**CLIVAR P16N Leg-2**

R/V *Thomas G. Thompson*, 3250TT191b

10 -- 30 March 2006

Honolulu, HI -- Kodiak, AK USA

Chief Scientist: Richard A. Feely

NOAA Pacific Marine Environmental Laboratory

Co-Chief Scientist: Sabine Mecking

University of Washington -- Applied Physics Laboratory

![](media/image1.png){width="3.717361111111111in"
height="5.997222222222222in"}

**Cruise Report**

**30 March 2006**

**Table of Contents**

**1.0
Summary............................................................................\...2**

**2.0
Introduction........................................................................\...2**

**3.0 Description of Measurements from Vertical
Profiles........................4**

***3.1 CTD/Hydrographic Measurements
Program..........................................4***

***3.2
LADCP......................................................................................18***

***3.3 Salinity
Measurements...................................................................19***

***3.4 Oxygen
Measurements................................................\...\...\...\...\...\...\...\....20***

***3.5 Nutrient
Measurements..................................................................21***

***3.6 CFC
Measurements.......................................................................22***

***3.7 DIC
Measurements...............\.........................................................24***

***3.8 TA
Measurements......\....................................................................24***

***3.9 pH Discrete
Measurements............................................................\...25***

***3.10 Discrete
pCO~2~...............................................................................26***

***3.11 Carbon/Oxygen
Isotopes.................................................................27***

***3.12 Dissolved Organic Carbon/Dissolved Organic Nutrients
..........................28***

***3.13 CDOM, chlorophyll, bacterial
suite....................................................28***

***3.14
Helium-tritium.............................................................................28***

***3.15 Trace
Metals..........................................................\......................29***

***3.16 Optical
Casts...............................................................................30***

**4.0 Underway
Measurements........................\.................................30**

***4.1 USF Underway DIC/pCO~2~/pH
........................................................31***

***4.2 NOAA/PMEL Underway
pCO~2~...................................................\...\.....31***

***4.3 UM Underway
pH\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...31***

**5.0 Other
Measurements.............................\.................................32**

***5.1 Net tows/Pteropods
.......................................................................32***

***5.2 Floats
.................................................................................\...\.....32***

**6.0
Acknowledgements................................................................32**

**7.0
References...........................................................................32**

**1.0 Summary**

The R/V *Thomas G. Thompson* completed the second half of a hydrographic
survey in the North Pacific Ocean, nominally along 152°W between 22°S
and 55°N, from 10 - 30 March 2006. Thirty-five scientists from 11
academic institutions and two NOAA laboratories participated in the
cruise. Full-depth CTD/rosette/LADCP casts were collected every 60
nautical miles. Water samples were collected from the 36-bottle rosette
at each station and analyzed for salinity, nutrients, dissolved oxygen,
four inorganic carbon parameters, radiocarbon, dissolved organic matter,
colored dissolved organic matter, chlorofluorocarbons, helium/tritium,
oxygen isotopes, chlorophyll, and a suite of bacterial measurements.
Trace metal casts to 1000m were conducted at approximately every other
station. Optical profiles were collected once each day. Plankton tows
were conducted at about 10 stations at night. Argo floats were deployed
at 8 locations. Near surface seawater and atmospheric measurements were
also made along the cruise track. No major problems were encountered on
the cruise and all major cruise objectives were achieved.

**2.0 Introduction**

The P16N Leg 2 cruise is the second half of a meridional hydrographic
section nominally along 152°W in the Pacific Ocean. This cruise is part
of a decadal series of repeat hydrography sections jointly funded by the
NOAA Office of Global Programs (now the [[Climate Program
Office]{.underline}](http://www.climate.noaa.gov/index.jsp?pg=/news/news_index.jsp&news=story_co2.html))
and the [[National Science Foundation Division of Ocean
Sciences]{.underline}](http://www.nsf.gov/div/index.jsp?div=OCE) as part
of the Climate Variability and Predictability Study (CLIVAR) CO~2~
Repeat Hydrography Program (http://ushydro.ucsd.edu). The repeat
hydrography program focuses on the need to monitor inventories of CO~2~,
heat and freshwater and their transports in the ocean. Earlier programs
under WOCE and JGOFS have provided baseline observational fields for
these parameters. The new measurements will reveal much about the
changing patterns on decadal scales. The program will serve as a
structure for assessing changes in the ocean's biogeochemical cycle in
response to natural and/or man-induced activity.

Thirty-five scientists from 11 academic institutions and two NOAA
research laboratories participated in leg 2 (Table 1) covering the
northern portion of the P16N line from Honolulu, HI to Kodiak, AK. The
R/V *Thomas G. Thompson* departed Honolulu, HI on 10 March 2006 for the
start of leg 2. Leg 1 of P16N from Papeete, Tahiti to Honolulu, HI was
conducted just prior to leg 2 from 14 February -- 3 March 2006. The
first station of leg 2 was at 22°N, 152°W. The ship then proceeded north
while we conducted a full-depth CTD/rosette/LADCP cast every 60 nautical
miles to 55°N, 152°W, where we conducted a series of 8 closely-spaced
stations normal to the Alaskan coast. Thirty-six 12L Niskin-type bottles
were used to collect water samples from throughout the water column at
each station. Each Niskin was sub-sampled on deck for a variety of
analyses. Twenty projects were represented on Leg 2 of the cruise (see
Table 1). A 1000 m trace metal cast was conducted approximately every
other station for a total of 17 trace metal casts. The trace metal casts
were conducted at approximately the same locations as the primary
profiles and were either before or after the full-depth casts depending
on time of day. One optical profile was collected each day on stations
that occurred between 10:00 and 14:00 local time. A total of 41 stations
were occupied on leg 2 (Table 2). In addition, net tows were conducted
at night at about 10 stations either while steaming into a station or
upon departure. As part of the Argo program, floats were deployed at
about 8 locations usually upon departure from a station. Underway
measurements of surface seawater properties (temperature, salinity,
pCO~2~, ADCP) and atmospheric concentrations of CO~2~, CFCs, and
aerosols were also made along the cruise track. The last station was
completed on Wednesday, 29 March, 2006. The cruise ended in Kodiak, AK
on 30 March, 2006.

