optical cell. A tungsten filament lamp and fiber optic cable direct
light into the optical cell, which has a 5 µl volume and path length of
0.75 cm. Another fiber optic cable guides light out of the cell to a 1X3
fiber optic splitter. The splitter ends are each connected to a port in
a photodiode detector. Each port is covered with interference filters,
one at each of the following wavelengths, 434 nm (acid), 620 nm (base)
and 740 nm (reference). The blank solution is deionized water. Data is
acquired using the TFX-11 data logger (Onset Computers).

**Rationale for Shipboard Analysis:**

The SAMI is usually deployed on ocean moorings at varying depths for
time periods of up to one year. Since its inception in the commercial
realm, few intensive intercomparisons have been made with the
conventionally-used equilibrator-infrared method. The goal of underway
testing is to provide extensive equilibrator-IR data to evaluate the
SAMI-CO~2~'s precision, accuracy, time response and temperature
coefficient. Shipboard testing is also being used to evaluate different
SAMI designs and to determine the potential for using SAMIs as a
shipboard underway system on research vessels and volunteer observing
ships.

For the A16 cruise in 2005, the SAMI-CO~2~s (2) were fitted with
flow-through chambers and connected to the same seawater line as the
equilibrator-IR. The equilibrator-IR was operated by Rik Wanninkhof's
group from NOAA AOML. Two SAMIs were used for this study, an older model
SAMI 16 and the newly built SAMI 48. The SAMIs took measurements every
15 minutes. Water blank measurements were taken every three days.

**Results:**

Data collected from the two SAMIs and equilibrator-IR are shown in
Figure 2.5. One can see from these results that SAMI 48 had \~10 μatm
offset until the end of the cruise when the offset approached 20 μatm.
SAMI 16 matched more closely with the equilibrator-IR except during some
periods when the pump failed (after Year Day \~12, data not shown) and
or did not pump efficiently (Year Day 25-30). One weakness in the SAMI
technology is the Lee solenoid pump. Factors leading to pump failures
are backpressure and general wear on pumps. As stated above, the SAMI
periodically records the transmittance through a blank solution. If the
pump does not flush the indicator from the optical cell, poor blank
readings are obtained which subsequently affect all *p*CO~2~
measurements after the blank. Although we are still evaluating the
results, poor flushing of the blank appears to be the source of the
large offset between YD 25 and 30 (SAMI 16).

Two other factors may have contributed to the observed *p*CO~2~ offsets
between the SAMIs and the equilibrator-IR. First, during the south to
north cruise transect the temperature increased from \~1 to 27^o^C. This
large change leads to a large temperature correction from the
calibration temperature (18^o^C). Small errors in the temperature
coefficient could lead to \~5-10 μatm errors in the calculated *p*CO~2~,
based on our recent calculations. We are completing a thorough
re-evaluation of the SAMI temperature response based on these results.
Secondly, we have found a variable offset in our calibration based on
intercomparisons with NOAA CMDL standards that we purchased after
completion of the A16 cruise. We are now requantifying the offset to
determine the most accurate correction to the A16 data.

![](media/image29.jpeg){width="5.471527777777778in"
height="3.834722222222222in"}

**Figure 2.5.** Comparison of the results from the two SAMIs and the
underway pCO~2~ system (Licor). See text for discussion.

References

DeGrandpre, M.D., M.M. Baehr, and T.R. Hammar, 1999: Calibration-free
optical chemical sensors. *Anal.Chem*., v. 71, pp. 1152-1159.

DeGrandpre, M.D., M.M. Baehr, and T.R. Hammar, 2000: Development of an
optical chemical sensor for oceanographic applications: The Submersible
Autonomous Moored Instrument for Seawater CO~2~. In *Chemical Sensor in
Oceanography*, M. Varney (ed.). Gordon and Breach Publ., Amsterdam, pp.
123-141.

