ORNL/CDIAC-132 NDP-077 CARBON DIOXIDE, HYDROGRAPHIC, AND CHEMICAL DATA OBTAINED DURING THE R/V KNORR CRUISES 138-3, -4, AND -5 IN THE SOUTH PACIFIC OCEAN (WOCE SECTIONS P6E, P6C, AND P6W, MAY 2 - JULY 30, 1992) Contributed by Kenneth M. Johnson*, Meredith Haines**, Robert M. Key***, Craig Neill*, Bronte Tilbrook****, Rick Wilke*, and Douglas W. R. Wallace***** *Department of Applied Science, Brookhaven National Laboratory, New York, U.S.A. **Department of Marine Science, University of South Florida, Florida, U.S.A. ***Department of Geosciences, Princeton University, Princeton, New Jersey, U.S.A. ****Division of Oceanography, Commonwealth Scientific and Industrial Research Organisation, Hobart, Tasmania, Australia *****Forschungsbereich Marine Biogeochemie, Institut fuer Meereskunde Universitaet Kiel, Kiel, Germany Prepared by Alexander Kozyr Carbon Dioxide Information Analysis Center Oak Ridge National Laboratory Oak Ridge, Tennessee, U.S.A. Date Published: August 2001 Prepared for the Environmental Sciences Division Office of Biological and Environmental Research U.S. Department of Energy Budget Activity Numbers KP 12 04 01 0 and KP 12 02 03 0 Prepared by the Carbon Dioxide Information Analysis Center OAK RIDGE NATIONAL LABORATORY Oak Ridge, Tennessee 37831-6335 managed by UT-BATTELLE, LLC for the U.S. DEPARTMENT OF ENERGY under contract DE-AC05-00OR22725 ACRONYMS ADCP acoustic Doppler current profiler BOD biological oxygen demand BNL Brookhaven National Laboratory 14C radiocarbon CALFAC calibration factor CDIAC Carbon Dioxide Information Analysis Center CFC chlorofluorocarbon CO2 carbon dioxide CTD conductivity, temperature, and depth sensor CSIRO Commonwealth Scientific and Industrial Research Organisation CRM certified reference material CUV Catholic University Valparaiso DOE U.S. Department of Energy FTP file transfer protocol GC gas chromatograph GLODAP Global Ocean Data Analysis Project GMT Greenwich mean time GSV gas sampling valve IAPSO International Association for the Physical Sciences of the Ocean JGOFS Joint Global Ocean Flux Study LDEO Lamont-Doherty Earth Observatory nm nautical mile NDP numeric data package NOAA National Oceanic and Atmospheric Administration ODF Ocean Data Facility ONR Office of Naval Research OSU Oregon State University pCO2 partial pressure of CO2 PMEL Pacific Marine Environmental Laboratory PSS Practical Salinity Scale PU Princeton University QA quality assurance QC quality control R/V research vessel RSMAS Rosenstiel School of Marine and Atmospheric Sciences SIO Scripps Institution of Oceanography SOMMA Single-Operator Multiparameter Metabolic Analyzer TALK total alkalinity TCO2 total carbon dioxide UW University of Washington VFC voltage to frequency converter WHOI Woods Hole Oceanographic Institution WHPO WOCE Hydrographic Program Office WOCE World Ocean Circulation Experiment WHP WOCE Hydrographic Program ABSTRACT Johnson, K. M., M. Haines, R. M. Key, C. Neill, B. Tilbrook, R. Wilke, D. W. R. Wallace. 2001. Carbon Dioxide, Hydrographic, and Chemical Data Obtained During the R/V Knorr Cruises 138-3, -4, and -5 in the South Pacific Ocean (WOCE Sections P6E, P6C, and P6W, May 2 - July 30, 1992), A. Kozyr (ed.). ORNL/CDIAC-132, NDP-077. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee. This data documentation discusses the procedures and methods used to measure total carbon dioxide (TCO2) and partial pressure of carbon dioxide (pCO2) at hydrographic stations during the research vessel (R/V) Knorr oceanographic cruises 138-3, -4, and -5 in the South Pacific Ocean (Section P6). The work was divided into three legs designated as P6E, P6C, and P6W which correspond to cruises 138-3, -4, and -5, respectively. Conducted as part of the World Ocean Circulation Experiment (WOCE), the P6 section began in Valparaiso, Chile, on May 2, 1992, and ended 81 days later in Sydney, Australia, on July 30, 1992. Measurements made along WOCE Section P6 included pressure, temperature, salinity [measured by a conductivity, temperature, and depth sensor (CTD)], bottle salinity, bottle oxygen, silicate, nitrate, nitrite, phosphate, radiocarbon (14C), TCO2, and pCO2. TCO2 was measured coulometrically by use of two Single-Operator Multiparameter Metabolic Analyzers (SOMMAs). The precision and accuracy of the measurements was ±1.65 µmol/kg. The pCO2 in discrete samples was measured using a headspace-equilibration technique and gas chromatography with precision of ~1 to 2%. The CO2-related measurements aboard the R/V Knorr were supported by the U.S. Department of Energy. The P6 data set is available free of charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center. The NDP consists of three oceanographic data files, three station inventory files, two FORTRAN 90 data retrieval routine files, a readme file, and this printed documentation that describes the contents and format of all files as well as the procedures and instructions for accessing the data. Keywords: carbon dioxide; TCO2; pCO2; coulometry; gas chromatography; World Ocean Circulation Experiment; Pacific Ocean; hydrographic measurements; carbon cycle. PART 1: OVERVIEW 1. BACKGROUND INFORMATION The World Ocean Circulation Experiment (WOCE) Hydrographic Program (WHP) was a major component of the World Climate Research Program, whose overall goal was to obtain a better understanding of the ocean's role in climate and climatic changes resulting from both natural and anthropogenic causes. The need for this experiment arose from the serious concern over the rising atmospheric concentrations of carbon dioxide (CO2) and their effect on the heat balance of the global atmosphere. The increasing concentrations of these gases may intensify the earth's natural greenhouse effect and alter the global climate in ways that are not well understood. Carbon in the oceans is unevenly distributed because of poorly characterized and complex circulation patterns and biogeochemical cycles. Although total carbon dioxide (TCO2) was not an official WOCE measurement, a coordinated effort, supported in the United States by the Department of Energy (DOE) and National Oceanic and Atmospheric Administration (NOAA), was made on WOCE cruises through 1998 to measure the global spatial and temporal distributions of TCO2 and other related parameters. Goals were to estimate the meridional transport of inorganic carbon in a manner analogous to the estimates of oceanic heat transport (Bryden and Hall 1980; Brewer et al. 1989; Holfort et al. 1998; Roemmich and Wunsch 1985) and to build a database 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 WHP cruises during this period, and the final data set is expected to cover on the order of 23,000 stations. Wallace (2001) has recently reviewed the goals, conduct, and initial findings of the Joint Global Ocean Flux Study (JGOFS)/WOCE Global CO2 Survey. This report discusses carbonate system parameters TCO2 and the partial pressure of CO2 (pCO2) measured aboard the research vessel (R/V) Knorr on the three legs comprising WOCE Zonal Section P6. The section began in Valparaiso, Chile, on May 2, and ended in Sydney, Australia, on July 20, 1992, with stops at Easter Island, Chile, and Auckland, New Zealand. The P6 Section was divided into three legs (P6E, P6C, and P6W) and scientists from Brookhaven National Laboratory (BNL) were responsible for the carbonate system measurements on all of these legs. The Chief Scientists, scientific crew, and CO2 measurement groups from BNL were exchanged after each leg. Based on the measurements from these sections and the data from other Pacific sections occupied during the WOCE Survey (Lamb et al. 2001), the large-scale three-dimensional distribution of temperature, salinity, and chemical constituents including the carbonate system parameters will be mapped. Knowledge of these parameters and their initial conditions will allow determination of heat and water transports as well as carbon transport. An understanding of these transports will contribute to the understanding of processes that are relevant for climate change. The work aboard the R/V Knorr was supported by the U.S. DOE under contract DE- ACO2-76CH00016. The authors are grateful to the Sonderforschungsbereich 460 at the University of Kiel, which was lead by Dr. F. Schott, and funded by the Deutsche Forschungsgemeinschaft, for their support and assistance in completing the written documentation. The authors would also like to acknowledge the invaluable assistance of the members of the CO2 measurement group with whom they have lost contact in the years intervening since the P6 section was done. Without the help of Victoria (Nee) Coles, David Hunter, and Kevin Wills this work could not have been completed. 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 in 1971 for operation under a charter agreement with the Office of Naval Research (ONR). 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 feet, respectively. Beginning on February 6, 1989, it underwent a major mid-life retrofit or "jumbo-izing" at the McDermott Shipyard in Amelia, Louisiana. A midsection was added to the ship to stretch its length by 34 feet to 279 feet, and fore and aft azimuthing propulsion systems were added to make it one of the most maneuverable and stable ships in the oceanographic fleet while on station. By the time it was returned to the Woods Hole Oceanographic Institution in late 1991, the retrofit had consumed 32 months. The P6 Section was the first scientific cruise after the retrofitting. The R/V Knorr was designed for a wide range of oceanographic operations, possesses anti-roll tanks and an ice strengthened bow, and 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, while Table 2 provides individual cruise information, parameter measured, institution, and responsible personnel. 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 -> × Mak6M 322 = 4 × 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 gallons 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 ˝ inch 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 ft2 Portable van space Machine shop Fume hoods Uninterruptable power supply Air conditioning Library/lounge, 3680 ft2 of laboratory space for multidisciplinary research Table 2. R/V Knorr Cruise Information, Parameter Measured, Institution, and Responsible Personnel Cruise number 138-3 (Leg P6E) 138-4 (Leg P6C) 138-5 (Leg P6W) Ports of call Valparaiso, Chile Easter Islands, Chile Auckland, New Zealand Easter Islands, Chile Auckland, New Zealand Sydney, Australia Dates May 2-May 26 May 30-July 7 July 13-July 31 Chief Scientist Dr. H. Bryden, WHOI Dr. M. McCartney, WHOI Dr. J. M. Toole, WHOI Parameter Responsible personnel ADCP* M. Kosro, OSU M. Kosro, OSU M. Kosro, OSU S. Pierce, OSU S. Pierce, OSU Chilean Observer S. Marchant, CUV Chlorofluorocarbons R. Weiss, SIO R. Weiss, SIO R. Weiss, SIO (CFCs) K. Sullivan, RSMAS F. Van Woy, SIO F. Van Woy, SIO CTD**, salinity H. Bryden, WHOI M. McCartney, WHOI J. Toole, WHOI M. Schwartz, WHOI M. Schwartz, WHOI Nutrients L. Gordon, OSU L. Gordon, OSU L. Gordon, OSU A. Ross, OSU J. Jennings, OSU J. Jennings, OSU H. Garcia, OSU Oxygen G. Knapp, WHOI M.Stalcup, WHOI G. Knapp, WHOI PCO2 C. Neill, BNL M. Haines, BNL V. Coles, BNL K. Johnson, BNL R. Wilke, BNL K. Johnson, BNL Radiocarbon (14C) R. Key, PU R. Key, PU R. Key, PU R. Rotter, PU G. McDonald, PU G. McDonald, PU TCO2 K. Johnson, BNL R. Wilke, BNL K. Johnson, BNL K. Wills, BNL D. Hunter, BNL D. Hunter, BNL Tritium, Helium B. Jenkins, WHOI B. Jenkins, WHOI B. Jenkins, WHOI M. Mathewson, WHOI S. Birdwhistell, WHOI M. Mathewson, WHOI Underway pCO2 R. Weiss, SIO R. Weiss, SIO R. Weiss, SIO Participating institutions: Brookhaven National Laboratory, Upton, NY (BNL); Commowealth Scientific and Industrial Research Organisation, Australia (CSIRO); Catholic University, Valparaiso, Chile (CUV); Oregon State University, Corvallis, OR (OSU); Princeton University, Princeton, NJ (PU); Rosensteil School of Marine and Atmospheric Science, University of Miami, Miami, FL (RSMAS); Scripps Institution of Oceanography, University of California, San Diego, CA (SIO); University of Washington, Seattle, WA (UW); and Woods Hole Oceanographic Institution, Woods Hole, MA (WHOI). ___________________________________________ *Acoustic Doppler current profiler. **Conductivity, temperature, and depth sensor. 