Table 1. Projects and participants on P16N leg 2

+----------------+----------------+-----------------+-----------------+
| **Research     | #### PI        | ####### Le      | ## Par          |
| Project**      |                | g 2 Participant | ticipant E-mail |
+----------------+----------------+-----------------+-----------------+
| Chief          |                | Richard Feely   | richard.a       |
| Scientist      |                | (PMEL)          | .feely@noaa.gov |
+----------------+----------------+-----------------+-----------------+
| Co-chief       |                | Sabine Mecking  | smecking@apl    |
| Scientist      |                | (APL/UW)        | .washington.edu |
+----------------+----------------+-----------------+-----------------+
| Student        | David Archer   | Samantha        | siedle          |
| Support to     | (UChi)         | Deringer (UChi) | sa@uchicago.edu |
+----------------+----------------+-----------------+-----------------+
|   Chief        | Victoria Fabry | David Faber     | d               |
| Scientists     | (CSUSM)        | (CSUSM)         | faber@csusm.edu |
+----------------+----------------+-----------------+-----------------+
| Data           | Woody          | Frank Delahoyde | fdel            |
| Management     | Sutherland     | (UCSD)          | ahoyde@ucsd.edu |
|                | (UCSD)         |                 |                 |
+----------------+----------------+-----------------+-----------------+
| C              | Gregory        | Kristy          | kristene.e.mct  |
| TD-Hydrography | Johnson (PMEL) | McTaggart       | aggart@noaa.gov |
|                |                | (PMEL)          |                 |
+----------------+----------------+-----------------+-----------------+
|                | Molly Baringer | David Bitterman | david.bit       |
|                | (AOML)         | (AOML)          | terman@noaa.gov |
+----------------+----------------+-----------------+-----------------+
|                |                | Grant Rawson    | <grant.r        |
|                |                | (CIMAS/UM)      | awson@noaa.gov> |
+----------------+----------------+-----------------+-----------------+
| Argo Floats    | Howard         | Kristy          | kristene.e.mct  |
|                | Freeland (IOS) | McTaggart       | aggart@noaa.gov |
|                |                | (PMEL)          |                 |
+----------------+----------------+-----------------+-----------------+
| LADCP          | Andreas        | Debra Tillinger | debrat@ld       |
|                | Thurnherr      | (LDEO)          | eo.columbia.edu |
|                | (LDEO)         |                 |                 |
+----------------+----------------+-----------------+-----------------+
| Oxygen         | Chris Langdon  | Chris Langdon   | clangdon@       |
| Measurements   | (RSMAS/UM)     | (RSMAS/UM)      | rsmas.miami.edu |
+----------------+----------------+-----------------+-----------------+
| Nutrients      | Calvin Mordy   | Peter Proctor   | peter.p         |
|                | (PMEL)         | (PMEL)          | roctor@noaa.gov |
+----------------+----------------+-----------------+-----------------+
|                | Jia Zhang      | Charlie Fisher  | charles.f       |
|                | (AOML)         | (AOML)          | ischer@noaa.gov |
+----------------+----------------+-----------------+-----------------+
| CFC            | John Bullister | Mark Warner     | mwarner@ocea    |
| Measurements   | (PMEL)         | (UW)            | n.washingon.edu |
+----------------+----------------+-----------------+-----------------+
|                | Mark Warner    | Wendy Ruef (UW) | wruef@u         |
|                | (UW)           |                 | .washington.edu |
+----------------+----------------+-----------------+-----------------+
| DIC            | Christopher    | Dana Greeley    | dana.g          |
| Measurements   | Sabine (PMEL)  | (PMEL)          | reeley@noaa.gov |
+----------------+----------------+-----------------+-----------------+
|                | Rik            | Dave Wisegarver | david.wise      |
|                | Wa             | (PMEL)          | garver@noaa.gov |
|                | nninkhof(AOML) |                 |                 |
+----------------+----------------+-----------------+-----------------+
|                | Richard Feely  |                 |                 |
|                | (PMEL)         |                 |                 |
+----------------+----------------+-----------------+-----------------+
| TA             | Frank Millero  | Taylor Graham   | tgraham@        |
| M              | (RSMAS/UM)     | (RSMAS/UM)      | rsmas.miami.edu |
| easurements/pH |                |                 |                 |
| Discrete       |                | Ben West        | <sharke         |
|                |                | (RSMAS/UM)      | y585@yahoo.com> |
| Measurements   |                |                 |                 |
| (              |                | Mareva Chanson  | mchanson@       |
| secondary)/Un- |                | (RSMAS/UM)      | rsmas.miami.edu |
|                |                |                 |                 |
| derway pH      |                |                 |                 |
+----------------+----------------+-----------------+-----------------+
| pH Discrete    | Robert Byrne   | Robert Byrne    | byrne           |
| Measurements   | (USF)          | (USF)           | @marine.usf.edu |
+----------------+----------------+-----------------+-----------------+
| (primary)      |                | Zhaohui 'Aleck' | awang           |
|                |                | Wang (USF)      | @marine.usf.edu |
|                |                |                 |                 |
|                |                | Johan Schijf    | schijf          |
|                |                | (USF)           | @marine.usf.edu |
+----------------+----------------+-----------------+-----------------+
|                |                | Ryan Bell (USF) | rbell           |
|                |                |                 | @marine.usf.edu |
+----------------+----------------+-----------------+-----------------+
| Discrete       | Rik Wanninkhof | Bob Castle      | robert.         |
| pCO~2~         | (AOML)         | (AOML)          | castle@noaa.gov |
+----------------+----------------+-----------------+-----------------+
| Underway       | Robert Byrne   | Zhaohui 'Aleck' | awang           |
| DIC/pCO~2~/pH  | (USF)          | Wang (USF)      | @marine.usf.edu |
+----------------+----------------+-----------------+-----------------+
| Underway       | Richard Feely  | David           | david.wise      |
| pCO~2~         | (PMEL)         | Wisegarver      | garver@noaa.gov |
|                |                | (PMEL)          |                 |
+----------------+----------------+-----------------+-----------------+
| Biologist/Net  | Victoria Fabry | Victoria Fabry  | fabry@csusm.edu |
| Tows           | (CSUSM)        | (CSUSM)         |                 |
+----------------+----------------+-----------------+-----------------+
| Carbon         | Ann McNichol   | Laurie Juranek  | juranek@ocean   |
| Isotopes       | (WHOI)         | (UW)            | .washington.edu |
+----------------+----------------+-----------------+-----------------+
|                | Paul Quay (UW) |                 |                 |
+----------------+----------------+-----------------+-----------------+
| Dissolved      | Dennis Hansell | Wenhao Chen     | wenchen@        |
| Organic Carbon | (RSMAS/UM)     | (RSMAS/UM)      | rsmas.miami.edu |
+----------------+----------------+-----------------+-----------------+
| CDOM,          | Dave Siegel    | Chantal Swan    | swan            |
| chlorophyll,   | (UCSB)         | (UCSB)          | @icess.ucsb.edu |
| bacteria,      |                |                 |                 |
+----------------+----------------+-----------------+-----------------+
| CDOM           | Craig Carlson  | Elisa Wallner   | wallner@l       |
| fluorometer on | (UCSB)         | (UCSB)          | ifesci.ucsb.edu |
| rosette        |                |                 |                 |
+----------------+----------------+-----------------+-----------------+
| Helium-tritium | Peter          | Anthony         | dachille@ld     |
|                | Schlosser      | Dachille (LDEO) | eo.columbia.edu |
|                | (LDEO)         |                 |                 |
+----------------+----------------+-----------------+-----------------+
| Trace Metals   | Chris Measures | Bill Landing    | w               |
| (seawater and  | (UH)           | (FSU)           | landing@fsu.edu |
+----------------+----------------+-----------------+-----------------+
|  aerosols)     | Bill Landing   | Cliff Buck      | cbuc            |
|                | (FSU)          | (FSU)           | k@ocean.fsu.edu |
+----------------+----------------+-----------------+-----------------+
|                |                | Paul Hansard    | hansar          |
|                |                | (FSU)           | d@ocean.fsu.edu |
+----------------+----------------+-----------------+-----------------+
|                |                | Bill Hiscock    | his             |
|                |                | (UH)            | cock@hawaii.edu |
+----------------+----------------+-----------------+-----------------+
|                |                | Lyle Leonard    | l               |
|                |                | (UH)            | ylel@hawaii.edu |
+----------------+----------------+-----------------+-----------------+
| Oxygen/Argon   | Paul Quay (UW) | Laurie Juranek  | juranek@ocean   |
| Measurements   |                | (UW)            | .washington.edu |
+----------------+----------------+-----------------+-----------------+
| T              | Wilf Gardner   | Chantal Swan    | swan            |
| ransmissometer | (TAMU)         | (UCSB)          | @icess.ucsb.edu |
| on rosette     |                |                 |                 |
+----------------+----------------+-----------------+-----------------+

**3.0 Description of Measurements from Vertical Profiles**

***3.1 CTD/Hydrographic Measurements Program***

The basic CTD/hydrographic measurements consisted of salinity, dissolved
oxygen and nutrient measurements made from water samples taken on
LADCP/CTD/rosette casts, plus pressure, temperature, salinity, dissolved
oxygen, transmissometer and fluorometer from CTD profiles. A total of 43
casts (78/1 and 83/1 were aborted) were conducted on leg 2, usually to
within 10-20m of the bottom (Table 2). Figure 1 shows the sample
locations of the discrete water samples. No major problems were
encountered during the operation; however, one station was lost due to
bad weather conditions.

*3.1.1 Water Sampling Package*

CTD/rosette casts were performed with a package consisting of a
36-bottle rosette frame (PMEL), a 36-place pylon (SBE32) and 36 12-liter
Niskin type Bullister bottles (PMEL). Underwater electronic components
consisted of a Sea-Bird Electronics SBE9plus CTD with dual pumps, dual
temperature sensors (SBE3plus), dual conductivity sensors (SBE4), a
dissolved oxygen sensor (SBE43),transmissometer (Wetlabs), fluorometer
(Wetlabs), load cell (PMEL), altimeter (Simrad), pinger (Benthos) and
upward and downward looking LADCPs (RDI) (see table 3).

The CTD was mounted vertically in an SBE CTD frame attached to a plate
welded in the center of the rosette frame, under the pylon. The SBE4
conductivity and SBE3plus temperature sensors and their respective pumps
were mounted vertically as recommended by SBE. Pump exhausts were
attached to inside corners of the CTD cage and directed downward. The
transmissometer was mounted horizontally and the fluorometer vertically,
attached to a rigid plastic screen that did not impede water flow. The
altimeter was mounted on the inside of the bottom frame ring. The RDI
LADCPs were mounted vertically on the top and bottom frame rings. The
LADCP battery pack was mounted on the bottom of the frame.

The WetLabs UV fluorometer was designed to stimulate and measure
fluorescence of CDOM. We were evaluating the use of this instrument to
supplement or enhance bottle CDOM measurements, as bottle samples often
do not have the depth resolution needed to resolve the observed strong
near-surface gradients in CDOM concentration, and on cruises such as
this we were not able to sample CDOM on every station. On three of the
stations, the fluorometer was covered with duct tape to quantify the
background "dark" readings for calibration purposes. This fluorometer
was ganged to a WetLabs C-star 660 nm 0.1m pathlength beam
transmissometer belonging to Dr. Wilf Gardner, TAMU. The transmissometer
developed troubles on the upcast of station 56. The instrument remained
on on the CTD, but the data beyond this station may not be correctable.

The rosette system was suspended from a UNOLS-standard three-conductor
(0.322") electro-mechanical sea cable using the R/V Thompson's forward
winch on the aft starboard side. This cable replaced the 0.322" cable
used on leg 1 (spooled on the aft winch) since it was found that the aft
cable had flat spots in the lower layers on the drum which limited the
maximum wireout to 5200m. Despite initial concerns that the weight of
the 36 bottle rosette would put an extensive amount of stress on the
older replacement wire, especially at deep stations and under rough
seas, no significant winch or wire problems were encountered on leg 2.