***2.7.4. Underway Spectrophotometric Measurements of pCO~2~, TCO~2~,
and pH***

**Principal Investigator:** Robert H. Byrne, College of Marine Science

University of South Florida, 140 7^th^ Avenue South

St. Petersburg, FL 33701

byrne@marine.usf.edu

**Shipboard Analysts:** Zhaohui Aleck Wang, Research Associate

College of Marine Science, University of South Florida

140 7^th^ Avenue South, St. Petersburg, FL 33701

awang@seas.marine.usf.edu

Brittany Doupnik, Graduate Student

College of Marine Science, University of South Florida

140 7^th^ Avenue South, St. Petersburg, FL 33701

bdoupnik@marine.usf.edu

**Data Reduction:** Zhaohui Aleck Wang

**Equipment and Analytical Techniques: Underway CO~2~ System, USF:**

As part of the USF instrumental development effort, the USF automated
underway CO~2~ system was tested to simultaneously measure surface sea
water *p*CO~2~, TCO~2~, pH, and air XCO~2~. The resulting data can then
be compared to measurements either from the AOML underway LiCOR *p*CO~2~
system (surface sea water *p*CO~2~ and air XCO~2~) or discrete surface
sampling (surface sea water pH and TCO~2~) to evaluate performance.

The system consists of three sea water channels (surface sea water
*p*CO~2~, TCO~2~, and pH) and an air channel (atmospheric XCO~2~). All
measurements (four channels) are based on the same spectrophotometric
principles. The system can operate continuously with a sample period of
around 9 minutes.

Spectrophotometric pH measurements are based on the method described in
Clayton and Byrne (1993), but use thymol blue as the pH indicator (Yao
and Byrne, 2001). Sea water samples are directly injected with thymol
blue (1 mM) and changes of absorbances are monitored by a
spectrophotometer.

The method for sea water TCO~2~ measurements is based on Byrne *et al.*
(2002), while sea water *p*CO~2~ and air XCO~2~ measurements are similar
to those described in Wang *et al.* (2003) (significant differences will
be reported elsewhere). In these measurements, Teflon AF 2400 (DuPont)
is used as both a CO~2~ permeable membrane and a long liquid-core
waveguide (LCW). For the *p*CO~2~ and XCO~2~ measurements, phenol red (2
µM) is used as the indicator, while Bromcresol purple (2 µM) is used as
the indicator in TCO~2~ measurements after sea water samples are
acidified. During each measurement, the indicator solution in each of
three channels is motionless inside the LCW. The sea water or air
samples are directed to flow outside the LCW. After CO~2~ molecules
equilibrate through LCW, the internal indicator solution changes its
equilibrium pH. At equilibrium, absorbances are recorded by
spectrophotometers.

In each of four channels, three wavelengths are chosen for measurement
of absorbances. Two wavelengths assess the absorbance peaks of acid and
base forms of the indicator, while a third wavelength serves as a
reference wavelength. Absorbances vary at the acid and base wavelengths
in response to pH changes, but not at the reference wavelength.
Absorbance ratios between acid and base wavelengths are calculated, and
used to evaluate CO~2~ system parameters. The wavelengths chosen for the
four channels are listed in Table 2.15.

  -------------------- --------------- -------------- -------------- --------------
  **Table 2.15.                                                      
  Wavelengths used for                                               
  spectrophotometric                                                 
  determination of                                                   
  inorganic carbon                                                   
  species.**                                                         

  **Channel**          **Indicator**   **Acid         **Base         **Reference
                                       Wavelength**   Wavelength**   Wavelength**

  Sea water *p*CO~2~   Phenol red      434 nm         558 nm         700 nm

  Air XCO~2~           Phenol red      434 nm         558 nm         700 nm

  TCO~2~               Bromcresol      432 nm         589 nm         700 nm
                       purple                                        

  pH                   Thymol blue     435 nm         596 nm         730 nm
  -------------------- --------------- -------------- -------------- --------------

Four Ocean Optic 2000 spectrophotometers are used to detect the light
signals of the four channels. Lamps, spectrophotometers, and detecting
channels are connected through optic fibers. The light source of each
channel is custom-made with blue and IR glass filters in order to
balance the signals at the acid and base wavelengths.

