ORNL/CDIAC-150

NDP-086

DETERMINATION OF CARBON DIOXIDE, HYDROGRAPHIC, AND CHEMICAL PARAMETERS
DURING THE R/V *NATHANIEL B. PALMER* CRUISE

IN THE SOUTHERN INDIAN OCEAN (WOCE SECTION S04I, 3 MAY--[4
J]{.smallcaps}ULY, 1996)

Contributed by

Taro Takahashi,^1^ Frank Millero,^2^ Robert Key,^3^ David Chipman,^1^
Esa Peltola,^2^ Stefany Rubin,^1^

Colm Sweeney,^1^ and Stewart Sutherland^1^

^1^Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY

^2^Rosentiel School of Marine and Atmospheric Research, University of
Miami, Miami, FL

^3^Princeton University, Princeton, NJ

Prepared by

Alex Kozyr

Carbon Dioxide Information Analysis Center

Oak Ridge National Laboratory

Oak Ridge, Tennessee, USA

Date Published: March 2006

Prepared for the Climate Change Research Division

Climate Change Research Division

Office of Biological and Environmental Research

U.S. Department of Energy

Budget Activity Numbers KP 12 04 01 0 and KP 12 02 03 0

Prepared by the

Carbon Dioxide Information Analysis Center

OAK RIDGE NATIONAL LABORATORY

Oak Ridge, Tennessee 37831-6335

managed by

UT-BATTELLE, LLC

for the

U.S. DEPARTMENT OF ENERGY

under contract DE-AC05-00OR22725

# CONTENTS

LIST OF FIGURES v

LIST OF TABLES vii

ABBREVIATIONS AND ACRONYMS ix

ABSTRACT xi

1\. BACKGROUND INFORMATION 1

2\. DESCRIPTION OF THE EXPEDITION 2

2.1 R/V *Nathaniel B. Palmer* Technical Details 2

2.2 R/V *Nathaniel B. Palmer* S04I Cruise Information 4

2.3 Brief Cruise Summary 5

3\. DESCRIPTION OF VARIABLES AND METHODS 5

3.1 Hydrographic Measurements 5

3.2 Total CO~2~ Measurements 6

3.3 Total Alkalinity Measurements 11

3.3.1 Titration total alkalinity, total CO~2~, and pH measurement
results 12

3.4 Discrete pCO~2~ Measurements 23

3.4.1 Comparison of observed and calculated pCO~2~ 25

3.4.2 Comparison of observed and calculated total alkalinity 29

3.5 Radiocarbon Measurements 30

3.5.1 Radiocarbon data summary 31

4\. HOW TO OBTAIN THE DATA AND DOCUMENTATION 36

5\. REFERENCES 36

# LIST OF FIGURES

1 Cruise track during the R/V *Nathaniel B. Palmer* Indian Ocean section
of the Southern\
Ocean survey expedition along WOCE section S04I. 1

2 Change in the coulometer calibration factor as a function of the
amount of CO~2~ titrated. 9

3 The results of TCO~2~ analyses of the certified reference solutions
using the coulometer\
during the expedition. 10

4 Deviations of total alkalinity for certified reference material over
the course of the cruise. 13

5 Deviations of total CO~2~ for certified reference material over the
course of the cruise. 14

6 Deviations of pH for certified reference material over the course of
the cruise. 14

7 Differences in total alkalinity of cells 18 and 19 over the course of
the cruise using\
reference surface water. 15

8 Differences in total CO~2~ of cells 18 and 19 over the course of the
cruise using reference\
surface water. 15

9 Differences in pH of cells 18 and 19 over the course of the cruise
using reference surface water. 16

10 Sample replicates of total alkalinity, total CO~2~, and pH on cell 18
17

11 Sample replicates of total alkalinity, total CO~2~, and pH on cell 19
18

12 Cell to cell replicate measurements of total alkalinity, total CO~2~,
and pH 19

13 Surface water total alkalinity and total CO~2~ for each station. 20

14 Linear relationship between surface total alkalinity and salinity. 20

15 Normalized surface water total alkalinity and total CO~2~. 21

16 Measured total alkalinity vs. depth. 21

17 Measured total CO~2~ vs. depth. 22

18 Measured pH vs. depth. 22

19 Difference between the observed and computed pCO~2~ values at 4°C as
a function of the measured pCO~2~ values. 26

20 Difference between the observed and computed pCO~2~ values at 4°C as
a function of the measured TCO~2~ values. 27

21 Difference between the observed and computed pCO~2~ values at 4°C as
a function of the measured total alkalinity/total CO~2~ ratio. 28

22 Difference between the observed and computed total alkalinity values
is plotted against\
the measured total CO~2~/total alkalinity in seawater. 29

23 AMS ^14^C station map for WOCE Section S04I. 30

24 Δ^14^C results for S04I stations shown with 2σ error bars. 32

25 Δ^14^C as a function of silicate for S04I AMS samples. 33

26 Samples that plot above the line and have potential alkalinity values
less than about 2400 mol/kg are contaminated with bomb-produced ^14^C.
33

27 ^14^C concentrations along the main east-west section of S04I at
approximately 62S are indicated by color 34

28 ^14^C along \~65°E near the Antarctic slope. 34

29 ^14^C along \~90°E near the Antarctic slope 35

# LIST OF TABLES

1 Detailed description of R/V *Nathaniel B. Palmer* 2

2 Comparison of LDEO shipboard analyses with SIO shore-based manometric
analyses 8

3 Specification of the CRM batch 31 (November 25, 1996) 10

4 Summary of the CRM Measurements. 13

5 Summary of Replicate Analyses 31

# ABBREVIATIONS AND ACRONYMS

ALACE autonomous Lagrangian circulation explorer

AMS Accelerator Mass Spectrometry

^14^C radiocarbon

CDIAC Carbon Dioxide Information Analysis Center

CFC chlorofluorocarbon

CO~2~ carbon dioxide

CRM certified reference material

CTD conductivity, temperature, and depth sensor

DMSO dimethylsulfoxide

DOE U.S. Department of Energy

GC gas chromatograph, gas chromatography

GO General Oceanic

JGOFS Joint Global Ocean Flux Study

LADCP lower acoustic Doppler current profiler

LDEO Lamont-Doherty Earth Observatory

NDP numeric data package

NOAA National Oceanic and Atmospheric Administration

NOSAMS National Ocean Sciences AMS Facility

NSF National Science Foundation

NTA normalized total alkalinity

ODF oceanographic data facility

ORNL Oak Ridge National Laboratory

pCO~2~ partial pressure of CO~2~

PU Princeton University

QA quality assurance

QC quality control

RSMAS Rosentiel School of Marine and Atmospheric Research

R/V research vessel

SIO Scripps Institution of Oceanography

SOMMA single-operator multi-parameter metabolic analyzer

TALK total alkalinity

TAMU Texas A&M University

TCO~2~ total carbon dioxide

UH University of Hawaii

UM University of Miami

UW University of Washington

WHOI Woods Hole Oceanographic Institution

WHP WOCE Hydrographic Program

WOCE World Ocean Circulation Experiment

# ABSTRACT

Takahashi, T., F. Millero, D. Chipman, E. Peltola, S. Rubin, C. Sweeney,
and S. Sutherland, 2005. Determination of Carbon Dioxide, Hydrographic,
and Chemical Parameters during the R/V *Nathaniel B. Palmer* Cruise in
the Southern Indian Ocean (WOCE Section S04I, 3 May--[4
J]{.smallcaps}uly, 1996), ed. A. Kozyr. ORNL/CDIAC-150, NDP-086. Carbon
Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S.
Department of Energy, Oak Ridge, Tennessee, 50 pp.

This report discusses the procedures and methods used to measure total
carbon dioxide (TCO~2~), total alkalinity (TALK), and partial pressure
of CO~2~ (pCO~2~) at hydrographic stations during the cruise of research
vessel (R/V) *Nathaniel B. Palmer* in the Southern Indian Ocean on the
S04I Section as a part of the Joint Global Ocean Flux Study
(JGOFS)/World Ocean Circulation Experiment (WOCE). The carbon-related
measurements were sponsored by the U.S. Department of Energy (DOE). The
expedition started in Cape Town, South Africa, on May 3, 1996, and ended
in Hobart, Australia, on July 4, 1996. Instructions for accessing the
data are provided.

The TCO~2~ was measured in discrete water samples using the
Lamont-Doherty Earth Observatory (LDEO) coulomteric system with an
overall precision of 1.7 µmol/kg. TALK was determined by potentiometric
titration with an overall precision of 1.7 µmol/kg. During the S04I
cruise pCO~2~ was also measured using the LDEO equilibrator-gas
chromatograph system with a precision of 0.5% (including the
station-to-station reproducibility) at a constant temperature of 4.0ºC

The R/V *Nathaniel B. Palmer* S04I data set is available free of charge
as a numeric data package (NDP) from the Carbon Dioxide Information
Analysis Center. The NDP consists of the oceanographic data files and
this printed documentation, which describes the contents and format of
all files as well as the procedures and methods used to obtain the data.

**Keywords**: carbon dioxide, TCO~2~, TALK, partial pressure of CO~2~,
carbon cycle, coulometry, potentiometry, hydrographic measurements,
World Ocean Circulation Experiment.

# 1. BACKGROUND INFORMATION

The World Ocean Circulation Experiment--World Hydrographic Program
(WOCE-WHP) was a major component of the World Climate Research Program.
The primary goal of WOCE was to understand the general circulation of
the global ocean well enough to be able to model its present state and
predict its evolution in relation to long-term changes in the
atmosphere. The need for carbon system measurements arose from the
serious concern over the rising atmospheric concentrations of carbon
dioxide (CO~2~). Increasing atmospheric CO~2~ may intensify the earth's
natural greenhouse effect and alter the global climate.