Table 2. P16N leg 2 CTD rosette station locations

**Sta Date UTC Latitude Longitude Depth^1^ Hab^2^ Wire^3^ Pmax^4^**

44 12 Mar 06 1330 22 0.02 N 152 0.02 W 5156 10 5188 5252

45 13 Mar 06 0058 23 0.00 N 152 0.00 W 5397 9 5546 5547

46 13 Mar 06 1347 24 0.00 N 152 0.01 W 5526 10 5628 5700

47 13 Mar 06 2350 24 59.97 N 152 0.01 W 5361 8 5417 5486

48 14 Mar 06 1131 26 0.01 N 152 0.02 W 5292 10 5381 5448

49 14 Mar 06 2114 27 0.00 N 152 0.00 W 5347 9 5396 5463

50 15 Mar 06 0828 28 0.01 N 152 0.01 W 5467 11 5547 5617

51 15 Mar 06 2012 29 0.00 N 152 0.00 W 5508 10 5655 5730

52 16 Mar 06 0708 30 0.00 N 152 0.00 W 5326 10 5417 5480

53 16 Mar 06 1644 30 59.98 N 152 0.02 W 5301 10 5578 5446

54 17 Mar 06 0327 31 59.99 N 152 0.02 W 5194 9 5288 5354

55 17 Mar 06 1342 32 59.98 N 152 0.00 W 5373 10 5451 5522

56 18 Mar 06 0002 33 59.98 N 152 0.03 W 5507 10 5643 5619

57 18 Mar 06 1040 35 0.00 N 152 0.00 W 5652 16 5739 5809

58 18 Mar 06 2107 36 0.00 N 152 0.01 W 5510 14 5575 5662

59 19 Mar 06 1048 36 59.99 N 152 0.00 W 5530 20 5603 5682

60 19 Mar 06 2302 37 59.98 N 152 0.03 W 4930 19 4988 5051

61 20 Mar 06 0953 39 0.00 N 152 0.00 W 5782 13 5862 5948

62 20 Mar 06 2018 40 0.00 N 152 0.00 W 5177 n/a n/a 5324

63 21 Mar 06 0837 41 0.00 N 152 0.00 W 4995 20 5054 5120

64 21 Mar 06 2008 41 59.98 N 151 59.92 W 5035 21 5099 5166

65 23 Mar 06 0952 44 0.01 N 151 59.97 W 5497 22 5632 5716

66 23 Mar 06 2116 44 59.99 N 151 59.98 W 5282 19 5354 5428

67 24 Mar 06 1006 46 0.00 N 152 0.01 W 5230 20 5343 5416

68 24 Mar 06 1938 47 0.00 N 152 0.01 W 5073 15 5143 5218

69 25 Mar 06 0612 48 0.10 N 151 59.92 W 4896 22 4885 4950

70 25 Mar 06 1628 49 0.01 N 151 59.96 W 4980 10 5043 5110

71 26 Mar 06 0248 50 0.00 N 151 59.97 W 4908 21 4963 5031

72 26 Mar 06 1159 50 59.99 N 151 59.99 W 4951 9 5011 5081

73 26 Mar 06 2238 51 59.99 N 151 59.93 W 5087 12 5130 5201

74 27 Mar 06 1007 53 0.00 N 152 0.00 W 4446 11 4483 4541

75 27 Mar 06 2018 54 0.00 N 152 13.21 W 4393 19 4450 4508

76 28 Mar 06 0637 55 0.00 N 152 39.58 W 4199 19 4122 4266

77 28 Mar 06 1429 55 30.00 N 152 52.82 W 5352 19 5404 5482

78 29 Mar 06 0105 55 40.20 N 152 57.00 W 4954 16 5035 5106

79 29 Mar 06 0713 55 46.19 N 153 0.02 W 3920 13 4048 4095

80 29 Mar 06 1203 55 51.01 N 153 1.81 W 3429 20 3292 3324

81 29 Mar 06 1645 55 55.18 N 153 3.59 W 2422 10 2361 2380

82 29 Mar 06 2147 56 0.60 N 153 5.98 W 1832 20 1795 1809

83 30 Mar 06 0313 56 13.19 N 153 11.38 W 1084 20 1125 1134

84 30 Mar 06 0711 56 16.81 N 153 13.21 W 399 9 391 395

^1^Depth \[m\] is uncorrected bottom depth from shipboard Knudsen
echosounder

^2^Height above bottom \[m\] at maximum pressure from Simrad altimeter

^3^Wire out \[m\] of winch cable at maximum pressure

^4^Maximum pressure \[db\] of CTD package

![](media/image2.jpeg){width="6.4006944444444445in"
height="4.801388888888889in"}

The deck watch prepared the rosette 10-15 minutes prior to each cast.
The bottles were cocked and all valves, vents and lanyards were checked
for proper orientation. The CTD was powered up about 10 minutes prior to
station. Once stopped on station, the data acquisition system in the
computer lab was started when directed by the deck watch leader. The
rosette was unstrapped from its tiedown location on deck. The pinger was
activated and syringes were removed from the CTD intake ports. The winch
operator was directed by the deck watch leader to raise the package, the
squirt boom and rosette were extended outboard and the package quickly
lowered into the water. The package was lowered to at least 10 meters
and held there for 1 minute after the sensor pumps had turned on. The
winch operator was then directed to bring the package back to the
surface (0 winch wireout) and to begin the descent.

At each station the CTD rosette was lowered to within 10-20 meters of
the bottom (Table 2) depending on weather conditions and bottom slope,
using both the pinger and altimeter to determine the height above
bottom. During the upcast the winch operator was directed to stop the
winch at each bottle trip depth. The CTD console operator waited 30
seconds before tripping a bottle to insure the package wake had
dissipated and the bottles were flushed, then an additional 10 seconds
after bottle closure to insure that stable CTD comparison data had been
acquired. Once a bottle had been closed, the console operator directed
the winch operator to haul in the package to the next bottle stop.
Standard sampling depths that were staggered at every other station were
used throughout the cruise (Figure 1).

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. The rosette was secured on deck under the block 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. No bottles were
replaced on this cruise, but various parts of bottles were occasionally
changed or repaired.

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

The SBE32 carousel frequently didn\'t release properly causing
mistripped bottles. This continual problem worsened toward the end of
the cruise, in spite of several repair attempts.

Two rosette casts (78/1 and 83/1) were aborted because of a sudden loss
of shipboard power. The casts were brought back on deck and the ship
repositioned before deploying the rosette again.

*3.1.2 Underwater Electronics Packages*

CTD data were collected with a SBE9plus CTD (Table 3). This instrument
provided pressure, dual temperature (SBE3), dual conductivity (SBE4),
dissolved oxygen (SBE43), fluorometer (Wetlabs), transmissometer
(Wetlabs), load cell (PMEL) and altimeter (Simrad 807) channels. The CTD
supplied a standard SBE-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 into one pump circuit and secondary
temperature and conductivity into the other. The sensors were deployed
vertically. The primary temperature and conductivity sensors (Table 3)
were used for reported CTD temperatures and conductivities on all casts
except cast 81/1 where biofouling occurred on the sensors. The secondary
temperature and conductivity sensors were used in this case as well as
for calibration checks otherwise.

The SBE9plus CTD was connected to the SBE32 36-place pylon providing for
single-conductor sea cable operation. The sea cable armor was used for
ground (return). Power to the SBE9plus CTD (and sensors), SBE32 pylon
and Simrad 807 altimeter was provided through the sea cable from the
SBE11plus deck unit in the main lab.

*3.1.3 Navigation and Bathymetry Data Acquisition*

Navigation data were acquired at 1-second intervals from the ship\'s
P-Code GPS receiver by a Linux system that provided a web-page with
continuous updates to the ship's position and to the arrival times for
upcoming stations throughout the cruise. Bathymetric data were collected
using the Ship\'s 12khz Knudsen echosounder system. These data were
logged using the R/V *Thompson's* DAS system as well as a direct
connection to the above Linux system about half-way through leg 2.
Interruptions to the acquisition of the bathymetric data occurred when
the Knudsen system was switched to receive the frequency of the pinger
to track the distance between the CTD rosette package and the bottom
starting at about a 1000m above the bottom.

Table 3. P16N leg 2 underwater electronics

  ------------------------------ ---------------------- ----------- ------------
  **Sensor**                     **Serial Number**      **Calib.    **Calib.
                                                        Date**      Facility**

  Sea-Bird SBE32 36-place        S/N 3229650-0431       N/A         N/A
  Carousel Water Sampler                                            

  Sea-Bird SBE9plus CTD          S/N 09P8431-0315       N/A         N/A

  Paroscientific Digiquartz      S/N 53960              25-MAY-05   SBE
  Press. Sensor                                                     

  Sea-Bird SBE3plus Temp. Sensor S/N 03P-4341 (Primary) 15-NOV-05   SBE

  Sea-Bird SBE3plus Temp. Sensor S/N 03P-4335           15-NOV-05   SBE
                                 (Secondary)                        

  Sea-Bird SBE4C Conductivity    S/N 04-2887 (Primary)  15-NOV-05   SBE
  Sensor                                                            

  Sea-Bird SBE4C Conductivity    S/N 04-3068            15-NOV-05   SBE
  Sensor                         (Secondary)                        

  Sea-Bird SBE43 DO Sensor       S/N 43-0664            29-NOV-05   SBE

  Sea-Bird SBE43 DO Sensor       S/N 43-0313            03-DEC-05   SBE

  Wetlabs CDOM Fluorometer       S/N FLCDRTD-428        09-DEC-05   Wetlabs

  Wetlabs CST Transmissometer    S/N CST-327DR          26-JAN-06   Wetlabs

  PMEL LoadCell                  S/N 1109               N/A         N/A

  Simrad 807 Altimeter           S/N 98110              N/A         N/A

  Benthos Pinger                 S/N 1134               N/A         N/A

  RDI WH300 Workhorse LADCP      LDEO #299 (Upward)     N/A         N/A

  RDI WH300 Workhorse LADCP      LDEO #149 (Downward)   N/A         N/A
  ------------------------------ ---------------------- ----------- ------------

*3.1.4 CTD Data Acquisition and Rosette Operation*

The CTD data acquisition system consisted of an SBE-11plus (V2) deck
unit and a networked generic PC workstation running Windows XP. 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 had 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 meters. The CTD sensor pumps were configured with a 60 second
startup delay, and were usually on by this time. 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 (wire-out). The profiling rate was no more than
30m/min to 50m, no more than 45m/min to 200m and no more than 60m/min
deeper than 200m varying with 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, pinger and bathymetric depth were all monitored to determine
the distance of the package from the bottom, usually allowing a safe
approach to within 10 meters. Bottles were closed on the up cast by
operating an on-screen control. Bottles were tripped 30 seconds after
stopping at the trip location to allow the rosette wake to dissipate and
the bottles to flush. The winch operator was instructed to proceed to
the next bottle stop 10 seconds after closing bottles to insure that
stable CTD data were associated with the trip. After the last bottle was
closed, the console operator directed the deck watch to bring the
rosette on deck. Once out of the water, the console operator terminated
the data acquisition, turned off the deck unit and assisted with rosette
sampling.

