TO VIEW PROPERLY YOU MAY NEED TO SET YOUR BROWSER'S CHARACTER ENCODING TO UNICODE 8 OR 16 AND USE YOUR BACK BUTTON TO RE-LOAD A. CRUISE REPORT: AR21 (Updated Jun 2008) A.1. HIGHLIGHTS WHP CRUISE SUMMARY INFORMATION WOCE section designation AR21 Expedition designation (EXPOCODE) 3175MB91 Ship R/V Malcolm Baldrige Chief Scientists & affiliations LEG 1: Rik Wanninkhof/AOML Scott Doney/NCAR LEG 2: Donald K. Atwood/AOML Denis W. Frazel/AOML Dates Leg 1: 4 JUL 1993 to 24 JUL 1993 Leg 2: 2 AUG 1993 to 30 AUG 1993 Ports of call Leg 1: Fortaleza, Brazil; Cape Verde; Madeira Leg 2: Madeira Number of stations 83 63°14'38" N Geographic boundaries 29°2'8.5" W 18°8'59" W 5°0'19.8" S Floats and drifters deployed 0 Moorings deployed or recovered 0 Contributing Authors G. Berberian J.L. Bullister R.D. Castle S.C. Doney R.A. Feely D. Frazel D. Greeley B.E. Huss E. Johns M. Lamb K. Lee F. Menzia F.J. Millero L.D. Moore R. Wanninkhof D. Wisegarber Chief Scientists' Contact Information: Rik Wanninkhof • NOAA/AOML • 4301 Rickenbacker Causeway * Miami, FL 33149 tel: (305) 361-4379 • fax: (305) 361-4392 • Email: Rik.Wanninkhof@noaa.gov Scott Doney • Department of Marine Chemistry and Geochemistry • MS #25 Woods Hole Oceanographic Institution • Woods Hole, MA 02543-1543 Tel: (508) 289-3776 • Fax: (508) 457-2193Email: Email: sdoney@whoi.edu Donald K. Atwood • NESDIS Office of Research and Applications World Weather Bldg. Room 601-18 • 5200 Auth Road • Camp Springs, MD 20746-4304 Tel: 301-763-8102 Ext 206 • Fax 305-763-8580 • Email: Don.Atwood@noaa.gov Denis W. Frazel NOAA/AOML • 4301 Rickenbacker Causeway, Miami, FL 33149 NOAA Data Report ERL AOML-32 CHEMICAL AND HYDROGRAPHIC PROFILES AND UNDERWAY MEASUREMENTS FROM THE EASTERN NORTH ATLANTIC DURING JULY AND AUGUST OF 1993 Atlantic Oceanographic and Meteorological Laboratory Miami, Florida February 1998 NOAA UNITED STATES NATIONAL OCEANIC AND Environmental Research DEPARTMENT OF COMMERCE ATMOSPHERIC ADMINISTRATION Laboratories William M. Daley D. JAMES BAKER James L. Rasmussen Secretary Under Secretary for Oceans Director and Atmosphere/Administrator NOTICE Mention of a commercial company or product does not constitute an endorsement by NOAA/ERL. Use of information from this publication concerning proprietary products or the tests of such products for publicity or advertising purposes is not authorized. LOCATION OF DATA FILES Data files can be downloaded from AOML's web site (http:Hwww.aoml.noaa.gov/ocd/oaces/data) or by anonymous ftp (ftp.aoml.noaa.gov) from the directory pub/ocd/carbon/pc/natl93. For help in downloading, contact either: Betty Huss 305-361-4395 huss@aoml.noaa.gov Bob Castle 305-361-4418 castle@aoml.noaa.gov or by regular mail to either of the above at: NOAA/AOML/OCD 4301 Rickenbacker Causeway Miami, FL 33149 TABLE OF CONTENTS PRINCIPAL INVESTIGATORS AND PROJECT PARTICIPANTS ABSTRACT 1. INTRODUCTION 1.1. Description of the Study Area 2. DATA COLLECTION AND ANALYTICAL METHODS 2.1. Hydrographic Methods 2.1.1. CTD and Hydrographic Operations 2.1.2. Nutrient Analysis 2.1.2A. AOML Nutrients 2.1.2B. University of Washington Nutrients 2.1.3. CFC Analysis 2.2. Carbon Parameters 2.2.1. Total Dissolved Inorganic CO2(TCO2) 2.2.2. Discrete Fugacityof CO2(ƒCO2) 2.2.3. Total Alkalinity and pH 2.3. Underway Measurement Methods 2.3.1. Underway ƒCO2 Measurements 3. ACKNOWLEDGMENTS 4. REFERENCES APPENDIX A: Contour Plots LIST OF FIGURES 1. North Atlantic 1993 Cruise Track 2. North Atlantic 1993 CTD Bottle Trip Depths 3. Oxygen vs. Pressure 4. CTD Salinity vs. Pressure 5. Potential Temperature vs. Pressure 6. Sigma Theta vs. Pressure 7. Sigma-2 vs. Pressure 8. Sigma-4 vs. Pressure 9. AOML N03 vs. Pressure 10. U.W. & AOML N03 vs. Pressure 11. AOML P04 vs. Pressure 12. U.W. & AOML P04 vs. Pressure 13. AOMLS SiO(4) vs. Pressure 14. U.W. & AOMLS SiO(4) vs. Pressure 15. CFC-11 vs. Pressure 16. CFC-12 vs. Pressure 17. Total CO2 vs. Pressure 18. ƒCO2 vs. Pressure 19. pH vs. Pressure 20. Total Alkalinity vs. Pressure 21. Underway ƒCO2 and Sea Surface Temperature (Leg 0) 22. Underway ƒCO2 and Sea Surface Temperature (Leg 1) 23. Underway ƒCO2 and Sea Surface Temperature (Leg 2) 24. Underway ƒCO2 and Sea Surface Temperature (Leg 3) 25. Thermometer vs. Thermistor Comparison (Underway fCO2 System) 26. Comparison of U.W. & AOML N03 27. Comparison of U.W. & AOML PO4 28. Comparison of U.W. & AOMLS SiO(4) PRINCIPAL INVESTIGATORS AND PROJECT PARTICIPANTS PROJECT PRINCIPAL INVESTIGATORS PROJECT FUNDED PI AFFILIATION -------------- ----------------------------------- ----------- CTD, Sal, & O2 Dr. R. Wanninkhof AOML Nutrients Dr. D. Atwood & Dr. R. A. Feely AOML/PMEL CFCs Dr. J. L. Bullister PMEL TCO2 & fCO2 Dr. R. Wanninkhof & Dr. R. A. Feely AOML/PMEL TAlk & pH Dr. F. Millero RSMAS 13C Dr. P. Quay U.W. Productivity Dr. F. Chavez MBARI Underway pH Dr. A. Dickson SIO Ozone & CO Dr. T. P. Carsey AOML CRUISE PARTICIPANTS LEG 1 Chief Scientist: Dr. Rik Wanninkhof AOML Co-Chief Scientist: Dr. Scott Doney NCAR ANALYST DATA TYPE AFFILIATION ------------------- ----------------------------------- ----------- Jennifer Aicher TAlk, pH RSMAS Lloraine J. Bell UW pH SIO George Berberian Nutrients AOML Kurt Buck Productivity MBARI Robert Castle Data Management AOML Hua Chen Discrete ƒCO2 AOML, CIMAS Dana Greeley CFCs PMEL Kirk Hargreaves CFCs PMEL Elizabeth House 13C U.W. Kathy Krogslund Nutrients U.W. Tom Lantry TCO2 AOML Kitack Lee TAlk, pH RSMAS Sanjay Mane TAlk, pH RSMAS Lloyd Moore Nutrients AOML Sonia Olivella TAlk, pHR SMAS Robert Roddy CTD operations & O2 AOML Marta Sanderson Productivity MBARI Sue Service Productivity MBARI Michael Shoemaker Electronics Technician AOML Margie Springer-Young Atmospheric O2 & CO2 AOML Matt Steckley Discrete & UW ƒCO2 AOML Gregg Thomas CTD operations & Salinity AOML Kevin Wills TCO2 PMEL Dave Wisegarver CFCs PMEL LEG 2 Chief Scientist: Dr. Donald K. Atwood AOML Co-Chief Scientist: Dr. Denis W. Frazel AOML ANALYST DATA TYPE AFFILIATION --------------------- ----------------------------------- ----------- Jennifer Aicher TAlk, pH RSMAS Lloraine J. Bell UW pH SIO George Berberian Nutrients AOML Dave Bitterman CTD operations AOML Kurt Buck Productivity MBARI Hua Chen Discrete ƒCO2 AOML, CIMAS Cathy Cosca Discrete ƒCO2 PMEL Dana Greeley CFCs PMEL Kirk Hargreaves CFCs PMEL James Hendee Data management AOML Tom Lantry TCO2 AOML Kitack Lee TAlk, pH RSMAS Sanjay Mane TAlk, pH RSMAS Fred Menzia CFCs PMEL Lloyd Moore Nutrients AOML Victor Ross CTD data reduction, survey AOML Brian Salem 13C U.W. Marta Sanderson Productivity MBARI Michael Shoemaker Electronics Technician AOML Margie Springer-Young Atmospheric O2 & CO AOML Matt Steckley Discrete & UW ƒCO2 AOML Gregg Thomas CTD operations & Salinity AOML Jia-Zhong Zhang TAlk, pHR SMAS KEY TO AFFILIATION ABBREVIATIONS AOML Atlantic Oceanographic and Meteorological Laboratory CIMAS Cooperative Institute for Marine and Atmospheric Studies MBARI Monterey Bay Aquarium Research Institute NCAR National Center for Atmospheric Research PMEL Pacific Marine Environmental Laboratory RSMAS Rosenstiel School of Marine and Atmospheric Sciences SIO Scripps Institution of Oceanography U.W. University of Washington KEY TO DATA TYPE ABBREVIATIONS 13C 13C/12C stable isotopic ratio of TCO2 CFCs Chlorofluorocarbons ƒCO2 Fugacity of Carbon Dioxide O2 Dissolved Oxygen Talk Total Alkalinity TCO2 Total Carbon Dioxide ABSTRACT From July 4 to August 30, 1993, the National Oceanic and Atmospheric Administration's (NOAA) Ocean-Atmosphere Carbon Exchange Study (OACES) and Radiatively Important Trace Species (RITS) programs participated in an oceanographic research cruise aboard the NOAA ship MALCOLM BALDRIGE. The objectives of the OACES component were to determine the source and sink regions of CO2 in the Equatorial and North Atlantic during the summer and to establish a baseline of total carbon inventory in the region. Data were collected from 5°S to Iceland along a nominal longitude of 20°W. This report presents only the OACES-related data from legs 1, 2A, and 2B, including hydrography, nutrients, carbon species, dissolved oxygen, total inorganic carbon, chlorofluorocarbons, total alkalinity, pH, and salinity. Included are contour plots of the various parameters and descriptions of the sampling techniques and analytical methods used in data collection. KEY WORDS: alkalinity, carbon dioxide, CFC, chlorofluorocarbons, CO2, CTD, dissolved inorganic carbon, fugacity, hydrography, North Atlantic, nutrients, oxygen, pH, salinity, sigma-theta, temperature. 