Although CO~2~-related measurements---specifically, total CO~2~
(TCO~2~), total alkalinity (TALK), partial pressure of CO~2~ (pCO~2~),
and pH---were not official WOCE measurements, a coordinated effort was
supported as a core component of the Joint Global Ocean Flux Study
(JGOFS). This effort received support in the United States from the U.S.
Department of Energy (DOE), the National Oceanic and Atmospheric
Administration (NOAA), and the National Science Foundation (NSF).

This report discusses results of the research vessel (R/V) *Nathaniel B.
Palmer* expedition along the WOCE Section S04I. The cruise started from
Cape Town, South Africa, on May 3, 1996, and disembarked at Hobart,
Australia, on July 4, 1996. The ship occupied 108 stations along
60--62°S latitude from 20°E to 120E meridian, plus two north-to-south
sections south from this line to the Antarctic continental shelf (Fig.
1).

+-----------------------------------------------------------------------+
| ![](media/image1.jpeg){width="6.001388888888889in"                    |
| height="3.754861111111111in"}                                         |
+-----------------------------------------------------------------------+
| > Fig. 1. Cruise track during the R/V *Nathaniel B. Palmer* Indian    |
| > Ocean section of the Southern Ocean survey expedition along WOCE    |
| > section S04I.                                                       |
+-----------------------------------------------------------------------+

This cruise had the following objectives:

-   To better constrain the fluxes of carbon, both organic and
    inorganic, in the Southern Ocean and to place these fluxes into the
    context of the contemporary global carbon cycle. There is a great
    interest in understanding the CO~2~ system in the oceans because of
    the so-called greenhouse effect of CO~2~ on the climate.
    Approximately 30% of CO~2~ added to the atmosphere from the burning
    of fossil fuels is thought to be going into the oceans.

-   To identify the factors and processes which regulate the magnitude
    and variability of primary productivity, as well as the fate of
    biogenic materials.

-   To determine how the Southern Ocean has responded in the past to
    naturally occurring climate changes.

-   To monitor and predict the response of the Southern Ocean to global
    climate change.

The measurements along S04I section provide a rare look at the far south
Indian Ocean in an oceanographically important time of year, when the
sea surface is cooling and dissolved gases and other properties are
being mixed downward.

# 

# 2. DESCRIPTION OF THE EXPEDITION

## 2.1 R/V *Nathaniel B. Palmer* Technical Details

The R/V *Nathaniel B. Palmer* is a large icebreaker in the service of
the U.S. National Science Foundation. It is tasked with extended
scientific missions in the Antarctic. The vessel carries a helicopter
and about four dozen scientists on expeditions that last for months. The
vessel is named after the first American credited with sighting
Antarctica. This R/V, built for the NSF and launched in 1992, is
chartered and operated by the Raytheon Company. Table 1 provides a
detailed description of the ship.

+---------------------+------------------------------------------------+
| Table 1. Detailed   |                                                |
| description of R/V  |                                                |
| *Nathaniel B.       |                                                |
| Palmer*             |                                                |
+=====================+================================================+
| Ship Specifications |                                                |
+---------------------+------------------------------------------------+
| **General**         |                                                |
+---------------------+------------------------------------------------+
| Type of vessel:     | Antarctic Research Vessel Ice Breaker          |
+---------------------+------------------------------------------------+
| Classification:     | ABS A1, AMS, E, ACC, Ice Class A2              |
+---------------------+------------------------------------------------+
| Ice-breaking        | 3 ft of ice at 3 knots                         |
| capability:         |                                                |
+---------------------+------------------------------------------------+
| Year of             | 1992                                           |
| construction:       |                                                |
+---------------------+------------------------------------------------+
| Builder:            | North American Shipbuilding, Larose, Louisiana |
+---------------------+------------------------------------------------+
| **Principal         |                                                |
| Dimensions**        |                                                |
+---------------------+------------------------------------------------+
| Length overall:     | 308 ft (93.9 meters)                           |
+---------------------+------------------------------------------------+
| Breadth (molded):   | 60 ft (18.3 meters)                            |
+---------------------+------------------------------------------------+
| Depth:              | 30 ft (9.1 meters)                             |
+---------------------+------------------------------------------------+
| Maximum draft (load | 19.417 ft (5.9 meters)                         |
| line):              |                                                |
+---------------------+------------------------------------------------+
| Main science deck   | 9 ft above water surface                       |
| (aft):              |                                                |
+---------------------+------------------------------------------------+
| Pilot house:        | 54 ft above water surface                      |
+---------------------+------------------------------------------------+
| Aloft observation   | 80 ft above water surface                      |
| station (deck       |                                                |
| height):            |                                                |
+---------------------+------------------------------------------------+
| Helicopter hangar:  | 40 ft × 32 ft. (1300 sq. ft)                   |
+---------------------+------------------------------------------------+
| Flight deck:        | 54 ft × 44 ft. (2500 sq. ft)                   |
+---------------------+------------------------------------------------+
| **Main Propulsion   |                                                |
| Machinery**         |                                                |
+---------------------+------------------------------------------------+
| Installed power:    | 12,720 hp from four Caterpillar Diesels        |
+---------------------+------------------------------------------------+
| Propeller diameter  | 13.12 ft (4.0 meters)                          |
+---------------------+------------------------------------------------+
| **Bow Thruster**    |                                                |
+---------------------+------------------------------------------------+
| Rating:             | 1400 BHP, 1050 KW                              |
+---------------------+------------------------------------------------+
| **Stern Thruster**  |                                                |
+---------------------+------------------------------------------------+
| Rating:             | 800 HP, 1050 KW                                |
+---------------------+------------------------------------------------+
| **Tank Capacities** |                                                |
+---------------------+------------------------------------------------+
| Fuel capacity:      | 425,000 U.S. gal (1,608,795 L)                 |
+---------------------+------------------------------------------------+
| Helicopter fuel     | 7,200 U.S. gal (27,250 L)                      |
| capacity:           |                                                |
+---------------------+------------------------------------------------+
| Endurance:          | 75 days                                        |
+---------------------+------------------------------------------------+
| **Accommodations**  |                                                |
+---------------------+------------------------------------------------+
| Crew:               | 22                                             |
+---------------------+------------------------------------------------+
| Scientists and      | 43                                             |
| staff:              |                                                |
+---------------------+------------------------------------------------+
| Owner:              | 5                                              |
+---------------------+------------------------------------------------+
| Spare:              | 2                                              |
+---------------------+------------------------------------------------+
| Total               | 72                                             |
| Accommodations:     |                                                |
+---------------------+------------------------------------------------+
| Facilities          |                                                |
| available for an    |                                                |
| emergency personnel |                                                |
| increase of 35      |                                                |
| people:             |                                                |
+---------------------+------------------------------------------------+
| **Boating Support** |                                                |
+---------------------+------------------------------------------------+
| Zodiac Mark V with  | 2 onboard                                      |
| 45-hp outboard      |                                                |
| motor:              |                                                |
+---------------------+------------------------------------------------+
| **Work Boat**       |                                                |
+---------------------+------------------------------------------------+
| Length:             | 28.8 ft. (8.8 m)                               |
+---------------------+------------------------------------------------+
| Breadth:            | 10.75 ft. (3.3 m)                              |
+---------------------+------------------------------------------------+
| **Miscellaneous**   |                                                |
+---------------------+------------------------------------------------+
| -   Drinking water  |                                                |
|     made from       |                                                |
|                     |                                                |
|   seawater\--12,000 |                                                |
|     gal/day maximum |                                                |
|     production      |                                                |
|                     |                                                |
| -                   |                                                |
|    Water/antifreeze |                                                |
|     mixture         |                                                |
|     circulated      |                                                |
|     under working   |                                                |
|     decks to        |                                                |
|     prevent         |                                                |
|     freezing and    |                                                |
|     ice build-up    |                                                |
|                     |                                                |
| -   Steel plate in  |                                                |
|     the bow is 1 ft |                                                |
|     9/16 in. thick  |                                                |
|     and is twice    |                                                |
|     the strength of |                                                |
|     regular steel   |                                                |
|                     |                                                |
| -   Hull steel made |                                                |
|     of a special    |                                                |
|     low-temperature |                                                |
|     alloy that can  |                                                |
|     withstand       |                                                |
|     temperatures of |                                                |
|     −60ºC           |                                                |
|                     |                                                |
| -   Total           |                                                |
|     electrical      |                                                |
|     generating      |                                                |
|     capacity, 4.63  |                                                |
|     million watts   |                                                |
|                     |                                                |
| -   Vessel is       |                                                |
|     capable of      |                                                |
|     carrying twenty |                                                |
|     20-ft cargo     |                                                |
|     containers      |                                                |
+---------------------+------------------------------------------------+

##  

## 2.2 R/V *Nathaniel B. Palmer* S04I Cruise Information

  ---------------------- ------------------------------------------------
  Ship Name              *Nathaniel B. Palmer*

  EXPOCODE               320696_3

  WOCE section           S04I

  Ports of call          Cape Town, South Africa; Hobart, Australia

  Dates                  May 3--July 4, 1996

  Funding support        NSF, DOE

  Chief scientist        Dr. Thomas Whitworth III, Texas A&M University
  ---------------------- ------------------------------------------------

