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CRUISE REPORT:  AR24
(Updated: AUG 2008)



A.  HIGHLIGHTS 

A.1.  WHP Cruise Summary Information

         WOCE section designation  AR24
Expedition designation (EXPOCODE)  316N147_2
                  Chief Scientist  Dr. Michael McCartney/WHOI
                            Dates  1996 NOV 02 - 1996 DEC 05
                             Ship  R/V KNORR
                    Ports of call  Ponta Delgada, Azores
                                               64° 54.17' N
  Stations' geographic boundaries  43°29.67' W              11°10.12' W
                                                39°8.17' N
               Number of stations  190
     Floats and drifters deployed  0
   Moorings deployed or recovered  0

                       Chief Scientist Contact Information
                              Dr. Michael McCartney
    Department of Physical Oceanography • Woods Hole Oceanographic Institution   
                        Clark 344 • Woods Hole, MA • 02543
        Phone: 508-289-2797 • Fax: 508-457-2181 • email: mike@gaff.whoi.edu





                                                                  ORNL/CDIAC-143
                                                                         NDP-082


CARBON DIOXIDE, HYDROGRAPHIC, AND CHEMICAL DATA OBTAINED DURING THE R/V KNORR
             CRUISES IN THE NORTH ATLANTIC OCEAN ON WOCE SECTIONS
                    AR24 (NOVEMBER 2 - DECEMBER 5, 1996) AND
                 A24, A20, AND A22(MAY 30 - SEPTEMBER 3, 1997)

                                Contributed by
   Kenneth M. Johnson,1      Robert M. Key,2           Frank J. Millero,3
   Christopher L. Sabine,4   Douglas W. R. Wallace,5   Christopher D. Winn,6
   Linda Arlen,7             Kenneth Erickson,8        Karsten Friis,5
   Meridith Galanter,3       Jamie Goen,3              Richard Rotter,2
   Carrie Thomas,2           Richard Wilke,8           Taro Takahashi,9  
   Stewart C. Sutherland9

     1 Department of Applied Science, 
       Brookhaven National Laboratory, Upton, NY, U.S.A.
       Retired, now at P.O. Box 483, Wyoming, RI, U.S.A.
     2 Department of Geosciences, Princeton University, Princeton, NJ, U.S.A.
     3 Rosenstiel School of Marine and Atmospheric Science, 
       University of Miami, Miami, FL, U.S.A.
     4 Pacific Marine Environmental Laboratory, NOAA, Seattle, WA, U.S.A.
     5 Institute for Marine Sciences, Kiel, Germany
     6 Hawaii Pacific University, Kaneohe, HI, U.S.A.
     7 James J. Howard Laboratory, NOAA, Sandy Hook, NJ, U.S.A.
     8 Department of Applied Science, Brookhaven National Laboratory, 
       Upton, NY, U.S.A.
     9 Lamont-Doherty Earth Observatory, Palisades, NY, U.S.A.

Prepared by 
   Alexander Kozyr
   Carbon Dioxide Information Analysis Center
   Oak Ridge National Laboratory
   Oak Ridge, Tennessee, U.S.A.

Date Published: September 2003

Prepared for the
   Climate Change Research Division
   Office of Biological and Environmental Research
   U.S. Department of Energy

Prepared by the
   Carbon Dioxide Information Analysis Center
   OAK RIDGE NATIONAL LABORATORY
   Oak Ridge, Tennessee 37831-6335

     Budget Activity Numbers:           KP 12 04 01 0  and  KP 12 02 03 0
     managed by UT-BATTELLE, LLC        for the U.S. DEPARTMENT OF ENERGY
     under contract DE-AC05-00OR22725   ORNL/CDIAC-143            NDP-082



ACRONYMS

ACCE      Atlantic Circulation and           NDP    numeric data package
          Climate Change Experiment          NOAA   National Oceanic and 
A/D       analog-to-digital                         Atmospheric Administration
ADCP      acoustic Doppler current           nm     nautical mile
          profiler                           NSF    National Science Foundation
ALACE     autonomous Lagrangian              ODF    Ocean Data Facility
          circulation explorer               ODV    Ocean Data View
BOD       biological oxygen demand           ORNL   Oak Ridge National Laboratory
BNL       Brookhaven National Laboratory     OSU    Oregon State University
14C       radiocarbon                        PC     personal computer
CALFAC    calibration factor                 PDF    Portable Document Format
CDIAC     Carbon Dioxide Information         PI     principal investigator
          Analysis Center                    PU     Princeton University
CFC       chlorofluorocarbon                 QA     quality assurance
CMDL      Climate Monitoring and             QC     quality control
          Diagnostics Laboratory             R/V    research vessel
CO2       carbon dioxide                     RSMAS  Rosenstiel School of Marine 
CTD       conductivity, temperature, and            and Atmospheric Sciences
          depth sensor                       SIO    Scripps Institution of 
CRM       certified reference material              Oceanography
DOE       U.S. Department of Energy          SOMMA  single-operator multipara- 
emf       electro-magnetic fields                   meter metabolic analyzer
EXPOCODE  expedition code                    SSW    standard seawater
FTP       file transfer protocol             TALK   total alkalinity
GMT       Greenwich mean time                TCO2   total carbon dioxide
GPS       global positioning system          TD     to-deliver
IAPSO     International Association for the  UH     University of Hawaii
          Physical Sciences of the Ocean     UM     University of Miami
I/O       input-output                       UW     University of Washington
IR        infrared                           VFC    voltage to frequency converter
JGOFS     Joint Global Ocean Flux Study      WHOI   Woods Hole Oceanographic 
kn        knots                                     Institution
LADCP     lowered ADCP                       WHPO   WOCE Hydrographic Program 
LDEO      Lamont-Doherty Earth                      Office
          Observatory                        WOCE   World Ocean Circulation 
MATS      Miami University alkalinity               Experiment
          titration systems                  WHP    WOCE Hydrographic Program
NBIS      Neil Brown Instrument system




                                     ABSTRACT

Johnson K., R. Key, F. Millero, C. Sabine, D. Wallace, C. Winn, L. Arlen, K. 
    Erickson, K. Friis, M. Galanter, J. Goen, R. Rotter, C. Thomas, R. Wilke, 
    T. Takahashi, and S. Sutherland. 2003. Carbon Dioxide, Hydrographic, and 
    Chemical Data Obtained During the R/V Knorr Cruises in the North Atlantic 
    Ocean on WOCE Sections AR24 (November 2-December 5, 1996) and A24, A20, and 
    A22 (May 30-September 3, 1997) A. Kozyr (ed.) ORNL/CDIAC-143, NDP-082. 
    Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, 
    U.S. Department of Energy, Oak Ridge, Tennessee, 41 pp.  

This documentation describes the procedures and methods used to measure total 
carbon dioxide (TCO2) total alkalinity (TALK), and partial pressure of CO2 
(pCO2) at hydrographic stations on the North Atlantic Ocean sections AR24, A24, 
A20, and A22 during the R/V Knorr Cruises 147-2, 151-2, 151-3, and 151-4 in 
1996 and 1997. Conducted as part of the World Ocean Circulation Experiment 
(WOCE), the expeditions began at Woods Hole, Massachusetts, on October 24, 
1996, and ended at Woods Hole on September 3, 1997. Instructions for accessing 
the data are provided.  

A total of 5,614 water samples were analyzed for discrete TCO2 using two 
single-operator multiparameter metabolic analyzers (SOMMAs) coupled to a 
coulometer for extracting and detecting CO2. The overall accuracy of the TCO2 
determination was ± 1.59 µmol/kg. The TALK was determined in a total of 6,088 
discrete samples on all sections by potentiometric titration using an automated 
titration system developed at the University of Miami. The accuracy of the TALK 
determination was ± 3 µmol/kg. A total of 2,465 discrete water samples were 
collected for determination of pCO2 in seawater on sections A24, A20, and A22. 
The pCO2 was measured by means of an equilibrator-IR system by scientists from 
Lamont-Doherty Earth Observatory. The precision of the measurements was 
estimated to be about ± 0.15%, based on the reproducibility of the replicate 
equilibrations on a single hydrographic station. 

The North Atlantic data set is available as a numeric data package (NDP) from 
the Carbon Dioxide Information Analysis Center. The NDP consists of 12 ASCII 
data files, one Ocean Data View-formatted data file, a NDP-082 ASCII text file, 
a NDP-082 PDF file, and this printed documentation, which describes the 
contents and format of all files, as well as the procedures and methods used to 
obtain the data.  

Keywords: carbon dioxide; TCO2; total alkalinity; partial pressure of CO2; 
          coulometry; gas chromatography; World Ocean Circulation Experiment; 
          North Atlantic Ocean; hydrographic measurements; carbon cycle.




1. BACKGROUND INFORMATION  

The World Ocean Circulation Experiment (WOCE) Hydrographic Program (WHP) was a 
major component of the World Climate Research Program. The primary WOCE goal 
was to understand the general circulation of the global ocean well enough to be 
able to model its present state and predict its evolution in relation to long-
term changes in the atmosphere. The impetus for the carbon system measurements 
arose from concern over the rising atmospheric concentrations of carbon dioxide 
(CO2). Increasing atmospheric CO2 may intensify the earths natural greenhouse 
effect and alter the global climate. 

Although CO2-related measurements [total CO2 (TCO2), total alkalinity (TALK), 
partial pressure of CO2 (pCO2), and pH] were not an official WOCE measurements, 
a coordinated effort to make the carbon measurements was supported as a core 
component of the Joint Global Ocean Flux Study (JGOFS). This effort received 
support in the United States from the U.S. Department of Energy (DOE), the 
National Oceanic and Atmospheric Administration (NOAA), and the National 
Science Foundation (NSF) for WOCE cruises through 1998 to measure the global 
spatial and temporal distributions of CO2 and related parameters. Goals were to 
estimate the meridional transport of inorganic carbon in a manner analogous to 
the oceanic heat transport (Bryden and Hall 1980; Brewer, Goyet, and Drysen 
1989; Holfort et al. 1998; Roemmich and Wunsch 1985), and to build a data base 
suitable for carbon-cycle modeling and the estimation of anthropogenic CO2 
increase in the oceans. The CO2 survey took advantage of the sampling 
opportunities provided by the WOCE cruises during this period, and the final 
data set was expected to cover on the order of 23,000 stations. Wallace (2002) 
recently reviewed the goals, conduct, and initial findings of the survey. 

This report discusses the results of the research vessel (R/V) Knorr expedition 
along the WOCE Sections AR24, A24, A20, and A22 [cruises 147-2, 151-2, 151-3, 
and 151-4, respectively (Fig. 1)]. The latter three cruises not only were part 
of WOCE but also were a component of the Atlantic Circulation and Climate 
Change Experiment (ACCE). The ACCE was intended to improve the understanding of 
the entrainment and transformation of warm saline subtropical water into the 
subpolar North Atlantic waters, with special emphasis on sampling the North 
Atlantic Current region. This region plays an important role in the exchange of 
CO2 between the subtropical and subpolar gyres. The exchange between these 
gyres affects the magnitude and direction of air-sea CO2 exchange in the North 
Atlantic and is therefore an important factor in the global carbon cycle. By 
1997 the goal of high-quality measurements of chemical and physical parameters 
had been completed in all of the major oceans except the North Atlantic. Hence 
the cruises documented here also represent the concluding phase of the DOE-
sponsored Global CO2 Survey. 

The expedition (section AR24) started at Woods Hole, Massachusetts, USA, on 
October 24, 1996, with a transit to the Azores; the station work began on 
November 2, 1996. The 1997 cruises started from Ponta Delgada, Azores, on May 
30, 1997, and ended in Woods Hole on September 3, 1997, after stops in Halifax, 
N.S., Canada, and Port of Spain, Trinidad. The large-scale three-dimensional 
distribution of temperature, salinity, and chemical constituents, including the 
carbonate system parameters measured on these cruises (TCO2, and TALK on the 
AR24 section and TCO2, TALK, and pCO2 on A24, A20, and A22 sections), will be 
plotted using the data from these sections. Knowledge of these parameters and 
their initial conditions will enable researchers to determine heat and water 
transport, as well as carbon transport, which will contribute to the 
understanding of processes affecting climate change. The sections described in 
this report include WOCE Section A22, the only Caribbean transect of the WOCE 
program. In addition, the stations occupied on these cruises repeated some 
sections sampled in previous years during the International Geophysical Year 
during the 1950s. They also included measurements from the eastern subpolar gyre 
of source and overflow waters from the Labrador, Norwegian, Greenland, and 
Iceland Seas. They give good coverage of boundary currents, particularly the 
Deep Western Boundary Current; and repeating AR24 and A24 provides some insight 
into seasonal variation in the North Atlantic.