1. INTRODUCTION Human industrial and agricultural activity produces various gases such as carbon dioxide (CO2), chlorofluorocarbons, nitrous oxide, and methane which enter the atmosphere and absorb heat radiated by the earth's surface. This results in a net warming of the atmosphere and creates the phenomenon commonly called the "greenhouse effect." Only about half the anthropogenic carbon remains, however. Many believe that the global ocean provides the primary sink for the "missing" CO2. The potential climatic impact of the increasing concentration of these gases requires a thorough understanding of the absorption and storage properties of the oceans. The National Oceanic and Atmospheric Administration's (NOAA) Ocean-Atmosphere Carbon Exchange Study (OACES) and Radiatively Important Trace Species (RITS) programs participated in a multifaceted oceanographic research cruise conducted aboard the NOAA ship MALCOLM BALDRIGE from July 4 to August 30, 1993. The objectives of the OACES component of the cruise were to determine the source and sink regions of CO2 in the Equatorial and North Atlantic during the summer and to establish a baseline of total carbon inventory in the region in order to measure the uptake rate of atmospheric CO2 in future cruises. The objective of the RITS cruise was to evaluate the distribution and transport of tropospheric ozone and ozone precursors in the North Atlantic and was performed in association with the North Atlantic Regional Experiment (NARE), a component of the International Global Atmospheric Chemistry GGAC) Project. This report presents only the OACES-related data from the cruise, including hydrography, nutrients, carbon species, dissolved oxygen(O2), total inorganic carbon (TCO2), chlorofluorocarbons (CFCs), total alkalinity (TAlk), pH, and salinity. Biological productivity data is covered in the report by Michisaki et al., (1995). The full chemical and hydrographic data set may be downloaded from the Atlantic Oceanographic and Meteorological Laboratory's (AOML) anonymous ftp site at ftp.aoml.noaa.gov (see Appendix B for further details). Part I of this report contains a description of the study area and a map showing the cruise track. Part 2 describes the sampling techniques and analytical methods used, and contains three subsections covering hydrographic methods, carbon parameters, and underway measurements. The first subsection includes CTD, salinity, O2, nutrients, and CFC analysis methods. Subsection two covers TAlk, pH, TCO2, and discrete fugacity of CO2 WOO. The last subsection describes underway fCO2 measurements. Acknowledgments and references are contained in Parts 3 and 4 respectively. Contour plots of each parameter and various other graphs appear in Appendix A. 1.1. DESCRIPTION OF THE STUDY AREA This study comprised two consecutive research cruise legs during 1993, repeating a section carried out by R. V. OCEANUS cruise 202 during July and August of 1988. Leg 1 sailed from Fortaleza, Brazil on July 4, 1993 and, after a test station, proceeded to the first station at 50°S and 250°W. From there the ship steamed north along the 25°W line to approximately 6°N. The ship then turned NW and continued to 14°N and 29°W. At that point malfunctioning boilers and the previous shutdown of the reverse osmosis system made the production of fresh water impossible and forced a diversion to Cape Verde and subsequently to Madeira. The second leg was divided into two parts: Leg 2A and Leg 2B. Leg 2A included the stations missed in Leg 1 and departed Madeira on August 2. After occupying a station to test all over-the-side systems, the ship proceeded to 34°N and 21.2°W. There the ship turned W-SW and steamed to about 20°N and 29°W where it turned S, following the 29°W line to 16°N, occupying stations at 2° intervals. After moving S to a station at 15°N the ship reversed course and retraced its route, occupying stations at 2° intervals and returning to Madeira on August 16. Leg 2B left Madeira on August 17 and proceeded to an initial station at 35°N, 20.6°W. The ship then steamed northward along the 20° line to the final station at 63.20°N and arrived in Reykjavik, Iceland on August 30, 1993. The cruise tracks for Legs 1, 2A, and 2B are shown in Figure 1. 2. DATA COLLECTION AND ANALYTICAL METHODS During July and August 1993, a total of 83 stations were occupied between Fortaleza, Brazil and Reykjavik, Iceland and 94 CTD casts were made. Thirty- nine CTD casts occurred during Leg 1, 22 during Leg 2A, and 33 during Leg 2B. The CTD instrumentation consisted of three Neil Brown Instruments™ Mark III systems, including pressure, temperature, and conductivity sensors, and a General Oceanics™ 24-bottle rosette. CTD data were recorded during the downcast and upcast, and discrete water samples were collected in 10-L Niskin™ bottles during the upcast. Samples were collected in the following order: CFCs, O2, ƒCO2, TCO2, pH, TAlk, inorganic carbon-13 (13C), nutrients, chlorophyll, phaeopigments, and salinity. CTD casts were taken to within 25 m of the bottom in most cases where instrument problems did not preclude this (see Figure 2 for bottle trip depths and positions). CTD data were acquired and processed at sea using the software package of Millard (1993). Salinities and sea surface temperatures were also measured continuously during the entire cruise by a thermosalinograph located at the bow intake at 5 m depth. 2.1. HYDROGRAPHIC METHODS 2.1.1. CTD and Hydrographic Operations Several problems occurred with the three Neil Brown Instruments™ CTDs (serial numbers 1148, 2156, and 2769). These included a noisy conductivity sensor, sensor drift, unrealistically high temperature offsets on isolated casts, bottle mistrips, problems with the new software data acquisition package, and deck unit troubles. The latter required frequent swapping of deck units during the cruise. At the second Madeira inport (between Legs 2A and 2B), a "fourth" CTD was constructed from the three originals. Although it performed better, doubt was cast on the relevance of the pre-cruise pressurO and temperature calibrations. During post-cruise data reduction, these problems were dealt with on a cast by cast basis using various methods. For example, incorrect bottle depths were adjusted using a careful comparison of the bottle salinities (BOTS) and the CTD salinity profiles (CTDS), using knowledge of the history and trend of the BOTS-CTDS residuals. On several casts where the upcast bottle trip CTD values failed to be logged due to software problems, downcast values were matched to the nominal bottle trip depths and the BOTS-CTDS residuals were used to confirm the match. For the few stations exhibiting large temperature offsets, corrections were made based on interpolation over