Parameters measured, institution, and responsible investigators

+---------------------+--------------------+--------------------------+
| **Parameter**       | **Institution**    | **Responsible            |
|                     |                    | Personnel**              |
+---------------------+--------------------+--------------------------+
| CTD                 | SIO                | J. Swift                 |
+---------------------+--------------------+--------------------------+
| Bottle sal., oxy.   | SIO                | J. Swift                 |
| nutrients           |                    |                          |
+---------------------+--------------------+--------------------------+
| ALACE floats        | SIO                | R. Davis                 |
+---------------------+--------------------+--------------------------+
| LADCP               | UH                 | E. Firing/P. Hacker      |
+---------------------+--------------------+--------------------------+
| CFCs                | LDEO/ UW           | W. Smethie/M. Warner     |
+---------------------+--------------------+--------------------------+
| Current meters      | TAMU               | W. Nowlin/T. Whitworth   |
+---------------------+--------------------+--------------------------+
| Transmissometer     | TAMU               | W. Gardner               |
+---------------------+--------------------+--------------------------+
| Tritium, He         | LDEO               | P. Schlosser             |
+---------------------+--------------------+--------------------------+
| ^14^C               | PU                 | R. Key                   |
+---------------------+--------------------+--------------------------+
| TCO~2~ , pCO~2~     | LDEO               | T. Takahashi             |
+---------------------+--------------------+--------------------------+
| TALK                | RSMAS/UM           | F. Millero               |
+---------------------+--------------------+--------------------------+
| ALACE = autonomous  |                    |                          |
| Lagrangian          |                    |                          |
| circulation         |                    |                          |
| explorer            |                    |                          |
|                     |                    |                          |
| CTD = conductivity, |                    |                          |
| temperature, and    |                    |                          |
| depth sensor        |                    |                          |
|                     |                    |                          |
| TAMU = Texas A&M    |                    |                          |
| University          |                    |                          |
|                     |                    |                          |
| SIO = Scripps       |                    |                          |
| Institution of      |                    |                          |
| Oceanography        |                    |                          |
+---------------------+--------------------+--------------------------+

Participating institutions

  -------------------- --------------------------------------------------
  SIO                  Scripps Institution of Oceanography

  TAMU                 Taxes A&M University

  LDEO                 Lamont-Doherty Earth Observatory

  UW                   University of Washington

  PU                   Princeton University

  UH                   University of Hawaii

  RSMAS/UM             Rosentiel School of Marine and Atmospheric
                       Research, University of Miami
  -------------------- --------------------------------------------------

## 2.3 Brief Cruise Summary

The S04I section constituted the Indian Ocean portion of WOCE line S04,
a meridional circumnavigation of Antarctica at a nominal latitude of
60°S. This segment covered the longitudes from 20°E to 120°E. R/V
*Nathaniel B. Palmer* departed Cape Town, South Africa, on May 3, 1996.
The cruise track proceeded south to near 58°S and 20°E where station
occupations began on May 16. The first station line was run southeast to
Gunnerus Ridge, about 50 miles south of the ice edge (see Fig.1). During
the transit to station 1 and continuing to 58°S, 17 autonomous
Lagrangian circulation explorer (ALACE) floats were launched. Stations
across the Enderby Abyssal Plain trended east-northeast from 66°S at
33°E to 61°S at 83°E on the Kerguelen Plateau. A line of stations
(35--42) was made north from the 500-m isobath on the continental slope
at 53°E, and three self-reporting current meters were deployed along the
slope. A line of stations (65--72) extending east from the crest of the
Kerguelen Plateau was made at about 59°S, and three more current meters
were placed in the boundary current on the eastern flank of the plateau.
On June 8, after station 72, science operations were suspended for seven
days when R/V *Nathaniel B. Palmer* was diverted to Mirnyi Station in
the Davis Sea to deliver emergency food supplies.

On June 14, R/V *Nathaniel B. Palmer* left Mirnyi and began a line of
stations (73--86) from the shelf break of the Davis Sea to Kerguelen
Plateau. One current meter was placed near the 3000-m isobath north of
the Antarctic Continental Slope, and two were deployed at the southern
end of Kerguelen Plateau. The zonal line of stations at a nominal
latitude of 62°S was resumed at 90°E. Ice conditions and fuel and time
considerations necessitated 45-mile station separation for most of the
final 22 stations. The last station, No. 108, was sampled at 120°E on
June 27, and *Nathaniel B. Palmer* then transited directly to Hobart,
Australia, arriving on July 7, 1996. For more information on the cruise
please see the chief scientist cruise report at
http://whpo.ucsd.edu/data/onetime/southern/s04/s04i/s04ido.txt.

# 3. DESCRIPTION OF VARIABLES AND METHODS

## 3.1 Hydrographic Measurements

The basic hydrography program consisted of salinity, dissolved oxygen,
and nutrient (nitrite, nitrate, phosphate, and silicate) measurements
made from bottles taken on CTD/rosette casts, plus pressure,
temperature, salinity, and dissolved oxygen from CTD profiles. Overall,
109 CTD/rosette casts were made at 108 stations, usually to within 5--15
meters of the bottom. Station 2 cast 1 was aborted at the surface
because of signal failure at 322 m on the down-cast. Water was found
inside the CTD case; after repairs, station 2 cast 2 was successfully
accomplished. Hydrographic casts were performed with a rosette system
consisting of a 36-bottle rosette frame \[Oceanographic Data Facility
(ODF)\], a General Oceanics (GO) 36-place pylon (Model 2216) and
thirty-six 10-L PVC bottles (ODF). Underwater electronic components
consisted of an ODF-modified NBIS Mark III CTD (ODF #3) and associated
sensors, SeaTech transmissometer \[Texas A&M University (TAMU)\] and
Benthos pinger (Model 2216).

Two Guildline Autosal Model 8400A salinometers were available for
measuring **salinities**. The salinometers were modified by ODF and
contained interfaces for computer-aided measurement. Autosal No.55-654
was used to measure salinity on all stations. Its water bath temperature
was set and maintained at 24ºC for all runs except stations 32--39,
where the bath temperature was set at 21ºC. The salinity analyses were
performed when samples had equilibrated to laboratory temperature,
within 7--28 hours after collection. The salinometer was standardized
for each group of analyses (typically one cast, usually 36 samples)
using two fresh vials of standard seawater per group. A computer (PC)
prompted the analyst for control functions such as changing sample,
flushing, or switching to "read" mode. At the correct time, the computer
acquired conductivity ratio measurements and logged results. The sample
conductivity was redetermined until readings met software criteria for
consistency. Measurements were then averaged for a final result.

Dissolved **oxygen** analyses were performed with an ODF-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 PC software.
Thiosulfate was dispensed by a Dosimat 665 burette driver fitted with a
1.0-mL burette. ODF used a whole-bottle modified-Winkler titration
following the technique of Carpenter (1965) with modifications by
Culberson *et al.* (1991), but with higher concentrations of potassium
iodate standard (approximately 0.012N) and thiosulfate solution (50
gm/L). Carbon disulfide was added to the thiosulfate as a preservative.
Standard solutions prepared from pre-weighed potassium iodate crystals
were run at the beginning of each session of analyses, which typically
included from 1 to 3 stations. Nine standards were made up during the
cruise and compared to ensure that the results were reproducible, and to
preclude the possibility of a weighing or dilution error.
Reagent/distilled water blanks were determined to account for presence
of oxidizing or reducing materials.

**Nutrient** analyses (phosphate, silicate, nitrate, and nitrite) were
performed on an ODF-modified 4-channel Technicon AutoAnalyzer II,
generally within a few hours after sample collection. Occasionally
samples were refrigerated up to a maximum of 8 hours at 2ºC to 6 ºC. All
samples were brought to room temperature prior to analysis. The methods
used are described by Gordon *et al.* (1993). The analog outputs from
each of the four channels were digitized and logged automatically by
computer (PC) at 2-second intervals.

Silicate was analyzed using the technique of Armstrong *et al.* (1967).
An acidic solution of ammonium molybdate was added to a seawater sample
to produce silicomolybdic acid, which was then reduced to
silicomolybdous acid (a blue compound) following the addition of
stannous chloride. Tartaric acid was also added to impede PO~4~ color
development. The sample was passed through a 15-mm flowcell and the
absorbance measured at 660 nm.

A modification of the Armstrong *et al.* (1967) procedure was used for
the analysis of nitrate and nitrite. For the nitrate analysis, the
seawater sample was passed through a cadmium reduction column where
nitrate was quantitatively reduced to nitrite. Sulfanilamide was
introduced to the sample stream followed by N-(1-naphthyl)
ethylenediamine dihydrochloride, which coupled to form a red azo dye.
The stream was then passed through a 15-mm flowcell and the absorbance
measured at 540 nm. The same technique was employed for nitrite
analysis, except the cadmium column was bypassed, and a 50-mm flowcell
was used for measurement.

Phosphate was analyzed using a modification of the Bernhardt and
Wilhelms (1967) technique. An acidic solution of ammonium molybdate was
added to the sample to produce phosphomolybdic acid, then reduced to
phosphomolybdous acid (a blue compound) following the addition of
dihydrazine sulfate. The reaction product was heated to \~55 ºC to
enhance color development then passed through a 50-mm flowcell and the
absorbance measured at 820 nm.

## 3.2 Total CO~2~ Measurements

The coulometric analysis system used to measure the total CO~2~ (TCO~2~)
concentration in seawater samples during this cruise was the same as
described in Chipman *et al.* (1993) and Takahashi *et al.* (1998),
except for the way the sample was introduced. The system consists of a
Model 5011 coulometer, manufactured by UIC Inc., Jolliet, IL, and a
sample introduction/CO~2~ extraction system of a Lamont-Doherty Earth
Observatory (LDEO) CO~2~ Group design. It differs from the
single-operator multi-parameter metabolic analyzer (SOMMA) system used
by other participants of the DOE/CO~2~ program. In the LDEO system, the
titration cell was maintained at a constant temperature (about 25°C)
using a water-jacketed cell to prevent drifts of the titration end
point. The temperature of the water circulating through the jacket was
kept at a constant temperature by a temperature-controlled heat
exchanger system. A precisely known volume of seawater sample was
introduced manually into a CO~2~ extraction vessel using a calibrated
syringe instead of the automated pipette used by the SOMMA system. The
syringe is a hand-ground Pyrex glass medical syringe with two firm
reference stops which allow the quantitative sampling of seawater. Our
experience with syringe and pipette methods is that accumulated coatings
on the glass surfaces from repeatedly being filled with and emptied of
seawater would not significantly affect the volume contained of either,
but that it will affect the volume delivered by the passively drained
pipette in the SOMMA system. The positive displacement of the plunger of
a syringe keeps the delivered volume constant, even in the presence of
surface coatings. Additionally, since the water sample in the syringe
has no air space, changes in TCO~2~ due to gas exchange with air in the
head space are eliminated. Unlike the SOMMA, our system allows multiple
samples from the same bottle. We can test the reproducibility of either
certified reference material (CRM) or seawater samples by taking two or
more samples with the syringes. For this reason, the total number of
analyses for CRM on the LDEO system was three times greater than if
SOMMA were used.