This data documentation is the result of the cooperative efforts of chemical 
oceanographers from Brookhaven National Laboratory (BNL), the University of 
Hawaii (UH), Lamont-Doherty Earth Observatory (LDEO), and the University of 
Miamis Rosenstiel School of Atmospheric and Marine Science (RSMAS), U.S.A. The 
work aboard the R/V Knorr was supported by the U. S. Department of Energy under 
contract DE-ACO2-76CH00016 and DE-FG02-93ER61540. The authors are also 
especially grateful to the Sonderforschungsbereich 460 at the University of 
Kiel (Dr. F. Schott, Leader), funded by the Deutsche Forschungsgemeinschaft, 
for their support and assistance in completing the written documentation. 


2. DESCRIPTION OF THE EXPEDITION 

2.1 R/V Knorr: Technical Details and History

The R/V Knorr, built in 1969 by the Defoe Shipbuilding Company in Bay City, 
Michigan, is owned by the U.S. Navy. It was turned over to the Woods Hole 
Oceanographic Institution (WHOI) in 1971 for operation under a charter 
agreement with the Office of Naval Research. It was named for E. R. Knorr, a 
hydrographic engineer and cartographer who in 1860 held the title of Senior 
Civilian and Chief Engineer Cartographer of the U.S. Navy Office. Its 
original length and beam were 245 and 46 ft, respectively. Beginning on 
February 6, 1989, it underwent a major midlife retrofit or jumbo-izing at the 
McDermott Shipyard in Amelia, Louisiana. A midsection was added to the ship 
to stretch its length by 34 ft, to 279 ft, and fore and aft azimuthing 
propulsion systems were added to make it one of the most maneuverable and 
stable ships in the oceanographic fleet. By the time it was returned to the 
Woods Hole Oceanographic InstitutionWHOI in late 1991, the retrofit had taken 
32 months. The WOCE section P6 was the vessels first scientific cruise after 
the retrofitting. The R/V Knorr was designed for a wide range of 
oceanographic operations and possesses antiroll tanks and a strengthened bow 
for duty in icy waters. Like its sister ship, the R/V Melville, it is used 
for ocean research and routinely carries scientists from many different 
countries. Table 1 provides a list of technical characteristics of the R/V 
Knorr. 
 

Table 1. Technical characteristics of the R/V Knorr
    ________________________________________________________________________

     Ship name:      R/V Knorr
     Call sign:      KCEJ

     Basic dimensions:
       Gross registered tonnage  2518 T              Displacement   2958 LT
       Overall length            279 ft              Beam           46 ft
       Draught (maximum)         16.5 ft             Service speed  12 kn
       Maximum speed             14.5 kn             Minimum speed  0.1 kn
       Main deck clear length    126 ft

     Personnel:
       Crew                      24
       Scientists                34

     Main engine:                4 X Mak6M 322 = 4 X 1000 kW at 750 rpm 
       Propulsion:               Twin lips diesel-electric, azimuthing 
                                 stern thrusters, 1500 SHP
       Bow thruster:             Lips retractable azimuthing 900 SHP
       Fuel capacity:            160,500 gal
       Maximum cruise duration:  60 days (12,000 nm)

    Nautical equipment:          Integrated navigation system
                                 Potable water generator
                                 2 instrument hangars     
                                 Winches:  1 heavy-duty trawl with 30,000 ft 
                                             of 1/2 -in. wire             
                                           2 hydrographic, both with 30,000 
                                             ft of hydrowire 
                                 Hydraulic cranes on the starboard side aft 
                                   and midships
                                 Scientific storage space of 1,320 ft^2
                                 Portable van space
                                 Machine shop
                                 Fume hoods
                                 Uninterruptible power supply
                                 Air conditioning
                                 Library/lounge
                                 3680 ft^2 of laboratory space for 
                                   multidisciplinary research
    ________________________________________________________________________



2.2  The North Atlantic Ocean CO2 Survey Cruises Information

2.2.1  WOCE Section AR24 

    Ship name:        R/V Knorr
    Expocode          316N147-2
    Cruise/Leg:       147-2/A24R
    Ports of call:    Ponta Delgada, The Azores
    Dates:            November 2, 1996 - December 5, 1996
    Funding support:  DOE, NSF
    Chief scientist:  Dr. Mike McCartney, WHOI

    Parameters measured, institution, and responsible Iinvestigators

    Parameter         Institution  Responsible investigators
    ----------------  -----------  --------------------------------------
    CTD*, Salinity    WHOI         M. McCartney
    Nutrients         WHOI         M. McCartney
    Oxygen            WHOI         M. McCartney
    CFCs**            SIO          R. Weiss
    Tritium, helium   LDEO         P. Schlosser
    TCO2              UH/BNL       R. Rotter, C. Winn, K. M. Johnson
    TALK              RSMAS        M. Galanter, J. Goen, F. Millero
    Underway pCO2     AOML         R. Wanninkhof
    C14               PU           R. Key, R. Rotter
    ADCP(3)/LADCP(4)  UH           E. Firing

2.2.2  WOCE Section A24

    Ship Name         R/V Knorr
    Expocode          316N151-2
    Cruise / Leg      151-2/A24
    Ports of call     Ponta Delgado, St. Michael, Azores; Halifax, N.S., CAN
    Dates             May 30, 1997 - July 5, 1997
    Funding support   DOE, NSF
    Chief Scientist   Dr. Lynne Talley, SIO

    Parameters measured, institution, and responsible investigators

    Parameter         Institution  Responsible Iinvestigators
    ----------------  -----------  --------------------------------------
    CTD, Ssalinity    SIO          L. Talley, F. Delahoyde, C. Mattson
    Nutrients         SIO/ODF      J. Swift, D. Masten, S. Becker
    Oxygen            SIO/ODF      J. Swift, J. Boaz           
    CFCs              SIO          R. Weiss, F. Van Woy, M. Vollmer
    Tritium, helium   LDEO         P. Schlosser, D. Smith, S. Khatiwala
    TCO2              BNL          D. Wallace, K. Johnson, L. Arlen
    TALK              RSMAS        F. Millero, M. Galanter, J. Goen
    pCO2, discrete    LDEO         T. Takahashi, A. Wilson       
    Underway pCO2     SIO          R. Weiss, F. Van Woy
    14C               PU           R. Key, R. Rotter
    ADCP/LADCP        UH           E. Firing

2.2.3  WOCE Section A20

    Ship Nname        R/V Knorr
    Expocode          316N151_3
    Cruise/leg        151-3/A20
    Ports of call     Halifax, N.S, Canada, Port of Spain, Trinidad
    Dates             July 17, 1997 - August 10, 1997
    Funding support   DOE, NSF
    Chief Sscientist  Dr. Robert Pickart, WHOI

    Parameters measured, institution, and responsible Iinvestigators

    Parameter         Institution  Responsible investigators
    ----------------  -----------  --------------------------------------
    CTD, salinity     WHOI         R. Pickart, M. Swartz
    Nutrients         OSU          L. Gordon, J. Jennings, B. Sullivan
    Oxygen            WHOI         R. Pickart
    CFCs              LDEO         W. Smethie, E. Gorman, L. Baker, 
                                   D. Chaky       
    Tritium, He       WHOI         W. Jenkins, P. Landry, S. Birdwhiste
    TCO2              BNL          D. Wallace, R. Wilke, K. Erickson, 
                                   K. M. Johnson 
    pCO2, discrete    LDEO         T. Takahashi, J. Goddard
    TALK              RSMAS        F. Millero, C. Sabine, C. Thomas
    Underway pCO2     SIO          R. Weiss
    14C               PU           R. Key, C. Sabine, C. Thomas
    Bio-Ooptics       LDEO         C. Knudson
    Halocarbons       DU           R. Moore, P. Morneau, W. Groszko
    ADCP/LADCP        WHOI         D. Torres
    ALACE(5) floats   UW           D. Swift

2.2.4 WOCE Section A22

    Ship Nname        Knorr
    Expocode          315N151_4
    Cruise/leg        151-4/A22)
    Ports of call     Port of Spain, Trinidad; Woods Hole, MA, USA
    Dates             August 15, 1997 - September 3, 1997
    CO2 Funding       DOE, NSF
      support  
    Chief Sscientist  Dr. Terrence Joyce, WHOI

    Parameters measured, institution, and responsible Iinvestigators

    Parameter         Institution  Responsible investigator  
    --------------    -----------  --------------------------------------  
    CTD, salinity     WHOI         T. Joyce, G. Knapp, L. Stein
    Nutrients         OSU          L. Gordon, A. Ross, J. Arrington
    Oxygen            WHOI         G. Knapp, D. Wellwood
    CFC's             LDEO         W. Smethie, L. Baker, D. Chaky, 
                                   E. Gorman, R. Swartz
    Tritium, He       WHOI         W. Jenkins, J. Curtis, P. Landry
    TCO2              BNL          D. Wallace, K. M. Johnson, K. Erickson
    pCO2, discrete    LDEO         T. Takahashi, A. Wilson
    Underway pCO2     SIO          R. Weiss
    14C               PU           R. Key, C. Thomas, R. Rotter
    ADCP, LADCP       WHOI         F. Bahr
    Halocarbons       DU           W. Groszko
    pALACE floats     UW           D. Swift
    Observer          Venezuela    Antonio Perez-Aguirre
    _______________
    (1) CTD  conductivity, temperature, and depth sensor;
    (2) CFC  clorofluorocarbon;
    (3) ADCP  acoustic Doppler current profiler;
    (4) LADCP  lower ADCP;
    (5) ALACE  autonomous Lagrangian circulation explorer.

    Participating institutions

    AOML    Atlantic Oceanographical and Meterological Laboratory
    BNL     Brookhaven National Laboratory
    LDEO    Lamont-Doherty Earth Observatory
    UH      University of Hawaii
    OSU     Oregon State University
    PU      Princeton University
    RSMAS   Rosensteil School of Marine and Atmospheric Science, U. of Miami
    SIO     Scripps Institution of Oceanography
    SIO/ODF Ocean Data Facility Scripps Institution of Oceanography
    UW      University of Washington
    WHOI    Woods Hole Oceanographic Institution
    DU      Dalhousie University


2.3  Brief Cruise Summary 

For the section AR24 (cruise 147-2), the TCO2 and TALK systems were placed on 
board and set up on the R/V Knorr in Woods Hole, Massachusetts, during the 
period October 21-24, 1996, by the University of Miami TALK and the UH/BNL 
TCO2 measurement groups. The systems were successfully tested, and the Knorr 
departed Woods Hole on October 24, for the Azores with Mike McCartney as 
chief scientist. C. Winn was the CO2 group leader during the transit to the 
Azores and was present when one of the benches supporting one of the SOMMA-
coulometer systems broke loose, threatening to destroy the analytical system. 
Fortunately, the analytical equipment suffered only minor damage, and the 
minor repairs required were completed by the time the ship was ready to begin 
the AR24 section. C. Winn left the ship in the Azores and was replaced by 
R.Rotter, A. Adams, and J. Tegeder, with R. Rotter serving as the group 
leader. The ship departed on the AR24 cruise from Ponta Delgada on November 
1, 1996. The cruise track was, with minor deviations, basically a winter 
version of the two transoceanic A24 sections completed during the summer of 
1997 (see Fig. 1).  

During the AR24 section, the principal problem with the TCO2 SOMMA systems 
Nos. 004 and 030 was the malfunctioning of the solenoid pinch valves used to 
dispense the sample. Some were damaged and ceased to work, while others were 
sensitive to power fluctuations and worked intermittently. Replacement valves 
were quickly consumed, souch that SOMMA system No.30 became the primary 
system. As a consequence, the bulk of the sample TCO2 analyses completed 
during the AR24 section (see Table 4 in Sect. 3.2) were made on system 030. 
These problems also resulted in the sampling of 10 fewer stations sampled for 
TCO2 than for TALK during the cruise, with most of the discrepancies 
occurring between November 14 and 20, 1996. After the concluding station 176 
on December 2, 1996, the Knorr docked in South Hampton, United Kingdom, on 
December 3, 1996.  