*3.1.5 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 XP workstation
were copied onto the Linux database and web server system, then
processed to a 0.5 second time series. Bottle trip values were extracted
and a 2 decibar 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 were also available for
distribution). During and after the deployment the data were redundantly
backed up to another Linux system. 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. T, S and theta-O~2~ comparisons were made between
down and up casts as well as between groups of adjacent deployments.
Vertical sections of measured and derived properties from sensor data
were checked for consistency. Few CTD acquisition and processing
problems were encountered during P16N. A clogged bleeder valve in the
primary pump circuit led to using the upcasts of 50/1 and 51/1. DO
sensor offsets appearing on the downcasts during unscheduled winch stops
on 60/2 and 64/1 led to replacement of the DO sensor prior to 67/1, and
filtering-out the offsets. Cast 78/1 and 83/1 were aborted due to
shipwide power failures. Biofouling of the primary sensors on 81/1 led
to using T2 and C2 sensors for reported T and C data, and filtering the
downcast O2 data. A total of 43 casts were made (including 2 aborted
casts) using the

36-place CTD/LADCP rosette.

*3.1.6 CTD Sensor Laboratory and Shipboard Calibrations*

Laboratory calibrations of the CTD pressure, temperature, conductivity
and dissolved oxygen sensors were performed prior to P16N. Serial
numbers and calibration dates are listed in table 3. In-situ salinity
and dissolved O~2~ samples collected during each cast were used in
addition to calibrate the conductivity and dissolved O~2~ sensors.

Calibration coefficients derived from the calibration of the
Paroscientific Digiquartz pressure transducer were applied to raw
pressures during each cast. Residual pressure offsets (the difference
between the first and last submerged pressures) were examined to check
for calibration shifts. All were \< 0.7dbar, and the sensor exhibited \<
0.2 dbar offset shift over the period of use. No additional adjustments
were made to the calculated pressures.

*3.1.7 CTD Shipboard Calibration Procedures*

CTD 09P8431-0315 was used for all P16N casts (Table 3). The CTD was
deployed with all sensors and pumps aligned vertically, as recommended
by SBE. The primary temperature and conductivity sensors (T1 & C1) were
used for all reported CTD data on all casts except 81/1, the secondary
sensors (T2 & C2) serving as calibration checks. In-situ salinity and
dissolved O2 check samples collected during each cast were used to
calibrate the conductivity and dissolved O2 sensors.

*3.1.8 CTD Pressure*

The Paroscientiﬁc Digiquartz pressure transducer (S/N 53960) was
calibrated in May2005 at SBE (Table 3). Calibration coefﬁcients derived
from the calibration were applied to raw pressures during each cast.
Residual pressure offsets (the difference between the ﬁrst and last
submerged pressures) were examined to check for calibration shifts. All
were \< 0.7db, and the sensor exhibited \< 0.2 db offset shift over the
period of use. No additional adjustments were made to the calculated
pressures.

*3.1.9 CTD Temperature*

A single primary temperature sensor (SBE 3, S/N 03P-4341) and secondary
temperature sensor (SBE 3, S/N 03P-4335) served the entire cruise (Table
3). Calibration coefficients derived from the pre-cruise calibrations
were applied to raw primary and secondary temperatures during each cast.
Calibration accuracy was monitored by comparing the primary and
secondary temperatures at each rosette trip. Calibration accuracy was
examined by tabulating T1-T2 over a range of pressures and temperatures
(bottle trip locations) for each cast. No significant temperature or
pressure slope was evident. These comparisons are summarized in Figure 2
for all stations from legs 1 and 2. Since the primary and secondary
conductivity sensors had been stable, analysis of the differences
between salinity calculated from sensor pairs with bottle salinities
identified the drifting temperature as T2.

The 95% confidence limit for the mean of the differences is +/-0.0073°C.
The variance is relatively high in spite of the small spatial separation
of the sensors (\<0.5 meters) because of package wake effects.

*3.1.10 CTD Conductivity*

A single primary conductivity sensor (SBE 4, S/N 04-2887) and secondary
conductivity sensor (SBE 4, S/N 04-3068) served the entire leg (Table
3). 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
(calculated from bottle salinities) were used to derive conductivity
corrections. To reduce the contamination of the comparisons by package
wake, differences between primary and secondary temperature sensors were
used as a metric of variability and used to qualify the comparisons. The
coherence of this relationship is illustrated in Figure 3.

Neither of the sensors exhibited a secondary pressure response. The
uncorrected comparison between the primary and secondary sensors is
shown in Figure 4, and between C2 and the bottle salinities in Figure 5
for legs 1 and 2. Note that the bottle salinities were unusable for
check sample purposes due to analytical temperature problems for casts
1/2-7/1.

Since C2 showed no significant conductivity slope or offset relative to
bottle conductivities, and since the comparison to C1 showed only minor
(\<0.001mS/cm) drift and shifts), C1 was calibrated to C2. No correction
was made to C2. The comparison of the primary and secondary conductivity
sensors by cast after applying shipboard corrections is summarized in
Figure 6.

![](media/image3.jpeg){width="6.288194444444445in" height="3.4875in"}

C1 was calibrated against C2 on the previous leg, and the sensors
continued to track to within ±0.74 mS/cm over both legs. No changes in
conductivity slopes or secondary responses were noted during leg 2. The
bottle salinities are problematic after cast 71/1. The salinometer dial
setting was changed from 525 to 545 and standard drift rates increased
sharply for subsequent runs. It appears that the lab temperature was
fluctuating, and the standard dial setting was changed to attempt to
compensate for the fluctuation. C1-C2 differences indicate that these
check samples have a mean offset of +0.002. Salinities are reported
using the Practical Salinity Scale of 1978 (PSS-78). Salinity residuals
after applying shipboard T1/C1 corrections are summarized in Figures 7
and 8. Figures 7 and 8 represent estimates of the salinity accuracy on
P16N.

A single SBE43 dissolved O~2~ (DO) sensor was used for most of leg 2
(S/N 43-0663). The sensor was plumbed into the primary T1/C1 pump
circuit after C1. The sensor was replaced prior to cast 67/1 against a
different SBE43 DO sensor (S/N 43-0313) because of offsets that began to
appear after unscheduled winch stops on the downcasts of 60/2 and 64/1.
The DO sensors were calibrated to dissolved O~2~ check samples at bottle
stops by calculating CTD dissolved O~2~ then minimizing the residuals
using a non-linear least-squares fitting procedure. The fitting
procedure determined the calibration coefficients for the sensor model
conversion equation, and was accomplished in stages. The time constants
for the exponential terms in the model were first determined for each
sensor. These time constants are sensor-specific but applicable to an
entire cruise. Next, casts were fit individually to check sample data.
The resulting calibration coefficients were then smoothed and held
constant during a refit to determine sensor slope and offset. Standard
and blank values for bottle oxygen data were smoothed and the bottle
oxygen recalculated prior to the final fitting of CTD oxygen. The
residuals are shown in Figures 9-11.

The standard deviations of 5.63 uM/kg for all oxygens and 1.29 uM/kg for
low-gradient oxygens are only presented as general indicators of
goodness of ﬁt. ODF makes no claims regarding the precision or accuracy
of CTD dissolved O~2~ data.

The general form of the ODF O~2~ conversion equation for Clark cells
follows Brown and Morrison (1978), Millard (1982) and Owen 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 1st-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. 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)

where:

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

Oc = Sensor current (µamps);

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

S = Salinity at O~2~ response-time;

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 (µamps/secs);

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

*3.1.11 Bottle Sampling*

At the end of each rosette deployment water samples were drawn from the
bottles in the following order:

o CFCs

o He

o O~2~

o Ar and O~2~ isotopes

o pCO~2~

o Dissolved Inorganic Carbon (DIC)

o pH

o Total Alkalinity

o C-13/C-14

o Dissolved Organic Carbon (DOC)

o CDOM

o Bacterial Suite

o Salinity

o Nutrients

o Tritium

o PIC/POC

Water samples for analyses of dissolved SF~6~ and pteropods were
collected at a few stations throughout the cruise. These samples were
collected to support laboratory experiments onboard the ship.

The correspondence between individual sample containers and the rosette
bottle position (1-36) 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 sole
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.

*3.1.12 Bottle Data Processing*

Water samples collected and properties analyzed shipboard were managed
centrally in a relational database (PostgreSQL-8.0.3) run on a Linux
system. A web service (OpenAcs-5.2.2 and AOLServer-4.0.10) front-end
provided ship-wide access to CTD and water sample data. 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. Quality flags associated with sampled properties
were set to indicate that the property had been sampled, and sample
container identifications were noted where applicable (e.g., oxygen
flask number). Analytical results were provided on a regular basis by
the various analytical groups and incorporated into the database. 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 and Corry, 1994).
Various consistency checks and detailed examination of the data
continued throughout the cruise.