2.2 Brief Cruise Summary The P6 Section really began in mid-April 1992 in Jacksonville, Florida, when BNL personnel (K. M. Johnson, R. Ramirez, and R. Wilke) placed two Single-Operator Multiparameter Metabolic Analyzers (SOMMA, S/Ns 004 and 006) and a gas chromatograph (GC) system for measuring discrete pCO2 aboard the R/V Knorr. The ship was berthed in Jacksonville for the final adjustments following its first shake-down cruise after refitting. The BNL CO2 group trucked its scientific gear to Jacksonville to save the cost and trouble of shipping it to Chile. Preliminary operational tests of the measurement systems were made, customs declarations filled out, and the instruments were secured for transit to Valparaiso before the BNL group departed ship. The equipment placed on board the ship in Jacksonville was used for the entire P6 Section so that subsequent staging was minimal. The BNL CO2 group, consisting of K. M. Johnson, C. Neill, and K. Wills, departed New York on April 28, 1992, and arrived in Santiago, Chile, on the 29th. Upon arrival to the pier, the R/V Knorr was docking, and the group boarded the ship almost immediately and began the testing of the SOMMA and pCO2 GC systems placed aboard in Jacksonville. A number of problems developed during the testing phase. The SOMMAs were plagued with contamination and noise from unknown sources. Trouble-shooting was interrupted temporarily while a CO2 group moved aboard the ship on May 1, 1992, and the P6E Leg began with the departure of the ship from Valparaiso at 0900 on May 2 under the command of Captain Carl Swanson with Harry Bryden as Chief Scientist. Trouble-shooting and repair continued, and two serious problems with the SOMMA systems were determined. The first finding was that very brief electrical surges were spontaneously causing the 8-port gas sample valve used in the gas calibration procedure to attempt to switch from the "load" to the "inject" position. The surges were not powerful enough to cause the valve to actually switch or cause the operator to hear the valve trying to switch, but they were strong enough to enable "cross talk" between the valve ports. Cross-talk momentarily connects the calibration gas, in this case pure CO2, to the carrier gas line, and the unwanted sporadic introduction of CO2 into the analytical stream interfered with sample titrations. This was only discovered after three very frustrating days by resting the palm of the hand on the gas sample valve chassis. In this way the silent and spontaneous surges could be felt through the metal valve cover. This problem was corrected by placing an uninterruptable power supply (UPS) in-line and by unplugging the gas sample valve from the mains when it was not needed. This left a second problem a much smaller, steadier, but still unsatisfactory source of noise manifesting itself as an unacceptably high blank. This noise resulted because the carrier gas cylinders of N2 were stored in a hangar external to the laboratory containing the SOMMA systems. Futhermore, thermoplastic lines (in some cases as long as 50 feet) were used to connect the cylinders to the SOMMA systems. These lines apparently allowed enough air (containing CO2) to diffuse through the tubing walls, thus interfering with the sample titrations. This problem was corrected by relocating the cylinders within the laboratory to within 6 to 10 feet of the SOMMAs. This relocation along with the installation of the normal CO2 scrubbers in the carrier gas lines reduced the blank to satisfactory levels. The pCO2 system also got off to a rocky start resulting from some initial software problems that required some code to be rewritten. The first WOCE CTD station on P6E was station No. 4 with a depth of only 100 m at 32° 30' S and 71° 30' W. Stations 1 through 3 were not included in Section P6E so that there were 69 WOCE CTD stations on this leg. A CO2 group collected samples at 34 of the 69 stations (~ 50%). Some 1,043 individual water samples along with 98 duplicates and 92 samples for a certified reference material (CRM) were analyzed for TCO2. The pCO2 was determined on 323 of these samples. Because of initial set-up problems, the pCO2 sampling could not begin until Station 23. As the analytical work proceeded during P6E, the members of the CO2 group became aware of an additional problem with one of the SOMMA systems (S/N 004). In this case, the recovery of the CO2 calibration gas during the gas calibration procedure was approximately 0.2% lower than expected based on prior experience with these systems (99.4 vs 99.6%). This lower recovery was associated with an analytical difference between the measured and CRM TCO2 of +3 to -4 µmol/kg (measured amount minus certified amount). This suggested that the gas-calibration was in error, however, the problem was identified and corrected. The relief measurement group was asked to bring a spare gas sample valve with them to Easter Island for installation at the conclusion of the P6E Leg. The ship's operations following the retrofit were not without incident. In addition to the power surges mentioned, at least 2 complete power black-outs were experienced, the ship vibrated strongly, and there was noticeable buckling of specific deck plates. The vibration was of particular concern because of the possibility of damage to the computer hard disks. With the exception of the power outages, these problems did not cause any instrumental downtime. A lack of fuel availability on Easter Island required conservation measures such as lower ship speeds for the P6 Legs. The P6E Leg ended with the anchoring of the R/V Knorr at 0800 on May 26, 1992, off the village of Hanga Roa on Easter Island. The first measurement group went ashore after lunch and obtained accommodations. The second measurement group consisting of R. Wilke, D. Hunter, and M. Anderson came aboard as the first group left. They carried with them some badly needed replacement parts including a gas sample valve, a refrigerated bath, silver electrodes, and fittings. Change-over between the groups took place on May 28 and 29, and the equipment was ready when the ship pulled anchor and departed on Leg P6C on May 30, 1992, with Mike McCartney as the Chief Scientist. The second leg, P6C, which crossed the Southwest Pacific Basins and occupied stations from the East Pacific Rise ridge crest to the Kermadec Islands, began with Station 73 which was a reoccupation of the last station of the P6E Leg (72). Both Stations 73 and 74 are co- located with Station 72. The leg continued along 32° 30' S from 112° 40' W until 178° 55' E, the location of Station 184. Thereafter P6C angled northward and ended with Station 188 at 31° 05' S and 177° 32' E. During this leg, additional duplicate stations were made such that Station 141 was co-located with 142 and 187 with 188. The CTD results from station 112 are unreliable because of the failure of the CTD. Of the 113 CTD stations occupied during P6C, 109 are unique WOCE stations. The CO2 group collected samples at 51 of the 109 stations or 47%. 1739 samples along with 157 duplicates and 162 CRM were analyzed for TCO2. Discrete measurements of pCO2 were made on 314 of these samples. With respect to the TCO2 systems, the gas sample valve for system 004 was replaced before the start of section P6C. However, the recovery of the CO2 calibration gas did not improve, and it remained constant and slightly low (99.4%) as on the first Leg P6E. No additional repairs were attempted. Otherwise sampling and analysis for the carbonate system parameters remained routine. Unfortunately, of the three legs comprising the P6 Section the P6C measurement group experienced the worst weather, and it was the longest of the three legs. The pCO2 system experienced numerous problems indicated by a loss of precision as this leg went on. Modifications were made in coordination with the shore-based BNL measurement group members, but precision continued to decline such that the last station run on P6C was Station 125 on June 19, 1992. In addition to poor precision, other problems reported included component temperature changes as a result of lack of sufficient insulation and traffic through the area where GC was located, exhaustion of the H2 generator's silica gel scrubber, unprogrammed gas sample valve switching in the GC (further evidence of electrical problems), dirty valve rotors, very rough weather that made trouble-shooting very difficult, and finally a thorough cleaning of the GC hardware on June 26 that resulted in the loss of all response upon restart. Daily efforts were made to bring the system back and response was gradually restored. It was not until the Knorr docked in Auckland and replacement parts brought by the relief crew were installed that the system was restored to function for the last Leg (P6W). Hence, pCO2 was not determined between Stations 126 and 190. The P6C station work concluded on July 4, and the R/V Knorr arrived at Auckland on July 7. The relief crew from BNL, consisting of K. M. Johnson and V. Coles, were joined in Auckland by Bronte Tilbrook from the CSIRO Division of Oceanography located in Tasmania, Australia. Change-over and coordination between the relieved and relief groups occurred between July 7 and July 9. Complaints from several sources about the electric power on board ship on both Legs P6E and P6C lead to the acquisition and installation of a harmonic filter for the ship's "clean power" supply. Repairs were also made to one of the CTD winches. The ship departed from Auckland to take on fuel for the third and final Leg (P6W) at 0900 on July 13, 1992, with John Toole as Chief Scientist and Carl Swanson as Master. At 1600, following fueling, the R/V Knorr headed north and picked up where P6C left off with Station 189 which is co-located with Stations 188, 187, and 190. It continued northward to 30° 05' S and 176° 30' E. From 176° 30' E the cruise continued along 30° 05' S to the Australian coast finishing with Station 246 at 153° 29' E. This station was followed by several additional CTD calibration stations (247 267) which are not considered or included in the WOCE data sets. During P6W, additional duplicate casts were made