Following the AR24 section, the analytical systems were repaired and re-
calibrated. They were then set up on the R/V Knorr in Woods Hole, during the 
week of May 1319, 1997, by the University of Miami TALK and the BNL TCO2 
measurement groups. Three SOMMA-coulometer systems and three TALK titrators 
were set up for the three WOCE sections (A24, A20, and A22). In addition to 
the discrete TCO2 systems (S/Ns 004 and 030), a third system (S/N 006) was 
set up for underway surface TCO2 measurements. The equilibrator-infrared (IR) 
gas analyzer system for the determination of partial pressure of CO2 (pCO2) 
in discrete sea water samples was set up by the scientists from LDEO. The 
discrete TCO2 systems were successfully calibrated using both CO2 calibration 
gas and the certified reference material (CRM) on May 17, 1997, while the 
calibration of the underway system (006) was completed on May 30. The Knorr 
departed Woods Hole on May 20 (Leg 151_1) with Dr. Tom Rossby as chief 
scientist. The TALK group remained onboard to test the instruments on the 
shake-down transit from Woods Hole to the embarkation point for Leg 151-2, 
Ponta Delgada on the island of St. Michael, Azores.  

Some 300 underway surface samples were drawn and analyzed for TALK during the 
shake-down cruise, but these data are not reported to the Carbon Dioxide 
Information Analysis Center (CDIAC). Greg Eischeid of WHOI completed the 
plumbing connections between the ships underway intake and the underway SOMMA 
(006). After correcting some minor problems, he obtained the required flow of 
1 L/min through the underway system. Problems with operating the underway 
pipette were also encountered, but they were eliminated by software changes 
coordinated through BNL, so that by the time the ship arrived in Ponta 
Delgada, the underway system was operational. The most serious problem with 
the discrete TCO2 systems was that an erratic transmission reading with the 
system 030 coulometer madeking titrations impossible. This program was 
temporarily corrected by jiggling the voltage -to -frequency converter (VFC) 
and ensuring that all associated chips were properly seated. System 004 was 
tested successfully during the shake-down cruise, which ended on May 29, 
1997, in Ponta Delgada. 

K. M. Johnson departed JFK Airport in New York on May 27, 1997, for Ponta 
Delgada via Lisbon and arriveding on May 28 in the Azores on May 28, where he 
joined   L. Arlen, who was already in Ponta Delgada. The TALK and TCO2 
measurement groups moved onboard ship on May 29, and readied the systems for 
the following day, when the ship departed Ponta Delgada on section A24 with 
Dr. Lynne Talley as chief scientist. Sample analysis began on system 004 
immediately, but the system 030 coulometer once again exhibited unstable 
erratic transmission readings and was immediately replaced with the back-up 
unit. Sample analysis with this unit began on May 31, 1997.  

The cruise track for section A24 was basically rectangular, encompassing four 
separate sections (see Fig. 1) starting and ending in the Azores. The first 
section began at Terceira, Azores, proceeding northeastward towards the Goban 
Spur and crossing the Mediterranean Water/Labrador Sea Water mixing zone 
obliquely. Upon completion of the first section, the ship was diverted to 
Cork, Ireland, for an emergency exchange of crew members. The second section 
crossed the southern Rockall Trough, from Porcupine Bank to the southern end 
of the Rockall Bank. The third section crossed the northern part of the 
subpolar gyre, from the Hebrides to Rockall Bank, to Hatton Bank, to the 
Reykjanes Ridge and to Greenland near Angmassalik, crossing the Rockall 
Trough just north of the Anton Dohrn Seamount. Ice conditions at Greenland 
were favorable, and sampling was completed at stations well onto the shelf 
(average depth 500 meters). After a transit southward to Cape Farewell, 
Greenland, the fourth section began at Cape Farewell and proceeded 
southeastward to the Charlie Gibbs Fracture Zone, and then back to Terceira 
with the last Station on June 28, 1997. After a 6-day transit, the ship 
docked in Halifax, Nova Scotia, on July 5.  

The weather remained uniformly good throughout Leg A24, and all carbonate 
measurement systems were operated essentially without major problems. Perhaps 
the biggest disappointment was the failure to rendezvous with the nearby R/V 
Meteor in early June for a social  gathering. Some 153 hydrographic stations 
were occupied during A24. TCO2 was measured on 92 of these stations and TALK 
was measured on 90. Therefore, roughly 60% of the stations occupied on this 
cruise were sampled for TALK and TCO2. This proportion was somewhat higher 
than the 50% of stations sampled on typical WOCE cruises due toas a result of 
an accelerated frequency of sampling. The increased frequency was brought 
about by making the A24 station interval dependent on bathymetry, which often 
varied radically over distances much less than the proscribed WOCE station 
interval of 30 nm. The carbon group sampled as many stations as possible 
given the limits imposed by the length of time required for the TCO2 and TALK 
determinations. In addition, discrete surface samples were taken at most 
stations, and the underway system was operated continuously on Section A24. 
Originally the A24 section was scheduled to terminate in St. Johns, but 
because repairs were required, the Knorr put into Halifax on July 4, 1997. An 
attempt was made to arrange for a back-up coulometer or to repair the damaged 
coulometer before the next cruise. Unfortunately, this did not work out, and 
scientists were still left without a back-up coulometer for the coming 
cruises. 

Because of the delay for repairs in Halifax, no direct handoff between CO2 
measurement crews was made. The TCO2 relief team consisting of Rick Wilke and 
Ken Erickson arrived well after the first crew had left and just prior to the 
Knorr's departure on July 17, 1997, on section A20. However, Wilke had been 
briefed at BNL concerning the performance of the TCO2 systems and possible 
problems due to de-powering of the ship during the repairs. The relief crew 
for TALK consisted of Chris Sabine and Carrie Thomas, who were also 
responsible for the 14C samples.  

The Knorr left Halifax bound for Port of Spain, Trinidad, on July 17, 1997, 
with Dr. Robert Pickart as chief scientist and 31 other scientists. From July 
17 until August 10, 1997, except for a couple of dog legs across the shelf 
regions, the Knorr occupied a series of stations in a straight line from the 
Newfoundland Shelf to the Suriname Shelf along approximately 52° W (WOCE 
Section A20). This Section is also a part of the ACCE and one of two North 
Atlantic WOCE meridional long-lines (the second long-line, A22, was visited 
during the subsequent cruise). In the early days of the cruise, heavy fog off 
of the Grand Banks made for slow going. Otherwise, the excellent weather 
experienced during the cruise allowed for the sampling of 95 hydrographic 
stations, which was more than planned. After the initial test station in 3000 
m at 57° W, the ship steamed to the 1000-m isobath and the work commenced. 
During A20, the water masses sampled included the slopewaters, the Laborador 
Current, the Labrador Sea Water, the Deep Western Boundary Current, the Gulf 
Stream with a warm core ring, the Sargasso Sea, and finally, as the ship 
turned toward Trinidad, the North Brazil Current system. On the depths less 
than  1000 m, a 24-position conductivity, temperature, and depth (CTD) sensor 
was used, while for greater depths, a 36-position CTD was used. Hydographic 
station intervals ranged from 3 nm on the shelf, to 10-15 nm across the 
slopes, to 15-25 nm across the Gulf Steam, and 40 nm in the Sargasso Sea. 
Other physical oceanographic tasks completed included the deployment of 11 
floats and drifters and the deployment or recovery of 4 moorings. The TCO2 
systems 004 and 006 continued to operate well, but system 030 required the 
replacement of one pinch valve and a faulty isolation valve on July 19. 
Thereafter, this instrument functioned satisfactorily. The Knorr arrived in 
Port of Spain, Trinidad, on August 10, 1997. 

K. Johnson left New York on August 12 to relieve R. Wilke of the TCO2 
measurement group, while K. Erickson and C. Thomas remained on board to 
continue the TCO2 and TALK measurements for the next section A22.  

The Knorr departed Port of Spain at 9 A.M. on August 15, and the first 
station was sampled only 12 hours out of port. Station 1 was a joint station 
with the R/V Hermano Gines from the EDIMAR Laboratory, Margarita, Venezuela, 
just outside the sill of the Cariaco Basin. Some joint nutrient samples were 
taken and analyzed aboard each ship. Then the Knorr began the Caribbean 
portion of the A22 transect, which ended with Station 23 on 300-m depth south 
of Puerto Rico on August 20, 1997. The Knorr jogged around the eastern end of 
the Island, and the transect was resumed north of Puerto Rico along 
approximately 66° W and continued until Station 77 in 200 m of water on the 
shelf south of Cape Cod, Massachusetts, on September 2, 1997. Some 77 WOCE 
hydrostations were occupied during the this leg. In addition, 10 floats and 9 
drifters were deployed and one mooring was recovered. All of the carbon 
parameter instruments, including the underway SOMMA, functioned 
satisfactorily until the end of the cruise; and fortunately a back-up 
coulometer was never needed. The R/V Knorr docked in Woods Hole on September 
3, where it was met by R. Wilke and E. Lewis from the BNL TCO2 group who 
helped pack the equipment,  and the entire TCO2 measurement group with its 
equipment departed Woods Hole on the afternoon of September 4, 1997. 



3. DESCRIPTION OF MEASUREMENTS AND METHODS

3.1 Hydrographic Measurements 

During the cruises, the responsibility for the hydrographic data was divided 
between Scripps Institution of Oceanography (SIO) (section A24) and WHOI 
(sections AR24, A20, and A22). Hence the hydrography description is given in 
separate sections for SIO and WHOI operations and methods.  3.1.1 SIO/Ocean 
Data Facility ODF Methods and Instrumentation (Section A24)
 

The SIO hydrographical procedures are described in detail by Lynne Talley in 
the chief scientists cruise report for WOCE Section A24, which can be 
obtained on the WHPO web site at 

         http://whpo.ucsd.edu/data/onetime/atlantic/a24/index.htm. 

Navigational data wereas logged automatically at 1-minute intervals on a Sun 
SPARC station. Underway bathymetry was acquired from the ships SeaBeam system at 
5-minute intervals. These data were merged with the navigation data to provide a 
time-series of underway position, course, speed, and bathymetry, which were used 
for all station positions, depths, and for bathymetry on vertical sections. A 
thermosalinograph (Falmouth Scientific Instruments) was mounted on the bow 
approximately 3 m below the surface for underway salinity. 

The hydrographic casts were made with a 36-position 10-L rosette system 
belonging to the Ocean Data Facility (ODF) at SIO. This unit consisted of a 
36-bottle frame, thirty-one 10-L Niskin bottles, an Neil Brown Instrument 
System (NBIS) Mark III CTD with dual conductivity and temperature sensors, 
transmissometer, LADCP, altimeter, and pinger. The rosette system was 
suspended from a three-conductor 0.322-inch electromechanical cable, and 
power to the CTD and pylon was provided through the cable from the ship. For 
the first 10 casts, a General Oceanics 1016 36-place pylon was used; 
thereafter a Sea Bird Electronics (SBE), 36-place pylon, and SBE 33 deck unit 
were used. The rosette was deployed from the starboard side hangar, and the 
port side Markey CTD winch was used throughout section A24. At the beginning 
of each station, the time, position, and bottom depth were logged,; the 
sensors were powered; and control was transferred to the CTD acquisition and 
control system in the ships laboratory and the CTD lowered to within 10 m of 
the bottom. The CTD provided real-time pressure, depth, temperature, salinity 
(conductivity), oxygen, and density, and these variables were used to select 
the sampling depths.  

At the end of each cast, water samples (full suite) were drawn in the 
following order: chlorofluorocarbons (CFCs), helium, oxygen, pCO2, TCO2, 
TALK, tritium, nutrients, and salinity. However, only salinity, oxygen, and 
nutrients were measured at every station. A log was kept to document the 
sampling sequence and to note anomalies (e.g., leaks, etc.), and WHP quality 
flags were assigned to each sample using the analyzed bottle salinities, 
oxygen, and nutrients. No major problems with the CTD operation were 
experienced, and the original set of 31 Niskin bottles was used throughout 
section A24. At the end of the cruise, the CTD and the entire acquisition and 
control system were packed and shipped back to SIO.  