Samples for TCO~2~ analysis were drawn from the Niskin bottles of the
rosette casts directly into 250-mL glass reagent bottles with ground
standard-taper stoppers, sealed with silicone grease and pressed in
using two strong rubber bands. Immediately after sample collection, 200
L of 50%-saturated mercuric chloride solution was added to prevent
biological alteration of the TCO~2~. A small head space (\~5 mL) was
left in the bottle to prevent thermal expansion of the water from
causing a leak or breaking the bottle. Samples were normally analyzed
within 24 hours of collection. For analysis, a water sample was sucked
into a syringe, and a calibrated volume (19--20 mL) of water sample was
introduced into a CO~2~ extraction chamber through a rubber septum. The
mass of the seawater sample delivered was determined from the density of
seawater, calculated using the measured salinity, the temperature at the
time of injection, and the International Equation of State of Seawater.
Prior to the expedition, the volume of each sampling syringe between two
reference stops was determined by repeatedly weighing aliquots of
distilled, deionized water dispensed. The measurements were corrected
for the buoyancy of air displaced by the water, amounting to about 0.1%
of the weight of the water. The volume was then computed using the
density of pure water at the temperature of the measurement. Repeated
measurements gave a precision of ±0.03% or better.

The seawater sample in the extraction vessel was acidified with \~1 mL
of 8.5% phosphoric acid introduced through a sidearm of the extraction
chamber. The evolved CO~2~ was stripped from the sample and transferred
into the electrochemical cell of the CO~2~ coulometer by a stream of
CO~2~-free air. In the coulometer cell, the CO~2~ was quantitatively
absorbed by a solution of ethanolamine in dimethylsulfoxide (DMSO).
Reaction between the CO~2~ and the ethanolamine formed the weak
hydroxyethylcarbamic acid. The pH change of the solution associated with
the formation of this acid resulted in a color change of the
thymolphthalein pH indicator in the solution. The color change, from
deep blue to colorless, was detected by a photodiode which continuously
monitored the transmissivity of the solution. The electronic circuitry
of the coulometer, in detecting the change in the color of the pH
indicator, caused an electrical current to flow through the cell,
generating hydroxyl (OH^-^) ions from a small amount of water in the
solution. The OH^-^ generated, then titrated the acid, returning the
solution to its original pH and color, at which point the current flow
was stopped. The product of current passed through the cell and time was
related by the Faraday constant to the number of moles of OH^-^
generated, and hence to the number of moles of CO~2~ absorbed to form
the acid. A thermostated, double-walled titration cell was used during
titration to eliminate the shifting of the titration endpoint due to a
change in the temperature of the cell solutions.

The coulometer was calibrated using research grade CO~2~ gas (99.998%
pure) introduced into the carrier gas line upstream of the extraction
chamber alternately using two fixed-volume sample loops on a
gas-sampling valve. The loops were vented to the atmosphere, and the
ambient atmospheric pressure in the laboratory was measured using a
high-precision electronic barometer with an accuracy of better than
0.05%. The loop temperatures were measured to ±0.05°C with a thermometer
calibrated against one traceable to the NIST. The non-ideality of CO~2~
was incorporated into the computation of the loop contents. Prior to the
expeditions, the volumes of the loops were determined by the difference
in weight of the loop injection valve assembly when empty and when
filled with water. Repeated measurements gave a precision of ±0.02%.
During the expedition the coulometer was calibrated several times a day
using this gas-sampling system.

The calibration factor, which represents the ratio between the number of
moles of CO~2~ in the loop and the reading of the coulometer, changes
during the use of a titration cell. Depending on the condition of the
solution in the titration cell, this factor varies around the ideal
ratio of unity by a few tenths of a percent. It commonly starts from
less than unity when the cell solution is new and increases to greater
than unity as increasing amounts of carbon are titrated. This change can
be represented by a quadratic equation relating values of calibration
factor with the total amount of carbon titrated in a given cell (see
Fig. 2). The CO~2~ concentration in each seawater sample was corrected
using a factor estimated from the equation fit to the calibration data
for each cell. Generally a cell had to be cleaned and filled with fresh
solution after about 40 samples. After this number the cell began to
behave erratically with unreliable analytical results.

For the purpose of quality control of total CO~2~ determinations,
Scripps Institution of Oceanography (SIO) CRM, Batch 31, was run through
our analytical system at sea as unknowns. The shipboard analyses compare
with the SIO manometric analyses shown in Table 2.

Table 2. Comparison of LDEO shipboard analyses with SIO shore-based
manometric analyses

+-----------+--------------------+-------------------+-----------------+
| **CRM     | **SIO Manometric   | **LDEO            | **Difference**  |
| Batch     | TCO~2~**           | Coulometric       |                 |
| No.**     |                    | TCO~2~**          | **(SIO −        |
|           | **Shore**          |                   | LDEO)**         |
|           |                    | **Sea**           |                 |
|           | **(μmol/kg)**      |                   | **(μmol/kg)**   |
|           |                    | **(μmol/kg)**     |                 |
+-----------+--------------------+-------------------+-----------------+
| 31        | 1876.57±1.27       | 1878.31±1.12      | -1.74           |
|           |                    |                   |                 |
|           | (N=10)^\*^         | (N=294)           |                 |
+-----------+--------------------+-------------------+-----------------+

^\*^N = number of analyses.

Since more than one sample was taken from each CRM bottle and analyzed,
number of analyses exceeded the number of the CRM bottles supplied. The
± values indicate one standard deviation from the mean. Figure 3 shows
the results graphically. The results of the shipboard analyses that were
made using a high-purity CO~2~ gas standard are 1.7 mol/kg greater than
the results of the SIO manometric analyses. The difference is, however,
within the combined standard deviation for each set of measurements, and
it is well within two standard deviations of each set. The TCO~2~ values
listed in this report are **not** adjusted for this difference. The
documentation for the CRM batch provided by Andrew Dickson is reproduced
in Table 3.

  -----------------------------------------------------------------------
  ![](media/image2.wmf){width="3.6013888888888888in"
  height="3.8333333333333335in"}

  **Fig. 2. Change in the coulometer calibration factor as a function of
  the amount of CO~2~ titrated.** The change is expressed as a ratio of
  the moles of CO~2~ found divided by the moles of CO~2~ injected.
  -----------------------------------------------------------------------

Fig. 3. The results of TCO~2~ analyses of the certified reference
solutions using the coulometer during the expedition.

![](media/image3.png){width="5.290277777777778in"
height="4.114583333333333in"}

Table 3. Specification of the CRM batch 31 (November 25, 1996)

  -----------------------------------------------------------------------
  Reference Material Batch 31

  Bottled on August 16, 1995

  Original certificate issued December 22, 1995

  Total alkalinity values certified August 16, 1996

  ***Certified Values***

  Salinity 32.899

  Total Dissolved Inorganic Carbon

  Mean: 1876.57 µmol/kg

  Standard Deviation: 1.27 µmol/kg

  Number of Analyses: 10

  Total Alkalinity\*

  Mean: 2130.33 µmol/kg

  Standard Deviation: 0.79 µmol/kg

  Number of Analyses: 17 (on 5 bottles)

  \*These values were not measured when the batch was certified, but are
  based on measurements on archived samples.

  ***Information values for nutrient levels measured at the time of
  bottling***

  Phosphate: 0.27 µmol/kg

  Silicate: 1.30 µmol/kg

  Nitrite: 1.34 µmol/kg

  Nitrate: 2.59 µmol/kg

  Note: Nutrient levels may have changed on storage, their stability has
  not been examined.
  -----------------------------------------------------------------------

## 3.3 Total Alkalinity Measurements

The titration system for TALK determination used during expedition along
WOCE section S04I was similar to the one used in our earlier studies
(Millero *et al.* 1993). The systems consisted of a titrator (Metrohm,
model 665 Dosimat) and pH meter (Orion, model 720A). Both instruments
were controlled by computer. 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) with an inner filling of 0.7 m NaCl. The
temperature of both the acid titrant in a water-jacketed burette and the
seawater sample in a water-jacketed cell were controlled to a constant
temperature of 25 0.1C with a constant temperature bath (Neslab, model
RTE 221). The Plexiglas water-jacketed cells used during the cruise were
similar to that used by Bradshaw et al*.* (1988) except with a larger
volume (about 200 cm3) to increase the precision. This cell had a fill
and drain valve, which increased the reproducibility of the volume of
sample contained in the cell. The volumes of the cells used at sea were
determined in the laboratory before and after the cruise by several
titrations using seawater of known TALK. The volumes of the cells did
not change during the cruise. The nominal volumes of all the cells were
about 200 cm^3^ and the values were determined to 0.03 cm^3^ (cell 18 --
204.34 cm3, cell 19 -- 203.76 cm3). A Lab Windows-C program was used to
run the titration and record the volume of the added acid and the emf of
the electrodes using RS232 interfaces. Seawater samples were titrated by
adding HCl to exceed the carbonic acid end point. During a typical
titration the emf readings are recorded after the readings become stable
(0.09 mV), and then a volume of acid is added to change the voltage to a
pre-assigned increment (13 mV). In contrast to the delivery of a fixed
volume increment of acid, this method gives an even distribution of data
points in the range of rapid increase in the emf near the endpoint. A
full titration (25 points) takes about 20 minutes. Using two systems, a
36-bottle station cast can be completed in 6 hours. Calibrations of the
burettes of the Dosimat with water at 25C indicate that the systems
deliver 3.000 cm^3^ (the value for a titration of seawater) to a
precision of 0.0004 cm^3^. This uncertainty results in an error of 0.4
mol/kg in TALK and TCO~2~. Corrections due to a small error in the
volume delivery have been applied to our titration data. The precision
of the values of TALK on a CRM (Dr. Andrew Dickson, Marine Physical
Laboratory, La Jolla, California) is 2mol/kg (Lee and Millero 1995).