such that Station 233 is co-located with 234, Station 246 with 247, and Stations 237 through 246 are co-located with Stations 248 through 257 and 258 through 267, so that of the 78 CTD stations occupied during P6W, only 55 represent unique WOCE stations. The CO2 group collected samples at 22 of these 55 stations (40%), and 502 water samples along with 47 duplicates and 41 CRM were analyzed for TCO2. Discrete measurements of pCO2 were made on 171 of these samples beginning with station 191. On this leg only one SOMMA (S/N 006) was used. The station work concluded on July 29, and the R/V Knorr arrived in Sydney on July 30, 1992 after uniformly good working conditions. As on previous cruises, not all stations could be sampled for TCO2 and pCO2 parameters because of the lack of the time required for analysis. With 46% of the P6 stations sampled and profiled for TCO2, the goal of 50% coverage was essentially achieved. The coverage for pCO2 was considerably less (25%). The standard WOCE parameters (temperature, oxygen, nutrients, and salinity) were analyzed on all samples, and the carbonate system samples were normally drawn in conjunction with the tracer samples which included He, 14C, and the CFCs. Sampling frequency was at least every 30 nautical miles, but shorter intervals as a function of bathymetry shallow waters or changing depths required more stations were common, especially on P6W. A minimum vertical depth resolution was maintained at 200 m throughout the P6 section. Table 3 presents a summary of the carbonate system measurements made on the WOCE section P6. Table 3. The number of stations sampled for carbonate system parameters (CSP) and the number of CSP determinations on WOCE Section P6 ____________________________________________________________________________________ | Leg | Stations | Number of CSP Determinations | |_______|___________________________|_______________________________________________| | | CTD | CSP | % | Discrete | Duplicate | CRM | Total | |_______|_________|________|________|______________|_____________|________|_________| TCO2 Measurements P6E 68 34 50 1043 98 92 1233 P6C 109 51 47 1739 157 162 2058 P6W 55 22 40 502 47 41 590 Totals 232* 107 46 3284 302 295 3881 pCO2 Measurements P6E 68 21 31 323 27 0 350 P6C 109 22 20 314 73 0 387 P6W 55 16 29 171 35 0 206 Totals 232* 59 25 808 135 0 943 ____________________________________________________________________________________ *Excludes duplicate and test CTD stations. On the P6C Leg one station (112) was thrown out because of a CTD malfunction so severe that the data could not be recovered. 3. DESCRIPTION OF VARIABLES AND METHODS 3.1 Hydrographic Measurements Position and depth were manually logged every 10 minutes on the P6 Section. A thermosalinograph (Falmouth Scientific Instruments) was mounted on the bow ~ 3 m below the surface and operated on all legs except the latter stages of Leg P6C. An underway fluorometer was operated on Legs P6E and P6C, until it also failed toward the end of Leg P6C and was not used again. Water samples were collected using a 36-position underwater frame and 10-L sample bottles designed and constructed by the Ocean Data Facility (ODF) at SIO. Modified Neil Brown MkIII CTD instruments mounted on the 36-bottle frame were used for data acquisition. The CTD (Nos. 7, 9, and 10) were supplied by the WHOI Group with No. 10 being used for the bulk of the work. CTDs 7 and 9 were used only very sparingly on Leg P6C when CTD 10 required electronic repairs. On the other legs their use was largely restricted to test stations. Small shifts between the pre- and post-cruise pressure and temperature CTD calibrations were found, but the P6 CTD data have been corrected according to procedures given by Millard et al. (1992), and the CTD salinity data have been empirically corrected to conform to the bottle salinity. The prescribed WOCE sample order was as follows: CFCs, helium, oxygen, CO2, nutrients, tritium, and salinity. Surface currents were measured continually during the cruise with a hull-mounted ADCP, and current profiles were also made during the CTD casts with an ADCP mounted on the rosette frame. Some problems were experienced with the CTD/rosette systems. The CTD oxygen sensor functioned poorly on Leg P6E particularly in the top several 100 m probably because of cavitation of a specially installed pump used to circulate water past the sensor. This pump was not used on Legs P6C or P6W. Problems with the data acquisition software were noted and corrected on Leg P6E. CTD No. 10 failed on Leg P6C at Station 75, and CTD No 9. was used through Stations 76-85 while CTD 10 was repaired. Careful post-cruise verifications using the complete bottle data sets have been carried out, and the sample pressures and salinity assigned for each sample are to our knowledge correct. Bottle salinity was measured on every water sample using 2 Guildline Autosal Model 8400A salinometers. The instruments (No. 10 and 11) were furnished by WHOI. The measurements were made in a climate-controlled portable laboratory secured to the deck of the ship. The temperature of the laboratory was kept at 22 ± 1°C. Salinity samples were the last water samples drawn from the rosette. The bottles and caps were rinsed twice and filled to ˝ inch of the neck to leave an air space for expansion. The samples were thermally equilibrated in the laboratory before measurement (5-6 h). The salinometers were standardized with International Association for the Physical Sciences of the Ocean (IAPSO) Standard Sea Water (Batch P116), and a description of the salinity measurement is given by Knapp et al. (1990). Salinometer 11 was used until June 18 when it began to give intermittently higher results during the standardization. From this point on salinometer 10 was used. The precision of the salinity determination was the mean difference between duplicate salinity samples. For samples taken at less than and greater than 3000 m the precision was 0.0012 (n = 107) and 0.0011 (n = 23), respectively. Bottle oxygen was measured on 50-mL aliquots of all P6 water samples by a modified Winkler titration technique (Knapp et al. 1990) using a computer-controlled titrator with amperometric end-point detection in a constant-temperature laboratory. Oxygen bottles were rinsed twice with sample water and carefully filled to overflowing to avoid air bubbles. Next the reagents were added (1 mL each of the MnCl2 and NaI-NaOH ), and the bottles shaken. Following thermal equilibration they were titrated with 0.01 sodium thiosulphate. The precision of the oxygen determination calculated from the mean difference and the standard deviation of the mean difference for 121 pairs of duplicate oxygen samples was ± 0.70 to ± 0.87 µmol/kg (n = 98) for depths <3000 m and ± 0.52 to ± 0.39 µmol/kg (n = 23) for depths >3000 m. Phosphate, nitrate, nitrite, and silicate were determined on every bottle drawn from Stations 3 through 257. The nutrient concentrations were determined on samples collected in high-density polyethylene 30-mL tubes that were directly transferred to an autoanalyzer (AlpKem, Model 300 Rapid Flow Analyzer) according to procedures given by anonymous (1985) and Gordon et al. (1992; 1994). Samples were transferred to a climate-controlled laboratory and were analyzed within a few hours of collection. Standards and reagents were provided by the OSU group, and working standards (i.e., solutions having nitrate, nitrite, phosphate, and silica concentrations similar to those of the Pacific deep and bottom waters) were prepared from stock solutions every 4 to 7 days. Standard and stock solutions were kept refrigerated. Precision was measured by the difference between duplicate samples taken from the same rosette bottle analyzed one after the other (not separated in time) or at the start and end of the run (separated in time). Together the differences between replicate analyses is the short-term precision, which includes short-term instrumental drift as well as random error. The mean standard deviations or short-term precision for the replicate analyses made on the three P6 Legs are: silicic acid ±0.16 to ±0.035 µmol/L; nitrite/nitrate ±0.05 to ±0.01 µmol/L phosphate ±0.011 to ±0.006 µmol/L. Long-term precision was estimated by comparing "old" working standard solutions made on the previous station with freshly made working standards (i.e., "new" standard solutions made for the current station). The long-term precision for the three P6 Legs are: silicic acid ±0.21 to ±0.028 µmol/L (n = 284); nitrate ± 0.087 to ±0.019 µmol/L (n = 284); phosphate ±0.015 to ±0.0006 µmol/L (n = 241); and nitrate ± 0.015 to ± 0.007 µmol/L (n = 284). Problems with the nutrient analyses included nonlinearity for the nitrate/nitrite on Leg P6E through Station 112 on Leg P6C at which time a plumbing error was discovered and corrected. Post-cruise corrections have been applied to the nitrate/nitrite data through Station 112. In addition, the phosphate analysis was lost from Stations 171 through 188 on Leg P6C when noise rendered the phosphate channel unusable. This was corrected in Auckland prior to Leg P6W when the air injection phasing board was replaced. 3.2 Total Carbon Dioxide Measurements TCO2 was determined using two automated dynamic headspace sample processors (SOMMAs) 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 system and sequence may be found in earlier publications (Johnson et al. 1993), and further details concerning the coulometric titration can be found in Huffman (1977) and Johnson et al. (1985). Samples were collected in 300-mL precombusted (450°C for 24 h) glass standard Biological Oxygen Demand (BOD) bottles, poisoned with 200-uL of a 50% saturated solution of HgCl2, and analyzed for TCO2 within 24 hours of collection (DOE Hand Book of Methods, 1994). Before analysis, they were stored in a refrigerator in darkness at ~15°C until analyzed. Analyses of duplicate samples separated in time by up to 8 hours showed no evidence of any significant biological consumption or production of CO2 during storage under the above conditions. CRMs were routinely analyzed according to DOE prescribed methods (1994). The CRMs were supplied by Dr. Andrew Dickson of the SIO, and during Section P6 batches 10 and 11 were used. The certified values for batch 10 were S = 34.5722 and Certified TCO2 = 1960.67 ± 0.39 µmol/kg (n = 5). The corresponding numbers for batch 11 were S = 38.5 and TCO2 = 2188.77 ± 0.56 µmol/kg (n = 5). The CRM TCO2 concentration was determined by Vacuum-Extraction/Manometry in the laboratory of C. D. Keeling at SIO. Seawater introduced from an automated "to-deliver" pipette into a stripping chamber was acidified, and the resultant CO2 from continuous gas extraction was dried and coulometrically titrated on a model 5011 UIC Coulometer with a maximum titration current of 50 mA in the counts mode [the number of pulses or counts generated by the Coulometer's voltage to frequency converter (VFC) during the titration was displayed]. In the coulometer cell, the acid (hydroxyethylcarbamic acid) formed from the reaction of CO2 and ethanolamine was 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 Faraday's constant to the number of moles of OH- generated and thus to the moles of CO2 that