The CTD was calibrated for pressure and temperature at the ODF calibration 
facility (La Jolla, CaliforniaA) in April 1997, prior to WOCE section A24. At 
sea, bottle salinity and oxygen were used to calibrate the conductivity and 
oxygen sensors, respectively, and the temperature calibration was checked 
with an SBE 35 laboratory-grade reference material. Further details 
concerning the pre- and post-cruise calibration of the CTD sensors can be 
found in the cruise report available from WHPO. ADCP and LADCP profiles were 
made throughout the section using the hull-mounted ADCP system permanently 
installed on the Knorr and the LADCP mounted vertically inside the rosette 
frame bottle rings. The quality of the shipboard ADCP to depths of 500 m was 
good throughout the cruise, as were the LADCP station profiles.  

Bottle salinity samples were collected after three rinses in 200-mL Kimax 
high alumina borosilicate bottles, sealed, and determined after thermal 
equilibration, usually within 8 to 12 hours of collection. Salinity was 
determined at 24°C on two Guildline Autosal Model 8400A salinometers located 
in a temperature-controlled laboratory (21.4 - 24.6°C). The salinometer was 
standardized with International Association for the Physical Sciences of the 
Ocean (IAPSO) standard seawater (SSW) batch P-127, using at least one fresh 

vial per cast. The accuracy of the determination was 0.002 relative to the 
SSW batch used. Salinity was then calculated for each sample (UNESCO, 1981) 
and merged into the data base.  

Bottle oxygen was determined by filling 125-mL iodine flasks to overflowing 
(3 x bottle volume) with a draw tube after two bottle rinses. Sample 
temperature was measured immediately with a thermometer imbedded in the draw 
tube. The Winkler reagents were added, the flasks stoppered, and shaken upon 
stoppering and shaken again 20 minutes later to ensure that the dissolved 
oxygen was completely fixed. Oxygen was determined according to the technique 
of Carpenter (1965), incorporating the modifications of Culberson et. al 
(1991) within 4 hours of collection on an SIO-designed automated oxygen 
titrator using photometric endpoint detection at an ultra-violet wave length 
of 365 nm. Standards prepared from pre-weighed potassium iodate were run each 
time the automated titrator was used, and reagent blanks were determined by 
analyzing distilled water. The final oxygen results have been converted to 
µmol/kg. Conversion was madedone using the in-situ temperature, not the 
temperature of the sample from the Niskin bottles, because of due to a 
software failure. Bottle volumes were precalibrated at SIO. The precision of 
the analysis calculated from 57 replicate pairs (duplicates drawn from the 
same Niskin bottle) was ± 0.004 mL/L.  

Phosphate, nitrate, nitrite, and silicate were determined on virtually every 
Niskin bottle closed from stations 1 through 153. The samples were collected 
in 45-mL high-density polypropylene, narrow-mouth, screw-capped centrifuge 
tubes whichthat were rinsed with HCL and then rinsed three times with sample 
before filling. The samples were analyzed on an ODF-modified four-channel 
Technicon AutoAnalyzer II, usually within 1 hour of the cast, in a 
temperature-controlled laboratory. If the samples were stored for longer than 
1 hour prior to analysis, they were stored at 4°C (no more than 4 hours). 
The Auto Analyzer instrumentation which incorporates the method of Armstrong, 
Stearns, and Strickland et al. (1967) for silicate, the method of Armstrong 
et al. (1967) as modified for nitrate and nitrite, and the method of 
Bernhardt and Wilhelms (1967) for phosphate is described by Gordon and co-
workers (Atlas et al., 1971; Hager et al., 1972; Gordon et al., 1992). 
Standards were analyzed at the beginning and end of each group of sample 
analyses with a set of secondary intermediate concentrations prepared by 
diluting pre-weighed primary standards. The primary standard for silicate was 
Na2SiF6; and for nitrate, nitrite, and phosphate, KNO3, NaNO2, and KH2PO4 
were used, respectively. Chemical purities ranged from 99.97% (NaNO3) to 
99.999% (KNO3). Deep seawater was also used as a substandard. Some 3439 
nutrient samples were analyzed during section A24. 


3.1.2 WHOI Methods and Instrumentation (Sections AR24, A20, and A22) 

Unless otherwise stated, procedures remain as in Section 3.1.1 above. The 
underway-Doppler speed log did not function during sampling of section A22, 
and the hull-mounted transducer had to be removed for repair. Otherwise, 
navigational and meteorological data wereas logged by the shipboard data 
acquisition system (dubbed Athena) at 1-minute intervals. These data include 
heading, time and date, geographic positioning system (GPS), wind speed and 
direction, sea surface temperature and conductivity, and additional 
meteorological data. A secondary suite of data calculated or derived from 
these data was also logged at 1-minute intervals. These files were also the 
source of event-specific data (e.g., station location). Underway salinity was 
calibrated with bottle salinity. 

For the WHOI sections, the Knorr was outfitted with equipment belonging to 
WHOI. For details see the chief scientists report for Sections A20 and A22 on 
the WHPO web site: http://whpo.ucsd.edu/data/onetime/atlantic/index.htm. The 
CTD used was a WHOI-modified NBIS Mark-III CTD with oxygen sensor, 
conductivity cell, LADCP, pressure transducer, temperature sensor, and pinger 
mounted on a 33-position 10-L Niskin bottle rosette frame. The AR24 section 
differed from the above A20 and A22 sections and virtually all other CO2 
survey work because a 24-bottle rosette was used with 4-L sampling bottles, 
instead of the usual 10-L Niskin bottles, in order to reduce sampling time at 
the rosette when in late fall when seas were expected to be rougher. A 
General Oceanics-1016 pylon was used and was controlled using an SIO-
furnished Surface Control Interface, a dedicated PC, and software provided by 
SIO/ODF. Temperature and pressure calibrations were performed at WHOI before 
section A20. The CTD was re-calibrated after its return to WHOI in December 
1997. For details concerning the pre-cruise, at-sea, and post-cruise CTD 
calibrations, see the cruise report and Millard and Yang (1993). 

Oxygen, nutrients, and salts were analyzed from virtually every Niskin bottle 
closed during the cruise. Bottle salinity samples were collected after two 
rinses in 8-ounce glass bottles. Then they were thermally equilibrated to 
22°C and analyzed on a Guildline Autosal Model 8400B salinometer. The 
salinometer was standardized once a day using IAPSO SSW Batch P-131 (dated 
October 10, 1996). The accuracy was ± 0.002.  

Bottle oxygen was determined by filling 15-mL brown glass tincture bottles. 
Oxygen was determined using a modified Winkler technique similar to that 
described by Strickland and Parsons (1972). The titration is automated using 
a PC controller and a Metrohm Model 665 Dosimat buret. The endpoint is 
determined amperometrically using a dual -plate platinum electrode, with a 
resolution of better than 0.001mL. The accuracy of the method is 0.02 mL/L 
with a standard deviation of replicate samples of ± 0.005. Standardization 
of the thiosulphate titrant was madedone daily. No problems were noted during 
the cruises. This technique is described further by Knapp, Stalcup, and 
Stanleyet al. (1990). 

The nutrient samples were collected in 30-mL high-density polypropylene 
bottles whichthat were loaded directly into the autosampler tray. The bottles 
were soaked in 10% HCl every other day, and rinsed three times with sample 
before filling. The samples were analyzed on the same SIO/ODF-modified four-
channel Technicon AutoAnalyzer II used on A24, except that an Alpkem Model 
303 autosampler was substituted for the ODF autosampler. The analytical 
methods are described in Gordon et al. (1994).  


3.2.  Total CO2 Measurements

As on previous cruises, TCO2 was determined using automated dynamic headspace 
sample processors (SOMMA) with coulometric detection of the CO2 extracted 
from acidified samples. A description of the SOMMA-Coulometry System and its 
calibration can be found in Johnson et al., (1987), Johnson and Wallace, 
(1992), and Johnson et al., (1993). A schematic diagram of the SOMMA 
analytical sequence may be found in earlier cruise reports (see Johnson et 
al. 1995;,1996), and further details concerning the coulometric titration can 
be found in Huffman (1977) and Johnson, King, and Sieburth (1985). The 
methods used for discrete TCO2 on WOCE sections have been extensively dealt 
with in previous reports (Johnson et al., 1998a) and only need onlyto be 
briefly summarized. 

The AR24 section required modification of the usual sampling procedures. As 
noted in Section 3.1.2 above, 4-L sampling bottles were employed on the 
rosette, which limitinged the amount of sample available for the carbonate 
system analysts to one 500-mL bottle. Hence, the TCO2 coulometric titration 
analysis had to be completed before the partially empty 500-mL bottle was 
passed to the TALK group for the potentiometric alkalinity titration. There 
was enough sample to complete both measurements, but not enough time or 
sample for TCO2 replicate analyses from the same 500-mL sample bottle. The 4-
L sampling bottles also made it impossible to draw duplicate samples from the 
same sampling bottle. Without duplicate samples from the hydrographic 
stations, standard measures of sample precision (DOE, 1994; Johnson, et al., 
1998b) could not be completed on the AR24 section. Samples were poisoned with 
100 µL of a 50% solution of HgCl2, and analyzed for TCO2 within 24 hours of 
collection (DOE, 1994).

For sections A24, A20, A224, single or duplicate samples were collected in 
300-mL biological oxygen demand (BOD) bottles, poisoned with 100 µL of a 50% 
solution of HgCl2, and analyzed for TCO2 within 24 hours of collection, 
according to standard operating procedures (DOE, 1994). The samples were 
stored in a dark refrigerator at 46°C until approximately 12 hours before 
analysis, when they were removed and placed in a temperature bath at 18-20°C 
and thermally equilibrated. The SOMMA sample pipette and sample bath were 
also kept at approximately 20°C. Duplicate samples were usually collected on 
each cast at the surface and from the bottom waters. For some casts, three 
sets of duplicates were taken. The duplicates were analyzed within the run of 
cast samples from which they originated souch that the time elapsed between 
duplicate analyses was 3-12 hours. As per standard operating procedure (DOE 
1994), Certified Reference Material (CRM) was routinely analyzed according to 
DOE (1994) guidelines. The CRM was supplied by Dr. Andrew Dickson of the SIO, 
and for the North Atlantic cruises, batches 33, 36, and 37 were used. The 
certified values for these batches were: TCO2 = 2009.85 µmol/kg @ salinity = 
33.781 for batch 33; TCO2 = 2050.21 µmol/kg @ salinity = 35.368 for batch 36; 
and TCO2 = 2044.15 µmol/kg @ salinity = 34.983 for batch 37. The CRM TCO2 
concentration was determined by vacuum-extraction/manometry in the laboratory 
of C. D. Keeling at SIO. 

An accurately known volume of seawater was injected from an automated to-
deliver (TD) pipette into a stripping chamber. Following acidification, the 
resultant CO2 from continuous gas extraction was dried, and coulometrically 
titrated on a model 5011 UIC Ccoulometer with a maximum titration current of 
50 mA in the counts mode (the number of pulses or counts generated by the 
coulometers VFC during the titration was displayed). In the coulometer cell, 
the acid (hydroxyethylcarbamic acid) formed from the reaction of CO2 and 
ethanolamine is titrated coulometrically (electrolytic generation of OH-) 
with photometric endpoint detection. The product of the time and the current 
passed through the cell during the titration (charge in coulombs) is related 
by Faradays constant to the number of moles of OH- generated and thus to the 
moles of CO2 whichthat reacted with ethanolamine to form the acid. The age of 
each titration cell is logged from its birth (time that electrical current is 
applied to the cell) until its death (time when the current is turned off). 
The age is measured in minutes from birth (chronological age) and in mgC 
titrated since birth (carbon age). 

Each system was controlled with an IBM -compatible PC equipped with two RS232 
serial ports (coulometer and barometer), a 24-line digital input/output card 
(solid state relays and valves), and an analog -to -digital (A/D) card 
(temperature, conductivity, and pressure sensors). Real Time Devices (located 
in State College, PA 16803) manufactured the cards. The SOMMA temperature 
sensors (model LM34CH, National Semiconductor, Santa Clara, CA) with a 
voltage output of 10 mV/F were calibrated against thermistors certified to 
0.02°F prior to the cruise using a certified mercury thermometer. These 
sensors monitored the temperature of SOMMA components, including the pipette, 
gas sample loops, and the coulometer cell. The SOMMA software was written in 
GWBASIC Version 3.20 (Microsoft Corp., Redmond, WA), and the instruments were 
driven from an options menu appearing on the PC monitor. With the coulometers 
operated in the counts mode, conversions and calculations were made using the 
SOMMA software rather than the programs and the constants hardwired into the 
coulometer circuitry. 