adjacent casts. Despite the problems, a reasonably high quality CTD data set was obtained which will be useful for most scientific purposes. Studies which by their nature push the limit of CTD technology and accuracy (for example, fine structure studies or comparative studies of long term temporal changes in temperature and/or salinity based on detailed comparisons with the results of other cruises, etc.) will probably not be possible with this data set. Details can be found in Table 1. Pre-cruise laboratory calibrations were performed on the pressure and temperature sensors. Typical laboratory accuracies are ±6.5 db for pressure and ±0.005°C for temperature. The conductivity sensor was also calibrated in the laboratory, but due to the nature of the conductivity cell there is the possibility of at-sea calibration drift, so bottle salinities collected during each CTD upcast were used for the final calibration of the CTD salinities. As explained above, it is not possible to quantitatively assess the accuracy of the temperature and pressure sensors as there was no post-cruise laboratory calibration available. However, comparisons with historical data and checks for internal consistency such as examination of the computed density profiles for each CTD cast did not raise any particular doubts about the pre-cruise calibration values. It is possible to quantitatively assess the accuracy of the conductivity sensor by comparison with the bottle salinities, which were accurate to within ±0.002. The average difference was 0.000±0.007 (n = 1942) after removing 9 outliers with difference greater than ±0.05. TABLE 1. Range of salinity correction (results of polynomial): ______________________________________________________________________________________ CTD ΔS(0M) ΔS(DEEP) COMMENT CASTS (1) (2) ----- ------ -------- ----------------------------------------------------------- 1-16 -0.001 0.006 17 0.009 0.004 18 -0.004 0.002 19-22 0 0.007 23 -0.083 -0.05 t=t-0.173^3; computer restart 28 0.006 0.007 29 0.001 0.013 30 0.013 0.015 casts 28-32: changing deck units nearly every cast 31 0.005 0.008 32 0.006 0.013 33-34 0 0.003 35 -0.343 -0.291 changed to CTD_1, 35 and 36 36 -0.3 -0.399 37 (no cast 37; same location as 38) back to CTD_2 for cast 38 38-42 0.001 0.007 no cast 4 1; at-sea memory loss 43 0 0.009 44-45 0.001 0.008 46 0.021 0.024 switched to CTD 246-53 47 0.019 0.024 48 -0.013 0.019 49 -0.045 0.038 50 -0.201 0.003 t=t-0.109^3 51 -0.083 0.032 t=t-0.109^3 52 -0.357 0.008 t=t-0.109^3 53 -0.2 0.091 t=t-0.109^3 54-57 0.002 0.007 switched to CTD_4 for duration 58 -0.041 0.009 59-61 0.001 0.007 62-65 0.003 0.009 66 -0.01 -0.009 67-70 0.004 0.01 71 0.005 0.009 72 (no 72; same location as 71) 73-79 0.005 0.009 (no 74) 80-81 0.01 0.012 82-84 0.005 0.01 85-86 0.005 0.008 87 0.005 0.01 88 0.015 0.013 89 0.007 0.009 90-94 0.008 0.01 (no 93) ______________________________________________________________________________________ Comments: 1. Bottle - CTD salinity upcast values (surface) 2. Bottle - CTD salinity upcast values (deep water) 3. Temperature correction OXYGEN Oxygen samples were collected in 150-mL ground-glass stoppered sample bottles and were analyzed using the method described by Carpenter, (1965), with computer-controlled colorimetric endpoint determination as described in Friederich, et al., (1984). Analyses of Niskin™ bottles tripped at the same depth were used to estimate the precision. The average deviation of analysis for these samples was 0.31 µmol/kg ±0.31 (n = 2 1). The average deviation is defined as (∑|x(1)-x(2)|)/n where x(1) and X(2) are the measured oxygen concentrations for each value of duplicates and n is the number of duplicates. Oxygen data were compared with data obtained on the Oceanus-202 cruise (Doney and Bullister, 1992; Tsuchiya et al., 1992) in order to discern any large scale offsets with historical deep water observations. These comparisons led to the conclusion that the North Atlantic 1993 O2 values were systematically lower by 7.5 µmol/kg than the Oceanus-202 data for the entire cruise. This offset has been observed on other cruises run by NOAA/AOML and we recommend adding 7.5 µmol/kg to all oxygen values in this report. Note that the O2 data in this report has not been adjusted. SALINITY Salinity samples were collected in 200-mL bottles. New caps were used for each sample. Bottle salinities were analyzed using a Guildline™ 8400B Autosal standardized with Wormley standard water batch #119 in a temperature controlled van. Conductivity ratios were converted to salinities conforming to the PSS78 standard. Analyses of NiskinTm bottles tripped at the same depth were used to estimate the precision. The average deviation (as defined in the oxygen section above) of analysis for these samples was 0.001 ±0.001 (n = 36). TEMPERATURE, DENSITY AND DEPTH Depth, potential temperature and density (σ(θ), σ(2), σ(4)) values were calculated using standard Woods Hole Oceanographic Institute (WHOI) hydrographic subroutines. Depth was calculated from pressure using methods based on Saunders and Fofonoff, (1976); density was determined using the calculations presented in F. Millero and A. Poisson, (1981); and potential temperature referenced to zero pressure(theta) is calculated by integrating the adiabatic lapse rate using a fourth-order Runge-Kutta algorithm. 2.1.2. Nutrient Analysis For Leg 1, two independent groups analyzed nutrients. The AOML nutrient group continued for the entire cruise, while the U.W. group's data is for Leg 1 only. Contour plots of nutrient concentrations are presented in two forms: a combination of AOML and U.W. data that uses U.W. data for Leg 1 and AOML data for Legs 2A and 2B, and all AOML data (see Figures A-9 - A-14). Figures A-26, A-27, and A-28 show a comparison between the two sets of nutrient data. 2.1.2A. AOML Nutrients DISOLVED NUTRIENTS Dissolved nutrient samples were collected in aged 60-mL linear polyethylene bottles after three complete seawater rinses and were stored in the dark at 4°C until analysis was completed (within 24 hours of sample collection). Concentrations of dissolved inorganic nitrate (NO3), nitrite (NO2), phosphate (PO4), and silicate (Si04), reported in μmol/kg, were determined using an ALPKEM™ RFA/2 Auto-Analyzer in a temperature controlled van. The water used for the preparation of standards, determination of blank, and wash between samples was filtered Gulf Stream seawater obtained from the surface waters of the Straits of Florida. At each station a 7-point standard curve was run prior to sample analysis. NITRITE AND NITRATE The automated colorimetric procedure and methodologies used in the analysis of nitrite and nitrate are essentially those described by Armstrong et al., (1967), with slight modifications described in Atlas et al., (1971). Standardizations were performed prior to each sample run with working solutions prepared aboard ship each day from pre-weighed "Baker Analyzed" reagent grade standards. Nitrite (NO2) was determined by diazotizing with sulfanilamide and coupling with N-1 napthylethelendiamine dihydrochloride (NEDA) to form an azo dye. The color produced is proportional to the nitrite concentration. Samples for nitrite+nitrate (NO2+NO3) analysis were passed through a copperized cadmium column, which reduces nitrate to nitrite, and the resulting nitrite concentration was then determined as described above. Nitrate is the difference between nitrite+nitrate and nitrite. The detection limits for nitrite and nitrate were 0.1 μmol/kg and 0.4 μmol/kg respectively. Analyses of Niskin™ bottles tripped at the same depth were used to estimate the precision. The