Standard acid was made by preparing a single large 55-gal batch of 0.25
M HCl acid by dilution of concentrated HCl, AR SelectMallinckrodt. The
acid was prepared in 0.45 M NaCl to yield a total ionic strength similar
to seawater of salinity 35.0 (IThe acid was standardized by a
coulometric technique (Taylor and Smith, 1959; Marinenko and Taylor,
1968). The acid is titrated with OH^-^ generated coulometrically at a Pt
electrode. The current is recorded as a function of time with data
acquisition measuring the voltage across a standard 1-ohm resistor. An
Orion combination electrode was used to measure the pH of the solution
during the titration. The endpoint is determined from the plot of the
concentration of H^+^ and OH^-^ in the solution as a function of the
coulombs delivered. The precision of the coulometric titration was 0.002
%. Sub-samples of the acid were sent to Dr. Andrew Dickson's laboratory
in La Jolla, California, for an independent laboratory determination of
the molarity. TALK titrations on the same seawater using different acids
calibrated by this technique agree to within 2 mol/kg. The calibrated
concentration of the acid used during this cruise was 0.24793 0.00009 M
HCl. The acid was bottled in 500-cm^3^ glass bottles for field use.

The TALK of seawater was evaluated from the proton balance at the
alkalinity equivalence point, pHequiv = 4.5, according to the exact
definition of TALK (Dickson 1981).

TALK = \[HCO~3~^−^\] + 2\[CO3^2−^\] + \[B(OH)~4~^−^\] + \[OH^−^\] +
\[HPO4^2−^\] + 2\[PO4^3−^\] + \[SiO(OH)~3~^−^\] + \[HS^−^\] + \[NH3\] −
\[H+\] − \[HSO4^−^\] − \[HF\] − \[H3PO4\]

The full titration is used to evaluate TALK from a given experiment.
This is accomplished with a program patterned after that developed by
Dickson (1981), Johansson and Wedborg (1982), and Dickson and Goyet (DOE
1994). The program determines pH, E\* (for the electrode), TALK, TCO~2~,
and pK~1~ for carbonic acid in the solution (Na~2~CO~3~, TRIS or
seawater). The program used the Levenberg-Marquardt nonlinear
least-squares algorithm to perform the calculations. The program assumes
that the nutrients are negligible in the calculation. This does not
affect the calculated TALK, which includes the alkalinity due to
nutrients. The concentration of the effect of nutrients on TALK,
however, must be considered when calculating the carbonate alkalinity
(\[HCO~3~^-^\] + 2 \[CO~3~^2-^\]).

**3.3.1** **Titration Total Alkalinity, Total CO~2~, and pH Measurement
Results**

Our effort during this cruise was to provide reliable TALK measurements
on all the collected samples. Measurements on CRM (batch No. 31) were
made before and during the cruise to monitor the performance of the
titrators. A summary of the titration results for TALK, TCO~2~, and pH
are given in Table 4. Deviations from the mean of TALK, TCO~2,~ and pH
for CRM over the course of the cruise are given in Figs. 4, 5, and 6.
The values of TALK of cell 18 (2130 2.3 mol/kg) and cell 19 (2129 3.5
mol/kg) determined at sea were in good agreement with the laboratory
results (2128 0.09 mol/kg). Measurements made on 47 CRM samples using
the two cells at sea also indicate that the systems have a
reproducibility of 2.9 mol/kg in TCO2 and 0.005 in pH.

The potentiometric measurements of pH at sea were 0.017 0.005 higher
than the laboratory spectroscopic values while the TCO~2~ values were 10
3 mol/kg higher. These differences are due to the non-Nernstian response
of the electrodes (Millero *et al.* 1993). Since the differences are
highly reproducible, we have adjusted all our pH and TCO~2~ measurements
using these corrections.

Two batches of surface seawater were also collected to check the
precision of the two titration systems during the cruise. TALK, TCO~2,~
and pH differences of cell 18 and cell 19 over the course of the cruise
using this reference surface water are shown in Figs. 7, 8, and 9. The
results show an agreement of 1.8 mol/kg in TALK, 1.7 mol/kg in TCO~2,~
and 0.006 in pH throughout the cruise.

The performance of the titrators was also checked by analyzing duplicate
samples from the same Niskin bottles for surface water and water
collected from 800 meters. The duplicates were analyzed on the same cell
and on different cells. The deviations of TALK, TCO~2~ and pH over the
course of the cruise are shown in Figs. 10, 11, and 12. The results
showed an agreement of 1.5--1.6 mol/kg for TALK, 1.3--1.7 mol/kg for
TCO2, and 0.005--0.008 for pH.

TALK and total carbon dioxide values of all the surface water samples
are plotted in Fig. 13 for the stations occupied. A linear relationship
between TALK and salinity is shown in Fig. 14 (TALK = 70.4 + 65.7 S, = 5
mol/kg). The Normalized TALK (NTA = TALK\*S/35) and TCO~2~ (NTCO~2~ =
TCO~2~\*S/35) are plotted versus station in Fig. 15. The values of NTA =
2370 5 mol/kg and NTCO~2~ = 2230 9 mol/kg for the surface waters do not
show large variations. They seem, however, to be higher on the first
north-to-south section at 63--65°S latitude and 52--54°E longitude
(stations 38--41). The salinity range is very narrow in the waters of
Antarctica (33.8--34.3), compared with, for example, the values of North
Atlantic waters (34.8--37.5). This narrow range is partly responsible
for the uniform values of TALK and TCO~2~ for the surface waters.

All the measurements for TALK, total carbon dioxide, and pH vs. depth
are presented in Figs. 16, 17, and 18. The CO~2~ properties of the deep
waters were quite uniform (TALK =2355 10 mol/kg, TCO~2~ = 2240 mol/kg
andpH = 7.60Lower values of pH were obtained at 62--63°S latitude and
between the longitudes 68--70E, 85--93E, and 104--118E (the same
stations that have slightly higher TCO~2~). The TALK data are combined
with the partial pressure of carbon dioxide (pCO~2~) and total carbon
dioxide (TCO~2~) measurements, which were performed by Dr. Taro
Takahashi's research group from Lamont-Doherty Earth Observatory,
Columbia University, to fully characterize the CO~2~ system in these
waters in future work.

Table 4. Summary of the CRM Measurements.

  -------------------------------- -------------- --------------- ----------------- ------------- -------
                                   **Salinity**   **TALK*^a^***   **TCO~2~*^b^***   **pH*^c^***   **N**

  Laboratory measurements of CRM   32.899         2128±0.9        1828±0.9          7.984±0.001   6
  Batch 31                                                                                        

  Measurements of CRM Batch 31 at                                                                 
  sea                                                                                             

  Cell 18                                         2130±2.3        1887±3.0          7.968±0.005   27

  Cell 19                                         2129±3.5        1887±2.2          7.965±0.004   20
  -------------------------------- -------------- --------------- ----------------- ------------- -------

*^a^*From weight titrations;

*^b^*Standard values assigned to the batch;

*^c^*From spectrophotometric measurements.

![](media/image4.jpeg){width="4.010416666666667in" height="3.875in"}

Fig. 4. Deviations of total alkalinity for certified reference material
over the course of the cruise.

![](media/image5.jpeg){width="4.3694444444444445in"
height="3.842361111111111in"}

Fig. 5. Deviations of total CO~2~ for certified reference material over
the course of the cruise.

![](media/image6.jpeg){width="4.253472222222222in"
height="3.7020833333333334in"}

Fig. 6. Deviations of pH for certified reference material over the
course of the cruise.

![](media/image7.jpeg){width="4.161111111111111in"
height="3.797222222222222in"}

Fig. 7. Differences in total alkalinity of cells 18 and 19 over the
course of the cruise using reference surface water.

![](media/image8.jpeg){width="4.215972222222222in"
height="3.8243055555555556in"}

Fig. 8. Differences in total CO~2~ of cells 18 and 19 over the course of
the cruise using reference surface water.

![](media/image9.jpeg){width="4.03125in" height="3.7284722222222224in"}

Fig. 9. Differences in pH of cells 18 and 19 over the course of the
cruise using reference surface water.

![](media/image10.jpeg){width="5.378472222222222in" height="7.75625in"}

Fig. 10. Sample replicates of total alkalinity, total CO~2~, and pH on
cell 18 (white circle--surface; black circle--800 m).

![](media/image11.jpeg){width="4.884722222222222in" height="7.625in"}

## 

Fig. 11. Sample replicates of total alkalinity, total CO~2~, and pH on
cell 19 (white circle--surface; black circle--800 m).

## ![](media/image12.jpeg){width="5.195138888888889in" height="7.626388888888889in"}

Fig. 12. Cell to cell replicate measurements of total alkalinity, total
CO~2~, and pH (white circle--surface; black circle--800 m).

## 

## 

## ![](media/image13.jpeg){width="4.2444444444444445in" height="3.7743055555555554in"}

Fig. 13. Surface water total alkalinity and total CO~2~ for each
station.

![](media/image14.jpeg){width="4.057638888888889in" height="3.50625in"}

Fig. 14. Linear relationship between surface total alkalinity and
salinity.

## ![](media/image15.jpeg){width="4.182638888888889in" height="3.740972222222222in"}

Fig. 15. Normalized surface water total alkalinity and total CO~2~.

![](media/image16.jpeg){width="3.933333333333333in"
height="3.622916666666667in"}

Fig. 16. Measured total alkalinity vs. depth.

## 

## ![](media/image17.jpeg){width="3.807638888888889in" height="3.515277777777778in"}

Fig. 17. Measured total CO~2~ vs. depth.

## 

## ![](media/image18.jpeg){width="3.9270833333333335in" height="3.579861111111111in"}

Fig. 18. Measured pH vs. depth.