reacted with ethanolamine to form the acid. The age of each titration cell was 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 was measured in minutes from birth (chronological age) and in mgC titrated since birth (carbon age). Each system was controlled with an IBM-compatible personal computer equipped with two RS232 serial ports (coulometer and barometer), a 24-line digital Input/Output (I/O) card (solid state relays and valves), and an Analog to Digital (A/D) card (temperature, conductivity, and pressure sensors). The A/D cards were manufactured by Real Time Devices (State College, Pa.). The temperature sensors (model LM34CH, National Semiconductor, Santa Clara, Calif.), with a voltage output of 10 mV/°F built into the SOMMA were calibrated against thermistors certified to 0.01°C (PN CSP60BT103M, Thermometrics, Edison, N.J.) using a certified mercury thermometer as a secondary standard. These sensors monitored the temperature of SOMMA components including the pipette, the gas sample loops, and the coulometer cell. The SOMMA software was written in GWBASIC Version 3.20 (Microsoft Corp., Redmond, Wash.), and the instruments were driven from an options menu appearing on the PC monitor. Since 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 "to-deliver" volumes (Vcal) of the sample pipettes were determined (calibrated) gravimetrically prior to the cruise and were checked periodically during the cruise by collecting aliquots of deionized water dispensed from the pipette into preweighed serum bottles. The serum bottles were crimp sealed and weighed immediately during the on-shore laboratory calibrations, or were returned to shore and reweighed on a model R300S (Sartorius, Göttingen, Germany) balance as soon as possible. The apparent weight (g) of water collected (Wair) was corrected to the mass in vacuo (Mvac) from Mvac = Wair + Wair (0.0012 / d - 0.0012 / 8.0) , where 0.0012 is the sea level density of air at 1 atm, d is the density of the calibration fluid at the pipette temperature and sample salinity, and 8.0 is the density of the stainless steel weights. The "to-deliver" volume was Vcal = Mvac / d . The calibration volumes (Vcal) at the calibration temperature (tcal) of the SOMMA System pipettes for the the three P6 Sections are given in Table 4. Table 4. The "to-deliver" pipette volume (Vcal) and calibration temperature (tcal) for the SOMMA-Coulometer systems used on WOCE Section P6 ___________________________________________________________ Leg | System* | Vcal | St. Dev. | n | tcal| | | (mL) | (mL) | | (°C)| ___________________________________________________________ P6E 004 25.5192 0.0069 6 14.93 P6C 004 25.5195 0.0059 8 15.62 P6E 006 29.6813 0.0000 2 15.83 P6C 006 29.6768 0.0045 17 14.86 P6W 006 29.6668 0.0030 8 14.87 ____________________________________________________________ *Note that system 004 was not used during the third Leg P6W. 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 × 10^-5/°C) and t is the temperature of the pipette at the time of a measurement. Table 4 shows a small decrease in Vcal for system 006 over time. This is consistent with other systems used daily for periods exceeding 30 days (Johnson et al. 1998a). The mean pipette temperature (t) during the P6 cruise was 15.12 ± 0.41°C (n = 3580). The Coulometers used to detect CO2 were periodically electronically calibrated as described in Johnson et al, (1993, 1996) and DOE (1994) throughout the P6 Section. For the calibration, at least two levels of current (usually 50 and 2 mA) were passed through an independent and very precisely known resistance (R) for a fixed time. The voltage (V) across the resistance was continuously measured, and the instantaneous current (I) across the resistance was calculated from Ohm's law and integrated over the calibration time. Then the number of pulses (counts) accumulated by the VFC during this time was compared with the theoretical number computed from the factory calibration of the VFC [frequency = 105 pulses (counts) generated per second at 200 mA] and the measured current. If the VFC was perfectly calibrated at the factory, the electronic calibration procedure would yield a straight line passing through the origin with an intercept (Int_ec) of 0 and a slope (Slope_ec) of 1. The factory- calibration of the VFC and the value of the Faraday (96489 Coulomb/mol) yields a scaling factor of 4.82445 × 103 counts/µmol, and the theoretical number of micromoles of carbon titrated (M) after extraction from water samples or the gas loops was M = [Counts / 4824.45 - (Blank × Tt) - (Int_ec × Ti)] / Slope_ec , where Tt was the length of the titration in minutes, Blank is the system blank in µmol/min, Intec the intercept in µmol/min, and Ti the time in minutes during the titration where current flow was continuous. 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 3 to 4 min) because the electronic calibration can only be carried out for periods of continuous current flow. The results of the electronic calibrations are given in Table 5. Table 5. Electronic calibration coefficients for SOMMA-Coulometer systems 004 and 006 on WOCE Section P6 _______________________________________________________________________ |Leg | System | Slope_ec | Int_ec | Period | | | | | µmol/min | | _______________________________________________________________________ P6E 004 1.000587 0.000049 May 2-May 7 P6E 004 1.000524 0.000394 May 8-May 18 P6E 004 0.999905 0.000372 May 19-May 22 P6E,C 004 0.999708 0.000745 May 23-June 5 P6C 004 0.999693 0.001237 June 6-June 17 P6C 004 0.999733 0.001298 June 18-July 6 P6E 006 0.999567 0.000164 May 2-May 9 P6E 006 0.999673 0.000017 May 10-May 22 P6E 006 0.999589 0.000170 May 23-May 30 P6C 006 0.999708 0.000823 May 31-June 5 P6C 006 0.999716 0.001146 June 6-June 12 P6C 006 0.999554 0.001439 June 13-June 28 P6C 006 0.999638 0.001564 June 29-July 14 P6W 006 0.999659 0.000339 July 15-July 30 __________________________________________________________________________ The SOMMA-Coulometry systems were also 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 et al. 1993) connected to the calibration gas through an isolation valve with the vent side of the GSV plumbed to a barometer. When a gas loop was filled with CO2, the mass (moles) of CO2 contained therein was calculated by dividing the loop volume (V) by the molar volume of CO2 at the ambient temperature (T) and pressure (P). The molar volume of CO2 [V(CO2)] was calculated iteratively from T, P, and the first viral coefficient B(T) for pure CO2: V(CO2) = RT / P × (1 + B(T) / V(CO2) . The gas calibration factor (CALFAC) the ratio of the calculated mass to that determined coulometrically was used to correct the subsequent titrations for small departures from 100% recoveries (DOE 1994). Pressure was measured with a barometer, model 216B-101 Digiquartz Transducer (Paroscientific, Inc., Redmond, Wash.) that is factory-calibrated for pressures between 11.5 and 16.0 psia. 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 3 to 6 mgC with the result of the third calibration taken as the CALFAC if consistent with the second (i.e., agreement to ± 0.1% or better)]. The CALFAC data for the P6 section are summarized in Table 6. Table 6. The mean gas calibration factors (CALFAC) obtained during the WOCE Section P6 _____________________________________________________________ |Leg | Cells | CALFAC | Carbon Age | | | (n) | Mean ± S.D. | Mean ± S. D. (MgC)| _____________________________________________________________ System 004 (CRM-based calibration) P6E 21 1.004037 ± 0.000777 10.1 ± 9.3 P6C 21 1.003932 ± 0.000538 10.9 ± 8.3 System 006 (pure-CO2 calibration) P6E 24 1.004632 ± 0.000555 5.4 ± 1.6 P6C 30 1.004535 ± 0.000988 8.5 ± 3.2 P6W 18 1.004129 ± 0.000755 6.7 ± 1.8 ______________________________________________________________ For water samples, the TCO2 concentration in µmol/kg was calculated from TCO2 = M × CALFAC × (1 / (Vt × p)) × dHg , where p is the density of seawater 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 P6 dHg = 1.00066). As noted above, the daily CALFAC determined for System 004 on the P6E Leg was too high (indicating lower recovery of CO2), and when substituted into the last equation it led to over-estimates of the CRM TCO2 concentration by 3 to 4 µmol/kg (> or = 0.1%). Unfortunately, the cause of this problem was not discovered until a later cruise aboard the R/V Meteor (WOCE Section A10) in early 1993 when a leaky plumbing fitting was found and replaced on System 004 as described by Johnson et al. (1998b). For convenience, the line carrying the calibration gas (CO2) to the GSV had been plumbed (prior to the P6 Section) with a tee connection on the upstream side of the GSV with one branch connected to the GSV through an isolation valve (IV) and the other branch to a Quick-Connect Fitting (Swagelok, Crawford Fitting). This plumbing configuration facilitated the rapid connection of the calibration gas to an external flow-meter and flow rate adjustments, however, the quick-connect fitting apparently allowed a very small of amount of air to infiltrate into the calibration gas line slightly diluting the calibration gas. The Quick-Connect and tee fittings were replaced early on the A10 Section and System 004 was successfully gas-calibrated thereafter. For the P6E and P6C Legs, a "CRM-based calibration factor" was also calculated for System 004 by taking the resulting counts for the first CRM analyzed on each cell and substituting it along with the certified TCO2 into the last equation and solving it for CALFAC. At the end of each leg, a leg-specific mean CRM-based CALFAC was calculated for System 004, and these data along with the mean CALFAC determined for System 006 are also given in Table 6. The TCO2 measurements from sample analyses made on SOMMA 004 were calculated using the mean CRM-based CALFAC shown in Table 7, while TCO2 on SOMMA 006 was calculated using the CALFAC determined daily using pure-CO2 gas for each new cell born according to DOE (1994). Taken together, Tables 4 ("to-deliver" pipette volume), 5 (electronic calibration), and 6 (gas or CRM calibration) show that the response of Systems 004 and 006 remained constant throughout the three legs of the P6 Section. In addition, water samples were collected periodically in duplicate and one of the duplicates was analyzed on each system (see Table 4). The SOMMA 006 was equipped with a conductance cell (Model SBE-4, Sea-Bird Electronics, Inc., Bellevue, Wash.) for the determination of a salinity measurement as described by Johnson et al. (1993). Whenever possible SOMMA and CTD salinity were compared to ensure that the salinity of the analyzed samples matched the CTD salinity. The agreement between CTD and SOMMA salinity was 0.04 or better, and several mistrips of the Niskin bottles were quickly identified using this comparison. Quality Control-Quality Assurance (QC-QA) was assessed from the results of 293 CRM analyses made on Systems 004 and 006. The mean differences between the measured and certified TCO2 (measured amount minus certified amount) were calculated for each leg, and the mean differences are summarized in Table 7. The individual differences for the Section P6 are plotted in Fig. 5 (see online document). Table 7. The mean analytical