***3.2 LADCP***

Two RDI 300-kHz Acoustic Doppler Current Profilers (ADCPs) were mounted
on the CTD frame with one transducer pointing downward and the other
pointing upward. They were powered by a \"DeepSea Power and Light \"
rechargeable sealed lead-acid battery pack. The battery was charged and
the instruments activated before each cast. While on deck, the ADCPs
were connected to a Macintosh computer that handled both instrument
setup and data processing. Both ADCPs were set up to record single-ping
beam-coordinate velocity ensembles in 10m bins. Between casts, the data
from the ADCPs were downloaded and processed using the LDEO (Columbia
University) processing software (Thurnherr, 2006). The processing
combined CTD, GPS, and shipboard ADCP data with the data from the
lowered ADCPs to produce both shear and inverse solutions of absolute
velocities. The results showed weak currents in most areas, with a
strong eastward surface current at station 49 (Figure 12). The strongest
flow was recorded in the Alaska current, which reached a westward
velocitity maximum of 60 cm/s at station 80. This current was noticeable
in the data from stations 78 through 82 (Figure 12).

![](media/image4.jpeg){width="6.407638888888889in"
height="4.830555555555556in"}

***3.3 Salinity Measurements***

A single Guildline Autosal Model 8400A salinometer (S/N 48-266), located
in a container lab on the aft deck , was used for all salinity
measurements. The salinometer was modified by SIO/ODF to contain an
interface for computer-aided measurement. The water bath temperature was
set and maintained at a value near the laboratory air temperature
(24°C). The salinity analyses were performed after samples had
equilibrated to laboratory temperature, usually within 6-8 hours after
collection. The salinometers were standardized for each group of
analyses (usually 1-2 casts, up to \~40 samples) using at least two
fresh vials of standard seawater per group. Salinometer measurements
were made by computer, the analyst prompted by the software to change
samples and flush.

3250 salinity measurements were made and approximately 200 vials of
standard water (SSW) were used. Salinity samples were drawn into 200 ml
Kimax high-alumina borosilicate bottles, which were rinsed three times
with sample prior to filling. The bottles were sealed with custom-made
plastic insert thimbles and Nalgene screw caps. This assembly provides
very low container dissolution and sample evaporation. Prior to sample
collection, inserts were inspected for proper fit and loose inserts
replaced to insure an airtight seal. The draw time and equilibration
time were logged for all casts. Laboratory temperatures were logged at
the beginning and end of each run. PSS-78 salinity (UNESCO, 1981) was
calculated for each sample from the measured conductivity ratios. The
difference (if any) between the initial vial of standard water and the
next one run as an unknown was applied as a linear function of elapsed
run time to the data. The corrected salinity data were then incorporated
into the cruise database.

The temperature in the salinometer laboratory varied from 21 to 24°C,
during the cruise. The air temperature change during any particular run
varied from -1.2 to +2.2°C. Insufficient sample equilibration times were
sometimes a problem as was having to collect samples on deck. The
salinometer standard dial setting which had been constant for most of
the cruise was changed from 525 to 545 after cast 71/1 and the standard
drift rates increased sharply for subsequent runs. These runs show a
mean offset of +0.002 relative to calibrated CTD conductivity. The
estimated accuracy of bottle salinities run at sea is usually better
than +/-0.002 relative to the particular standard seawater batch used.
The 95% confidence limit for residual differences between the bottle
salinities and calibrated CTD salinity relative to SSW batch P-145 was
+/-0.010 for all salinities, and +/-0.0035 for salinities collected in
low gradients. IAPSO Standard Seawater Batch P-145 was used to
standardize all casts.

***3.4 Oxygen Measurements***

Samples were drawn from Niskin bottles into calibrated 140 ml iodine
titration flasks using Tygon tubing with a Silicone adapted that fit
over the petcock to avoid contamination of DOM samples. Bottles were
rinsed twice and filled from the bottom, overflowing three volumes while
taking care not to entrain any bubbles. The draw temperature was taken
using a digital thermometer with a flexible thermistor probe that was
inserted into the flask while the sample was being drawn. These
temperatures were used to calculate μmol kg^-1^ concentrations, and a
diagnostic check of bottle integrity. One-ml of MnCl~2~ and one-ml of
NaOH/NaI were added using a Repipetor, 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 plus 1-2 duplicates were
drawn from each station except the shallow coastal stations where only
15-28 samples were drawn. Total number of samples collected was 1536;
total number of samples flagged after initial shipboard reduction of
quality control: Questionable (QC=3): Bad (QC=4): Not reported (QC=5).

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. Thiosulfate was dispensed by
a Dosimat 665 fitted with a 5.0 ml buret. The whole-bottle titration
technique of Carpenter (1965) with modifications by Culberson et al.
(1991) was used, but with a more dilute solution of thiosulfate (10 g
L^-1^). Standard curves were run each day. The reagent blank was taken
to be the intercept of the standard curve and compared to the reagent
blank determined by the convention two titration method. The
autotitrator and Dosimat generally performed well. Endpoints were noted
to be noisy during periods of particularly bad weather. Thiosulfate
molarities were calculated from titration of the standard iodate
solution dispensed using a calibrated Wheaton bottle top dispensor 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 recalculate. Oxygen flask volumes were determined gravimetrically
with degassed deionized water to determine flask volumes at AOML and
corrected for the buoyancy factor. The Dosimat and Wheaton positive
displacement dispenser used for dispensing the KIO~3~ were calibrated in
the same way. 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.

In addition to the photometric end-point technique, samples from several
stations during leg 2 were analyzed using an amperometric detection
method (Culberson and Huang, 1987) for comparison. This was done to test
amperometric detection method for future standard use. The difference
between the two techniques was on average \<1 μmol kg^-1^.

***3.5 Nutrient Measurements***

Nutrient samples were collected from the Niskin bottles in acid washed
25-ml linear polyethylene bottles after three complete seawater rinses
and analyzed within 1 hour of sample collection. Measurements were made
in a temperature-controlled laboratory (20±2°C). Concentrations of
nitrite (NO~2~^-^), nitrate (NO~3~^-^), phosphate (PO~4~^3-^) and
silicic acid (H~4~SiO~4~) were determined using an Alpkem Flow Solution
Auto-Analyzer aboard the ship. During this cruise approximately 3000
samples were analyzed along with their standards and baseline samples.
The following analytical methods were employed:

*3.5.1 Nitrate and Nitrite*

Nitrite was determined by diazotizing with sulfanilamide and coupling
with N-1 naphthyl ethylenediamine dihydrochloride to form an azo dye.
The color produced is measured at 540 nm (Zhang et al., 1997). Samples
for nitrate analysis were passed through a home made cadmium column
(Zhang et al., 2000), which reduced nitrate to nitrite and the resulting
nitrite concentration was then determined as described above. Nitrate
concentrations were determined from the difference of nitrate + nitrite
and nitrite.

*3.5.2 Phosphate*

Phosphate in the samples was determined by reacting with molybdenum (VI)
and antimony (III) in an acidic medium to form an
antimonyphosphomolybdate complex a temperature of 55°C. This complex was
subsequently reduced with hydrazine to form a blue complex and the
absorbance was measured at 815 nm (Zhang et al., 2001).

*3.5.3 Silicic Acid*

Silicic acid in the sample was analyzed by reacting the aliquote with
molybdate in a acidic solution to form molybdosilicic acid. The
molybdosilicic acid was then reduced by SnCl~2~ to form molybdenum blue
(Gordon et al., 1995). The absorbance of the molybdenum blue was
measured at 660 nm.

*3.5.4 Calibration and Standards*

Stock standard solutions were prepared by dissolving high purity
standard materials (KNO~3~, NaNO~2~, KH~2~PO~4~ and Na~2~SiF~6~ ) in
deionized water. Working standards were freshly made at each station by
diluting the stock solutions in low nutrient seawater. The low nutrient
seawater used for the preparation of working standards, determination of
blank, and wash between samples was filtered seawater obtained from
low-nutrient Pacific surface waters. Standardizations were performed
prior to each sample run with working standard solutions. Replicates
were usually collected at the deepest Niskin bottle from each cast. The
relative standard deviation from the results of these replicate samples
was used to estimate the overall precision obtained by the sampling and
analytical procedures. The precisions of these samples were 0.04 µmol/kg
for nitrate, 0.01 µmol/kg for phosphate and 0.1 µmol/kg for silicic
acid.

***3.6 CFC Measurements***

Samples for the analysis of dissolved CFC-11, CFC-12, and CFC-113 were
drawn from 960 of the 1300 water samples collected during the
expedition. Specially designed 12 liter water 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 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,
helium-3, dissolved oxygen, alkalinity and pH 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 3-way plastic stopcocks. The syringes were
immersed in a holding bath of freshwater until analyzed.

For air sampling, a \~100 meter 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 CFC van using an Air Cadet pump. The
air was compressed in the pump, with the downstream pressure held at
\~1.5 atm. using a back-pressure 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 SF~6~ analytical systems, while the bulk flow of the air
(\>7 l min^-1^) was vented through the back pressure regulator. Air
samples were generally analyzed when the ship was on station and 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 for
approximately 45 minutes prior to analysis to insure that the air inlet
lines and pump were thoroughly flushed. The average atmospheric
concentrations determined during the cruise (from a set of 5
measurements analyzed approximately once per day, n=23) were 252.9 +/-
4.4 parts per trillion (ppt) for CFC-11, 547.2 +/- 5.0 ppt for CFC-12,
and 76.3 +/- 1.9 ppt for CFC-113.

Concentrations of CFC-11 and CFC-12, and CFC-113 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 95 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^o^C) for the initial separation of
CFC-12, CFC-11 and CFC-113 from other compounds. 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^o^C) of GC1 (a HP 5890 Series II gas chromatograph with ECD),
the flow through the pre-column was reversed to backflush slower eluting
compounds. Both of the analytical systems were calibrated frequently
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 \~10.5 minutes.