## 3.4 Discrete pCO~2~ Measurements

A semi-automated equilibrator-gas chromatograph (GC) system was used
during the expedition for the determination of partial pressure of CO~2~
(pCO~2~) exerted by the seawater samples. Its design has been described
by Chipman et al*.* (1993) and is summarized in this report. The
schematic representation of the analytical system is shown in Chipman et
al*.* (1993) as well as in Takahashi et al*.* (1998).

The system consisted of a pair of circulation pumps plumbed to
recirculate air in a closed system through porous plastic gas dispersers
immersed in two separate seawater samples. Electrically driven Valco
4-port valves were used to isolate each of the equilibrators during the
initial equilibration. Manually operated 2-way and 3-way Whitey valves
allowed part of the water in each equilibrator to be replaced with air
of known initial CO~2~ concentration, creating the necessary headspace
for equilibration. A drain line in each equilibrator ensured that the
volume of water was constant at 500 mL. This allowed us to make accurate
corrections for the effect of the perturbation of the sample by the
headspace air. The equilibrators were open to the laboratory air through
isolation coils, keeping them at atmospheric pressure, and we measured
lab atmospheric pressure with a high precision electronic barometer with
an accuracy of better than 0.05%. Since the partial pressure of CO~2~ is
strongly affected by temperature, the equilibration flasks were kept
immersed in a water bath maintained at 4.00±0.01°C. An electrically
driven Valco 6-port valve allowed the entire equilibration system to be
isolated, while simultaneously connecting a calibration gas selection
valve. A 2-way Skinner solenoid valve (normally closed) on the output of
the calibration selection valve allowed the gas flow to be controlled by
the system controller. It also provided a necessary second means of
stopping the flow of the calibration gases to prevent accidental loss of
the calibration gases in case of a control malfunction.

The analysis of the CO~2~ in the equilibrated air or calibration gases
was performed using a Shimadzu Mini-2 GC, equipped with a flame
ionization detector. A 1-mL sample loop, a pre-column, and an analytical
column were attached to an electrically driven Valco 10-port valve
within the column oven of the GC. The pre-column, 0.2 m long, and
analytical column, 2.0 m long, were both packed with Chromosorb 102.
Ultra-high purity hydrogen gas served as the carrier gas. This carrier
gas is electrolytically generated by a hydrogen generator and purified
by diffusion through a palladium foil membrane. The use of hydrogen as a
carrier gas allowed the CO~2~ to be converted quantitatively to methane
in a catalytic converter prior to quantification by the flame ionization
detector. Our system used a catalyst of ruthenium metal on Chromosorb W
support, and did not require a palladium pre-catalyst as used by Weiss
(1981) to remove oxygen from the carrier gas stream. Hydrocarbon-free
air to support the combustion in the flame ionization detector was
provided by an Aadco Model 737 chromatographic air purifier. A Shimadzu
Model CR6A Chromatopac computing integrator controlled the equilibration
and calibrations procedure and integrated the output signal from the GC.

The analytical procedure is as follows. Water samples were drawn from
the 10-L Niskin bottles of a rosette directly into 500-mL, narrow-necked
volumetric Pyrex flasks. These served as both sample containers and
equilibration vessels. The samples were immediately inoculated with 200
L of 50%-saturated mercuric chloride solution, sealed airtight with
screw caps with conical plastic liners to prevent biological
modification of the pCO~2~, and stored in the dark until measurement.
Measurements were normally performed within 24 hours of sampling. A
headspace of 3 to 5 mL was left above the water to allow for thermal
expansion during storage. Prior to analysis the sample flasks were
brought to the water bath temperature of 4°C in the constant temperature
bath, and about 45 mL of water was displaced with air of known CO~2~
concentration. The air in the flasks and in the tubing connecting them
to the GC sampling loop was recirculated continuously for about 20
minutes through a gas disperser immersed in the water. This provided a
large surface area for gas exchange, and equilibrium for CO~2~ was
attained in 15 minutes.

The equilibrated air samples were saturated with water vapor at the
temperature of equilibration and had the same pCO~2~ as the water. By
injecting the air aliquot into the GC without removing the water vapor,
the partial pressure of CO~2~ is directly determined by the relationship
below:

pCO~2~ (atm) = \[C~meas~ (ppm)\] × \[total pressure of equilibration
(atm)\]

where C~meas~ is the mole fraction concentration of CO~2~ in
equilibrated moist air. CO~2~ gas is assumed to behave as an ideal gas
as well as mix ideally with water saturated air in dilute CO~2~ gas
mixtures. The total pressure of equilibrated air was measured by having
the head space in the equilibrator flask always at atmospheric pressure.
We measured the latter with an electronic barometer at the time each
equilibrated air sample was injected into the GC for CO~2~
determination. Since water vapor was **not** removed from the sample, we
do not have to know the water vapor pressure. C~meas~ was determined by
using a quadratic equation fit to all three of the standards. Although a
quadratic equation was used, the CO~2~ concentration was very close to a
linear function of the GC detector output signal.

The GC was calibrated using gas mixtures of CO~2~ in air, which have
been calibrated against a set of primary standard gas mixtures in our
laboratory. The primary standard gases used are traceable to the World
Meteorological Organization reference scale through analysis in the
laboratory of C. D. Keeling of SIO (in the case of the lower two of our
secondary gas mixtures) or to a primary standard of CO~2~ in nitrogen,
which was calibrated in our laboratory using gravimetrically prepared
sodium carbonate solutions (highest gas concentration only). The values
of the secondary standard gas mixtures used during the expedition and
the method used to determine their CO~2~ concentrations are as follows:

-   233.8 ppm CO~2~, measured using infrared analyzer,

-   555.3 ppm CO~2~, measured using GC, and

-   856.5 ppm CO~2~, mean of measurements using GC and coulometry (0.14%
    difference between those two determinations).

Corrections were made to account for the change in pCO~2~ of the sample
water due to the transfer of CO~2~ between the water and circulating air
during equilibration. We know the pCO~2~ in equilibrated, perturbed
water and TCO~2~ measured by coulometry before the equilibration. We can
also calculate the change in TCO~2~ in the water based on the change in
pCO~2~ between the post-equilibrium value and the known concentration in
the pre-equilibrium displacement gas. With the pre-equilibrium TCO~2~
plus the perturbation in TCO~2~ during equilibration, we obtain the
post-equilibrium TCO~2~ value. Using the post-equilibrium TCO~2~ and
measured pCO~2~ values, we can calculate TALK at the end of the
equilibration, knowing the temperature, salinity, phosphate, and
silicate data. Since the perturbation does not change the TALK, we can
calculate the pre-equilibrium pCO~2~ from the pre-equilibrium TCO~2~,
the calculated TALK, and the other parameters of temperature, salinity,
etc. This is the value that we report as pCO~2~, the pre-equilibrium
calculated value. The magnitude of this correction is generally less
than 2 microatmospheres (atm). Detailed computational procedures are
described in Takahashi et al*.* (1998).

The pCO~2~ values reported in this data set are in the unit of
microatmospheres at the temperature of 4°C at which they were measured.
In order to obtain pCO~2~ values at other temperatures, we recommend
using the following temperature effect determined by Takahashi et al*.*
(1993):

ln(pCO~2~)/t = (0.0433 − 8.7 × 10^-5^ t) × (C^-1^)

where "t" is temperature in degrees Celsius. This relationship is
independent of salinity within the normal open ocean range.

We estimate the precision of the pCO~2~ measurement for a single
hydrographic station to be about ±0.15% based on the reproducibility of
replicate equilibrations. We estimate the station-to-station
reproducibility to be about ±0.5%.

**3.4.1. Comparison of observed and calculated pCO~2~**

During this cruise, the TALK was measured by titration (see paragraph
3.3). This provided an opportunity to test the internal consistency
among the three measured CO~2~ chemistry parameters using the carbonate
equilibria relations. We used two measured CO~2~ parameters (for example
TALK and TCO~2~), and computed the third (for example pCO~2~) and
compared it with the measured value. The temperature, salinity, and the
total concentrations of silica and phosphate dissolved in each sample
are used for the input. The total boron concentration is computed using
the salinity. The TALK is defined according to Dickson (1981). The
following set of dissociation constants have been used in the
computation:

-   Solubility of CO~2~ in seawater = Reformulation of Weiss (1974)
    based on Murray and Riley (1971). Fugacity formulation;

-   Carbonic acid K~1~ and K~2~ = Reformulation by Dickson and
    Millero (1987) based upon the results of Mehrbach et al*.* (1973);

-   Boric acid K~1~ = Dickson (1990);

-   Silicic acid K~1~ = Sjoberg et al*.* (1979) and Baes and Mesmer
    (1977);

-   Phosphoric acid, K~1~, K~2~ and K~3~ = Millero (1974); Kester and
    Pytkowicz (1967); and Dickson and Riley (1979a);

-   Water, Kw = Dickson and Riley (1979b);

-   HSO~4~^-^ = Khoo et al*.* (1977);

-   HF^-^ = Dickson and Riley (1979b)

-   Total boron concentration (umol/kg) = 410.6 (salinity/35)

The computer program used for the computation of pCO~2~ from the input
data of TALK, TCO~2~, temperature, salinity, and the concentrations of
silica and phosphate dissolved in seawater.

Figure 19 compares the measured and computed pCO~2~ values obtained
during the WOCE S04I expedition. The difference between the observed and
computed pCO~2~ values is plotted as a function of the measured pCO~2~
value at 4°C. The horizontal solid line indicates the mean of the
observed minus computed pCO~2~ of +5.5 atm; the fine dotted lines
indicate the ±13.8 atm one standard deviation. A series of solid curves
(marked ±0.3%, ±0.2% and ±0.1%) indicate the errors in the computed
pCO~2~ due to errors in TCO~2~ (or combined errors in TCO~2~ and TALK).
The mean difference of 5.5 ± 13.8 atm appears to be well within the
uncertainties of measurements for the TALK (±0.3%) and TCO~2~ (± 0.1%).
This indicates that the pCO~2~ values measured at 4°C are consistent
mutually with the measured alkalinity and TCO~2~. This also suggests
that the measured carbonate parameters are consistent with the
dissociation constants of carbonic, boric, and other acids used for the
computation.