The SOMMA-coulometry systems were calibrated with pure CO2 (calibration gas) 
using hardware consisting of an 8-port gas sampling valve (GSV) with two 
sample loops of known volume [determined gravimetrically by the method of 
Wilke, Wallace, and Johnson et al., (1993)] connected to the calibration gas 
through an isolation valve; with the vent side of the GSV was plumbed to a 
barometer. When a gas loop was filled with CO2 at known temperature and 
pressure, the mass (moles) of CO2 contained therein was calculated, and the 
ratio of the calculated mass to that determined coulometrically iwas the 
calibration factor (CALFAC); the CALFAC which was used to correct the 
subsequent sample titrations for small departures from 100% recoveries (DOE, 
1994). The standard operating procedure was to make gas calibrations daily 
for each newly prepared titration cell ([normally, one cell per day and three 
sequential calibrations per cell at a carbon age of 39 mgC (mean age @ 6 
mgC), with the result of the third calibration taken as the CALFAC if it was 
consistent with the second, (i.e., agreement to ± 0.1% or better)]. Daily gas 
calibrations were made on both systems throughout the cruises. 

The "to-deliver" volume (Vcal) of the sample pipettes was determined 
(calibrated) gravimetrically prior to the cruise to ± 0.02% or better in 
October of 1996. The calibration was checked periodically during all cruises 
by collecting aliquots of deionized water dispensed from the pipette into 
pre-weighed serum bottles. The serum bottles were crimp-sealed and weighed 
immediately during the on-shore laboratory calibrations, or returned to shore 
where they were reweighed on a model R300S balance (Sartorius, Gttingen, 
Germany) balance as soon as possible. The apparent weight (g) of water 
collected (Wair) was corrected to the mass in vacuum (Mvac) with the to-
deliver volume being Mvac divided by the density of the calibration fluid at 
the calibration temperature. After the AR24 section in 1996, the system 
pipettes were dismounted and replaced with chemically cleaned pipettes in 
March, 1997. For the 1997 sections, the calibration volumes (Vcal) at the 
calibration temperature (tcal) of the sample pipettes were redetermined to ± 
0.01% from a set of calibration samples taken on July 3, 1997, on aboard the 
Knorr at the completion of section A24 and were weighed on September 17. The 
TCO2 pipette volumes for the four North Atlantic sections are summarized in 
Table 2.  


Table 2: The "to-deliver" pipette volume (Vcal) and calibration temperature 
         (tcal) for the discrete SOMMA-Coulometer Systems (S/N 004 and 030) 
         used on WOCE Section AR24 (1996) and Sections A24, A20, and A22 (1997)

         ______________________________________________________

               Section         System S/N  Vcal (mL)  tcal (C)
          -------------------  ----------  ---------  --------
                  AR24 (1996)      004      21.8927   19.91
           A24/A20/A22 (1997)      004      21.2630   19.19
                  AR24 (1996)      030      21.3733   20.91
           A24/A20/A22 (1997)      030      25.8544   19.52
         ______________________________________________________
    

The sample volume (Vt) at the pipette temperature was calculated from the 
expression:    
                        Vt = Vcal [1 + av (t - tcal)]
    
where av is the coefficient of volumetric expansion for pyrex-type glass (1 X 
10^-5/°C), and t is the temperature of the pipette at the time of a 
measurement. The mean pipette temperature on the AR24 section in 1996 was 
20.32 ± 0.51°C (n = 948), and on the 1997 North Atlantic Sections it was 
19.55 ± 0.52°C (n = 4666). 

The factory-calibrated coulometers were electronically calibrated 
independently in the laboratory before the cruise as described in Johnson et 
al. (1993, 1996) and DOE (1994), and the terms INTec and SLOPEec were 
obtained and entered into the software for each system. The micromoles of 
carbon titrated (M), whether extracted from water samples or the gas loops, 
was: 
          M = [Counts/4824.45-(Blank X Tt )-(INTec X Ti)]/SLOPEec

where 4824.45 (counts/µmol) is a scaling factor obtained from the factory 
calibration; Tt wais the length of the titration in minutes; Blank is the 
system blank in µmol/min; INTec is the intercept from electronic calibration 
in µmol/min; Ti is the time in minutes during the titration where current 
flow was continuous; and SLOPEec is the slope from electronic calibration. 
Note that the slope obtained from the electronic calibration procedure 
applied for the entire length of the titration, but the intercept correction 
applied only for the period of continuous current flow (usually 34 min) 
because the intercept can only be calculated only from calibrated levels of 
current flowing continuously. 

Unfortunately, the coulometer system 030, which was electronically calibrated 
prior to the AR24 cruise and again in March 1997, had to be replaced at the 
start of section A24 in May 1997. However, the replacement coulometer (S/N 
CBE-9010-V) was calibrated at the factory on March 20, 1997. Hence we assumed 
that the replacement coulometer was properly calibrated, and we entered the 
default calibration coefficients into the software (SLOPEec = 1.0 and INTec = 
0.0). The system 004 was also recalibrated in March 1997 following the AR24 
cruise with nearly identical results to those obtained in October 1996, and 
it was not recalibrated during the 1997 WOCE sections. The electronic 
calibration coefficients, along with the mean gas calibration factors 
determined for the North Atlantic section discrete TCO2 coulometers, are 
given in Table 3.

Table 3 illustrates an advantage of the independent laboratory electronic 
calibration procedure. The mean CALFAC for systems 004 and 030 using the 
laboratory-determined electronic calibration coefficients was approximately 
1.0036 (or 99.64% recovery of the theoretical mass of CO2 calibration gas 
measured coulometrically) vs 1.0053 (99.47% recovery) for the factory-
calibrated coulometer. Hence, a small percentage (0.17%) of the less than 
100% recovery for known masses of CO2 coulometrically titrated can be 
explained by a factory-calibration procedure whichthat is apparently slightly 
less accurate than the laboratory calibration. This difference has been 
consistent throughout the CO2 survey. 


Table 3: The electronic calibration and the mean gas calibration coefficients 
         for the discrete TCO2 systems on WOCE Section AR24 (1996) and 
         Sections A24, A20, and A22 (1997)

         __________________________________________________________________________

          Section      System  SLOPE    INT(ec)    CALFAC(n)    St. dev.  Rel. st.
                        S/N    (ec)     µmol/min                          dev. (%)
          -----------  ------ --------  --------  ------------  --------  --------
          AR24          004   0.999372  0.002528  1.003892(9)   0.000650   0.06
          A20/A22/A24   004   0.998905  0.001466  1.003361(63)  0.000740   0.07
          AR24          030   0.999306  0.003550  1.003780(26)  0.000497   0.05
          A20/A22/A24   030*  1.000000  0.000000  1.005344(59)  0.001369   0.13
          ------------------------------------------------------------------------
          *Factory-calibrated coulometer installed at the beginning of the A24 
           section in May 1997.
         __________________________________________________________________________
  

For water samples, the discrete TCO2 concentration in µmol/kg was calculated 
from:
                    TCO2 = M X CALFAC X [1/(Vt X P)] X dHg

where P is the density of sea water in g/mL at the measurement temperature 
and sample salinity calculated from the equation of state given by Millero 
and Poisson (1981), and dHg is the correction for sample dilution with 
bichloride solution (for the AR24 section in 1996 dHg = 1.0002 and for the 
1997 sections dHg = 1.000333). 

One of the SOMMA-Coulometry Systems (S/N 004) was equipped with a conductance 
cell (Model SBE-4, Sea-Bird Electronics, Inc., Bellevue, WA) for the 
determination of salinity measurement as described by Johnson et al. (1993). 
Whenever possible SOMMA and CTD salinity were compared to identify mistrips 
or other anomalies, but the bottle salinity (furnished by the chief 
scientist) was used to calculate TCO2. 

Quality control-quality assurance (QC-QA) was assessed from the results of 
the 275 CRM analyses made using systems 004 and 030 during the four North 
Atlantic sections. These data are summarized in Table 4, and the temporal 
distribution of the differences is plotted in Fig. 2 for section AR24 (1996) 
and in Fig. 3 for sections A24, A20, and A24 (1997). 


Table 4: The mean analytical difference (∆TCO2 = measured - certified) and 
         the standard deviation of the differences between measured and 
         certified TCO2 on WOCE Sections AR24, A24, A20, and A22
    
               _______________________________________________
                Section     System    ∆TCO2     St. dev.   n
                             S/N    (µmol/kg)  (µmol/kg)
                ----------  ------  ---------  ---------  ---
                  AR24       004      1.42       2.10      16
                  AR24       030      1.54       1.88      49
                Mean/total            1.51       1.92      65
                  A24        004      0.04       1.10      49
                  A20        004      0.23       1.20      42
                  A22        004      0.06       0.69      17
                Mean/total            0.10       1.08     108
                  A24        030      0.79       1.00      48
                  A20        030      0.44       1.43      35
                  A22        030      0.26       1.22      19
                Mean/total            0.57       1.21     102
                Overall mean/total    0.61       1.47     275
               _______________________________________________
 

The overall accuracy of the CRM analyses was better than 1 µmol/kg on both 
systems for the four North Atlantic sections, with a combined overall mean 
difference of + 0.61 µmol/kg (n = 275). However, Table 4 shows that on the 
AR24 section (1996), the mean difference and the standard deviation of the 
differences were noticeably larger for both systems compared towith the 1997 
sections (A24/A20/A22). This may be due in part to mechanical problems 
experienced by the AR24 measurement group, operator procedures, and possibly 
the relatively short time available to service and re-calibrate the systems 
prior to the AR24 section. The latter was brought about by the fact that the 
system 004 had been used in the Indian Ocean from 1994-1996, and was only 
returned to BNL for service, repair, and re-calibration in the fall of 1996. 
System 030, which was a newly built system returned to the laboratory after a 
test cruise in the North Atlantic, also was not returned until the summer of 
1996. For the 1997 sections, both systems were available in the laboratory 
for servicing from January through May of 1997. Indeed, the 1997 WOCE 
sections represented the only opportunity during the CO2 survey for the BNL 
measurement group to thoroughly service and test the systems, reagents, and 
analytical gases in the laboratory with real samples and CRM prior to 
shipment. As a result, the accuracy and precision of the CRM analyses made in 
1997 (see Table 4) probably represents the highest quality possible for these 
systems under field conditions. 

All CRM analyses made on the discrete systems (004 and 030) during the 1997 
sections are reported in Table 4. However, for section AR24, two CRM analyses 
were classified as outliers and dropped from the data set. These were CRM No. 
206 run on system 030 on November 23 (difference = + 10.17 µmol/kg) at a cell 
carbon age of 39.5 mgC, and CRM No. 600 on system 030 on November 28 
(difference = + 7.99 µmol/kg) at a carbon age of 35.7 mgC. One CRM analysis 
(CRM No. 352) run on system 004 on December 1 is not included in the data set 
because the titration did not attain an endpoint.   

The second phase of the QC-QA procedure was an assessment of precision. As 
described in the text, duplicate samples could not be taken during the AR24 
section in 1996. Hence the only estimate of AR24 sample precision was the 
standard deviation of the differences between the measured and certified TCO2 on 
both systems (see Table 4). Because differences from both systems have been 
combined, the CRM measurements are analogous to the sample duplicates analyzed 
on each system and should reflect both random and systemic error (bias). The 
decrease in precision for the CRM analyzed on the AR24 section in 1996 (± 1.92 
µmol/kg) compared towith the CRM analyzed in 1997 (± 1.20 µmol/kg) was 
consistent with the problems described for the 1996 leg. The good agreement in 
TCO2 between systems in 1996 (see Table 4) suggests that the analyzingsis of 
duplicate seawater samples on each system, as was the casedone in 1997, might 
have yielded a higher precision than the precision of the CRM differences. 
Nevertheless, without sample duplicates, the AR24 sample precision must be based 
on the CRM analyses. Hence the precision of the TCO2 determination for the AR24 
section in 1996 was ± 1.92 µmol/kg (n = 65). Because procedures and performance 
varied from 1996 to 1997, separate estimates of sample precision were required 
for each year; and the data for 1997 are given in Table 5.

By 1997 the deployment of two independent SOMMA systems side-by-side was 
routine, and the conventions employed for the estimation of precision in the 
earlier WOCE data reports are retained in Table 5. For sections A24, A20, and 
A22 in 1997, the single-system precision was determined from samples with 
duplicates analyzed on the same system (either 004 or 030). The sample 
precision was calculated using duplicates that were analyzed on both systems 
(004 and 030).