Concentrations of the CFCs in air, seawater samples and gas standards
are reported relative to the SIO98 calibration scale (Prinn 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 concentrations are given in units of
picomoles per kilogram seawater (pmol kg^-1^). CFC 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 (UW cylinder 45191
for CFC-11: 386.94 ppt, CFC-12: 200.92 ppt, and CFC-113: 105.4 ppt) into
the analytical instrument. The response of the detector to the range of
moles of CFC-12 and CFC-113 passing through the detector remained
relatively constant during the cruise. A thorough baking of the column
and trap after a power outage during trapping of a seawater sample
introduced an unknown contaminant into the column changed the response
of the detector to CFC-11. Full-range calibration curves were run at
intervals of 10 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=395) were ± 0.44% for CFC-12, 0.56% for CFC-11, and 3.0%
for CFC-113.

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 were
approximately \<1 % for all 3 compounds. A fit of the re-strip
efficiency as a function of temperature will be applied to the final
data set. No correction has been applied to the preliminary data set.
The determination of a blank due to sampling and analysis of CFC-free
waters was hampered by a contamination peak that co-eluted with CFC-11
and varied greatly in size during this leg. The size of the peak
decreased exponentially with time, but jumped to very high values (0.05
pmol kg^-1^) after each of the four power outages encountered during leg
2. Further investigation needs to be done to understand the origin of
this contamination. CFC-113 and CFC-12 sampling blanks were less than
0.005 pmol kg^-1.^ No sampling blank corrections have been made to this
preliminary data set.

On this expedition, based on the analysis of 38 duplicate samples, we
estimate precisions (1 standard deviation) of 0.45% or 0.004 pmol kg^-1^
(whichever is greater) for dissolved CFC-11, 0.36% or 0.003 pmol kg^-1^
for CFC-12 measurements, and 0.004 pmol kg^-1^ for CFC-113.

A very small number of water samples had anomalously high CFC
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 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 that were drawn from the rosette but
never analyzed due to a variety of reasons (e.g. power outage during
analysis).

***3.7 DIC Measurements***

The DIC analytical equipment was set up in a seagoing container modified
for use as a shipboard laboratory. The analysis was done by coulometry
with two analytical systems (PMEL-1 and PMEL-2) operated simultaneously
on the cruise by Dana Greeley and David Wisegarver of PMEL. Each system
consisted of a coulometer (UIC, Inc.) coupled with a SOMMA (Single
Operator Multiparameter Metabolic Analyzer) inlet system developed by
Ken Johnson (Johnson et al., 1985,1987,1993; Johnson, 1992) 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 to the seawater sample, and the evolved CO~2~ gas is
carried into the titration cell of the coulometer, where it reacts
quantitatively with a proprietary reagent based on ethanolamine to
generate hydrogen ions. These are subsequently titrated with
coulometrically generated OH-. CO~2~ is thus measured by integrating the
total change required to achieve this.

The coulometers were each calibrated by injecting aliquots of pure CO~2~
(99.99%) by means of an 8-port valve outfitted with two sample loops
(Wilke et al., 1993). The instruments were calibrated at the beginning
of each station with a set of the gas loop injections. Subsequent
calibrations were run either in the middle or end of the cast if
replicate samples collected from the same Niskin, which were analyzed at
different stages of analysis, were different by more than 2 µmol kg^-1^.
Secondary standards were run throughout the cruise on each analytical
system; these standards are Certified Reference Materials (CRMs)
consisting of poisoned, filtered, and UV irradiated seawater supplied by
Dr. A. Dickson of Scripps Institution of Oceanography (SIO), and their
accuracy is determined shoreside manometrically. On this cruise, the
overall accuracy for the CRMs on both instruments combined was 0.8
µmol/kg (n=66). Preliminary DIC data reported to the database have not
yet been corrected to the Batch 73 CRM value, but a more careful quality
assurance to be completed shoreside will have final data corrected to
the secondary standard on a per instrument basis.

Samples were drawn from the Niskin-type bottles into cleaned,
precombusted 300-mL Pyrex bottles using silicone tubing. Bottles were
rinsed three times and filled from the bottom, overflowing half a
volume, and care was taken not to entrain any bubbles. The tube was
pinched off and withdrawn, creating a 6-mL headspace, and then 0.2 mL of
50% saturated HgCl~2~ solution was added as a preservative. The sample
bottles were sealed with glass stoppers lightly covered with Apiezon-L
grease.

DIC values were reported for 1324 samples or approximately 80% of the
tripped bottles on this cruise (92% of the non-trace metal bottles).
Full profiles were completed at stations on whole degrees, with
replicate samples taken from the surface, oxygen minimum, and bottom
depths. Duplicate samples were drawn from 72 bottles and interspersed
throughout the station analysis for quality assurance of the coulometer
cell solution integrity. The average of the absolute value of the
difference between duplicates was 1.0 µmol kg^-1^ for both systems. No
systematic differences between the replicates were observed.

***3.8 TA Measurements***

Total alkalinity (TA) measurements were made potentiometrically using
closed cell systems consisting of: a ROSS 8101 glass and Orion 90-92
double junction Ag/AgCl reference electrode monitored by an Orion 720A
pH meter, Metrohm 665 Dosimat titrator that adds our 0.7m acid (0.25n
HCl and 0.45m NaCl) and a system of solenoid valves that controls the
rinsing and filling of the cell. The titration cell was thermostated to
25^o^C using a Neslab RTE 17 constant temperature bath. The titration
systems are controlled programmatically using National Instrument's
Labwindows/CVI environment (developed by Dr. Pierrot). A typical
titration (including rinse and fill) takes about 15 minutes, using two
systems a typical 36 bottle cast requires about six hours.

During the second leg of the P16N cruise, about 1444 TA samples were run
between the two systems, with Dickson certified reference material (CRM)
run between each station to monitor the accuracy of the instruments. If
the CRM run was outside of the standard error of our systems (3 μmol/kg)
a correction factor was applied to the reported TA (ratio of measured TA
to certified TA) with the systems generally giving ±2 μmol/kg. Duplicate
(same samples run on each system) and replicate (same samples run on the
same system) samples were taken to assess the precision of the
instruments, with duplicates giving a standard deviation of ±2.3 μmol/kg
and replicate on System A giving a standard deviation of ±1.2 μmol/kg
and System B giving ±1.0 μmol/kg.

***3.9 pH Discrete Measurements***

*3.9.1 UM pH*

pH measurement were made using the spectrophotometric techniques of
Clayton and Byrne (1993) with m-cresol purple (mCP) indicator determined
from:

pH = pKind + log\[(R- 0.0069)/(2.222 -- 0.133R)\] (2)

where Kind is the dissociation constant for the indicator and R
(A578/A434) is the ration of the absorbance of the acidic and basic
forms of the indicator corrected for baseline at 730 nm. The samples are
drawn from 50cc glass syringes using a Kloehn 50300 syringe pump and
injected into the 10cm optical cell. The syringe rinses and primes the
optical cell with 20 cm^3^ of sample and the software permits three
minutes of temperature stabilization before a blank is measured. The
automated syringe then draws 0.008 cm^3^ of indicator and 4.90 cm^3^ of
sample and allows for five minutes of temperature stabilization. A
typical pH measurement takes about 15 minutes to run, with a 36 bottle
cast taking about six plus hours. Values are reported with temperature
to allow the user the greatest quality in interpretation and calculation
with the data, but were made near 25°C reported in the seawater scale
(SWS).

During leg 2 of P16N, the pH system was converted to a flowing mode.
This entailed circulating the optical cell with underway seawater for
insitu pH measurements. Discrete pH samples were taken, for comparison
sake, on 8 stations (about 280 samples) throughout the course of the
second leg. These runs were measured at the insitu surface temperature
relative to the ship's position, and reported with the temperature of
the measurement. A normalization of theses pH measurement will be made
once on shore to a temperature of 25^o^C to be consistent with the
measurements made on the first leg.

*3.9.2 USF pH*

USF pH measurements were the primary pH measurements on leg 2. Discrete
USF pH measurements were made on all water samples for which discrete
DIC measurements were obtained by NOAA personnel. Measurements of
discrete pH were precise, and highly effective at prompt identification
of mistrips. Comparison with pH measurements obtained 15 years earlier,
using nearly identical procedures, revealed substantial decreases in pH
down to approximately 500 meters along the entire transect. The observed
decreases generally correlated well with observed 15-year DIC
differences along the transect. USF personnel measured seawater pH using
the procedures outlined in SOP 7 of DOE Handbook (1996) and in Clayton
and Byrne (1993). Samples were drawn from the Niskin bottles into 10 cm
glass cells using a 20cm long silicon tube. The samples were
thermostated to 25°C. After a blank was taken for each sample, an
aliquot of 10 μL (early in the transect) to 20 μL (late in the transect)
of m-cresol purple indicator dye (concentration \~ 10mM) was added using
a Gilmont pipette. The absorbance ratio, R, of A578/A434 was then
measured. The pH~T~ on the total scale is calculated using the following
equation:

pH~T~ = 1245.69/T +3.8275-0.00211(35-S) +
log((R-0.00691)/(2.222-0.1331R))

where T is the measurement temperature (T = 273.15 + t) and S is
salinity. The overall precision of pH measurements from duplicate
samples was better than 0.001 pH units.