Figure 20 shows a plot of the observed minus measured pCO~2~ at 4°C as a
function of the measured TCO~2~. The mean difference was 5.5 ± 13.8 atm,
and no systematic trend for the pCO~2~ difference was observed as a
function of TCO~2~. Figure 21 shows a plot of the observed minus
measured pCO~2~ at 4°C as a function of the TALK/TCO~2~ ratio. We
observe that the mean difference is 5.5 ± 13.8 atm, and no systematic
trend for the pCO~2~ difference was observed as a function of TCO~2~.
The mean (observed--measured) pCO~2~ value was within the uncertainties
expected from the errors in the measurements of TALK and TCO~2~ as
demonstrated in Fig. 19.

![](media/image19.jpeg){width="6.3694444444444445in"
height="4.754861111111111in"}

**Fig. 19. Difference between the observed and computed pCO~2~ values at
4°C as a function of the measured pCO~2~ values.**

![](media/image20.wmf){width="5.024305555555555in" height="5.25in"}

**Fig. 20. Difference between the observed and computed pCO~2~ values at
4°C as a function of the measured TCO~2~ values.**

![](media/image21.wmf){width="5.067361111111111in"
height="5.316666666666666in"}**Fig. 21. Difference between the observed
and computed pCO~2~ values at 4°C as a function of the measured total
alkalinity/total CO~2~ ratio.**

**3.4.2 Comparison of observed and calculated total alkalinity**

The TALK has been computed from the measured pCO~2~, TCO~2~, salinity,
and the concentrations of dissolved silica and phosphate. The
dissociation constants for carbonic, boric, silicic, and phosphoric
acids and that for water are same as those specified in the previous
section. The computed alkalinity has been compared with the alkalinity
values measured by the Miami group by plotting them against each other
(Fig. 22). The linear regression line (the solid line) is in a close
agreement with the ideal 1:1 line (the dashed line) well within the
scatter of the data points. The mean difference between the measured and
computed values is less than 1.5 eq/kg with a root means square
deviation of ±3.7 eq/kg. This indicates that the computed alkalinity
values are consistent with the measured TALK (or the titration
alkalinity) having an estimated uncertainty of about ±4 eq/kg. However,
it should be noted that while the computed alkalinity is in excellent
agreement with the measured values in a range below 2340 eq/kg, the
computed alkalinity values tend to be smaller than the measured values
by a few eq/kg in the higher alkalinity waters.

![](media/image22.wmf){width="4.810416666666667in" height="4.5in"}

Fig. 22. Difference between the observed and computed total alkalinity
values is plotted against the measured total CO~2~/total alkalinity in
seawater.

## 

**3.5 Radiocarbon Measurements.**

In all, 816 small volume ^14^C samples were collected at 31 stations.
The locations of Accelerator Mass Spectrometry (AMS) stations are shown
in Fig. 23. For this cruise, ^14^C sampling was carried out by Robert M.
Key (Princeton University); analyses for ^14^C (and accompanying ^13^C)
were performed at the National Ocean Sciences AMS Facility (NOSAMS) at
Woods Hole Oceanographic Institution. R. Key collected the data from the
originators, merged the files, assigned quality control flags to the
^14^C, and submitted the data files to the WOCE office. R. Key is
personal investigator for the ^14^C data and NOSAMS for the ^13^C data.
The replicate measurements were made on four water samples. Table 5
presents the replicate analyses results. The table shows the
error-weighted mean and uncertainty for each set of replicates.
Uncertainty is defined here as the larger of the standard deviation and
the error-weighted standard deviation of the mean. For these replicates,
the simple average of the normal standard deviations for the replicates
is 1.0‰. This precision estimate is lower than the average error for the
time frame over which these samples were measured (July 1996 − December
1998) and lower than the overall mean error for Pacific WOCE samples
(Elder et. al. 1998). Note that the errors given for individual
measurements in the final data report (with the exception of the
replicates) include only counting errors and errors due to blanks and
backgrounds. The uncertainty obtained for replicate analyses is
generally a better estimate of the true error since it includes errors
due to sample collection, sample degassing, etc. Close examination of
the data along 67S in the deep water indicates that 4‰ is a more
realistic interpretation of the true error associated with this data
set.

![](media/image23.jpeg){width="6.493055555555555in"
height="3.3604166666666666in"}

Fig. 23. AMS ^14^C station map for WOCE Section S04I.

Table 5. Summary of Replicate Analyses

  --------------------- ---------------- ------------ ------------------- ----------------------
  **Sta-Cast-Bottle**   **Δ^14^C**       **Err**      **E.W.Mean*^a^***   **Uncertainty*^b^***

  51-1-9                -161.31          2.92         -167.40             2.62

                        -176.84          2.91                             

  51-1-10               -167.33          3.26         -167.40             2.59

                        -167.51          4.29                             

  58-1-26               -151.72          5.74         -155.78             3.49

                        -156.65          2.67                             

  70-1-5                -176.29          4.42         -176.06             3.46

                        -175.69          5.55                             
  --------------------- ---------------- ------------ ------------------- ----------------------

*^a^*Error-weighted mean reported with data set

*^b^*Larger of the standard deviation and the error weighted standard
deviation of the mean.

Quality flag values were assigned to all ^14^C measurements using the
code defined in Table 0.2 of WHP Office Report WHPO 91-1 Rev. 2 section
4.5.2. (Joyce and Corry, 1994). Measurement flags values of 2, 3, and 6
have been assigned. The choice between values 2 (good) and 3
(questionable) involves some interpretation. There is little overlap
between this data set and any existing ^14^C data, so that type of
comparison was difficult. In general, the lack of other data for
comparison led to a more lenient grading on the ^14^C data.

When using this data set for scientific application, any ^14^C datum
flagged with a

"3" should be carefully considered. When flagging 14C data, the
measurement error was taken into consideration. That is, approximately
one-third of the ^14^C measurements are expected to deviate from the
true value by more than the measurement precision. No measured values
have been removed from this data set.

**3.5.1 Radiocarbon Data Summary**

Figures 24--29 summarize the ^14^C data collected on this leg. Only
^14^C measurements with a quality flag value of 2 ("good") or 6
("replicate") are included in each figure. Figure 24 shows the ^14^C
values with 2error bars plotted as a function of pressure. The mid depth
^14^C minimum, which normally occurs around 2500 meters in most of the
Pacific, is absent in this section. In fact, there is very little
variation in the deep and bottom water. All of the samples for the
entire cruise collected at a depth greater than 1000 meters have a mean
^14^C = −153.87.2‰ with a substantial fraction of this variance due to
the samples collected very near the Antarctic slope. This result
compares remarkably well with the mean of −156.08.5‰ calculated for the
WOCE Pacific Antarctic section (S04P). Figure 25 shows the ^14^C values
plotted against silicate. The straight line shown in the figure is the
least squares regression relationship derived by Broecker et al*.*
(1995) based on the GEOSECS global data set. According to the Broecker
et al. (1995) analysis, this line (^14^C = −70 − Si) represents the
relationship between naturally occurring radiocarbon and silicate for
most of the ocean. They interpret deviations in ^14^C above this line to
be due to input of bomb-produced radiocarbon, however, they note that
the technique cannot be applied at high latitudes as confirmed by this
data set. With the exception of the very near surface waters, this
region of the Pacific shows no change since GEOSECS, which strongly
implies that the data in Fig. 25 indicate a failure of the technique in
this area rather than bomb-produced contamination throughout the water
column.

Figure 27 shows all of the S04I radiocarbon values plotted against
potential alkalinity normalized to a salinity of 35 (defined as
\[alkalinity + nitrate\]\*35/salinity). The straight line is the
regression fit \[^14^C = −68 − (PALK_35 − 2320)\] derived by S. Rubin
(LDEO) to all of the GEOSECS results for waters which were assumed to
have no bomb-produced ^14^C (depths greater than 1000 meters, but
including high-latitude samples). Preliminary investigation indicates
that this new method for separating bomb-produced and natural ^14^C
works in high-latitude waters. For this data set, it appears that the
regression intercept derived from the GEOSECS data may be a bit too low.
Regardless, if the function is valid, then for these data, waters that
have alkalinity values less than \~2400 mol/kg have a significant amount
of bomb-produced radiocarbon. If this is true, and if the values have
changed little since GEOSECS, then most of the bomb contamination had to
have been distributed throughout most of the water column even as early
as the mid 1970s.

Figures 27--29 show gridded sections of the ^14^C data. The data were
gridded using the "loess" methods described in Chambers et al*.* (1983),
Chambers and Hastie (1991), Cleveland (1979), and Cleveland and Devlin
(1988).

![](media/image24.jpeg){width="6.177083333333333in"
height="3.9791666666666665in"} Figure 27 shows the main zonal cruise
section along \~62S. The colors in the image indicate ^14^C while the
contours are CFC-11 concentration \[pmol/kg; preliminary data from Bill
Smethie (LDEO) and Mark Warner (UW)\]. Significant resolution is lost in
the deep water ^14^C since most of the variability is near the surface.
Nevertheless, a strong correlation in the two distributions is
immediately apparent. The bottom waters both east and west of the
Kerguelen Ridge (\~80E) have appreciable chlorofluorocarbon
concentrations and are most likely contaminated with bomb-produced
radiocarbon. The highest near-bottom (pressure \>3750 dB) ^14^C values
along this section range between −140‰ and −130‰ and are comparable to
near-bottom waters at similar latitudes in the Pacific (Key and
Schlosser 1999). Figures 28 and 29 show contoured sections of the ^14^C
distribution along 65E and 90E respectively. Note that the contour
interval used in the two figures is different. The 65E and 90E sections
clearly show penetration of bomb radiocarbon along the Antarctic
continental slope.

Fig. 24. Δ^14^C results for S04I stations shown with 2σ error bars.