Table 5: Precision of the discrete TCO2 analyses on WOCE Sections A24, A20, and A22

         ___________________________________________________________________

          Section | Mean absolute difference | Pooled standard deviation
                  |--------------------------|-----------|-----------------
                  |    σbs    | ± St. |  K   |   Sp^2    |  K  |  n  | d.f.
                  | (µmol/kg) |  dev. |      | (µmol/kg) |     |     |     
          --------|--------------------------------------------------------
                  |                Single-system precision
          --------|--------------------------------------------------------
            A24   |   1.08    | 1.01  | 175  |   1.04    | 175 | 350 | 175
            A20   |   0.95    | 1.14  |  84  |   1.04    |  84 | 168 |  84
            A22   |   0.99    | 0.93  |  71  |   0.96    |  71 | 142 |  71
          --------|--------------------------------------------------------
                  |                   Sample precision
          --------|--------------------------------------------------------
            All   |   1.76    | 1.41  |  56  |   1.59    |  61 | 122 |  61
         ___________________________________________________________________


Single-system and sample precision have been separately assessed in Table 5 as:

 • "between-sample" precision (σbs), which is the mean absolute difference 
   between duplicates (n=2) drawn from the same Niskin bottle; and
 • the pooled standard deviation (Sp^2) calculated according to Youden (1951), 
   where K was the number of samples with duplicates analyzed, n was the total
   number of replicates analyzed from K samples, and n - K was the degrees of 
   freedom (d.f.).

Single-system precision provided a measure of drift in system response during 
a sequence of sample analyses. This is because the time elapsed between 
duplicate analyses on the same system using the same coulometer cell was 
deliberately kept at from 3 to 12 hours on the assumption that drift or change 
in response would be reflected in the single-system precision by an increase 
in the imprecision of the duplicate analyses. Sample precision, on the other 
hand, was measured because TCO2 measurements were made on two separate systems 
and an estimate of overall sample precision for the section (s), independent 
of which analytical system was used, was required. Sample precision is the 
most conservative estimate of precision, incorporating several sources of 
random or systematic (bias) error.

As on other sections in the Atlantic Ocean (e.g., A8 and A10) where SOMMA-
Ccoulometer systems have been run in parallel, the sample precision was 
slightly less precise than the single-system precision. This indicated that 
changes in system response during the coulometer cell lifetime in 1997 were 
clearly within the precision of the method (± 1.59 µmol/kg), while the slight 
but consistent decrease in sample precision compared towith single-system 
precision was probably due at least in part to a small bias between the 004 
and 030 systems. Although the precision was equivalent for both systems, 
system 030 gave on average slightly higher results than system 004. For 
example, the mean ∆TCO2 for system 004 CRM was +0.10 µmol/kg, but it was +0.57 
µmol/kg for system 030 CRM (see Table 4); while the mean of the seawater 
samples (n = 56, Table 5) analyzed on 030 was +1.17 µmol/kg higher than the 
mean for the same samples analyzed on system 004. Hence the uniformly 
excellent single-system precisions for 1997 can not be used for sample 
precision, and analyzing duplicate replicates on each system remains the 
definitive measure of the overall precision of the 1997 data set and the TCO2 
calibration procedures. The two discrete systems should give the same result 
for the same sample, and the extent to which they differ is a measure of the 
overall precision of the data set obtained with two independent systems. For 
TCO2 on the 1997 North Atlantic WOCE sections, the precision of the TCO2 
determination was ± 1.59 µmol/kg (K= 56). 

The North Atlantic sample precision for all four sections in 1996 and 1997 (± 
1.92 and ± 1.59 µmol/kg, respectively) is in good agreement with the published 
and unpublished sample precision for other WOCE sections where systems were 
run in parallel: AE1, 1991 (± 1.65 µmol/kg); P6, 1992 (± 1.65 µmol/kg); A10, 
1993 (± 1.92 µmol/kg); A8, 1994 (± 1.17 µmol/kg); Indian Ocean, 1995 (± 1.20 
µmol/kg). During the 1997 North Atlantic sections, a limited number of 
duplicate samples (K = 6) were analyzed from two different Niskin bottles 
closed at the same depth, and the mean absolute difference and standard 
deviation was 0.77 ± 0.50 µmol/kg, which was consistent with earlier findings 
(e.g., Johnson et al., 1998a,; Johnson et al. 2001) that there were likely no 
significant analytical effects due to gas exchange with the overlying 
headspace of the Niskin bottles during sampling. 

Tables 4 and 5 show an internally consistent data set of high quality with 
excellent accuracy (< or = 2.0 µmol/kg), high single-system precision (< or = 
± 1.0 µmol/kg), and a slightly higher imprecision for the sample precisions (± 
1.59 - 1.92 µmol/kg). Based on these data, the TCO2 data clearly meet survey 
criteriaon for accuracy (< or = 4.0 µmol/kg) and precision, and as with 
previous data submissions, no correction for instrumental bias or CRM 
analytical differences has been applied to the TCO2 data. 


3.3.  Total Alkalinity Measurements

TALK and pH, were measured using an automated potentiometric titration system 
developed at the University of Miami (hereafter designated as MATS). The MATS 
is described by Millero et al. (1993a). It consisted of two parts: a Metrohm 
model 665 Dosimat titrator and a pH meter (Orion, Model 720A) which are 
interfaced with a PC. A water-jacketed, fixed -volume (~200 mL), closed 
Plexiglass sample cell, of greater volume than but otherwise similar to those 
used by Bradshaw and Brewer (1988), was used to increase the precision of the 
measurements. The cell, titrant burette, and sample cell were theromstatted at 
25 ± 0.05°C using a constant temperature bath (Neslab, Model RTE 221). A Lab 
Windows/CVI program was used to run the titrators, record the volume of 
titrant added, and to record the measured electromagnetic frequency (emf) of 
the electrodes through RS232 serial interfaces. The electrodes for measuring 
the emf during the titration consisted of a ROSS glass pH electrode (Orion, 
Model 810100) and a double-junction Ag/AgCl reference electrode (Orion, Model 
900200). 

Seawater samples were titrated by adding enough HCl to exceed the carbonic 
acid end point of the titration. During a typical titration, the electro-
magnetic frequency (emf) readings were recorded until stable (± 0.05 mV). 
Normally, at this point, a fixed volume of acid would be added,; however, the 
MATS were designed to add enough acid to increase the voltage by a pre-
assigned increment (13 mV). This was done to give an even distribution of data 
points over the course of a full titration, which consists of 25 data points 
and takes about 20 minutes. With two systems, approximately 7 hours was 
required to run a 31-bottle station cast. As noted in Sections 3.1 and 3.2 
above, a 4-L Niskin sampling bottles were employed on the rosette, which 
limited the amount of sample available for the carbonate system analysts to 
one 500-mL bottle. Hence there was not enough sample to complete duplicate 
alkalinity analyses from the same bottle or to draw duplicate samples from the 
same sampling bottle. 

The titrant (acid) used throughout the cruises was prepared, standardized, and 
stored in 500-mL borosilicate glass bottles for use in the field. A single 55-
gallon batch of 0.25-m HCl acid was prepared by dilution of concentrated HCl 
(AR Select  Mallinckrodt). The acid was prepared in 0.45 m NaCl to yield a 
total ionic strength similar to that of seawater salinity 35.0 (I = ~ 0.7 M). 
The acid was standardized by coulometry (Taylor and Smith, 1959; Marinenko and 
Taylor, 1968). The acid molality was also checked by titration on seawaters 
with known alkalinities, and sub samples were sent to the laboratory of A. 
Dickson at SIO for an independent laboratory determination of the molality. 
The calibrated molality of the acid used for the North Atlantic WOCE Sections 
was 0.24892 ± 0.00003 m HCl. 

The consistency of the method was checked for each cast using low -nutrient 
surface seawater, and the accuracy of the method was checked by analyzing CRM 
Batches 33 (1996), 36, and 37 (1997) and comparing the analyzed values with 
the certified TALK in the same manoner as for TCO2 (see also Section 3.2 for 
batch data). The mean differences between at-sea measurements and the 
certified TALK values are given in Table 6. The TALK of each batch was also 
determined in the laboratory by weight titrations, which were found to agree 
with the certified values to ± 2 µmol/kg. In addition, the pH of the CRM 
batches was also determined in the laboratory spectrophotometrically according 
to the methods of Clayton and Byrne (1993) prior to the cruise. The at-sea 
titration pH measurements were also compared towith the pre-cruise 
spectrophotometric values, and and the reader is referred to Millero et al. 
(1999) for further details. 


Table 6: The mean analytical difference between analyzed and certified TALK 
         for the MATS on WOCE Section AR24 (1996), and Sections A24, A20, and 
         A22 (1997)
                                  
         __________________________________________________________

                                  CRM TALK  Measured TALK   ∆TALK
          Section   Cells     n   µmol/kg      µmol/kg     µmol/kg
          ------  ---------  ---  --------  -------------  -------
           AR24   2, 19, 17   59   2234.9      2233.3       -1.6
           A24    2, 18, 12  148   2283.9      2283.3       -0.6
           A20    2, 18, 12   96   2314.1      2217.1        3.0
           A22    2, 12       65   2314.1      2215.4        1.3
         __________________________________________________________


The mean differences between the at -sea measurements and the certified TALK 
were within 3.0µmol/kg (Table 6). Hence the measured and certified TALK were 
in good agreement. For pH and TCO2, the corresponding results were 0.021 and 9 
µmol/kg, respectively, with the larger deviation in pH attributable to the 
non-Nernstian behavior of the electrodes near a pH of 8 (Millero et al., 
1993b).
 
The at -sea sample alkalinity titrations were corrected using the results for 
the CRM. For TALK, the CALFAC used to correct the at sea measurements was:

              CALFAC = CRM (certified value)/(at- sea value),

and for pH the CALFAC was:

                       pH = pH (CRM)/pH (at-sea).

Duplicate samples were usually taken for each station in the same manner as 
for TCO2 (surface and deep) and analyzed to determine and monitor the 
precision of the MATS. The average difference between replicates was ± 1.0, 
±1.1, and ± 1.1 µmol/kg for sections A24, A20, and A22, respectively, which 
demonstrated the high precision of the MATS throughout the study. A 
preliminary description of the major trends in the data and the behavior of 
alkalinity over time in the North Atlantic is given by Millero et al. (1999).   


3.4.  Discrete pCO2 Measurements

The discrete measurements of pCO2 were performed by the LDEO group on three of 
four sections of the North Atlantic survey. During the WOCE sections A24, A20, 
and A22, a total of 2,465 samples were analyzed onboard the R/V Knorr (1,103, 
595, and 767 samples respectively). On the earlier WOCE section AR24, discrete 
pCO2 was not measured.

An automated equilibrator-infrared (IR) gas analyzer system was used during 
the expedition for the determination of partial pressure of CO2 in the 
seawater samples. Its design is similar to that described by Chipman et al., 
Marra, and Takahashi (1993) with the exception that the gas chromatograph was 
replaced with an infraredIR gas analyzer. The equilibrator-IR system is shown 
schematically in Fig. 4.  

The system consists of a circulation pump plumbed to re-circulate air in a 
closed system through porous plastic gas dispersers immersed in a 250 -mL 
seawater sample. The seawater sample is contained in a 250-mL Pyrex reagent 
bottle with a standard taper-ground glass stopper whichthat serves as an 
equilibration vessel. A Pyrex extension tube (~ 20 mL), thatwhich has a standard 
taper-ground glass male-joint to form an air-tight seal with the reagent bottle, 
is connected to the mouth of the reagent bottle to provide an extra headspace 
forto preventing seawater from entering the gas circulation line. Four sets of 
flasks and circulation pumps are used so that four water samples can be 
processed concurrently. Because the partial pressure of CO2 is sensitive to 
temperature, the equilibration flasks are kept immersed in a water bath 
maintained at 20°C. The temperature at which the water sample is equilibrated 
with circulating gas is measured with a precision of ± 0.01°C and is recorded. 