average deviation (as defined in the oxygen section above) of analysis for these samples was 0.066 μmol/kg ±0.099 (n = 26). PHOSPHATE The automated procedure for the determination of phosphate in seawater is described by Murphy and Riley, (1962), with modifications by Grasshoff, (1965). Phosphate was determined by the reaction with an acidic molybdate solution. The phosphomolybdic acid which formed was subsequently reduced with ascorbic acid. The resulting molybdenum blue complex is proportional to the phosphate concentration in the sample. The detection limit for phosphate was 0.08 μmol/kg. Analyses of Niskin™ bottles tripped at the same depth were used to estimate the precision. The average deviation (as defined in the oxygen section above) of analysis for these samples was 0.005 μmol/kg ±0.007 (n = 26). SILICATE The analytical procedures and methodologies used in the analysis of silicate are those described by Armstrong et al., (1967), with modifications described in Atlas et al., (1971). Silicate was determined from the reduction of silicomolybdate in acidic solution to molybdenum blue by stannous chloride. The color produced is proportional to the concentration of silicate in the sample. The detection limit for silicate was 0.4 μmol/kg. Analyses of Niskin™ bottles tripped at the same depth were used to estimate the precision. The average deviation (as defined in the oxygen section above) of analysis for these samples was 0.029 μmol/kg ± 0.056 (n = 26). 2.1.2B. University of Washington Nutrients Four nutrients (phosphate, silicate, nitrate, and nitrite) were analyzed using an ALPKEM™ RFA/2 rapid flow analyzer. The methodologies used are found in Whitledge, et al. (1981) and adapted to the RFA/2 as indicated by the AlpKem method number listed below. Primary standards were prepared in deionized water; working standards were prepared in low nutrient seawater. At each station fresh running standards were prepared, and a five point standard curve (adjusted to cover the entire ranges of the nutrients) was run prior to sample analysis. A calibration standard was analyzed at the end of each sample run. This allowed for regular monitoring of the response, drift, and linearity of each chemistry. PHOSPHATE Phosphate is converted to phosphomolybdic acid and reduced with ascorbic acid to form phosphomolybdous acid in a reaction stream heated to 37 °C. The analytical precision as determined by replicate measurements (usually 4-6 samples) from 9 different depths was 0.025 μmol/kg (1.09%). (ALPKEM Method #A303-S200-11) SILICATE Silicate is converted to silicomolybdic acid and reduced with stannous chloride to form silcomolybdous acid. The analytical precision as determined by replicate measurements (usually 4-6 samples) from 9 different depths was 0.20 μmol/kg (0.63%). (ALPKEM Method #A303-S220-11) NITRITE Nitrite is diazotized with sulfanilamide and coupled with NEDA to form a red azo dye. The analytical precision as determined by replicate measurements (usually 4-6 samples) from 9 different depths was 0.01 μmol/kg (1%). (ALPKEM Method #A303-SI80-07) NITRATE + NITRITE Nitrate+nitrite is measured by reducing nitrate to nitrite in a copperized Cd coil and then measuring for nitrite. Nitrate is the difference between nitrate+nitrite and the independently measured nitrite. The analytical precision as determined by replicate measurements (usually 4-6 samples) from 9 different depths was 0.07 μmol/kg (0.24%). (AlpKem Method # A303-S170-22) 2.1.3. CFC Analysis Specially designed 10-L water sample bottles were used on the cruise to reduce CFC contamination. These bottles have the same outer dimensions as standard 10-L Niskin™ bottles, but use a modified end-cap design to minimize the contact of the water sample with the end-cap O-rings after closing. The O-rings used in these water sample bottles were vacuum-baked prior to the first station. Stainless steel springs covered with a nylon powder coat were substituted for the internal elastic tubing normally used to close Niskin™ bottles. Water samples for CFC analysis were the first samples collected from the 10-L bottles. To minimize contact with air, the CFC samples were drawn directly through the stopcocks of the 10-L bottles into 100-mL precision glass syringes equipped with 2-way metal stopcocks. The syringes were immersed in a holding tank of clean surface seawater until analyses. To reduce the possibility of contamination from high levels of CFCs frequently present in the air inside research vessels, the CFC extraction/analysis system and syringe holding tank were housed in a modified 20' laboratory van on the deck of the ship. For air sampling, a ~100 meter length of 3/8" OD Dekoron™ tubing was run from the CFC lab van to the bow of the ship. Air was sucked through this line into the CFC van using an Air Cadet™ pump. The air was compressed in the pump, with the downstream pressure held at about 1.5 atm using a back pressure regulator. A tee allowed a flow (~100 mL/min) of the compressed air to be directed to the gas sample valves, while the bulk flow of the air (>7 L/min) was vented through the back pressure regulator. Concentrations of CFC-11 and CFC-12 in air samples, seawater and gas standards on the cruise were measured by shipboard electron capture gas chromatography (EC-GC), using techniques similar to those described by Bullister and Weiss (1988). For seawater analyses, a ~30-mL aliquot of seawater from the glass syringe was transferred into the glass sparging chamber. The dissolved CFCs in the seawater sample were extracted by passing a supply of CFC-free purge gas through the sparging chamber for a period of 4 minutes at ~70 mL/min. Water vapor was removed from the purge gas while passing through a short tube of magnesium perchlorate desiccant. The sample gases were concentrated on a cold-trap consisting of a 3" section of 1/8" stainless steel tubing packed with Porapak N (60-80 mesh) immersed in a bath of isopropanol held at -20°C. After 4 minutes of purging the seawater sample, the sparging chamber was closed and the trap isolated. The cold isopropanol in the bath was forced away from the trap which was heated electrically to 125°C. The sample gases held in the trap were then injected onto a precolumn (12" of 1/8" OD stainless steel tubing packed with 80-100 mesh Porasil C, held at 90°C), for the initial separation of the CFCs and other rapidly eluting gases from more slowly eluting compounds. The CFCs then passed into the main analytical column (10', 1/8" stainless steel tubing packed with Porasil C 80-100 mesh, held at 90°C), and then into the EC detector. The CFC analytical system was calibrated frequently using standard gas of known CFC composition. Gas sample loops of known volume were thoroughly flushed with standard gas and injected into the system. The temperature and pressure was recorded so that the amount of gas injected could be calculated. The procedures used to transfer the standard gas to the trap, precolumn, main chromatographic column and EC detector were similar to those used for analyzing water samples. Two sizes of gas sample loops were present in the analytical system. Multiple injections of these loop volumes could be done to allow the system to be calibrated over a relatively wide range of CFC concentrations. Air samples and system blanks (injections of loops of CFC- free gas) were injected and analyzed in a similar manner. The typical analysis time for seawater, air, standard and blank samples was about 12 minutes. Concentrations of CFC-11 and CFC-12 in air, seawater samples and gas standards are reported relative to the S1093 calibration scale (Cunnold, et. al., 