difference ( TCO2 = measured - certified) and the standard deviation of the differences between measured and certified TCO2 on WOCE Section P6 _______________________________________________________________ |Leg | System | CRM | delta TCO2 | St. Dev. | n | | | | (Batch) | (µmol/kg) | (µmol/kg) | | _______________________________________________________________ P6E 004 10, 11 -0.37 1.37 48 P6C 004 10, 11 +0.04 1.72 86 Total/Mean -0.11 1.61 134 P6E 006 10, 11 +0.52 1.35 43 P6C 006 10, 11 -0.43 1.43 75 P6W 006 10, 11 -0.54 1.06 41 Total/Mean -0.20 1.39 159 Overall/Total/Mean -0.16 1.49 293 ________________________________________________________________ The accuracy of the CRM analyses was much better than 1 µmol/kg on both systems throughout the P6 Section, and the overall mean difference is -0.16 µmol/kg (n = 293). The precision of the CRM determination on the P6 Section is the standard deviation of the difference between determined and certified TCO2 (±1.49 µmol/kg). The imprecision of the CRM analyses was slightly higher on the P6C Section for both systems, whereas the best precision was obtained on the final Leg P6W on System 006. There were two CRM analyses during Section P6 that were considered to be outliers, and these results have not been included in Table 7 or Fig. 5. An outlier was defined as an analytical difference between the measured and Certified TCO2 which exceeds ±5.0 µmol/kg. The two outliers were measured on System 006: CRM No. 171 on June 6 at a carbon age of 38.8 mgC; and CRM No. 170 on June 21 at an age of 8.6 mgC. Additional CRMs were analyzed on both cells to within 1 µmol/kg of the certified TCO2 even at very advanced carbon ages (55.5 and 46.1 mgC, respectively). Hence, the cause of the outlier values was likely not the behavior of the coulometric titration or cell, but may have been related to a temporary problem with the sample delivery system (pipette). Alternatively, the CRM may have been compromised during preparation or storage. Sample duplication with these cells was observed to be excellent, and accordingly the data obtained with them has been included in the data set described herein. The second phase of the QC-QA procedure was the assessment of sample precision on each system (single-system precision) and the assignment of an overall precision to the P6 TCO2 samples. This was the second cruise where two independent SOMMA systems were deployed side-by-side, and the conventions employed for the estimation of precision given for WOCE Sections A1E and A10 data (Johnson et al. 1996; 1998b) have been retained in Table 8. Table 8. Summary of sample precision for TCO2 analyses made during WOCE Section P6. ___________________________________________________________________________________________ | | Mean Absolute Difference | The Pooled Standard Deviation| | |__________________________________________________|______________________________| | System | sigma(bs) | S. D. | K | sigma(bn)| S. D.| K | Sp2 | K | n | d.f. | | |___________|_________| |__________|_______|____| | | | | | | µmol/kg | | µmol/kg |µmol/kg| | | | |________|_____________________|____|_______________________|_______|______|______|________| Single-System Precision 004 0.94 0.84 73 0.83 1.19 8 0.89 86 186 100 006 0.73 0.66 194 0.53 0.53 28 0.71 198 398 202 All 0.78 0.72 267 0.61 0.71 36 0.76 284 586 302 Sample Precision P6 1.90 1.58 24 1.65 37 74 37 ___________________________________________________________________________________________ The single-system precision was determined from samples with duplicates analyzed on the same system (either 004 or 006). The sample precision was calculated using duplicates that were analyzed on both systems (004 and 006). Single-system and sample precision have been separately assessed in Table 8 as: - "between-sample" precision [sigma(bs)] which is the mean absolute difference between duplicates (n = 2) drawn from the same Niskin bottle;  - "between-Niskin" precision [sigma(bn)] which was the mean absolute difference between duplicates (n = 2) drawn from two different Niskin bottles closed at the same depth;  - the pooled standard deviation (Sp2) 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 provides 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 between 3 and 12 hours. Any temporal drift in system response would therefore be reflected in the single-system precision by decreased precision of the duplicate analyses. Sample precision, on the other hand, provides an estimate of overall sample precision for the section(s) independent of which analytical system was used. It was estimated because TCO2 data were measured using two separate systems during the cruise. Sample precision is the most conservative estimate of precision, incorporating several sources of random or systematic (bias) error including errors associated with the inability to gas calibrate System 004. It should be noted that the sample precision calculation includes the results for some samples (K = 13) that were analyzed in triplicate (i.e., two replicates analyzed on one system and the third on the second system). For these cases, the mean of the two replicate analyses was used for calculating Sp2. Averaging the replicate results reduced the degrees of freedom term by making n = 1 for each system no matter how many replicates were actually run on each system. Without averaging (d.f. = 50), Sp2 was ±1.50 µmol/kg, whereas with averaging (Table 8, d.f. = 37) Sp2 increased to ±1.65 µmol/kg. For the P6 Section, the more conservative estimate of ±1.65 µmol/kg was chosen as the precision of the TCO2 determination. This was in excellent agreement with the precision of the CRM determination (±1.49 µmol/kg). As with other sections completed by the BNL measurement group using SOMMA- Coulometer systems run in parallel, the sample precision was slightly less precise than the single-system precision (1.65 µmol/kg vs < 1.0, respectively). This indicates that any error introduced from changes in system response (drift) during the coulometer cell lifetime were within the overall precision of the method. The excellent agreement between "between-sample" and "between-Niskin" precision suggests that there were no significant analytical effects caused by the gas exchange with the overlying headspace of the Niskin bottles during the on-deck sampling. This is consistent with the data collected during other cruises (Johnson et al. 1996; 1998b). The P6 sample precision (±1.65 µmol/kg) was also in good agreement with the sample precision for the BNL WOCE Sections A1E (±1.65 µmol/kg), A10 (±1.92 µmol/kg), A8 (±1.17 µmol/kg), and the North Atlantic sections (±1.59 µmol/kg). The difference between sample and single-system precision may be the result, in part, of the inability to perform daily gas-calibrations on System 004 during P6. Use of a single average CALFAC for an entire leg may, for example, have masked real cell-to-cell variations in CALFAC. This would have the effect of increasing imprecision but not necessarily altering overall accuracy (the positive and negative differences would cancel) as is suggested by Table 9. Table 9 provides additional proof of the overall accuracy and the absence of a bias between the two systems. Each system yields, within statistical precision, the same result for the same samples even though one system (006) was gas-calibrated daily and the other (004) was not (see also Tables 6, 7, and 8). Table 6 shows that the two calibration procedures gave stable and nearly identical results during the entire P6 Section. However, analyzing independent water sample duplicates on each system is the definitive test for accuracy, precision, and the calibration procedures used. The accuracy of System 004 was validated in this way. This is similar to the situation previously described for the A10 Section (Johnson et al. 1998b) where only one of the two systems used possessed a gas-calibration unit and the gas-calibrated system served as the reference system. Table 9. The mean TCO2 and the mean analytical difference (TCO2 = 006 004) for TCO2 from CRM and water samples analyzed on both systems (004 and 006) during WOCE Section P6 ____________________________________________________________________________ | Comparison | Mean | | |______________________________________________________________| | | System 004 TCO2 | System 006 TCO2 | delta TCO2 (006 - 004) | | | µmol/kg (n) | µmol/kg (n) | µmol/kg (n) | |_____________|__________________|__________________|________________________| CRM (Batch 10) 1960.63 (59) 1960.24 (73) -0.39 CRM (Batch 11) 2188.76 (75) 2188.84 (85) +0.08 Water samples 2171.58 (37) 2170.97 (37) -0.61 ____________________________________________________________________________ The final step in the QC-QA procedure was the ship-to-shore comparison. Here sample duplicates (commonly called the "Keeling Samples") were analyzed "in real time" at sea by continuous gas extraction/coulometry and later, after shipment and storage, on-shore by vacuum extraction/manometry at the laboratory of C. D. Keeling at SIO (Guenther et al. 1994). The "Keeling Samples" were collected in specially provided threaded 500-mL glass bottles with 4 mL of headspace volume, poisoned with 100 µL of a saturated HgCl2 solution, and then sealed air-tight with a greased ground glass stopper that was secured to the bottle with a threaded plastic screw cap. The latter was bored out to fit over the top of the stopper and mated to the bottle threads so that an air-tight seal was made by gently tightening the cap until a secure seal between the stopper and bottle was achieved. This procedure was carried out with 21 samples collected at 15 stations during P6. The results of the comparison are given in Table 10. The mean ship-to-shore analytical difference was -2.64 µmol/kg (n = 21). The lower ship- based results for P6 are consistent with the ship-to-shore comparisons from Sections A9, A1E, and A10 previously reported (Johnson et al. 1995; 1996; 1998b). This negative bias for water samples was greater than the sample precision and the analytical difference observed for the CRM analyses (Wallace 2001). The reason for the tendency of the ship-based results to be lower than the shore-based results is not known at this time. In aggregate, Tables 7-10 show an internally consistent data set with excellent accuracy, high single-system precision (<±1.0 µmol/kg), and a slightly higher imprecision for the sample precision (±1.65 µmol/kg). Based on Tables 7-10 and following the precedent of previous data submissions no correction for instrumental bias or CRM analytical differences has been applied to the sample data. Fig. 6 (see omline document) summarizes the analytical results as a contour section plot of the TCO2 data from the WOCE Section P6 along 32.5° S. Table 10. Comparison of the shipboard analyses of TCO2 by coulometry and the shore- based reference analyses by manometry on duplicate samples. (The manometric analyses were completed by February of 1995 in the laboratory of C.D. Keeling at SIO) _________________________________________________________________________________ |Station | Date | Niskin | Depth | TCO2 (P6) | TCO2 (SIO) | delta TCO2 (P6-SIO)| | | | | (m) | µmol/kg | µmol/kg | µmol/k | |_________|_______|________|_______|___________|_____________|____________________| 32 5/12 5 3006.9 2300.19 2302.70 -2.51 42* 5/15 8 3002.2 2294.39 2301.94 -7.55 46 5/16 36 18.6 2022.48 2023.65 -1.17 58 5/20 36 5.4 2016.23 2018.44 -2.21 58 5/20 5 3002.1 2294.45 2294.34 +0.11 68 5/23 36 12.2 2014.30 2014.72 -0.42 68 5/23 1 2771.9 2298.66 2302.19 -3.53 85 6/04 36 20.3 2010.10(2)** 2014.15 -4.05 98* 6/08 36 19.2 2015.00(2) 2017.40 -2.40 98* 6/08 7 2998.1 2298.90 2301.49 -2.59 123 6/18 35 61.3 2025.20 2027.79 -2.59 123 6/18 12 3117.9 2305.70 2310.94 -5.24 144 6/24 35 61.3 2033.70 2036.34 -2.64 144* 6/24 12 3007.5 2313.10 2316.60 -3.50 170 7/01 15 3041.2 2288.80 2290.42 -1.62 184 7/04 23 44.5 2045.50(2) 2049.16 -3.66 188 7/05 31 3029.0 2309.80 2311.48 -1.68 231 7/22 24 20.2 2005.20(2) 2009.57 -4.37 231 7/22 2 3135.3 2269.00 2272.61 -3.61 233 7/23 10 3001.6 2266.90 2268.49 -1.59 237 7/24 10 3004.6 2269.30 2267.89 +1.41 ___________________________________________________________________________________ Mean -2.64 S. D. 1.92 n 21 ___________________________________________________________________________________ *Analyzed on System 004. **Indicates TCO2 is the mean of 2 analyses (the SIO TCO2 values are always the mean of 2 analyses). 