An electrically driven Valco 10-port valve (the equilibrator selection valve 
in Fig. 4) is used to isolate each of the equilibrators during the initial 
equilibration. Manually operated 2-way and 3-way Whitey valves allow the 
headspace in each equilibrator to be filled with a calibration gas of known 
CO2 concentration, creating a known initial condition for the headspace (about 
40 mL) before equilibration. The equilibrator is open to the laboratory air 
through isolation coils attached to the low-pressure side of the equilibrator, 
keeping the total pressure of equilibration the same as the ambient 
atmospheric pressure. The atmospheric pressure is measured with a high-
precision electronic barometer with an accuracy of better than 0.05%, and is 
recorded. It takes about 20 minutes for each water sample to be thermally 
equilibrated with the constant-temperature water bath, and the headspace gas 
is re-circulated through the water sample throughout the period to iensure CO2 
equilibration. 

An electrically driven Valco 6-port valve (the sample selection valve in Fig. 
4) is connected to the equilibrator election valve and to the calibration gas 
selection valve. This allows toselection of the gas sample to be analyzed for 
CO2: the equilibrated sample gas or one of the four calibration gases. A 2-way 
normally-closed Skinner solenoid valve on the output of the calibration gas 
selection valve controls the flow of the calibration gases to the sample 
selection valve. It also providesd a necessary second means of stopping the 
flow of the calibration gases to prevent their accidental loss in case of a 
control malfunction. The concentration of CO2 in the gas equilibrated with the 
seawater sample is determined using IR gas analyzer (LICOR Model 6125) in a 
flow-through mode. A 0.5-mL aliquot of equilibrated headspace gas, 
representing less than 1% of the circulating gas, is isolated using a gas 
pipette (attached to the sampling valve in Fig. 4), and swept with CO2-free 
air (or pure nitrogen gas) flowing at a constant rate of about 50 mL/min. For 
low-pCO2 samples, a 1-mL gas pipette (attached to the sampling valve) is used. 
The sample gas is passed through a permeation drying tube for the removal of 
water vapor, and injected into the infraredIR gas analyzer cell (about 7 mL in 
volume) filled previously with CO2-free air. The displaced CO2-free air is 
discharged out of the cell into the laboratory. The small volume of the gas 
sample iensures that all of the CO2 from the gas pipette areis found in the 
analyzer cell at the same time, so that the peak height is proportional to the 
amount of CO2 present in the gas pipette. Drying of the sample gas avoids the 
effects of pressure-broadening of the CO2 absorption spectra and of dilution 
caused by water vapor. The amount of CO2 in the sampling pipette is a function 
of the loop volume, temperature, and pressure. The temperature is held 
constant and measured, and the pressure of the sample gas is same as the 
barometric pressure, which is measured with an accuracy of better than 0.05%. 
The peak height, which represents the number of moles of CO2 in the sample 
gas, is calibrated every 1.5 hours using a quadratic equation fitted to three 
calibration gas mixtures (366.52, 788.8 and 1211.4 ppm mole fraction in dry 
air).

The analytical procedure begins with water samples being drawn from the 10-L 
Niskin bottles off a rosette directly into 250-mL Pyrex reagent bottles. These 
served as both sample containers and equilibration vessels. The samples were 
immediately inoculated with 100 µL of 50% saturated mercuric chloride 
solution, sealed airtight with ground glass stoppers to prevent biological 
modification of the pCO2, and stored in the dark until analysis. Measurements 
were normally performed within 24 hours of sampling. A headspace of 3 to 5 mL 
was left above the water to allow for thermal expansion during storage. Prior 
to analysis, the sample flasks were brought to the water bath temperature of 
20°C in the constant -temperature bath. The equilibrator headspace, including 
the extension tube and the gas circulation tubings, wasere filled with a 
calibration gas of known CO2 concentration. The gas in the equilibrators, and 
in the tubing that connects them to the gas pipette loop, was re circulated 
continuously for about 20 minutes through a gas disperser immersed in the 
water. This provided a large surface area for gas exchange between the sample 
water and circulating gas, and equilibrium for CO2 was attained in 15 minutes. 
The temperature of the bath water was assumed to be that forf the sample 
water, and was measured at the time of equilibration with a precision of 
±0.01°C using a thermometer calibrated against a NIST-certified thermometer. 
This temperature is reported in the data tables as TEMP_PCO2 and showed no 
variation at a limit of ±0.01°C.

The equilibrated air samples awere saturated with water vapor at the 
temperature of equilibration and had the same pCO2 as the water. By injecting 
the air aliquot into the infraredIR analyzer after the water vapor iswas 
removed, the concentration of CO2 was measured. Therefore, the effect of water 
vapor must be taken into consideration for computing pCO2 as follows: 

     pCO2 (µatm) = [Cmeas (ppm)] X [total press. of equilibration (atm)
                         - water vapor press. (atm)]

where Cmeas is the mole fraction concentration of CO2 in dried equilibrated 
air. The total pressure of equilibrated air is measured by having the 
headspace in the equilibrator flask always at atmospheric pressure. The latter 
was measured with an electronic barometer at the time each equilibrated air 
sample iwas injected into the IR analyzer for CO2 determination. The water 
vapor pressure was computed at the equilibration temperature, and salinity of 
the seawater. Cmeas was determined by using a quadratic equation fit to three 
of the calibration gas mixtures.

The concentrations for standard gases used are traceable to the WMO reference 
scale through analysis in the laboratories of C. D. Keeling of SIO (La Jolla, 
California) and of Pieter P. Tans of NOAA/CMDL (Boulder, Colorado). The values 
of the standard gas mixtures used during this cruise were: 366.52 ppm CO2, 
788.0 ppm CO2, and 1211.4 ppm CO2.

Corrections were made to account for the change in pCO2 of the sample water 
due to the transfer of CO2 between the water and circulating air during 
equilibration. We know the pCO2 in equilibrated, perturbed water and the TCO2 
by coulometry before the equilibration. We can also calculate the change in 
TCO2 in the water based on the change in pCO2 between the post-equilibrium 
value and the known concentration in the pre-equilibrium condition. With the 
pre-equilibrium TCO2 plus the perturbation in TCO2 during equilibration, the 
post-equilibrium TCO2 value was obtained. Using the post-equilibrium TCO2 and 
measured pCO2 values, TALK at the end of the equilibration was calculated, 
knowingbased ousing the temperature, salinity, phosphate, and silicate data. 
Since the perturbation does NOT change the TALK, the pre-equilibrium pCO2 from 
the pre-equilibrium TCO2 was calculated, the calculated TALK, and the 
temperature, salinity, etc., were calculated. This is the value that was 
reported as pCO2, the pre-equilibrium calculated value. The magnitude of this 
correction is generally less than 2 µatm. Details of the computational scheme 
are presented in a DOE technical report by Takahashi, et al. (1998). 

The pCO2 values reported in this data set are expressed as micro-atmospheres 
at the temperature of equilibration. The precision of the pCO2 measurement for 
a single hydrographic station was estimated to be about ±0.15% based on the 
reproducibility of replicate equilibrations. The station-to-station 
reproducibility was estimated to be about ±0.5%.


4. DATA CHECKS AND PROCESSING PERFORMED BY CDIAC

An important part of the numeric data packaging process at the Carbon Dioxide 
Information Analysis Center (CDIAC) involves the quality assurance (QA) of 
data before distribution. Data received at CDIAC are rarely in a condition 
that would permit immediate distribution, regardless of the source. To 
guarantee data of the highest possible quality, CDIAC conducts extensive QA 
reviews that involve examining the data for completeness, reasonableness, and 
accuracy. The QA process is a critical component in the value-added concept of 
supplying accurate, usable data for researchers. 

The following information summarizes the data processing and QA checks 
performed by CDIAC on the data obtained during the R/V Knorr cruise along WOCE 
Sections AR24, A24, A20, and A22 in the North Atlantic Ocean.

 • The final carbon-related data were provided to CDIAC by the ocean carbon 
   measurement PIprincipal investigators listed in  Section 2. The final 
   hydrographic and chemical measurements and the station  information files 
   were provided by the WOCE  Hydrographic Program Office (WHPO) after 
   quality evaluation. A FORTRAN 90 retrieval code was written and used to 
   merge  and reformat all data files.

 • Every measured parameter for each station was plotted vs depth (pressure) 
   to identify questionable data points using the  Ocean Data View (ODV) 
   software (Schlitzer 2001) Station Mode (Fig. 5).

 • Section plots for every parameter were generated using ODVs Section Mode 
   in order to map a general distribution of each  property along all North 
   Atlantic Ocean sections (Fig. 6).

 • To identify noisy data and possible systematic, methodological errors, 
   property-property plots were generated (Fig. 7)  for all parameters, 
   carefully examined, and compared with plots from previous expeditions in 
   the North Atlantic.

 • All variables were checked for values exceeding physical limits, such as 
   sampling depth values that are greater than the  given bottom depths.

 • Dates, times, and coordinates were checked for bogus values (e.g., values 
   of MONTH < 1 or > 12; DAY < 1 or > 31;  YEAR < 1996 or > 1997; TIME < 0000 
   or > 2400; LATITUDE < 7.000 or > 67.000; LONGITUDE < -68.000 or > -8.000. 

 • Station locations (latitudes and longitudes) and sampling times were 
   examined for consistency with map and cruise  information supplied by 
   PIprincipal investigators.

 • The designation for missing values, given as -9.0 in the original files, 
   was changed to -999.9 for the consistency  with other oceanographic data 
   sets.


5. HOW TO OBTAIN THE DATA AND DOCUMENTATION (frrom CDIAC)

This data base (NDP-082) is available free of charge from CDIAC. The complete 
documentation and data can be obtained from the CDIAC oceanographic Web site 
(http://cdiac.ornl.gov/oceans/doc.html), through CDIAC's online ordering system 
(http://cdiac.ornl.gov/pns/how_order.html), or by contacting CDIAC (see below). 

The data are also available from CDIACs anonymous file transfer protocol (FTP) 
area via the Internet. Please note that, to access these files, your computer 
needs tomust have FTP software loaded on it (this is built in to most newer 
operating systems). Use the following commands to obtain the data base. 

                   ftp cdiac.ornl.gov or >ftp 160.91.18.18
                   Login: anonymous or ftp
                   Password: your e-mail address
                   ftp> cd pub/ndp082/
                   ftp> dir
                   ftp> mget (files)
                   ftp> quit
    
Contact information:

                   Carbon Dioxide Information Analysis Center
                   Oak Ridge National Laboratory
                   P.O. Box 2008
                   Oak Ridge, Tennessee 37831-6335
                   U.S.A.
                   
                   Telephone:  (865) 574-3645     
                   Telefax:    (865) 574-2232 
                   E-mail:     cdiac@ornl.gov 
                   Internet:   http://cdiac.ornl.gov/


6. REFERENCES


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    the Technicon AutoAnalyzer and associated equipment. Deep-Sea Research 
    14:381-9.

Atlas, E. L., S. W. Hager, L. I. Gordon, and P. K. Park. 1971. A Practical 
    Manual for Use of the Technicon AutoAnalyzer in Seawater Nutrient 
    Analyses (revised). Technical Report 215, Reference 71-22, Oregon State 
    University, Department of Oceanography, Oregon.

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

Bradshaw, A. L. and P. G. Brewer. 1988. High-precision measurements of 
    alkalinity and total carbon dioxide in seawater by potentiometric 
    titration: 1. Presence of unknown protolyte (s). Marine Chemistry 
    28:69-86.

Brewer, P. G., C. Goyet, and D. Dyrssen. 1989. Carbon dioxide transport by 
    ocean currents at 25° N latitude in the Atlantic Ocean. Science 
    246:477-79.

Bryden, H. L., and M. M. Hall. 1980. Heat transport by ocean currents across 
    25° N latitude in the North Atlantic Ocean. Science 207:884.

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

Chipman, D. W., J. Marra, and T. Takahashi. 1993. Primary production at 47° N 
    and 20° W in the North Atlantic Ocean: A comparison between the 14C 
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Culberson, C. H., G. Knapp, M. Stalcup, R. T. Williams, and F. Zemlyak. 1991. 
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Gordon, L. I., J. C. Jennings, Jr., A. A. Ross, and J. M. Krest. 1994. A 
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7.  DATA PACKAGE DESCRIPTIONS 

7.1  File Content and Format Descriptions 

This section describes the content and format of each of the data files that 
constitute NDP-082 (see Table 7).  