![](media/image25.jpeg){width="6.182638888888889in" height="4.03125in"}

**Fig. 25. Δ^14^C as a function of silicate for S04I AMS samples.** The
straight line shows the relationship

![](media/image26.jpeg){width="6.125in" height="3.8in"}proposed by
Broecker et al*.* 1995 (^14^C = −70 − Si with radiocarbon in ‰ and
silicate in mol/kg). 2σ error bars are given for the ^14^C measurements.

Fig. 26. Samples that plot above the line and have potential alkalinity
values less than about 2400 mol/kg are contaminated with bomb-produced
^14^C. Based on the new method devised by S. Rubin.

![](media/image27.jpeg){width="6.052083333333333in" height="4.0625in"}

Fig. 27. ^14^C concentrations along the main east-west section of S04I
at approximately 62S are indicated by color. Contour lines are
preliminary CFC-11 concentrations (pmol/kg).

![](media/image28.jpeg){width="6.426388888888889in"
height="3.4770833333333333in"}

Fig. 28. ^14^C along \~65°E near the Antarctic slope. The near bottom
values along the lower slope indicate entrainment of "new" bottom water.

![](media/image29.jpeg){width="6.348611111111111in"
height="4.245138888888889in"}

Fig. 29. ^14^C along \~90°E near the Antarctic slope. The near bottom
values along the lower slope indicate entrainment of "new" bottom water.

**4. HOW TO OBTAIN THE DATA AND DOCUMENTATION**

This database (NDP-086) is available free of charge from CDIAC. The
complete documentation and data can be obtained from the CDIAC
oceanographic website (http://cdiac.ornl.gov/oceans/ doc.html), through
CDIAC's online ordering system
(http://cdiac.ornl.gov/pns/how_order.html), or by contacting CDIAC.

The data are also available from CDIAC's anonymous file transfer
protocol (FTP) area via the Internet. Please note that your computer
needs to have FTP software loaded on it. (This is built in to most newer
operating systems.) Use the following commands to obtain the database.

ftp cdiac.ornl.gov or \>ftp 160.91.18.18

Login: "anonymous" or "ftp"

Password: your e-mail address

ftp\> cd pub/ndp086/

ftp\> dir

ftp\> mget (files)

ftp\> quit

Contact information:

Carbon Dioxide Information Analysis Center

Oak Ridge National Laboratory

P.O. Box 2008

Oak Ridge, Tennessee 37831-6335

USA

Telephone: (865) 574-3645

Telefax: (865) 574-2232

E-mail: cdiac@ornl.gov

Internet: http://cdiac.ornl.gov/

# 5. 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 Research*
14:381--9.

Baes, C. F. and R. E. Mesmer. 1977. *The Hydrosis of Cations.* John
Wiley & Sons, Inc., 489 pp.

Bernhardt, H. and A. Wilhelms. 1967. The continuous determination of
low-level iron, soluble phosphate and total phosphate with the
AutoAnalyzer. *Technicon Symposia* 1:385--9.

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)?" *Marine Chemistry*
23:69--86.

Broecker, W. S., S. C. Sutherland, and W. Smethie. 1995. "Oceanic
radiocarbon: Separation of the natural and bomb components." *Global
Biogeochemical Cycles* 9(2):263--88.

Carpenter, J. H. 1965. The Chesapeake Bay Institute technique for the
Winkler dissolved oxygen method. *Limnology and Oceanography* 10:141--3.

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
^14^C incubation method and the mixed layer carbon budget*.*" *Deep-Sea
Research* 40:151--69.

Chambers, J. M. and T. J. Hastie. 1991. *Statistical Models* in S.
Wadsworth & Brooks, Cole Computer Science Series, Pacific Grove, CA,
608pp.

Chambers, J. M., W. S. Cleveland, B. Kleiner, and P. A. Tukey. 1983,
*Graphical Methods for Data Analysis*. The Wadsworth
statistics/probability series, Belmont, CA.

Cleveland, W.S. 1979. "Robust locally weighted regression and smoothing
scatterplots." *J. Amer. Statistical Assoc.* 74:829--36.

Cleveland, W.S. and S. J. Devlin. 1988. "Locally-weighted regression: An
approach to regression analysis by local fitting." *J. Am. Statist.
Assoc*. 83:596--10.

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. WHP Office Report, WHPO 91-2. WOCE Hydrographic Program
Office, Woods Hole, Mass.

DOE (U.S. Department of Energy). 1994. "Handbook of Methods for the
Analysis of the Various Parameters of the Carbon Dioxide System in
Seawater. Version 2.0." ORNL/CDIAC-74. Ed. A. G. Dickson and C. Goyet.
Carbon Dioxide Information Analysis Center, Oak Ridge National
Laboratory, Oak Ridge, Tenn.

Dickson, A. G. and J. P. Riley. 1979a. "The estimation of acid
dissociation constants in seawater media from potentiometric titrations
with strong base. II. The dissociation of phosphoric acid." *Marine
Chemistry* 7**:**101--109.

Dickson, A. G. and J. P. Riley. 1979b. "The estimation of acid
dissociation constants in seawater media from potentiometric titrations
with strong base. I. The ionic product of water (Kw)." *Marine
Chemistry* 7**:**89--99.

Dickson, A. G. 1981. "An exact definition of total alkalinity and a
procedure for the estimation of alkalinity and total inorganic carbon
from titration data." *Deep-Sea Research* 28A:609--23.

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 Research* 34:1733--43.

Dickson, A. G. 1990. "Thermodynamics of the dissociation of boric acid
in synthetic seawater from 273.15 to 318.15K." *Deep-Sea Research*
37:755--66.

Elder, K. L., A. P. McNichol, and A. R. Gagnon. 1998. "Reproducibility
of seawater, inorganic and organic carbon ^14^C results at NOSAMS."
*Radiocarbon* 40(1):223--30.

Joyce, T., and C. Corry. 1994. *Requirements for WOCE Hydrographic
Programme Data Reporting.* Report WHPO 90-1, WOCE Report No. 67/91, WOCE
Hydrographic Programme Office, Woods Hole, Mass. U.S.A. pp. 52-55.
Unpublished Manuscript.

Johansson, O. and M. Wedborg. 1982. "On the evaluation of potentiometric
titrations of seawater with hydrochloric acid." *Oceanol. Acta*
5:209--18.

Kester, D. R. and R. M. Pytkowicz. 1967. "Determination of the apparent
dissociation constants of phosphoric acid in seawater." *Limnology and
Oceanography* 12:243--52.

Key, R. M. and P. Schlosser. 1999. *S4P: Final report for AMS ^14^C
samples*. Ocean Tracer Lab Technical Report 99-1, 11pp.

Khoo, K. H., R. W. Ramette, C. H. Culberson, and R. G. Bates. 1977.
"Determination of hydrogen ion concentrations in seawater from 5 to
40ºC: Standard potentials at salinities from 20 to 45‰." *Analytical
Chemistry* 49:29--34.

Lee, K. and F. J. Millero. 1995. "Thermodynamic studies of the carbonate
system in seawater." *Deep-Sea Research* 42:2035--61.

Lueker, T.J., A. G. Dickson, and C. D. Keeling. 2000. Ocean pCO~2~
calculated from dissolved inorganic carbon, alkalinity, and equations
for K1 and K2; validation based on laboratory measurements of CO~2~ in
gas and seawater at equilibrium. *Marine Chemistry* 70:105--19.

Marinenko, G. and J. K. Taylor. 1968. "Electrochemical equivalents of
benzoic and oxalic acid." *Analytical Chemistry* 40:1645--51.

Mehrbach, C., C. Culberson, J. E. Hawley, and R. M. Pytkowicz. 1973.
"Measurement of the apparent dissociation constants of carbonic acid in
seawater at atmospheric pressure." *Limnology and Oceanography*
18:897--907.

Millero, F. J. 1974. "Seawater as a multicomponent electrolyte
solution." In *The Sea*, Vol. 5, E. D. Goldberg ed. pp. 3--80.

Millero, F. J., J. Z. Zhang, K. Lee, and D. M. Campbell. 1993.
"Titration alkalinity of seawater." *Marine Chemistry* 44(2-4):153--65

Murray, C. N. and J. P. Riley. 1971. "The solubility of gases in
distilled water and seawater - IV. Carbon dioxide." *Deep-Sea Research*
18:533--41.

NOSAMS. 1999. *National Ocean Sciences AMS Facility Data Report
#99-043*, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543,
2/16/1999.

Sjorberg, S., N. Nordin, and N. Ingri. 1979 "Equilibrium and structural
studies of silicon (IV) and aluminum (III) in aqueous solution. II.
Formation constants for the monosilicate ions SiO(OH)^3-^ and
SiO~2~(OH)~2~^2-^. A precision study at 25ºC in a simplified seawater
medium." *Marine Chemistry* 19:521--32.

Takahashi, T., J. Olafsson, J. Goddard, D. W. Chipman, and S. C.
Sutherland. 1993. "Seasonal variation of CO~2~ and nutrients in the
high-latitude surface oceans: A comparative study." *Global
Biogeochemical Cycles* 7:843--78.

Takahashi, T., D. W. Chipman, S. Rubin, J. Goddard, and S. C.
Sutherland. 1998. *Measurements of the total CO~2~ concentration and
partial pressure of CO~2~ in seawater during WOCE Expeditions P-16,
P-17, and P-19 in the South Pacific Ocean, October, 1992-April, 1993*.
Final Technical Report of Grant No. DE-FGO2-93ER61539 to U. S.
Department of Energy, Lamont-Doherty Earth Observatory, Palisades, NY
10964, pp. 124.

Taylor, J. K. and S. W. Smith. 1959. "Precise coulometric titration of
acids and bases." *J.* *Res. Natl. Bur. Stds*. 63A:153--59.

Weiss, R. F. 1974. "Carbon dioxide in water and seawater: The solubility
of a non-ideal gas." *Marine Chemistry* 2:203--15.

Weiss, R. F. 1981. "Determinations of CO~2~ and methane by dual catalyst
flame ionization chromatography and nitrous oxide by electron capture
chromatography." *Journal of Chromatogr. Sci.* 19:611--16.