***3.10 Discrete pCO~2~***

Samples were drawn from the Niskin bottles into 500 ml volumetric flasks
using Tygon© tubing with a Silicone adapter that fit over the petcock to
avoid contamination of DOM samples. Bottles were rinsed while inverted
and filled from the bottom, overflowing half a volume while taking care
not to entrain any bubbles. About 5 ml of water was withdrawn to allow
for expansion of the water as it warms and to provide space for the
stopper, tubing, and frit of the analytical system. Saturated mercuric
chloride solution (0.2 ml) was added as a preservative. The sample
bottles were sealed with a screw cap containing a polyethylene liner.
The samples were stored in coolers at room temperature generally for no
more than 5 hours.

On previous cruises with this instrument the analyses were done at 20°C.
Due to the anticipated high pCO~2~ results for analyses at 20°C of
intermediate waters in the North Pacific, two water baths were used for
analyses at 20°C and 12°C. There were two secondary baths to get the
samples close to the analytical temperatures prior to analyses. As soon
as space was available in the secondary and then primary baths, the
sample flasks were moved into the more controlled temperature bath. No
flask was analyzed without spending at least 2.5 hours in a bath close
to the analytical temperature. The pCO~2~ in the intermediate water in
the North Pacific reaches the highest values in the world\'s oceans and
even with samples run at 12°C some analyses would exceed the working
range of the detector of about 2000 ppm. The depth interval where very
high pCO~2~ concentrations are encountered gets progressively greater
going northward. Therefore no pCO~2~ samples were taken between 700 and
1200 db at station 53 and the range progressively increased to 175 to
1500 db at station 77.

Generally when samples were taken, flasks were drawn on all the Niskins
including four duplicates. Two of the duplicates were analyzed at
different temperatures. Four hundred sixteen samples were collected at
fourteen stations (stations 44, 47, 56, 53, 56, 59, 62, 65, 68, 70, 73,
75, 77, 80). The data from eighteen of these samples was lost due to
power failures. The fifty-four pairs of duplicates include twenty-six
pairs run at different temperatures. The breakdown and precision of
replicates are:

Duplicates @ 12°C: 0.23+- 0.15 % N = 15

Duplicates @ 20°C: 0.17 +-0.15 % N =12 , one duplicate omitted (bad
analysis)

Duplicates 12° and 20°C\*: 0.64 +- 0.60 % N =25, one duplicate omitted
(bad analysis)

\*for comparison of the duplicates run at 12° and 20°C the 12°C results
were normalized to 20°C using the procedures and constants listed in the
Appendix of Peng et al. (1987) as incorporated in the GW BASIC data
reduction program.

The discrete pCO~2~ system is patterned after the instrument 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
two systems is that Wanninkhof instrument uses a LI-COR© (model 6262)
non-dispersive infrared analyzer, while the Chipman instrument utilizes
a gas chromatograph with a flame ionization detector.

Once the samples reach the analyses temperature, a 50-ml headspace is
created 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
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). This equilibration takes about 10 minutes. An
expandable volume in the circulation loop near the flask consisting of a
small, deflated balloon keeps the headspace of the flask at room
pressure.

In order to maintain analytical accuracy, a set of six gas standards is
run through the analyzer before and after every ten seawater samples.
The cylinder serial numbers and mole fractions of CO~2~ with balance
artificial air are:

CA5998 205.1 ppm

CA5989 378.7 ppm

CA5988 593.6 ppm

CA5980 792.5 ppm

CA5984 1037.0 ppm

CA5940 1533.7 ppm

The standards were obtained from Scott-Marin and referenced against
primary standards purchased from C.D. Keeling in 1991, which are on the
WMO-78 scale.

The calculation of pCO~2~ in water from the headspace measurement
involves several steps. The CO~2~ concentrations in the headspace are
determined via a second-degree polynomial fit using the nearest three
standard concentrations. Corrections for the water vapor concentration,
the barometric pressure, and the changes induced in the carbonate
equilibrium by the headspace-water mass transfer are made. The corrected
results are reported at the analytical temperature and at a reference
temperature of 20°C.

No instrumental problems occurred during the cruise. The relatively
time-consuming analyses and the presence of only one analyst limited the
spatial coverage. Sampling and analyses focused on precision and
accuracy rather than high throughput.

***3.11 Carbon/Oxygen Isotopes***

Samples for C-14/C-13 analysis were collected in 500 ml borosilicate
bottles with ground stoppers. The samples were preserved with 100 µl of
saturated mercuric chloride solution. The stoppers were greased with
Apezion grease and held in place with rubber bands. Samples were
collected from 32 Niskin bottles on stations 46, 50, 54, 58, 64, 68, 72,
76. Short casts of 16 bottles were collected at stations 44, 48, 52, 56,
60, 62, 66, 70, 74, 77, 80, 83. Samples will be returned to the WHOI
NOSAMS facility for analysis.

Samples for oxygen isotopes and oxygen:argon ratio were collected from a
near-surface (15-25 m) Niskin at all stations. Another 11 stations had 5
samples collected in the upper 300m. Samples were collected in 500 ml
evacuated glass sampling bottles and preserved with mercuric chloride.
Samples will be returned to the University of Washington for analysis.

***3.12 Dissolved Organic Carbon/ Dissolved Organic Nitrogen***

Water for DOC/DON analyses were collected into 60 ml high density
polyethylene (HDPE) bottles from every cast (2818 samples total). 
Samples from the upper 250 m were passed through GF/F filters using
in-line filtration from the Niskin bottles; at greater depths the
samples were whole (unfiltered) water. The samples then were frozen in a
-20°C freezer room and returned to RSMAS for analysis..

***3.13 CDOM, chlorophyll, bacterial suite***

Samples were collected from the rosette for absorption spectroscopy on
one deep ocean cast each day. CDOM is typically quantified as the
absorption coefficient at a particular wavelength or wavelength range
(we are using 325 nm). CDOM was determined at sea by measuring
absorption spectra (280-730 nm) of 0.2um filtrates using a liquid
waveguide spectrophotometer with a 200cm cell. Samples were concurrently
collected for bacterial abundance and carbohydrates to compare the
distribution of these quantities to that of CDOM. In surface waters (\<
300m) bacterial productivity of field samples was estimated by measuring
the uptake of bromo-deoxyuridine (BrdU), a non-radioactive alternative
to the standard bacterial productivity technique using tritiated
thymidine. Because of the connections to light availability and remote
sensing, samples were collected for chlorophyll, carotenoid, and
mycosporine-like amino acid pigment analysis (HPLC), chlorophyll a
(fluorometric), and particulate absorption (spectrophotometric). Large
volume (ca. 2L) samples were sporadically collected for CDOM photolysis
experiments back at UCSB, and occasionally large volume samples were
collected for POC analysis by Dr. Gardner\'s lab to compare with
transmissometer data. CDOM and chlorophyll a samples were analyzed at
sea. The rest of the samples were prepared for later analysis.

***3.14 Helium-tritium***

Helium samples were collected in stainless steel containers with
pneumatic valves ("bunnies"). To draw a sample, two pieces of tubing are
attached to the ends of the container, and one end is attached to the
spigot on the Niskin bottle. The sample is held vertically above the
water level in the Niskin bottle, the valve is opened to establish flow,
and the sample is lowered over a ten- to twenty-second period to
establish gravity flow. The relatively slow entry of the water into the
container minimizes trapped air and bubble formation. The amount of
water flushed through the tube is about six volumes. During the flush
period, the container is tapped to remove bubbles. The pneumatic valves
are closed and the sample is stored until it can be further processed.

After all samples were collected, the helium samples were degassed and
extracted into glass vials for analysis in the shore-based laboratory.
In general, the extraction and degassing procedures were executed with
several (\~8) samples in parallel, with extraction or degassing sections
coupled to a common vacuum manifold.

Tritium samples were collected in 1 liter flint glass bottles, sealed
with caps fitted with high density polyethylene cones to minimize water
vapor transpiration. To achieve a minimum contamination, the bottles
were pretreated to remove adsorbed water. The bottles are sealed with
argon inside. After the tritium samples were collected they are sealed
and retuned to the shore-based laboratory for analysis.

***3.15 Trace metals***

Hydrographic sampling for the trace elements Al and Fe was conducted
during leg 2 of P16N. Samples were collected using a specially designed
rosette system which consists of 12 x 12L Go-Flo bottles mounted on a
powder-coated rosette frame. The package is equipped with a SeaBird SBE
911 CTD that also has an SBE 43 oxygen sensor and a Wet Labs FL1
flourometer. The package is lowered using a Kevlar conducting cable and
bottles were tripped at pre-determined depths from the ship using a deck
box. Water samples were collected in the upper 1000 m at a total at 17
stations, collecting roughly 200 samples. Bad weather (high winds and
rough seas) prevented us deploying at only one station (station 64,
43N). Subsamples were taken from each GoFlo bottle for at-sea analysis
of salinity, nutrients, dissolved total Fe and Al (Bill Hiscock of the
Measures Group), and dissolved Fe(II).

*3.15.1 Aerosol Sampling*

Aeolian transport and deposition of soluble aerosol Fe is believed to
influence phytoplankton primary productivity in the majority of the open
ocean (far from Fe inputs from rivers and coastal sediments). The
purpose of the FSU aerosol sampling program is primarily to measure the
concentration of total aerosol Fe, and to quantify the aerosol Fe
fractions that are soluble in natural surface seawater and in ultra-pure
deionized water. Additional analyses are conducted on the samples in an
effort to understand the atmospheric processes that yield differences in
the aerosol Fe solubility.