1994). CFC concentrations in air and standard gas are reported in units of mole fraction CFC in dry gas, and are typically in the parts-per-trillion (ppt) range. Dissolved CFC concentrations are given in units of picomoles of CFC per kg seawater (pmol/kg). CFC concentrations in air and seawater samples were determined by fitting their chromatographic peak areas to multi- point calibration curves, generated by injecting multiple sample loops of gas from a CFC working standard (PMEL cylinder 32386) into the analytical instrument. The concentrations of CFC-11 and CFC-12 in this working standard were calibrated versus a secondary CFC standard (9944) before the cruise and a primary standard (36743) (Bullister, 1984) after the cruise. No measurable drift between the working standards could be detected during this interval. Full range calibration curves were run 10 times during the cruise. Single injections of a fixed volume of standard gas at one atmosphere were run much more frequently (at intervals of 1 to 2 hours) to monitor short term changes in detector sensitivity. Extremely low (<0.01 pmol/kg) CFC concentrations were measured in deep water (>2000 meters) from about 30°N to 5°N along the section, as expected from CFC measurements made during the earlier occupation of this section in 1988 (Doney and Bullister, 1992), and from other transient tracer studies made in this region of the eastern North Atlantic. Based on the median of CFC concentration measurements in the deep water of this region, which is believed to be nearly CFC-free, a blank correction of 0.007 pmol/kg for CFC- 11 and 0.003 pmol/kg for CFC-12 have been applied to the data set. For very low concentration water samples, subtraction of the water sample CFC blank from the measured CFC water sample concentration yields a small negative reported value. On this expedition, we estimate precisions (1 standard deviation) of about 1% or 0.005 pmol/kg (whichever is greater) for dissolved CFC-11 measurements and 2% or 0.005 pmol/kg for CFC-12 (see listing of replicate samples given in Tables 2 and 3). A number of water samples (-70 out of a total of ~1700) had clearly anomalous CFC-11 and/or CFC-12 concentrations relative to adjacent samples. At Station 44, a significant number of water samples had elevated levels of CFC-12, believed to be due to release of CFC-12 from the ship's air conditioning system. Other anomalous samples appeared to occur more or less randomly during the cruise, and were not clearly associated with other features in the water column (e.g. elevated oxygen concentrations, salinity or temperature features, etc.). This suggests that the high values were due to individual, isolated low-level CFC contamination events. These samples are included in this report and are given a quality flag of either 3 (questionable measurement) or 4 (bad measurement). A total of 7 analyses of CFC-11 were assigned a flag of 3 and 9 analyses of CFC-12 were assigned a flag of 3. A total of 27 analyses of CFC-11 were assigned a flag of 4 and 69 CFC-12 samples assigned a flag of 4. TABLE 2. NA93 Replicate dissolved CFC-11 analyses (in pmol/kg) __________________________________________________________________________ Replicate Number Replicate Number Stn Samp 1 2 3 Stn Samp 1 2 3 --- ----- ----- ------ ------ --- ----- ------ ------ ------ 1 413 0.018 0.028 25 7823 1.638 1.681 1 419 0.125 0.123 26 8018 0.775 0.778 1 420 0.116 0.388 26 8023 1.814 1.794 1 422 0.917 0.799 27 8603 0.003 -0.000 0.011 1 424 1.736 1.709 27 8814 0.030 0.044 2 1304 0.014 0.043 28 9117 0.522 0.528 0.518 2 1308 -0.00 0.008 28 9118 0.752 0.758 0.761 2 1318 1.752 1.678 28 9401 0.004 0.006 3 1505 0.000 0.004 28 9418 0.772 0.780 3 1524 1.771 1.749 29 9711 0.096 0.084 4 1705 0.008 0.012 29 9715 0.669 0.682 4 1709 0.051 0.041 30 10322 2.019 2.051 4 1713 0.019 0.021 0.020 31 10516 0.191 0.184 6 2304 0.031 0.017 31 10523 1.862 1.855 6 2312 0.030 0.024 32 11010 0.639 0.621 7 2424 1.743 1.790 32 11018 2.604 2.590 9 3107 0.011 0.010 33 11409 0.134 0.138 9 3124 1.759 1.767 33 11412 0.562 0.572 12 3706 0.033 0.036 33 11418 2.454 2.454 12 3724 1.754 1.744 34 12110 0.244 0.248 14 4507 0.054 0.053 34 12121 2.467 2.429 14 4518 1.277 1.268 35 12710 0.355 0.347 14 4524 1.739 1.737 35 12721 2.251 2.235 16 4808 0.012 0.016 35 12722 2.122 2.128 16 4824 1.690 1.613 36 13006 0.001 0.004 17 4918 1.144 1.134 36 13024 2.138 2.135 18 5709 0.028 0.026 37 13608 0.011 0.004 18 5724 1.649 1.674 37 13613 0.152 0.153 19 5807 0.001 0.005 37 13619 2.338 2.335 20 6008 0.013 0.011 38 13902 -0.001 0.010 20 6023 1.657 1.677 38 13915 0.967 0.964 22 6604 0.018 0.005 38 13923 2.096 2.043 22 6606 0.019 0.004 39 14415 1.616 1.655 22 6819 1.469 1.474 39 14421 2.108 2.129 23 7118 0.710 0.701 40 14908 -0.002 -0.000 23 7123 1.666 1.689 1.633 44 16801 0.007 0.002 24 7618 0.675 0.669 44 16805 -0.006 0.000 24 7619 0.882 0.885 45 17002 -0.006 -0.000 25 7812 0.007 0.002 45 17010 0.001 -0.00 25 7818 0.775 0.775 46 17205 -0.001 0.000 Replicate Number Replicate Number Stn Samp 1 2 3 Stn Samp 1 2 3 --- ----- ----- ------ ----- --- ----- ------ ------ ------ 47 17703 0.000 -0.005 63 23304 0.208 0.208 47 17710 0.001 -0.004 63 23322 3.245 3.230 48 18302 -0.002 -0.004 64 23909 1.745 1.766 48 18303 -0.002 -0.003 64 23915 2.800 2.783 48 18314 0.553 0.558 64 23920 3.145 3.144 48 18316 1.889 1.873 65 24206 0.636 0.641 49 18618 2.388 2.409 65 24210 2.017 2.010 49 18622 2.153 2.168 66 24717 3.361 3.337 50 19103 -0.002 0.000 0.001 68 25322 3.340 3.303 50 19112 0.179 0.174 69 25417 3.393 3.424 51 19604 0.000 0.001 69 25422 3.085 3.064 51 19611 0.218 0.216 71 25722 3.234 3.243 51 19613 0.758 0.763 71 25724 3.102 3.116 51 19615 2.060 2.066 72 26223 2.973 3.002 52 19805 0.006 0.010 74 26821 3.684 3.748 52 19821 2.412 2.478 75 27305 2.335 2.302 53 20405 0.004 0.002 75 27315 3.447 3.571 53 20409 0.228 0.225 78 28308 2.198 2.188 53 20421 2.748 2.661 78 28314 3.438 3.788 54 20605 0.019 0.020 78 28320 3.810 3.644 54 20610 0.471 0.480 80 28718 3.587 3.581 56 21609 0.546 0.534 81 28814 3.917 3.916 56 21622 2.883 2.836 81 28820 3.859 3.890 60 22716 3.218 3.218 81 28823 3.779 3.790 61 23109 1.633 1.646 83 29108 4.030 3.981 __________________________________________________________________________ TABLE 3. NA93 Replicate dissolved CFC-11 analyses (in pmol/kg) ________________________________________________________________________________ Replicate Number | Replicate Number Stn Samp 1 2 3 4 | Stn Samp 1 2 3 --- ----- ------ ------ ----- ----- | --- ----- ------ ------ ------- 1 413 0.010 0.012 | 38 13902 0.003 0.003 1 419 0.076 0.077 | 38 13915 0.496 0.518 1 422 0.448 0.424 | 38 13923 1.148 1.120 1 424 0.976 0.978 | 39 14415 0.816 0.869 2 1308 -0.003 0.003 | 39 14421 1.170 1.205 2 1313 0.440 0.441 | 40 14908 0.000 0.002 2 1318 0.980 0.943 | 44 16805 0.003 -0.002 3 1505 0.004 0.000 | 45 17002 -0.003 -0.003 4 1705 0.010 0.006 | 45 17010 -0.003 0.000 4 1709 0.021 0.017 0.022 | 46 17205 0.000 0.000 4 1713 0.010 0.010 0.012 | 47 17703 -0.001 -0.003 4 1724 0.933 0.933 | 47 17710 -0.003 -0.005 6 2304 0.011 0.038 | 48 18302 0.004 0.000 6 2312 0.014 0.010 | 48 18303 -0.002 -0.001 9 3107 0.006 0.004 | 48 18316 0.936 0.992 9 3124 0.985 0.988 | 49 18618 1.234 1.252 12 3706 0.023 0.030 | 49 18622 1.156 1.164 12 3724 0.973 0.990 | 50 19103 -0.001 -0.0020 -0.002 14 4507 0.029 0.034 | 50 19112 0.095 0.086 14 4518 0.695 0.644 | 51 19604 0.001 0.000 14 4524 0.967 0.970 | 51 19611 0.107 0.117 16 4808 0.008 0.017 | 51 19613 0.376 0.398 16 4824 0.943 0.906 | 51 19615 1.053 1.050 17 4918 0.601 0.602 | 52 19805 0.000 0.006 18 5709 0.015 0.025 | 52 19821 1.322 1.353 18 5724 0.946 0.963 | 53 20405 0.004 