3.3 Discrete pCO2 Measurements Samples for discrete pCO2 analyses were collected by overfilling 60-mL precalibrated serum bottles in the same manner as for oxygen and TCO2. During Section P6 and following the static-headspace procedure of Johnson et al. (1990) for CH4, a plastic pipette tip was inserted into the bottles making a water-tight seal at the bottle mouth. Then the bottles were inverted so that the volume of water displaced into the pipette was decanted. Next, the pipette was quickly withdrawn and the bottles were crimp-sealed leaving a headspace (gas phase) volume in each bottle of (nominally) 5 mL and a liquid phase of (nominally) 55 mL, constituting a closed or static system. The pipette method yields a highly reproducible headspace volume, and the headspace and water volume for each (numbered) serum bottle was determined gravimetrically prior to the cruise. The bottles were prepared and sealed outside on deck at the CTD site usually within 1 minute of collection. The atmospheric pressure was measured just prior to sealing so that the pre-equilibrated serum-bottle gas phase contained air at a known mixing ratio of CO2 (determined regularly throughout the cruise) at a known total pressure (P). The initial liquid phase temperature was taken to be the potential temperature (T) of the sample. The bottles were laid in a thermostatted shaking water bath and equilibrated, by shaking, for 3 h at 20°C. After equilibration, the serum-bottle gas phase was displaced by a brine solution to flush and fill a gas sample loop whose contents were analyzed by gas chromatography. The mole fraction of CO2 in the gas phase (xCO2eq) was determined after the catalytic conversion of CO2 to CH4 with a flame ionization detector through comparison with a calibration curve based on CO2 in air standards. These standards were subsequently intercalibrated with standards maintained by Taro Takahashi and Dave Chipman at the Lamont- Doherty Earth Observatory (LDEO). Erroneously, in the original work (Johnson et al. 1990), no provision was made to measure the total gas phase pressure in the serum bottle after equilibration (Peq). Because Peq was not measured during WOCE Section P6, it had to be estimated. This was done by first calculating the moles of N2, O2, and Ar in the liquid phase prior to equilibration using potential temperature, the measured O2 concentrations, and by assuming that each water sample was saturated at the surface with N2 and Ar with moist air at 1 atm at the potential temperature of the sample. Next, the total number of moles of each gas in the introduced gas phase was calculated. Hence the total number of moles of each gas present in the closed system (serum- bottle) was known. After equilibration, a small correction for glass expansion and the phase ratio volume change caused by the change in temperature during equilibration (usually warming) was applied. The partial pressure of each gas at the equilibration temperature (20°C) was then calculated from the total number of moles for each gas, and these gas partial pressures along with the equilibrium partial pressure of water vapor were summed to give Peq in the headspace after equilibration. Then xCO2eq and Peq were multiplied to convert xCO2eq to pCO2 hereafter called pCO2eq. Subsequent laboratory tests (C. Neill and D. Wallace, unpublished data) confirmed that the serum bottles were not subject to leakage and that the predicted pressure closely matched the actual headspace pressure. The close correspondence between measured and predicted headspace pressure has also been confirmed during extensive field tests (see Neill et al. 1997). TCO2 was measured on an unequilibrated duplicate sample, and the TCO2 of the liquid phase after equilibration (repartioning of CO2 between the gas and liquid phases) was calculated using a mass balance approach (hereafter designated TCO2eq). The carbonate alkalinity (CA) of the equilibrated sample was calculated using pCO2eq and TCO2eq with the thermodynamic constants of Roy et al. (1993) and software developed by Lewis and Wallace (1998). Because carbonate alkalinity is conserved during the equilibration, the derived CA (µmol/kg) is the in situ value prior to equilibration. Hence both the in situ TCO2 (measured independently by coulometry) and CA are known for each sample prior to the equilibration, and these two parameters were used to calculate the sample in situ pCO2 at the equilibration temperature using the Lewis and Wallace (1998) software and the Roy et al. (1993) constants. The pCO2 in µatm is reported at the equilibration temperature and the equilibration temperature is also reported. Subsequently, the nutrient data became available and Total Alkalinity (TALK) was also calculated for each sample according to DOE procedures (1994) using the software given by Lewis and Wallace (1998). TALK values are not reported in this NDP. The precision of the pCO2 determination and the TALK calculated from pCO2 and TCO2 was assessed, when possible, according to the same procedures used for TCO2. The precision of the pCO2 determination and the derived TALK is given in Table 11 as follows: - "between-sample" precision [sigma(bs)] for pCO2, which is the mean absolute difference between duplicates (n = 2) of K samples drawn from the same Niskin bottle; - the pooled standard deviation (Sp2) for pCO2, calculated according to Youden (1951) where K was the number of samples with duplicates analyzed (n> or=2), n was the total number of replicates analyzed from K samples, and n-K was the degrees of freedom (d.f.); - the geometric mean (GM) of the relative standard deviation (Rel. S. D.) for pCO2 from K samples with duplicates (n>or=2) analyzed where the Rel. St. Dev. (%) was: (S. D. / mean) × 100;  - the pooled standard deviation (Sp2) for TALK calculated according to Youden (1951) from K pCO2 samples with duplicates analyzed (n>or=2), with n being the total number of TALK calculated from K samples with n-K degrees of freedom; and  - the Rel. S. D. (%) for TALK calculated as (Sp2 / mean TALK) × 100. Table 11. Summary of sample precision for pCO2 and the derived TALK for WOCE Section P6 ______________________________________________________________________________________ |Leg | sigma(bs) (K) | Sp2 | K | n | d.f. | GM (K) | TALK (Sp2) | Rel. S. D.| | | (±µatm) |(±µatm) | | | | (%) | (±µmol/kg) | (%) | |_____|_________________|________|____|_____|_______|________|____________|___________| P6E 13.4 (19) 12.8 21 48 27 0.70 (21) 2.36 0.10 P6C 23.5 (45) 19.8 55 127 72 0.97 (55) 3.82 0.16 P6W 16.0 (32) 15.2 32 66 34 0.88 (33) 3.08 0.13 All 19.0 (96) 17.4 109 243 134 0.88 (109) 3.39 0.14 ______________________________________________________________________________________ In all, duplicates for 109 of the 808 pCO2 samples were taken during WOCE Section P6. Based on these samples, the sample precision (Sp2) for pCO2 was ±17.4 µatm. Because of the large dynamic range of the pCO2 measurements (>1000 µatm), the geometric mean of the Rel. S. D. was considered to be the best measure of overall sample precision on a percentage basis (±0.88%). For the derived variable TALK, the sample precision (Sp2) was ±3.39 µmol/kg and the Rel. St. Dev. [(Sp2 / mean) × 100] was 0.14%. The corresponding result for TCO2 is approximately 0.08%. The best precision was found for P6E and the worst for P6C, which is consistent with the difficulties for the pCO2 system reported during the P6C cruise. However, the precision for the TALK derived from the pCO2 and the greater imprecision of the TALK determination in comparison with the precision of the TCO2 determination, particularly for P6W (factor of 2), were consistent with results from other WOCE cruises (Millero et al. 1998). 3.3.1 Crossover Analysis for pCO2 Measurements Made During WOCE Section P6 Because the pCO2 method was still under development and because of the instrument difficulties experienced during the WOCE Section P6, additional QC-QA assessment was required. Final results of the P6 pCO2 analyses were checked by comparing the deep water results with those obtained on other WOCE cruises that intersected the P6 line. With this test it was assumed that deep and bottom water results have not changed at a given location over the relatively short time interval of a few years separating the different cruises. The stations selected for each crossover are those which are close to the crossover point and on which carbon measurements were made. The number of stations selected was somewhat subjective but was such that sufficient measurements were present for the analysis without getting too far away from the crossover location. In all cases the stations were within approximately 1° of latitude and longitude of the crossover point. Table 12 lists the stations used for each crossover. Once the stations were chosen the results were plotted against potential density referenced to 3000 dbar (sigma3). Only data from pressures greater than 2500 dbar were included in order to minimize the influence of possible lateral gradients. A smooth curve was fitted to the combined station data from each leg so long as there were seven or more data points that could be used for the fit. The fitting curve chosen was a "robust loess" function designed to minimize the influence of outliers (Feely et al. 1999). In cases having fewer than 7 points, linear segments were used to "connect the dots." Only data which had been marked with a quality control flag of 2 (good) or 6 (replicate) were included in the analyses. Reported pCO2 results were converted to fCO2 using the Weiss function (Weiss 1974) and the measured temperature prior to the comparison. fCO2 values are not reported in this NDP. In order to quantitatively estimate the mean difference between legs, each of the two fitted curves was evaluated at 50 evenly spaced intervals covering the range of space common to the selected stations from both legs. The 50 differences were then averaged. Table 12 summarizes the mean differences and standard deviations for each crossover, and indicates the differences in terms of the cruise leg designations. Table 12. WOCE Section P6 fCO2 crossover results __________________________________________________________________________ |Crossover Cruise 1 Stations Cruise 2 Stations Differences| | no.