The aerosol sampling equipment consists of four replicate filter holders
deployed on a 20' fold-down aerosol tower mounted on the forward,
starboard corner of the 03 deck of the ship. One of the replicate
filters (0.4 μm Nuclepore polycarbonate track-etched) is used for total
aerosol measurements (see below); one replicate filter (0.45 μm
polypropylene) is used to quantify the seawater-soluble fraction; one
replicate filter (0.45 μm polypropylene) is used to quantify the
ultra-pure deionized water soluble fraction; and one replicate filter
(0.45 μm polypropylene) is used for precision (QA) tests or stored as a
backup sample. Size-fractionated aerosols are also collected for 48 hour
intervals starting every 3^rd^ day using a MOUDI cascade impactor (\>3.2
μm, 1.0 μm, 0.56 μm, 0.056 μm). Air is pulled through the filters using
two high-capacity vacuum pumps. The sampling is controlled by a Campbell
Scientific CR10 datalogger that immediately shuts off the flow when the
wind might blow stack exhaust forward towards the sampling tower, or
when the wind drops below 0.5 m/s. Air flow is measured using Sierra
mass-flow meters.

We have collected 24-hour integrated aerosol samples each day for the
entire leg (24 days of sampling) for the following analyses:

1\. Total aerosol Si, Al, Fe (to be analyzed using Energy Dispersive
X-Ray Fluorescence by Dr. Joe Resing at NOAA/PMEL).

2\. Seawater-soluble aerosol Al and Fe (to be run back at FSU).

3\. Ultra-pure water soluble Si, Al, Ti, Fe, chloride, sulfate, nitrate,
sodium (to be run back at FSU). The MOUDI size-fractionated aerosol
filters are also leached with ultra-pure water for these same analyses.

*3.15.2 Dissolved Fe(II)*

The purpose of the dissolved Fe(II) sampling program is to study the
effects of photochemical reduction and biological remineralization on
the redox chemistry of iron in seawater. Filtered samples (0.2 μm) are
collected from the Trace Metal Go-Flo bottles immediately upon recovery
into polyethylene bottles that have been pre-charged with a small amount
of ultrapure 6M HCl to drop the pH to 6.0-6.2. This stabilizes the
existing Fe(II) from rapid oxidation, but is not low enough to trigger
thermochemical Fe(III) reduction. The samples are quickly analyzed for
dissolved Fe(II) using the FeLume chemiluminescent method. Samples for
dissolved Fe(II) analysis have been collected from each depth on every
Trace Metal cast (17 stations, approx. 200 samples).

Additional experiments being conducted on the ship include laboratory
photochemical exposure experiments to study the wavelength dependence of
Fe(II) photoproduction and to quantify the maximum extent to which
photochemical Fe reduction might occur in surface waters. We are also
measuring H~2~O~2~ on selected profiles since H~2~O~2~ is known to
enhance the chemiluminescent response of the Fe(II) measurement. A
correction to the Fe(II) concentrations must therefore be applied, and
we conducted Fe(II) and H~2~O~2~ spike experiments to quantify the
effect.

*3.15.3 Other Sampling*

We collected archived samples from each trace metal cast (17 stations,
approx. 200 samples) for FSU shore-based analysis of dissolved Fe, Ni,
Cu, Zn, Cd, and Pb using isotope dilution ICPMS.

The Total Suspended Matter (TSM) from each trace metal cast was
collected on 47 mm 0.4 um Nuclepore filters for EDXRF analysis of total
particulate Si, Mn, Fe, and Al (Joe Resing, NOAA/PMEL).

We collected approximately 200 filtered seawater samples for dissolved
Mn, Ga and Sc analysis by Alan M. Shiller (University of Southern
Mississippi). These samples will be shipped back to USM for later
shore-based analysis.

We collected approximately 100 samples for Dave Krabbenhoft (USGS,
Madison) for dissolved total mercury and methyl mercury analyses. Human
exposure to environmental mercury is mainly through consumption of
marine fish containing methyl mercury, so these samples will help us
understand the marine mercury cycle and the production of methyl
mercury.

***3.16 Optical Casts***

Once each day, an optical cast with a hand-deployed free-fall Satlantic
MicroPro II multichannel UV/Visible spectroradiometer was conducted.
This instrument has 14 upwelling radiance sensors and 14 downwelling
irradiance sensors in wavelength bands ranging from 305 to 683 nm. The
package also mounts a WetLabs chlorophyll fluorometer and scattering
meter, plus ancillary sensors including X-Y tilt, internal and external
temperatures. The instrument is allowed to trail away behind the port
quarter, then free-falls to 150m and is hand-recovered. The radiometric
data will be used to study the effects of CDOM on the underwater light
environment, to validate satellite ocean radiance sensor data, and to
develop new algorithms employing satellite and in situ optical sensor
data to retrieve ocean properties such as CDOM light absorbance,
chlorophyll concentration, and particulate backscattering.

**4.0 Underway Measurements**

*4.1 USF Underway DIC/pCO~2~/pH*

An automated CO~2~ system analyzer was set up on board to measure
underway surface seawater CO~2~ parameters (7 samples per hour),
including total CO~2~ (DIC), pH, air and seawater pCO~2~ at 25^o^C. DIC
was measured by equilibrating acidified seawater across a liquid-core
waveguide membrane with a known alkalinity standard solution (Byrne et
al., 2002). pCO~2~ was analyzed by equilibrating seawater or air across
a liquid-core waveguide membrane with a known alkalinity standard
solution. The equilibrium pH was measured, and DIC and pCO~2~ were
calculated. The assessed precisions are 2 μM for DIC, 2 ppm for pCO~2~
and 0.001 for pH.

Underway measurements of surface pH, DIC and pCO~2~ along the transect
generally went smoothly and correlated well with discrete measurements.
Underway surface pH measurements were in excellent agreement with
discrete measurements, even though the procedures for the measurements
had distinct differences. Underway and discrete DIC measurements were in
very good agreement with the exception of one short segment of stations
over an approximately two to three day period. Comparisons of USF and
NOAA underway pCO~2~ measurements were somewhat compromised by the
limited flow of seawater to the PMEL underway system. Comparisons with
AOML discrete measurements should eventually shed light on underway
pCO~2~ measurement issues.

*4.2 NOAA/PMEL Underway pCO~2~*

The NOAA/PMEL underway surface pCO~2~ system was started shortly after
leaving Honululu, HI. The semi-autonomous system analyzes surface water
collected from the ship's uncontaminated seawater supply and marine air
from the ship's bow on a repeating hourly cycle. The first quarter of
each hour is devoted to calibration with four CO~2~ standards (Feely et
al., 1998). A second order polynomial calibration curve is calculated
for the LiCor 6262 infrared detector. The remaining time in each hour is
used to measure equilibrator air (15 min), bow air (15 min), and
equilibrator air once again (15 min). The analytical precision of the
system is estimated to be approximately 0.3-0.4 ppm for seawater and for
air.

The underway system experienced some problems throughout cruise because
of low water flow rate and air contamination in the equilibrator.

*4.3 UM Underway pH*

pH measurement were made using the spectrophotometric techniques of
Clayton and Byrne (1993) with m-cresol purple (mCP) indicator determined
from:

pH = pKind + log\[(R- 0.0069)/(2.222 -- 0.133R)\] (2)

where Kind is the dissociation constant for the indicator and R
(A578/A434) is the ration of the absorbance of the acidic and basic
forms of the indicator corrected for baseline at 730 nm. The samples are
drawn from a SBE 45, which measured the temperature and salinity, using
a Kloehn 50300 syringe pump and injected into the 10cm optical cell. The
syringe rinses and primes the optical cell with 20 cm^3^ of sample and
the software permits three minutes of temperature stabilization before a
blank is measured. The automated syringe then draws 0.008 cm^3^ of
indicator and 4.90 cm^3^ of sample and allows for five minutes of
temperature stabilization. The program was set to measure an underway
sample every ten minutes and reported with a timestamp (the GPS line
provided by the ship was not compatible the software) that will have to
be matched with the ship's GPS position. The system was stopped while on
station, and restarted during the transit between stations, this yielded
about 1480 samples. The values reported are with the measured
temperature and are in terms of the sea water scale.

**5.0 Other Measurements**

*5.1 Net tows/Pteropod*

In an add-on project funded by the NSF Chemical Oceanography Program, V.
Fabry (CSUSM), R. Byrne (USF), and J. Schijf (USF) worked on the
dissolution of freshly collected pteropod shells. At about 10 stations,
plankton tows were conducted in the upper 25 m at night. Pteropod shells
were quickly sorted and used in dissolution experiments employing a high
precision, spectrophotometric method to measure pH. The main objective
of this cruise work was to test a newly constructed experimental cell.
We conducted dissolution experiments at 25 stations between Honolulu and
Kodiak. In addition, we conducted preliminary experiments on live
pteropods at 8 stations. Samples were shipped back to CSUSM for
laboratory analysis.

*5.2 Floats*

Eight Web Research Corporation APEX floats were launched for Howard
Freeland of the Institute of Ocean Sciences in British Columbia. These
floats are part of the Canadian Argo project and were deployed at the
northern end of the P16N section to better populate this area. Floats
were deployed after the completion of all station work at 31˚N, 34˚N,
37˚N, 40˚N, 44˚N, 47˚N, 50˚N, and 55˚N. Each deployment required 30
minutes of startup time to unpack, inspect, and test the float. All
floats passed their self-check routines and were launched successfully.
Immediately following deployment, an email was sent to Dr. Freeland to
report the exact time and position of the float. Return emails from Dr.
Freeland confirmed that all floats were working properly.

**6.0 Acknowledgements.** The scientific party of the P16N cruise would
like to express sincere thanks to Captain Al McClenaghan and all of the
crew of the R/V Thompson for their outstanding work in support of our
cruise despite some very difficult wintertime weather conditions in the
North Pacific Ocean.

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