0.007 20 6023 0.917 0.972 | 53 20409 0.128 0.130 22 6606 0.004 0.005 | 53 20421 1.443 1.400 23 7123 1.032 0.967 | 54 20605 0.011 0.015 24 7618 0.393 0.366 | 54 20610 0.249 0.227 24 7619 0.471 0.478 | 56 21609 0.271 0.280 25 7812 0.000 -0.001 | 56 21622 1.527 1.479 25 7818 0.432 0.427 | 60 22716 1.586 1.635 25 7823 0.915 0.942 | 61 23109 0.793 0.769 26 8018 0.421 0.418 | 63 23322 1.627 1.640 26 8023 1.014 1.020 | 64 23909 0.780 0.813 27 8814 0.027 0.025 | 64 23915 1.353 1.312 28 9117 0.302 0.302 0.306 | 64 23920 1.537 1.534 28 9118 0.416 0.414 0.403 | 65 24206 0.327 0.324 28 9401 0.015 0.014 | 65 24210 0.932 0.935 28 9418 0.433 0.432 | 66 24702 0.024 0.019 29 9711 0.056 0.062 | 66 24717 1.713 1.697 29 9715 0.379 0.397 | 68 25322 1.726 1.723 30 10322 1.109 1.132 | 69 25417 1.722 1.771 31 10516 0.118 0.118 | 69 25422 1.578 1.587 32 11010 0.329 0.325 | 71 25722 1.654 1.682 32 11018 1.365 1.368 | 71 25724 1.622 1.626 33 11408 0.054 0.064 | 72 26223 1.572 1.576 33 11418 1.287 1.331 | 74 26821 1.902 1.940 34 12110 0.149 0.149 | 75 27305 1.139 1.120 34 12121 1.348 1.347 | 75 27315 1.744 1.807 35 12710 0.210 0.200 | 78 28308 1.069 1.059 35 12721 1.219 1.238 | 78 28314 1.737 1.973 35 12722 1.195 1.187 | 78 28320 1.868 1.894 36 13006 -0.003 0.005 | 80 28718 1.838 1.836 36 13024 1.177 1.175 | 81 28814 2.056 2.010 37 13608 0.001 0.003 | 81 28820 2.003 2.004 37 13613 0.077 0.076 | 81 28823 1.968 1.980 37 13619 1.271 1.271 1.248 1.268 | 83 29108 2.091 2.054 ________________________________________________________________________________ TABLE 4. NA93 CFC air measurements for Leg 1 __________________________________________________________ Date Time Latitude Longitude F11(PPT) F12(PPT) --------- ---- -------- --------- -------- -------- 5-Jul-93 1624 04 10.6S 033 19.6 261.5 514.6 5-Jul-93 1708 04 10.6S 033 19.6 261.9 515.3 5-Jul-93 1722 04 10.6S 033 19.6 260.2 515.7 8-Jul-93 606 04 03.3S 024 59.5 -9.0 -9.0 8-Jul-93 1158 03 42.9S 025 00.1 262.7 509.7 8-Jul-93 1211 03 42.9S 025 00.1 262.6 508.0 8-Jul-93 1226 03 42.9S 025 00.1 262.6 507.6 8-Jul-93 1239 03 42.9S 025 00.1 263.6 509.0 9-Jul-93 712 03 42.9S 025 00.1 262.3 510.8 9-Jul-93 725 03 42.9S 025 00.1 262.7 510.0 9-Jul-93 754 02 10.9S 025 00.4 263.4 510.3 9-Jul-93 809 02 10.9S 025 00.4 264.1 510.3 9-Jul-93 824 02 10.9S 025 00.4 263.1 509.4 10-Jul-93 2246 01 08.6S 025 00.8 263.4 508.0 1O-Jul-93 2258 01 08.6S 025 00.8 263.5 504.9 1O-Jul-93 2312 01 08.6S 025 00.8 263.3 506.3 12-Jul-93 1450 04 48.8 026 04.5 264.7 -9.0 12-Jul-93 1504 04 48.8 026 04.5 264.5 511.2 12-Jul-93 1517 04 48.8 026 04.5 -9.0 -9.0 13-Jul-93 144 04 48.8 026 04.5 -9.0 -9.0 13-Jul-93 157 04 48.8 026 04.5 -9.0 -9.0 13-Jul-93 210 04 48.8 026 04.5 -9.0 -9.0 13-Jul-93 2112 09 00.0 027 00.0 261.2 507.7 13-Jul-93 2125 09 00.0 027 00.0 261.3 504.8 13-Jul-93 2141 09 00.0 027 00.0 260.7 503.0 13-Jul-93 2160 09 00.0 027 00.0 264.4 512.0 14-Jul-93 1811 10 46.4 028 03.1 264.3 513.0 14-Jul-93 1825 10 46.4 028 03.1 -264.1 515.0 14-Jul-93 1838 10 46.4 028 03.1 263.9 514.9 14-Jul-93 1852 10 46.4 028 03.1 264.9 514.6 15-Jul-93 1200 11 52.1 028 27.9 267.9 -9.0 15-Jul-93 1227 11 52.1 028 27.9 265.9 521.4 15-Jul-93 1252 11 52.1 028 27.9 268.8 521.4 15-Jul-91 318 11 52.1 028 27.9 266.5 518.4 17-Jul-93 122 15 00.3 028 17.0 265.7 517.6 17-Jul-93 135 15 00.3 028 17.0 268.3 515.7 17-Jul-93 155 15 00.3 028 17.0 266.7 517.5 17-Jul-93 209 15 00.3 028 17.0 268.8 516.9 17-Jul-93 1645 16 45.1 025 19.7 267.0 523.8 17-Jul-93 1659 16 45.1 025 19.7 266.5 521.2 17-Jul-93 1725 16 45.1 025 19.7 267.6 521.9 17-Jul-93 1741 16 45.1 025 19.7 267.0 -9.0 __________________________________________________________ TABLE 5. NA93 CFC air measurements for Leg 2 __________________________________________________________ Date Time Latitude Longitude F11(PPT) F12(PPT) --------- ---- -------- --------- -------- -------- 2-Aug-93 928 33 45.9 020 31.7 266.8 515.2 2-Aug-93 940 33 45.9 020 31.7 267.1 519.0 2-Aug-93 953 33 45.9 020 31.7 267.7 520.8 3-Aug-93 1233 32 00.0 022 24.2 266.6 517.1 3-Aug-93 1259 32 00.0 022 24.2 267.5 514.9 4-Aug-93 354 29 44.1 023 41.6 264.2 515.8 4-Aug-93 408 29 44.1 023 41.6 264.6 513.1 4-Aug-93 422 29 44.1 023 41.6 265.0 512.6 5-Aug-93 858 25 59.2 025 46.5 264.9 521.3 5-Aug-93 911 25 59.2 025 46.5 266.5 524.1 5-Aug-93 923 25 59.2 025 46.5 266.4 521.8 6-Aug-93 1447 21 50.6 028 01.4 264.5 519.9 6-Aug-93 1460 21 50.6 028 01.4 265.9 519.0 6-Aug-93 1513 21 50.6 028 01.4 264.8 519.8 8-Aug-93 1044 19 58.7 029 02.2 267.5 519.3 8-Aug-93 1056 19 58.7 029 02.2 268.6 519.3 8-Aug-93 1108 19 58.7 029 02.2 266.9 520.6 9-Aug-93 1717 14 59.2 029 00.2 262.4 523.6 9-Aug-93 1742 14 59.2 029 00.2 264.1 512.8 11-Aug-93 1333 23 00.0 027 26.1 267.7 524.3 11-Aug-93 1345 23 00.0 027 26.1 270.2 524.2 11-Aug-93 1358 23 00.0 027 26.1 267.5 523.5 12-Aug-93 1407 26 38.7 025 26.5 265.9 523.0 12-Aug-93 1420 26 38.7 025 26.5 266.5 524.2 12-Aug-93 1433 26 38.7 025 26.5 266.0 524.0 13-Aug-93 11 27 38.6 024 53.0 271.7 521.0 13-Aug-93 24 27 38.6 024 53.0 269.7 517.4 13-Aug-93 37 27 38.6 024 53.0 270.0 516.7 13-Aug-93 1225 28 59.7 024 07.5 266.3 521.0 13-Aug-93 1238 28 59.7 024 07.5 266.5 518.2 13-Aug-93 1251 28 59.7 024 07.5 266.4 521.2 20-Aug-93 2203 41 00.0 020 00.0 271.2 523.6 20-Aug-93 2215 41 00.0 020 00.0 269.0 530.1 22-Aug-93 2042 45 58.0 020 00.0 266.2 521.1 22-Aug-93 2055 45 58.0 020 00.0 267.0 524.9 22-Aug-93 2108 45 58.0 020 00.0 265.1 515.6 25-Aug-93 750 52 00.0 020 00.0 266.2 516.6 25-Aug-93 803 52 00.0 020 00.0 267.4 523.7 25-Aug-93 815 52 00.0 020 00.0 272.7 514.8 29-Aug-93 51 62 59.2 019 59.9 265.3 517.5 29-Aug-93 104 62 59.2 019 59.9 266.5 518.7 29-Aug-93 117 62 59.2 019 59.9 267.3 518.5 __________________________________________________________ TABLE 6. NA93 CFC Air values (interpolated to station locations) __________________________________________________________ Date Time Latitude Longitude F11(PPT) F12(PPT) --------- ---- -------- --------- -------- -------- 2-Aug-93 928 33 45.9 020 31.7 266.8 515.2 2-Aug-93 940 33 45.9 020 31.7 267.1 519.0 2-Aug-93 953 33 45.9 020 31.7 267.7 520.8 3-Aug-93 1233 32 00.0 022 24.2 266.6 517.1 3-Aug-93 1259 32 00.0 022 24.2 267.5 514.9 4-Aug-93 354 29 44.1 023 41.6 264.2 515.8 4-Aug-93 408 29 44.1 023 41.6 264.6 513.1 4-Aug-93 422 29 44.1 023 41.6 265.0 512.6 5-Aug-93 858 25 59.2 025 46.5 264.9 521.3 5-Aug-93 911 25 59.2 025 46.5 266.5 524.1 5-Aug-93 923 25 59.2 025 46.5 266.4 521.8 6-Aug-93 1447 21 50.6 028 01.4 264.5 519.9 6-Aug-93 1460 21 50.6 028 01.4 265.9 519.0 6-Aug-93 1513 21 50.6 028 01.4 264.8 519.8 8-Aug-93 1044 19 58.7 029 02.2 267.5 519.3 8-Aug-93 1056 19 58.7 029 02.2 268.6 519.3 8-Aug-93 1108 19 58.7 029 02.2 266.9 520.6 9-Aug-93 1717 14 59.2 029 00.2 262.4 523.6 9-Aug-93 1742 14 59.2 029 00.2 264.1 512.8 11-Aug-93 1333 23 00.0 027 26.1 267.7 524.3 11-Aug-93 1345 23 00.0 027 26.1 270.2 524.2 11-Aug-93 1358 23 00.0 027 26.1 267.5 523.5 12-Aug-93 1407 26 38.7 025 26.5 265.9 523.0 12-Aug-93 1420 26 38.7 025 26.5 266.5 524.2 12-Aug-93 1433 26 38.7 025 26.5 266.0 524.0 13-Aug-93 11 27 38.6 024 53.0 271.7 521.0 13-Aug-93 24 27 38.6 024 53.0 269.7 517.4 13-Aug-93 37 27 38.6 024 53.0 270.0 516.7 13-Aug-93 1225 28 59.7 024 07.5 266.3 521.0 13-Aug-93 1238 28 59.7 024 07.5 266.5 518.2 13-Aug-93 1251 28 59.7 024 07.5 266.4 521.2 20-Aug-93 2203 41 00.0 020 00.0 271.2 523.6 20-Aug-93 2215 41 00.0 020 00.0 269.0 530.1 22-Aug-93 2042 45 58.0 020 00.0 266.2 521.1 22-Aug-93 2055 45 58.0 020 00.0 267.0 524.9 22-Aug-93 2108 45 58.0 020 00.0 265.1 515.6 25-Aug-93 750 52 00.0 020 00.0 266.2 516.6 25-Aug-93 803 52 00.0 020 00.0 267.4 523.7 25-Aug-93 815 52 00.0 020 00.0 272.7 514.8 29-Aug-93 51 62 59.2 019 59.9 265.3 517.5 29-Aug-93 104 62 59.2 019 59.9 266.5 518.7 29-Aug-93 117 62 59.2 019 59.9 267.3 518.5 __________________________________________________________ 2.2. CARBON PARAMETERS 2.2.1. Total Dissolved Inorganic CO2 (TCO2) SAMPLING Samples were drawn from 10-L Niskin™ bottles into 0.5-L Pyrex™ bottles using Tygon™ tubing. Bottles were rinsed once and filled from the bottom, overflowing half a volume while taking care not to entrain any bubbles. The tube was pinched off and withdrawn, creating a 5 mL headspace volume. 