* | |_________________________________________________________________________| 66a P16S/P17S 179 P6W 108 6.7 ± 8.6 66c P16A/P17A 119 P6W 108 7.6 ± 11.3 76 P18 73 P6E 56, 58 -12.9 ± 6.4 81 P19C 299 P6E 32, 34, 36 3.6 ± 7.3 ___________________________________________________________________________ *Crossover number taken from the Global Ocean Data Analysis Project (GLODAP) list for the entire Pacific Ocean (Lamb et al. 2001). Samples from one of the intersecting cruises, P18, were analyzed by Rik Wanninkhof of the Atlantic Oceanographic and Meteorological Laboratory while the other three were analyzed by scientists from Taro Takahashi's group of LDEO. Previous crossover tests have indicated that the P18 fCO2 results may be somewhat low as a result of minor sample loss, and the checks preformed at CDIAC tend to support that finding. Differences between the P6 results and those measured by the LDEO group are well within the precision (Table 12) of the technique. Based on these checks, the prototype pCO2 method appears to have performed adequately, and no additional corrections to the pCO2 data have been made. Nevertheless, the P6 Section work showed that the pCO2 method could be improved. Before the next deployment in 1994, the pCO2 method incorporated automated and highly accurate measurements of P, Peq, and analytical temperatures throughout, rigorous control of the phase volume ratio and the headspace gas composition prior to equilibration, and new software (Neill et al. 1997). Figure 7 (see online document) summarizes the analytical results as a contour section plot of the pCO2 data from the WOCE Section P6. 3.4 Radiocarbon Measurements During the R/V Knorr expedition along WOCE Section P6, 649 accelerator mass spectrometry (AMS) delta 14C samples were collected at 30 stations. In addition 17 replicate measurements of 14C were performed. Sampling of 14C during the cruise was carried out by the scientists from the Ocean Tracer Laboratory at Princeton University, with R. Key as the principal investigator for these data. For a detailed description of the methods and instrumentation used for 14C measurements please read the reprint of pertinent literature: "P6 Final Report for AMS 14C Samples" in Appendix A of omline documentation or hard copy. 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 Section P6 in the South Pacific Ocean. 1. The final carbon-related data were provided to CDIAC by D. W. R. Wallace and K. M. Johnson of Brookhaven National Laboratory. 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. 2. To check for obvious outliers, all data were plotted by use of a PLOTNEST.C program written by Stewart C. Sutherland (Lamont-Doherty Earth Observatory). The program plots a series of nested profiles, using the station number as an offset; the first station is defined at the beginning, and subsequent stations are offset by a fixed interval (Figs. 8-13 in online doc.). Several outliers were identified and marked with the quality flags of "3" (questionable measurement) or "4" (bad measurement) (see File Descriptions in Part 2 of this documentation). 3. To identify "noisy" data and possible systematic, methodological errors, property-property plots for all parameters were generated (Fig. 14 in online documentation), carefully examined, and compared with plots from previous expeditions in the Pacific Ocean. 4. All variables were checked for values exceeding physical limits, such as sampling depth values that are greater than the given bottom depths. 5. Dates, times, and coordinates were checked for bogus values (e.g., values of MONTH < 1 or > 12; DAY < 1 or > 31; YEAR < or > 1992; TIME < 0000 or > 2400; LATITUDE < 25.000 or > 32.000; LONGITUDE < 150.000 or > 80.000. 6. Station locations (latitudes and longitudes) and sampling times were examined for consistency with maps and cruise information supplied by D. W. R. Wallace and K. M. Johnson of BNL. 7. 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 This database (NDP-077) is available free of charge from CDIAC. The complete documentation and data can be obtained from the CDIAC oceanographic Web site (http://cdiac.esd.ornl.gov/oceans/doc.html), through CDIAC's online ordering system (http://cdiac.esd.ornl.gov/pns/how_order.html), or by contacting CDIAC. The data are also available from CDIAC's anonymous file transfer protocol (FTP) area via the Internet. Please note that your computer needs to have FTP software loaded on it (this is built in to most newer operating systems). Use the following commands to obtain the database. ftp cdiac.esd.ornl.gov or >ftp 160.91.18.18 Login: "anonymous" or "ftp" Password: your e-mail address ftp> cd pub/ndp077/ 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.esd.ornl.gov/ 6. REFERENCES Anonymous. 1985. RFA-300 Rapid Flow Analyzer Operation Manual. Alpkem Corporation, Clackamas, Oregon, U.S.A. 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. DOE (U.S. Deapartment of Energy). 1994. Handbook of Methods for the Analysis of the Various Parameters of the Carbon Dioxide System in Sea Water. Version 2.0. ORNL/CDIAC-74. A. G. Dickson and C. Goyet (eds.). Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tenn., U.S.A. Feely, R. A., M. F. Lamb, D. J. Greeley, and R. Wanninkhof. 1999. Comparison of the carbon system parameters at the global CO2 survey crossover locations in the North and South Pacific Ocean, 1990 1996. ORNL/CDIAC-115. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, U.S.A. Gordon, L. I., J. C. Jennings, Jr., A. A. Ross, and J. M. Krest. 1992. A suggested protocol for continuous flow automated analysis of seawater nutrients (phosphate, nitrate, nitrite and silicic acid) in the WOCE Hydrographic Program and the Joint Global Ocean Fluxes Study. Grp. Tech. Rpt. 92-1. Chemical Oceanography Group, Oregon State University, College of Oceanography, Oregon, U.S.A. Gordon, L. I., J. C. Jennings, Jr., A. A. Ross, and J. M. Krest. 1994. A suggested protocol for continuous flow automated analysis of seawater nutrients (phosphate, nitrate, nitrite and silicic acid) in the WOCE Hydrographic Program and the Joint Global Ocean Fluxes Study. In WOCE Operations Manual. WHP Office Report WHPO 91-1. WOCE Report No. 68/91. Revision 1. Woods Hole, Mass., U.S.A. Guenther, P. R., C. D. Keeling, and G. Emanuele. 1994. Oceanic CO2 measurements for the WOCE hydrographic survey in the Pacific Ocean, 1990-1991: Shore based analyses. SIO Reference Series, No. 94-28. Scrips Institution of Oceanography, University of California San Diego, La Jolla, California, U.S.A. Holfort, J., K. M. Johnson, B. Schneider, G. Siedler, and D. W. R. Wallace. 1998. Meridional transport of dissolved inorganic carbon in the South Atlantic Ocean. Global Biogeochemical Cycles. 12:479-99. Huffman, E. W. D., Jr. 1977. Performance of a new automatic carbon dioxide coulometer. Microchemical Journal 22:567-73. Johnson, K. M., A. E. King, and J. McN. Sieburth. 1985. Coulometric TCO2 analyses for marine studies: An introduction. Marine Chemistry 16:61-82. Johnson, K. M., P. J. Williams, and L. Brandstroem, and J. McN. Sieburth. 1987. Coulometric TCO2 analysis for marine studies: Automation and calibration. Marine Chemistry 21:117-33. Johnson, K. M., J. E. Hughes, P. L. Donaghay, and J. McN. Sieburth. 1990. Bottle-calibration static head space method for the determination of methane dissolved in seawater. Analitical Chemistry 62:2408-12. Johnson, K. M., and D. W. R. Wallace. 1992. The single-operator multiparameter metabolic analyzer for total carbon dioxide with coulometric detection. DOE Research Summary No. 19. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Tenn., U.S.A. Johnson, K. M., K. D. Wills, D. B. Butler, W. K. Johnson, and C. S. Wong. 1993. Coulometric total carbon dioxide analysis for marine studies: Maximizing the performance of an automated gas extraction system and coulometric detector. Marine Chemistry 44:167-87. Johnson, K. M., D. W. R. Wallace, R. J. Wilke, and C. Goyet. 1995. Carbon dioxide, hydrographic, and chemical data obtained during the R/V Meteor Cruise 15/3 in the South Atlantic Ocean (WOCE Section A9, February March 1991). ORNL/CDIAC-82, NDP-051. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tenn., U.S.A. Johnson, K. M., B. Schneider, L. Mintrop, and D. W. R. Wallace. 1996. Carbon dioxide, hydrographic, and chemical data obtained during the R/V Meteor Cruise 18/1 in the North Atlantic Ocean (WOCE Section A1E, September 1991). NDP-056. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tenn., U.S.A. Johnson, K. M., A. G. Dickson, G. Eischeid, C. Goyet, P. R. Guenther, R. M. Key, F. J. Millero, D. Purkerson, C. L. Sabine, R. G. Schotle, D. W. R. Wallace, R. J. Wilke, and C. D. Winn. 1998a. Coulometric total carbon dioxide analysis for marine studies: Assessment of the quality of total inorganic carbon measurements made during the U.S. Indian Ocean CO2 Survey 1994 1996. Marine Chemistry 63:21-37. Johnson, K. M., B. Schneider, L. Mintrop, and D. W. R. Wallace. 1998b. Carbon dioxide, hydrographic, and chemical data obtained during the R/V Meteor Cruise 22/5 in the South Atlantic Ocean (WOCE Section A10, December 1992 January 1993). NDP-066. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tenn., U.S.A. Knapp, G. P., M. C. Stalcup, and R. J. Stanley. 1990. Automated oxygen and salinity determination. WHOI Technical Report No. WHOI-90-35. Woods Hole Oceanographic Institution, Woods Hole, Mass., U.S.A. Lamb, M. F., C. L. Sabine, R. A. Feely, R. Wanninkhof, R. M. Key, G. C. Johnson, F. J. Millero, K. Lee, T.-H. Peng, A. Kozyr, J. L. Bullister, D. Greeley, R. H. Byrne, D. W. Chipman, A. G. Dickson, C. Goyet, P. R. Guenther, M. Ishii, K. M. Johnson, C. D. Keeling, T. Ono, K. Shitashima, B. Tilbrook, T. Takahashi, D. W. R. Wallace, Y. Watanabe, C. D. Winn, and C. S. Wong. 2001. Consistency and synthesis of Pacific Ocean CO2 survey data, Deep-Sea Research (in press). Lewis, E. and D. W. R. Wallace. 1998. Program developed for CO2 system calculations. ORNL/CDIAC-105. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A. Millard, R., G. Boud, and J. Toole. 1992. Implementation of a titanium strain gauge pressure transducer for CTD applications. Deep-Sea Research 15:1009-21. Millero, F. J., and A. Poisson. 1981. International one-atmosphere equation of state for sea water. Deep-Sea Research 28:625-29. Millero, F. J., A. G. Dickson, G. Eischeid, C. Goyet, P. R. Guenther, K. M. Johnson, K. Lee, E. Lewis, D. Purkerson, C. L. Sabine, R. Key, R. G. Schottle, D. R. W. Wallace, and C. D. Winn. 1998. Total alkalinity measurements in the Indian Ocean during the WOCE hydrographic program CO2 survey cruises 1994 1996. Marine Chemistry 63:9-20. Neill, C., K. M. Johnson, E. Lewis, and D. W. R. Wallace. 1997. Accurate headspace analysis of fCO2 in discrete water samples using batch equilibration. Limnology & Oceanography 42:1774-83. Roemmich, D., and C. Wunsch. 