Indicator and reference solutions for all measurements are stored in
aluminum bags and pumped through separate lines into their respective
channels by digital peristaltic pumps. Surface sea water is pumped on
board by a shipboard pumping system. It first flows through a Sea Bird
CTD that records salinity and temperature. Sea water samples are then
pumped through three sea water channels (*p*CO~2~, TCO~2~, and pH).
Before entering the TCO~2~ channel, sea water samples are acidified with
\~3 M HCl using another peristaltic pump. The mixing ratio is
approximately \~1000 (sea water to HCl). An in-line mixing coil is used
to facilitate mixing. Thymol blue is mixed with sea water samples for pH
measurement with a mixing ratio of \~800 (sea water to thymol blue). An
in-line mixing coil is also used in this case. Air samples are drawn
from a shipboard air sample line set up for the LiCOR IR underway
*p*CO~2~ measurement. The air flow rate is controlled at 20 \~ 30 ml/min
using a gas flow controller. Atmospheric pressure is recorded by a
barometer.

All channels are thermostated in a Lauda E100 water bath that is set to
25 ± 0.1°C. All samples, reference and indicator solutions are also
temperature pre-equilibrated in the water bath to 25°C through glass or
copper coils. All measurements, as well as calibrations, are taken at
this temperature.

All units of the system are connected to a custom-made electronic
motherboard and controlled by a laptop computer. The program run cycles
to operate the CO~2~ system continuously. The time required for each
measurement cycle varies depending on the equilibration time (5 to 7
minutes) and flushing time for the indicator/reference solution and
samples (2 to 3 minutes). The following sequence is taken during a
measurement cycle:

1.  Flush pH reference (sea water samples without indicator solution).

2.  Flush reference for *p*CO~2~, XCO~2~, and TCO~2~.

3.  Read and store reference readings.

4.  Flush indicator solutions for *p*CO~2~, XCO~2~, and TCO~2~, mix
    thymol blue with sea water samples (pH), and acidify TCO~2~ samples.

5.  *p*CO~2~, XCO~2~, TCO~2~ equilibration (5 -- 7 minutes).

6.  Read and store measurements.

7.  Repeat step 4-6 four times.

8.  End of one measurement cycle and repeat from the beginning.

During measurements, the sea water and air samples are continuously
flowing through the channels.

**Standards**:

*p*CO~2~ and XCO~2~ are calibrated every few days during the cruise
against four standard CO~2~ gases (315.25, 357.18, 380.98, and 411.42
\[or 531.98\] ppm) provided by AOML. TCO~2~ is calibrated using a
Certified Reference Material (CRM) every few days. pH is internally
calibrated in the spectrophotometric method and does not need
calibration onboard.

**Data Processing:**

The absorbance ratio R for each measurement (all four parameters) is
given as:

R = (A~2~-A~ref~)/(A~1~-A~ref~)

$\text{pH } = \text{ log }(\frac{\text{R - }\varepsilon 2(\text{HA})\varepsilon 1(\text{HA})}{\varepsilon 2(A)\varepsilon 1(\text{HA})\text{ - R} \cdot \varepsilon 1(A)\varepsilon 1(\text{HA})}) - pK\text{a2}$where
A~1~ and A~2~ are the peak absorbance at acid and base wavelengths,
respectively; and A~ref~ is the absorbance at the reference wavelength.
For all four parameters measured, R is used to calculate pH via the
following equation:

where ε~1(HA)~ and ε~2(HA)~ are the molar absorptivities of the acid
form (HA^-^) of indicator at two peak-absorbance wavelengths; ε~1(A)~
and ε~2(A)~ are the molar absorptivities of the A^2-^ (fully
unprotonated) form of indicator at two peak-absorbance wavelengths; and
K~a2~ is the second dissociation constant of the indicator used. Molar
absorptivities and K~a2~ for all indicators are determined in the
laboratory at 25°C before the cruise. They are treated as constants
since we only measure samples at 25°C.