0.2 mL of saturated mercuric chloride (HgCl(2)) solution was added as a preservative. The sample bottles were sealed with glass stoppers lightly covered with Apiezon-L™ grease. The samples were stored at room temperature in the dark for a maximum of two days. ANALYSIS The TCO2 analyses were performed by extracting the inorganic carbon in a seawater sample by acidification and subsequent displacement of the gaseous CO2 into a coulometer cell. Two coulometers were used on the cruise. Both were equipped with a SOMMA (Single Operator Multiparameter Metabolic Analyzer) inlet system developed by Ken Johnson of Brookhaven National Laboratory (BNL). The first system, "AOML-1" was previously used on the NOAA S-Atl-91 and EqPac-92 cruises (Forde et al., 1994; Lantry et al., 1995). The second system, "AOML-2", was brought into service in February 1993 and this was its first use at sea. For analysis on the SOMMA system, a 0.5 L sample bottle was inserted in a water bath at 20°C. Water from the bottle was displaced by pressurization into a thermostated pipette using a (700 parts per million by volume (ppm)CO2 in air) gas. The sample was injected into an extraction chamber which contained 1 mL 10% H(3)PO4 solution previously stripped of CO2. The evolved CO gas from the sample was run through a condenser and a magnesium perchlorate drying column to dry the gas stream, and through an ORBO- 53™ tube to remove volatile acids, using a carrier stream of CO2-free ultra high purity nitrogen. In the coulometer cell the CO2 is absorbed by a proprietary solution procured from Utopia Instrument Company (UIC). This solution changes color from blue to colorless by addition of the (acid) CO2 gas. A photodiode detects the color change and causes a current to pass through the cell with electrolytic production of hydroxide ions at the cathode. The titration current is turned off when the solution reaches the original color. The current passed through the cell is measured by a counter and is directly proportional to the amount of CO2 injected. The details of the system can be found in Johnson, (1992) and Johnson et al., (1993). The coulometer cell solution was replaced after 30 mg of carbon was titrated or when the coulometer runs were less then 9 minutes. This typically was after 18-20 hours of continuous use. Typical sample titration times were 9 to 16 minutes. Both coulometers were calibrated by injecting aliquots of pure CO2 using an 8-port valve with two sample loops. The CO2 gas volumes bracketed the amount of CO2 extracted from the water samples for the two AOML systems. The gas loops were calibrated at BNL. Liquid certified reference materials (CRMs) consisting of poisoned, filtered, and UV irradiated seawater supplied by Dr. A. Dickson of Scripps Institution of Oceanography (SIO) were run on each cell. The results were close to the values determined manometrically by Keeling at SIO as shown below. Av. value of CRMs run on AOML-1: 2033.46 μmol/kg ± 1.15 n = 55 Av. value of CRMs run on AOML-2: 2032.86 μmol/kg ± 0.96 n = 51 The manometric value (SIO reference material batch #16) was 2034.54 μmol/kg±0.91 n = 9. Note: Only the first replicate of the analyses, which were run early in coulometer cells, were used for the averages. Replicate seawater samples were taken from the deepest Niskin™ sample and run at different times during the cell. The first replicate was used at the start of the cell with fresh coulometer solution, the second at the end of the cell after about 30 mg of C were titrated, while the third analysis was performed using a new coulometer cell solution. No systematic difference between the replicates was observed. As example, the replicate samples run on SOMMA AOML-I had an average absolute difference from the mean of 1 μmol/kg with a standard deviation of 1.9 μmol/kg for 40 sets of triplicates. The deviation is very similar to that observed for the CRMs and suggest no strong dependency of results with amount of carbon titrated for a particular cell. The data of the two instruments were normalized using the averages of the reference material for the cruise. The following corrections were applied to the data: AOML-1, + 1.08 μmol/kg; AOML-2, + 1.68 μmol/kg. CALCULATIONS The instruments were calibrated three times during each cell solution with a set of CO2 gas loop injections. Calculation of the amount of CO2 injected was according to the Department of Energy (DOE) CO2 handbook (DOE, 1994). The gas loops yielded a calibration factor for the instrument defined as: Cal. factor = calculated moles of CO2 injected from gas loop ------------------------------------------------------------ (1) actual moles of CO2 injected The concentration of CO2 ([CO2]) in the samples was determined according to: (Counts - Blank * Run Time) * K μmol/count [CO2] = Cal. factor* ------------------------------------------ (2) pipette volume * density of sample where "Counts" is the instrument reading at the end of the analysis, "Blank" is the counts/minute determined from blank runs performed at least once for each cell of the solution, "Run Time" is the length of coulometric titration (in minutes), and K is the conversion factor from counts to μmol which is dependent on the slope and intercept relation between instrument response and charge. For a unit with slope of 1 and intercept of 0, the constant is 2.0728 * 10^(-4) μmol/count. The pipette volume was determined by taking aliquots at known temperature of distilled water from the volumes prior to, during, and after the cruise. The weights with the appropriate densities were used to determine the volume of the syringes and pipette. Calculation of pipette volumes, density, and final CO2 concentration were performed according to procedures outlined in the DOE CO2 handbook (DOE, 1994). Based on weighings of distilled water aliquots the volume of the AOML-1 pipette was 28.715 mL (20°C, 1 atm) with a standard deviation of 0.013 mL. The pipette volume of AOML-2 was 27.177 mL with a standard deviation of 0.014 mL. Assuming that the standard deviation represents the uncertainty in the delivery to the extraction chamber this accounts for approximately 90% of the variance in the CRM value. All TCO2 values are corrected for dilution by 0.2 mL of mercuric chloride solution assuming the solution is saturated with atmospheric CO2 levels and total water volume in the sampling bottles is 540 mL. The correction factor used is 1.00037. This is in addition to the correction to the CRM values for AOML-1 of + 1.08 μmol/kg and for AOML-2 of + 1.68 μmol/kg as listed above. 2.2.2 Discrete Fugacity of CO2 (fCO2)(1) SAMPLING Samples were drawn from 10-L Niskin™ bottles into 500 mL Pyrex™ volumetric flasks using Tygon™ tubing. Bottles were rinsed once and filled from the bottom, overflowing half a volume while taking care not to entrain any bubbles. Five mL of water was withdrawn with a pipette to create a small expansion volume. 