Table 7. Content, size, and format of data files

    _____________________________________________________________________
    
     File number, name, and description       File size in bytes
     ----------------------------------       --------------------------
     1-2.       ndp082.txt                        106,779
                ndp082.pdf                      5,101,440
     A detailed description of  the cruise network, and  oceanographic 
     data files in  simple text and PDF formats
    
     3-6.       a20sta.dat                          7,838
                a22sta.dat                          6,926
                a24sta.dat                         12,702
                ar24sta.dat                        15,438
     A listing of the station locations,  sampling dates, and sounding 
     bottom depths for each station of WOCE  Sections A20, A22, A24, 
     and AR24 in the original WOCE format
    
     7-10.      a20.dat                           476,060
                a22.dat                           403,860
                a24.dat                           657,510
                ar24.dat                          598,397
     Hydrographic, carbon dioxide, and  chemical data from all stations  
     occupied on WOCE Sections A20, A22,  A24, and AR24. The files are 
     reported  in the original WOCE format
    
     11-14.     a20_hy1.csv                       857,377
                a22_hy1.csv                       701,706
                a24_hy1.csv                     1,050,215
                ar24_hy1.csv                      932,634
     Hydrographic, carbon dioxide, and  chemical data from all stations  
     occupied on WOCE Sections A20, A22,  A24, and AR24. The files are 
     provided  as WOCE exchange format files  [comma-separated value 
     (CSV) files].
    
     15.        NA_ODV_data.txt                 2,410,877
     The Ocean Data View Sspread Ssheet  data file. The file consists 
     of data from all four sections of the North  Atlantic survey 
    
                              Total size       13,339,759
    _____________________________________________________________________


7.2   Descriptions of Variables 

The station inventory file (*sta.dat) variables are defined as follows:

EXPOCODE   Character (A10)  expedition code of the cruise
SECT       Character (A4)   WOCE section number
STNBR      Numeric   (I3)   station number
CAST       Numerixc  (I1)   cast number
DATE       Character (A10)  sampling date (month/day/year)
TIME       Character (A4)   sampling time [Greenwich mean time (GMT)]
LATITUDE   Numeric   (F7.3) latitude of the station (in decimal degrees; 
                            negative values indicate the Southern Hemisphere)
LONGITUDE  Numeric   (F8.3) longitude of the station (in decimal degrees; 
                            negative values indicate the Western Hemisphere)
DEPTH      Numeric   (I4)   sounding depth of the station (in meters)

The data file (*.dat) variables are defined as follows:

STNBR      Numeric   (I3)   station number
CASTNO     Numeric   (I1)   cast number
SAMPNO     Numeric   (I2)   sample number
BTLNBR*    Numeric   (I2)   bottle number
CTDPRS     Numeric   (F7.1) CTD pressure (dbar)
CTDTMP     Numeric   (F7.4) CTD temperature (°C)
CTDSAL*    Numeric   (F7.4) CTD salinity 
CTDOXY*    Numeric   (F7.1) CTD oxygen (µmol/kg)
THETA      Numeric   (F7.4) potential temperature (°C)
SALNTY*    Numeric   (F9.4) bottle salinity 
OXYGEN*    Numeric   (F7.1) oxygen concentration (µmol/kg)
SILCAT*    Numeric   (F7.2) silicate concentration (µmol/kg)
NITRAT*    Numeric   (F7.2) nitrate concentration (µmol/kg)
NITRIT*    Numeric   (F7.2) nitrite concentration (µmol/kg)
PHSPHT*    Numeric   (F7.2) phosphate concentration (µmol/kg)
CFC11*     Numeric   (F8.3) chlorofluorocarbon 11 (picamole/kg)
CFC12*     Numeric   (F8.3) chlorofluorocarbon 12 (picamole/kg)
TCARBN*    Numeric   (F7.1) total carbon dioxide concentration (µmol/kg)
ALKALI*    Numeric   (F7.1) total alkalinity (µmol/kg)
PCO2*      Numeric   (F7.1) partial pressure of CO2 (?atm)
PH*        Numeric   (F8.3) pH
QUALT1     Character (A15)  15-digit character variable that contains 
                            data-quality flag codes for parameters 
                            underlined with asterisks (*******) in the 
                            file header
___________________________________
*Variables that are underlined with asterisks in the data files header indicate 
 they have a data-quality flag.  Data-quality flags are defined as follows:
    1 = sample for this measurement was drawn from water bottle but analysis was 
        not received
    2 = acceptable measurement
    3 = questionable measurement
    4 = bad measurement
    5 = not reported
    6 = mean of replicate measurements
    9 = sample not drawn for this measurement from this bottle



CCHDO DATA PROCESSING NOTES

Date        Contact     Data Type       Event            Summary
----------  ----------  --------------  ---------------  ----------------------
1999-09-29  Anderson    SUM             Update Needed    being reformatted
            I have added Mike McCartney's Knorr cruise to the AR24's.  Expocode 
            is 316N147_2.  Dates are (from the sum file) Nov 2 - Dec 3, 1996.  
            Chi Sci was Mike McCartney of WHOI.  Currently we just have a 
            sumfile that is being passed off to Sarilee for reformatting.  I 
            have requested the bottle and ctd data from Ruth Curry as per 
            Lynne's request.

2000-03-15  McCartney   CTD/BTL/SUM     Submitted        Data available online.
            Take the data from the subpolar ACCE site.

2000-03-16  Curry       CTD/BTL/SUM     Data are Public  Data are public
            Yes.  We consider these to be in the public domain now.

2000-03-21  Chapman     Tracer          Not Measured     See note:
            I asked Mke Mccartney what, if any data were taken on AR24 other 
            than CTDO data.  He said that no tracer data were collected on 
            either of these repeat cruises, and that nutrients were collected 
            only on the first of them.

2001-08-21  Uribe       SUM             Website Updated  SUM file reformatted
            Sumfile was missing WOCE SECT names. It was filled in with AR24. 
            Extra space in header was removed. Sumfile now passes whpo format 
            checks.

2002-01-17  Uribe       CTD             Website Updated  Exchange file online
            CTD has been converted to exchange using the new code and put 
            online.

2002-05-01  Bartolacci  CTD/BTL/SUM     Update Needed    Need WOCE fmttng.
            BOT in multple files. CTD exchg made. Still no DOC from Curry. WOCE 
            frmt all files. Create BOT exchg. Write Curry for DOC.

2002-05-23  Bartolacci  CTD/SUM         Website Updated  Exchng files corrected
            As per email from Raymond Pollard an error in the summary file 
            longitude for the BE code of station 141 has been corrected. 
            Minutes were changed from 19 to 15. This error was also corrected 
            in CTD exchange file for station 141.

            The NetCDF file for the CTD has not been remade at this time.

            Current online index.htm page has also been updated to reflect 
            recent changes in all files.

2003-06-18  Bartolacci  BTL             Data Reformatted/OnLine
            It was brought to our attention that the bottle file for this 
            cruise was never completely reformatted.  This was because we never 
            heard from McCartney the Chief Scientist. However we did recieve 
            directions on reformatting from Ruth Curry for this bottle file.  
            McCartney was supposed to follow up.  This has not happened and 
            neither Curry nor McCartney have sent a doc file as of this date. I 
            have reformatted the bottle file according to Curry's instructions.
            **NOTE** All values for oxygen are in ML/L and all values for 
            nutrients are in UMOL/L at this time. No conversions have been 
            performed during reformatting.
            • Concatenated all 3 .sea files together. (s1t60.sea, s61t131.sea, 
              s131t190.sea) new file called ar24_allstns.sea which was copied 
              to ar24_ahy.txt.
            • Added WHF to bottle file numbers for stations 1-60 to match all 
              other stations' bottle file numbers.
            • Realigned the SILCAT data column.
            • Changed all parameter units to uppercase.
            • Changed expocode from 31KN47 to 316N147_2 to match sumfile.
            • Added name/date stamp.
            • Ran wocecvt with no errors.
            • Created exchange and netCDF files and checked files in JOA.  No 
              apparent errors were produced.
            • Created bottle file inventory file with no apparent errors.
            • placed all new files on line and regenerated web pages.

2003-06-20  Sanborn     Cruise Report   Submitted        Preliminary
            This is an internal report and should not be published.

2003-06-23  Bartolacci  BTL             Website Updated  files online
            I have concatenated and formatted the bottle file for this cruise.  
            File was format checked, units for oxygen and nutrients were 
            converted and exchange, inventory and netcdf files were created.  
            Files were checked with JOA and placed online. Web page files were 
            updated. Notes on formatting were sent to Jerry Kappa. NOTE no 
            documentation file has yet been received for this cruise.


Date        Contact     Data Type       Event            Summary
----------  ----------  --------------  ---------------  ----------------------
2003-06-24  Bartolacci  NUTs            Update Needed    Questions about converting nutrients
            Bottle file contains all nutrients in UMOL/L and O2 in ML/L.  We've 
            never heard from Mike McCartney on any questions regarding the 
            files and Ruth Curry was the one who offered help on reformatting 
            although it wasn't her cruise.

            I recall just using a piece of code from Sarilee for converting CTD 
            oxygens, but is there something for converting bottle oxygens too? 
            and what should I do about the nutrient units?  It converted to 
            exchange with the current precision and units, should I  put up 
            what we have right now?

2003-07-01  Bartolacci  CTDSAL/OXY      Website Updated  Q1 flags removed
            As per Alex Kozyr and Jim Swift, I have removed the Q1 flags 
            associated with CTD salinity and oxygen. Previously, these bytes 
            were set to 1& with no DQE information available or pending. 
            Asterisks were also removed from the appropriate headers. All files 
            were regenerated, format tested and placed online.

            As per Alex Kozyr's inquiry regarding the the Q1 flags for CTD 
            salinity and oxygen (they were both set to 1 in the bottle file), I 
            have reformatted the bottle file at Jim Swift's request.
            • Removed the Q1 bytes for CTD salinity and oxygen.  Removed 
              the asterisks under the headers corresponding to these values.
            • Reran wocecvt with no errors
            • Added name/date stamp.
            • Regenerated exchange, netCDF and inventory files with no errors produced.
            • loaded files into JOA with no errors.
            • replaced all current files, moved old files to original directory.

2003-07-11  Bartolacci  CTDOXY/ALK/CO2  Website Updated  ALK & CO2 flags corrected
            After recommendation from A. Kozyr to edit specific flags for 
            alkalinity and carbon parameters, a new file was sent by Kozyr 
            containing these corrected flags. This new bottle file was checked 
            then used to generate new exchange and netcdf files. 

            New files were tested with JOA and placed online. Old files were 
            renamed and moved to the original directory.

2003-07-11  Kozyr       CTDOXY/ALK/CO2  Update Needed    Correct ALK & CO2 flags
            The CTD oxygen of station No.1 should be changed all to -9.00, as we 
            do not have flags for it anymore, otherwise they would make no 
            sense. Could you change all ALKALI and TCARBN flags were no data was 
            measured from 1 to 9. In the following instances the flag 4 should 
            be changed to 5: sta-cast-sample
                      11-1-18   ALKALI
                      16-1-23   TCARBN
                      16-1-4    TCARBN
                      16-1-3    TCARBN
                      28-1-3    TCARBN
                      30-1-1    TCARBN
                      47-1-18   ALKALI
                      47-1-12   ALKALI
                      49-1-16   TCARBN
                      51-1-8    ALKALI
                      51-1-1    TCARBN
                      71-1-7    TCARBN
                      74-1-6    TCARBN
                      97-1-21   ALKALI - also look at the nutrients values, 
                                         they all should be -9.00
                      97-1-20   ALKALI
                      107-1-4   TCARBN
                      118-1-18  TCARBN
                      118-1-3   ALKALI
                      120-1-24  TCARBN
                      120-1-21  ALKALI
                      123-1-7   ALKALI


Date        Contact     Data Type       Event            Summary
----------  ----------  --------------  ---------------  ----------------------
2008-08-25  Berys       sum             Data Update      Fixed lat/lon errors
            In regards to a couple of errors in station locations in the sum 
            file for AR24, expocode 316N147_2, Matthew and I made the following 
            changes on Friday, 8/22/08.
                      Station:  66
                      Cast:     1
                      Time:     09:32
                      Error:    Longitude read: 63 33.92 W
                      Change:   The "63" was changed to "36"
                      Station:  139
                      Cast:     1
                      Time:     20:44
                      Error:    Lattitude read: 55 21.33 N
                      Change:   The "55" was changed to "53"

2008-09-09  Kappa       Cruise Report   Website Updated  CDIAC Data report (NDP 082)