From the above equations, pH can be directly calculated from absorbance
ratios and *p*CO~2~/XCO~2~ and TCO~2~ are calculated by referencing R to
their respective standards.

Our sea water *p*CO~2~ measurement reflects *p*CO~2~ at 25°C with 100%
water vapor content. It can be corrected for temperature and water vapor
to compare with LiCOR underway *p*CO~2~ measurement.

The precisions of all parameters measured, estimated by replicate
measurements, are given as follows:

  -------------------------------------- --------------------------------
  pH                                     ± 0.001

  XCO~2~/*p*CO~2~                        ± 1 uatm

  TCO~2~                                 ± 3 umol/kg
  -------------------------------------- --------------------------------

Details on the mathematical treatment and calculation procedure are
being prepared for publication.

**Problems:**

Due to the huge temperature difference between surface sea water and the
water bath, a 10 foot pre-heating Tygon tube was added to the sea water
sample line and resided in the water bath during the first three weeks
of the cruise. Over time, organisms grew inside this tube and
contaminated the sea water samples. This problem was identified on
February 03, 2005 and measures were taken to prevent contamination
thereafter.

The air channel experienced a drift problem throughout the cruise. After
each calibration of the air channel, the air XCO~2~ readings drifted
away from the LiCOR air XCO~2~ readings within a few days of continuous
measurement. The drift seemed to stop thereafter, and the difference
between the two systems was approximately 10 ppm. Many measures were
taken to identify the problem. Unfortunately, we did not resolve the
issue during the cruise.

References

Byrne, R.H., L. Xuewu, E. Kaltenbacher, and K. Sell, 2002:
Spectrophotometric measurement of total inorganic carbon in aqueous
solutions using a liquid core waveguide. *Anal. Chim. Acta*, v. 451, pp.
221-229.

Clayton, T.D., and R.H. Byrne, 1993: Spectrophotometric seawater pH
measurements: Total hydrogen ion concentration scale calibration of
m-cresol purple and at-sea results. *Deep-Sea Res.,* v. 40, pp.
2315-2329.

Wang, Z.A., W. Cai, Y. Wang, and B.L. Upchurch, 2003: A long pathlength
liquid-core waveguide sensor for real-time *p*CO~2~ measurements at sea.
*Mar. Chem.*, v. 84, pp. 73-84.

Yao, W. and R.H. Byrne, 2001: Spectrophotometric determination of
freshwater pH using bromocresol purple and phenol red. *Environ. Sci.
Technol.*, v. 35, pp. 1197-1201.

**2.8. Aerosol Sampling**

**Principal Investigator:** Anne M. Johansen, Central Washington
University

Department of Chemistry, 400 East University Way

Ellensburg, WA 98926-7539

Phone: (509) 963-2164; Fax: (509) 963-1050

johansea@cwu.edu

**Sampler:** Matt Lenington

Central Washington University

Phone: (509) 963-1086

leningtm@cwu.edu

**Aerosol Sampling Setup:**

Atmospheric aerosols and acidic gases were collected with two types of
collectors: 1) A high volume cascade impactor (ChemVol Model 2400,
Rupprecht and Patashnik) to separate aerosols into four size fractions
(large particles (\>10 um aerodynamic diameter (AD)), coarse particles
(10 to 1 um AD), fine particles (1 to 0.1 um AD), and ultrafine
particles (\< 0.1 um AD)), and 2) Two low volume collectors to collect
total suspended particulates (TSP) and acidic gaseous species in a
filter pack configuration. On the first part of the leg, to
approximately 30°S, these collectors were located on the O~3~ deck
forward of the captain's cabin to avoid excessive seaspray from reaching
the collector. However, this location turned out to be unsatisfactory
due to eddying of the air and once the seas got milder (north of 30°S)
the whole setup was moved forward and down to the forward edge of the
O~2~ deck to assure the collection of uncontaminated air.