1985. Two transatlantic sections: Meridional circulation and heat flux in the subtropical North Atlantic Ocean. Deep Sea Research 32:619-64. Roy, R. N., L. N. Roy, K. M. Vogel, C. Porter-Moore, T. Pearson, C. E. Good, F. J. Millero, and D. M. Campbell. 1993. The dissociation constants of carbonic acid in seawater at salinities 5 to 45 and temperatures 0 to 45°C. Marine Chemistry 44:249-67. Schlitzer, R. 2001. Ocean Data View. http://www.awi-bremerhaven.de/GEO/ODV. Online publication. Alfred-Wegener-Institute for Polar and Marine Research. Bremerhaven, Germany. Wallace, D. W. R. 2001. Storage and transport of excess CO2 in the oceans: The JGOFS/WOCE Global CO2 Survey. In J. Church, G. Siedler, and J. Gould (eds.)., Ocean Circulation and Climate, Academic Press, (in press). Weiss, R. F. 1974. Carbon dioxide in water and seawater: The solubility of a non-ideal gas. Marine Chemistry 2:203-15. Wilke, R. J., D. W. R. Wallace, and K. M. Johnson. 1993. A water-based, gravimetric method for the determination of gas sample loop volume. Analitical Chemistry 65:2403-06. Youden, W. J. 1951. Statistical Methods for Chemists. Wiley, New York. PART 2: CONTENT AND FORMAT OF DATA FILES 7. FILE DESCRIPTIONS This section describes the content and format of each of the nine files that comprise this NDP (see Table 13). Because CDIAC distributes the data set in several ways (via the Web, CDIAC's online ordering system, or anonymous FTP), each of the nine files is referenced by both an ASCII file name, which is given in lowercase, bold-faced type (e.g., ndp077.txt), and a file number. The remainder of this section describes (or lists, where appropriate) the contents of each file. Table 13. Content, size, and format of data files File number, name, Logical File size and description records in bytes 1. ndp077.txt: 1,881 118,354 a detailed description of the cruise network, the two FORTRAN 90 data-retrieval routines, and the six oceanographic data files 2. stainv.for: 45 1,337 a FORTRAN 90 data-retrieval routine to read and print p6esta.dat (File 4), p6csta.dat (File 5), and p6wsta.dat (File 6) 3. p6ecwdat.for: 54 2,242 a FORTRAN 90 data-retrieval routine to read and print p6e.dat (File 7), p6c.dat (File 8), and p6w.dat (File 9) 4-6. p6esta.dat, p6csta.dat, p6wsta.dat: 82 6,146 a listing of the station locations, sampling dates, 124 9,338 and sounding bottom depths for each station of the 90 6,754 WOCE Sections P6E, P6C, and P6W 7-9. p6e.dat, p6c.dat, p6w.dat: 2,353 412,952 hydrographic, carbon dioxide, and chemical data 3,982 699,656 from all stations occupied on WOCE Sections P6E, 1,564 274,088 P6C, and P6W ______ _________ Total 10,175 1,530,867 7.1 ndp077.txt (File 1) This file contains a detailed description of the data set, the two FORTRAN 90 data- retrieval routines, and the six oceanographic data files. It exists primarily for the benefit of individuals who acquire this database as machine-readable data files from CDIAC. 7.2 stainv.for (File 2) This file contains a FORTRAN 90 data-retrieval routine to read and print p6*sta.dat (Files 4-6). The following is a listing of this program. For additional information regarding variable definitions, variable lengths, variable types, units, and codes, please see the description for p6*sta.dat in Sect. 7.4. c******************************************************************** c* FORTRAN 90 data retrieval routine to read and print the files c* named "p6*sta.dat" (File 4-6). c******************************************************************** c*Defines variables* INTEGER stat, cast, depth REAL latdcm, londcm CHARACTER expo*9, sect*4, date*10, time*4 OPEN (unit=1, file='p6*sta.dat') OPEN (unit=2, file='p6*.sta') write (2, 5) c*Writes out column labels* 5 format (1X,'EXPOCODE',3X,'SECT',1X,'STNBR',2X,'CAST',9X, 3 'DATE',2X,'TIME',2X,'LATITUDE',2X,'LONGITUDE',2X, 4 'DEPTH',/) c*Sets up a loop to read and format all the data in the file* read (1, 6) 6 format (///////////) 7 CONTINUE read (1, 10, end=999) expo, sect, stat, cast, date, time, 1 latdcm, londcm, depth 10 format (A9, 3X, A4, 3X, I3, 5X, I1, 3X, A10, 2X, A4, 3X, 1 F7.3, 3X, F8.3, 3X, I4) write (2, 20) expo, sect, stat, cast, date, time, 1 latdcm, londcm, depth 20 format (A9, 3X, A4, 3X, I3, 5X, I1, 3X, A10, 2X, A4, 3X, 1 F7.3, 3X, F8.3, 3X, I4) GOTO 7 999 close(unit=5) close(unit=2) stop end 7.3 p6ecwdat.for (File 3) his file contains a FORTRAN 90 data-retrieval routine to read and print p6*.dat (Files 7-9). The following is a listing of this program. For additional information regarding variable definitions, variable lengths, variable types, units, and codes, please see the description for p6*.dat in Sect. 7.5. c******************************************************************** c* FORTRAN 90 data retrieval routine to read and print the files c* named "p6*.dat" (Files 7 9). c******************************************************************** c*Defines variables* CHARACTER qualt*12, bot*7 INTEGER sta, cast, samp REAL pre, ctdtmp, ctdsal, ctdoxy, theta, sal, oxy, silca REAL nitrat, nitrit, phspht, dc14, c14er, tco2, pco2, pco2tmp OPEN (unit=1, file='p6e.dat') OPEN (unit=2, file='p6e.data') write (2, 5) c*Writes out column labels* 5 format (2X,'STNNBR',2X,'CASTNO',2X,'SAMPNO',2X,'BTLNBR', 1 2X,'CTDPRS',2X,'CTDTMP',2X,'CTDSAL',2X,'CTDOXY',3X,'THETA', 2 4X,'SALNTY',2X,'OXYGEN',2X,'SILCAT',2X,'NITRAT',2X,'NITRIT', 3 2X,'PHSPHT',2X,'DELC14',2X,'C14ERR',2X,'TCARBN',4X,'PCO2',1X, 4 'PCO2TMP',7X,'QUALT1',/,36X,'DBAR',2X,'ITS-90',2X,'PSS-78', 5 1X,'UMOL/KG',2X,'ITS_90',4X,'PSS-78',1X,5('UMOL/KG',1X), 6 1X,'/MILLE',2X,'/MILLE',1X,'UMOL/KG',4X,'UATM',3X,'DEG_C',12X, 7 '*',/,25X,'*******',17X,2('*******',1X),10X,7('*******',1X), 8 8X,2('*******',1X),19X,'*') c*Sets up a loop to read and format all the data in the file* read (1, 6) 6 format (/////////////) 7 CONTINUE read (1, 10, end=999) sta, cast, samp, bot, pre, ctdtmp, 1 ctdsal, ctdoxy, theta, sal, oxy, silca, nitrat, nitrit, 2 phspht, dc14, c14er, tco2, pco2, pco2tmp, qualt 10 format (5X, I3, 7X, I1, 6X, I2, 1X, A7, 1X, F7.1, 1X, F7.4, 1 1X, F7.4, 1X, F7.1, 1X, F7.4, 1X, F9.4, 1X, F7.1, 1X, F7.2, 2 1X, F7.2, 1X, F7.2, 1X, F7.2, 1X, F7.1, 1X, F7.1, 1X, F7.1, 3 1X, F7.1, 1X, F7.1, 1X, A12) write (2, 20) sta, cast, samp, bot, pre, ctdtmp, 1 ctdsal, ctdoxy, theta, sal, oxy, silca, nitrat, nitrit, 2 phspht, dc14, c14er, tco2, pco2, pco2tmp, qualt 20 format (5X, I3, 7X, I1, 6X, I2, 1X, A7, 1X, F7.1, 1X, F7.4, 1 1X, F7.4, 1X, F7.1, 1X, F7.4, 1X, F9.4, 1X, F7.1, 1X, F7.2, 2 1X, F7.2, 1X, F7.2, 1X, F7.2, 1X, F7.1, 1X, F7.1, 1X, F7.1, 3 1X, F7.1, 1X, F7.1, 1X, A12) GOTO 7 999 close(unit=1) close(unit=2) stop=2) stop end 7.4 p6*sta.dat (Files 4-6) These files, p6esta.dat, p6csta.dat, and p6wsta.dat, provide station inventory information for each station occupied during the R/V Knorr cruise along WOCE Sections P6E, P6C, and P6W. Each line in the files contains an expocode, section number, station number, cast number, sampling date (month/date/year), sampling time, latitude, longitude, and sounding depth. The files are sorted by station number and can be read by using the following FORTRAN 90 code (contained in stainv.for, File 2): INTEGER stat, cast, depth CHARACTER expo*9, sect*4, date*10, time*4 REAL latdcm, londcm read (1, 10, end=999) expo, sect, stat, cast, date, time, 1 latdcm, londcm, depth 10 format (A9, 3X, A4, 3X, I3, 5X, I1, 3X, A10, 2X, A4, 3X, 1 F7.3, 3X, F8.3, 3X, I4) Stated in tabular form, the contents include the following: Variable Variable Variable Starting Ending type width column column expo Character 9 1 9 sect Character 4 13 16 stat Numeric 3 20 22 cast Numeric 1 28 28 date Character 10 32 41 time Character 4 44 47 latdcm Numeric 7 51 57 londcm Numeric 8 61 68 depth Numeric 4 72 75 The variables are defined as follows: expo is the expedition code of the cruise; sect is the WOCE section number; stat is the station number; cast is the cast number; date is the sampling date (month/day/year); time is the sampling time [Greenwich mean time (GMT)]; latdcm is the latitude of the station (in decimal degrees; negative values indicate the Southern Hemisphere); londcm is the longitude of the station (in decimal degrees; negative values indicate the Western Hemisphere); depth is the sounding depth of the station (in meters). 7.5 p6*.dat (Files 7-9) These files, p6e.dat, p6c.dat, and p6w.dat, provide hydrographic, carbon dioxide, and chemical data for all stations occupied during the R/V Knorr cruise along WOCE Sections P6E, P6C, and P6W. Each line consists of a station number, cast number, sample number, bottle number, CTD pressure, CTD temperature, CTD salinity, CTD oxygen, potential temperature, bottle salinity, bottle oxygen, silicate, nitrate, nitrite, phosphate, del14C, del14C error, TCO2, pCO2, pCO2 temperature, and data-quality flags. The files are sorted by station number and pressure and can be read by using the following FORTRAN 90 code (contained in p6ecwdat.for, File 3): CHARACTER qualt*12, bot*7 INTEGER sta, cast, samp REAL pre, ctdtmp, ctdsal, ctdoxy, theta, sal, oxy, silca REAL nitrat, nitrit, phspht, dc14, c14er, tco2, pco2, pco2tmp read (1, 10, end=999) sta, cast, samp, bot, pre, ctdtmp, 1 ctdsal, ctdoxy, theta, sal, oxy, silca, nitrat, nitrit, 2 phspht, dc14, c14er, tco2, pco2, pco2tmp, qualt 10 format (5X, I3, 7X, I1, 6X, I2, 1X, A7, 1X, F7.1, 1X, F7.4, 1 1X, F7.4, 1X, F7.1, 1X, F7.4, 1X, F9.4, 1X, F7.1, 1X, F7.2, 2 1X, F7.2, 1X, F7.2, 1X, F7.2, 1X, F7.1, 1X, F7.1, 1X, F7.1, 3 1X, F7.1, 1X, F7.1, 1X, A12) Stated in tabular form, the contents include the following: Variable Variable Starting Ending Variable type width column column sta Numeric 3 6 8 cast Numeric 1 16 16 samp Numeric 2 22 24 bot Character 7 26 32 pre Numeric 7 34 40 ctdtmp Numeric 7 42 48 ctdsal Numeric 7 50 56 ctdoxy Numeric 7 58 64 theta Numeric 7 66 72 sal Numeric 9 74 82 oxy Numeric 7 84 90 silca Numeric 7 92 98 nitrat Numeric 7 100 106 nitrit Numeric 7 108 114 phspht Numeric 7 116 122 dc14 Numeric 7 124 130 c14er Numeric 7 132 138 tcarb Numeric 7 140 146 pco2 Numeric 7 148 154 pco2tmp Numeric 7 156 162 qualt Character 12 164 175 The variables are defined as follows: sta is the station number; cast is the cast number; samp is the sample number; bot* is the bottle number; pre is the CTD pressure (dbar); ctdtmp is the CTD temperature (°C); ctdsal* is the CTD salinity [on the Practical Salinity Scale (PSS)]; ctdoxy* is the CTD oxygen (µmol/kg); theta is the potential temperature (°C); sal* is the bottle salinity (on the PSS); oxy* is the oxygen concentration (µmol/kg); silca* is the silicate concentration (µmol/kg); nitrat* is the nitrate concentration (µmol/kg); nitrit* is the nitrite concentration (µmol/kg); phspht* is the phosphate concentration (µmol/kg); dc14* is the radiocarbon delta 14C (per mille); c14er is the error of delta 14C (percent); tcarb* is the total carbon dioxide concentration (µmol/kg); pco2* is the partial pressure of CO2 (µatm); pco2tmp is the temperature of equilibration of the pCO2 samples in equilibrator (°C); qualt is a 14-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 file's 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; 7 = manual chromatographic peak measurement; 8 = irregular digital chromatographic peak integration; 9 = sample not drawn for this measurement from this bottle. APPENDIX A: REPRINT OF PERTINENT LITERATURE (in online or printed documentation)