The vacuum pumps for the collectors were controlled by a datalogger
through a series of relay boxes whereby they were automatically shut off
when rain was sensed with a rain sensor or when the wind speed and
direction were unfavorable as determined by a weather vane; the low
limit wind speed cut-off was 0.2 m s^-1^ and, while the wind direction
varied throughout the trip, a guideline of 60 degrees in either
direction off the bow was used to set the limits.

Flow rates on the high volume collector were determined by measuring the
pressure drop across a critical orifice. A valve was used to adjust the
flowrate to 760+-5% L min^-1^ to ensure correct size fractionation. The
flow rate for the low volume collectors was fixed with a critical
orifice to approximately 12 L min^-1^ and checked with a flowmeter.

Although the goal was to collect daily samples, collection periods had
to be adjusted due to two factors: low ambient concentrations of
particulates in the southern part of the Atlantic Ocean and the reduced
collection times due to rain (or heavy fog) and the wind direction being
out of sector. A collection time of 30 hours per set of filters was used
as a guideline to collect enough material to ensure analysis above
detection limits. Typically, sample change occurred at dawn.

**Substrate Handling and Storage:**

All sample handling was carried out in a laminar flow hood with HEPA
filtration and all substrates had been precleaned in lab following
established procedures. For the high volume collector flat segments of
polyurethane foam (PUF) were used for the impaction of particles in the
three larger size fractions. These are rings of PUF of varying width,
depending on the size fraction. The outer diameter is approximately 17
cm. The final collection stage (i.e., for the ultrafine particles) is
based on filtration through a multilayer polypropylene filter of
approximately 17 cm diameter. Storage of these substrates required
cutting into segments that could be placed in precleaned polystyrene
Petri dishes of 15 and 9 cm diameter. Cutting was performed with ceramic
scissors or ceramic exacto knives on a sheet of Teflon. For the low
volume collectors, a 47 mm diameter Teflon membrane filter was used to
collect particles followed by two carbonate impregnated paper filters in
series to trap acidic gaseous species. These filters were stored in 47
mm polystyrene Petri dishes. All Petri Dishes were sealed with Teflon
tape, doubly bagged and stored in the freezer.

Samples were sent to the lab overnight on ice in coolers and are stored
in a freezer until analysis.

**Analysis:**

16 sets of samples were collected. Since each sample set consists of 4
high volume and 6 low volume substrates, overall there are 16x10 = 160
aerosol samples. In addition, 5 sets of field blanks were obtained,
amounting to a total of 210 samples that will be analyzed with the
following procedures.

Chemical analysis on all high volume size fractions will consist of iron
speciation with long pathlength UV-Vis, trace metals with ICP-MS, and
anions and cations with IC. The Teflon filters from the low volume
collectors will be weighed (they were preweighed in a microbalance
before the trip) and analyzed for trace metals and anions and cations.
The carbonate impregnated filters will be analyzed for anions of the
corresponding acidic gases. These analyses are expected to be carried
out within a year. Subsequently, data will be analyzed statistically
with principal component and linear regression analyses and interpreted
in conjunction with air mass trajectories computed with HYSPLIT.

Furthermore, during this cruise, blue agar plates were inoculated with
extracts of filter from 10 different samples sections in an attempt to
look for siderophore producing microorganisms in the remote marine
atmosphere. The blue plates did turn orange for most of the inoculations
thus indicating the production of siderophores. As of now (Aug 05) these
organisms have been further cultured and are being characterized.

This study is part of a project (NSF-ATM 0137891) to further elucidate
mechanisms that influence iron speciation, and thus iron
bioavailability, in aerosol particles over the remote open oceans.