0.2 mL of saturated HgCl(2) solution was added as a preservative. The sample bottles were sealed with a screw cap containing a polyethylene liner. The samples were stored upside down at room temperature for a maximum of one day. ANALYZER DESCRIPTION The discrete ƒCO2 system is patterned after the setup described in Chipman, et al., (1993) and is discussed in detail in Wanninkhof and Thoning (1993) and Chen, et al., (1995). The major difference between the systems is that our system uses a LICOR™ model 6262 non-dispersive infrared (IR) analyzer, while the system of Chipman, et al. (1993) utilizes a gas chromatograph with a flame ionization detector and a methanizer that quantitatively converts CO2 into CH4 for analysis. Samples collected in 500-mL volumetric flasks are brought to a temperature of 20.00 ±0.02°C, by first inserting the flasks upside down in a pre-bath at 19- 21°C, and subsequently in a Neslab™ model RT-220 controlled temperature bath for equilibration and analysis. A 60-mL headspace is created in the sample flask by displacing the water using a compressed standard gas with a CO2 mixing ratio close to the ƒCO2 of the water. The headspace is circulated in a closed loop through the infrared analyzer which measures CO2 and water vapor levels in the sample cell. The headspaces of two flasks are equilibrated simultaneously in two separate channels. ___________________________________ (1) The fugacity of CO2 (ƒCO2) is the partial pressure of CO2 corrected for non-ideality of CO2 in air. At ambient temperature, fCO2 - 0.995* PCO2. While headspace from the flask in the first channel goes through the IR analyzer, the headspace of the flask in the second channel is recirculated in a closed loop. After the first sample is analyzed a valve is switched to put the second channel in line with the analyzer. The samples are equilibrated till the running mean of twenty consecutive 1-second readings from the analyzer differ by less than 0.1 ppm, which on average takes about 10 minutes. An expandable volume consisting of a balloon keeps the content of flasks at room pressure. In order to maintain measurement precision, a set of six gas standards is run through the system after every 8 to 12 seawater samples. The standards have mixing ratios of 201.4, 354.1, 517.0, 804.5, 1012.2, and 1515 ppm which bracket the fCO2 at 20°C (fCO2(20)) values observed in the water column. The determination of ƒCO2(20) in water from the headspace measurement involves several steps. The IR detector response for the standards is normalized for temperature, the IR analyzer voltage output for samples is normalized to 1 atm pressure, and the IR detector response is corrected for the influence of water vapor. The sample values are converted to a mixing ratio based on the compressed gas standards. The mixing ratio in the headspace is converted to fugacity and corrected to fugacity of CO2 in the water sample prior to equilibration by accounting for change in total CO2 in water during the equilibration process (for details see Wanninkhof and Thoning, (1993)). The change in ƒCO2(20) caused by the change in TCO2 is calculated using the constraint that TAlk remains constant during exchange of CO2 gas between the headspace and the water. The calculation is outlined in the appendix of Peng et al., (1987). Relative errors for ƒCO2 analysis for the North Atlantic 1993 cruise were determined from duplicates taken from the same Niskin™ bottle (Table 7). The deviation is defined as: (difference in duplicates/(2*mean)*100) and is expressed both in parts per million by volume (ppm) and in percent. TABLE 7. fCO2 Measurement Error _________________________________________________________ Deviation Leg Sta. Sample Pressure Temp fCO2 ppm % --- ---- ------ -------- ----- ----- ----- ---- 1 2 1302 3152.4 2.40 749.1 0.9 0.11 1 2 1303 2600.8 2.69 762.2 2.4 0.32 1 6 2303 4651.3 0.46 961.3 4.5 0.47 1 16 4824 0.2 27.14 263.9 0.6 0.22 1 19 5803 3803.2 2.07 764.2 4.3 0.56 1 29 9721 20.5 26.86 266.0 1.8 0.68 1 29 9722 0.0 27.13 272.5 0.9 0.32 1 30 10303 5000.8 1.82 772.2 1.5 0.20 2A 32 11010 1000.4 9.09 687.7 0.9 0.13 2A 32 11023 0.0 22.03 331.2 0.2 0.06 2A 40 14903 3999.1 2.04 759.2 1.1 0.15 2A 40 14923 19.7 24.37 296.5 0.5 0.17 2A 44 16822 3.0 24.45 304.2 0.2 0.06 2A 48 18320 99.7 19.87 332.6 1.7 0.52 2B 57 21703 4010.7 2.20 758.0 1.1 0.15 2B 57 21704 3507.7 2.35 753.6 0.8 0.11 2B 59 22522 19.2 19.87 341.3 0.2 0.05 2B 61 23122 25.2 19.77 340.5 0.1 0.02 2B 76 27503 1196.1 4.62 770.8 0.2 0.03 2B 76 27517 250.1 9.43 599.0 0.6 0.10 -------- ---- average% 0.22 _________________________________________________________ 2.2.3. Total Alkalinity and pH pH MEASUREMENTS The pH measurements of seawater were made using the spectrophotometric techniques of Clayton and Byrne (1993). The pH of samples using the m-cresol purple (mCP) is determined from: pH = pK(ind) + log[(R - 0.0069)/(2.222 - 0.133 R)] (3) where K(ind) is the dissociation constant for the indicator and R (A(578)/A(434))is the ratio of the absorbance of the acidic and basic forms of the indicator corrected for baseline absorbance at 730 nm. The pH of the samples is perturbed by the addition of an indicator. The magnitude of this perturbation is a function of the difference between the seawater acidity and indicator acidity; therefore this correction was quantified for each batch of dye solution. To a sample of seawater (~30 mL), a normal volume of mCP (0.080 mL, in this case) was added and the absorbance ratio was measured. From a second addition of mCP and absorbance ratio measurement, the change in absorbance ratio per mL of added indicator (ΔR) was calculated. From a series of such measurements over a range of seawater pH, ΔR was described as a linear function of the value of the absorbance ratio (R(m)) measured subsequent to the initial addition of the indicator (i.e. R = 0.02959 - 0.1288 R(m)). In the course of routine seawater pH analyses, this correction was applied to every measured absorbance ratio (Rm); i.e. the corrected absorbance ratio is calculated as R = R(m) + (0.02959 - 0.1288 R(m)) (4) Clayton and Byrne (1993) calibrated the m-cresol purple indicator using TRIS Buffers (Ramette et al., 1977) and the pH equations of Dickson (1993). They found that pK(ind)= 1245.69/T + 3.8275 + (2. 11 x 10^(-3))(35-S) (5) where T is temperature in Kelvin and is valid from 293.15 to 303.15 K and S = 30 to 37. The values of pH calculated from equations (3) and (5) are on the total scale in units of mol/(kg-soln). The total proton scale (Hansson, 1973) defines pH in terms of the sum of the concentrations of free hydrogen ion, [H+], and bisulfate, [HS0(4)^-] pH(T) = -log[H+](T) = -log{[H+]+[HS04^-]} (6) = -log[H+](1+[SO(4)^2-]/k(HSO(4) where the concentration of total sulfate, [S04^(2-)] = 0.0282 x 35/S and K(HS04) is the dissociation constant for the bisulfate in seawater (Dickson, 1990a). We have redetermined the value of PK(ind) from 273.15 to 313.15 K using a 0.04 M TRIS buffer (Ramette et al., 1977). The pH of the TRIS buffer was determined from the emf measurements made with the H2,Pt| AgCI,Ag electrode system (Millero et al., 1993a). At 25°C the buffer had a pH of 8.076 and yielded spectrophotometric values of pH that were in excellent agreement (~0.0001) with those found using equations (3) and (5). Our results from 273.15 to 313.15 K (0 to 40°C) were fitted to the equation (S = 35) pK(ind) = 35.913 - 216.404/T - 10. 9913 log (T) (7) with the standard error of 0.001 in PK(ind) where the constants are on the total proton scale {mol/(kg-H20). The use of equation (3) and (7) from 0 to 40°C makes the assumption that R is independent of the temperature. The values of pH calculated from equation (3) and (7) are on the total scale in units of mol/(kg-H20). The conversion of the pH(T) {mol/(kg-H20)) to the seawater pH(SWS) {mol/(kg-soln)) can be made using (Dickson and Riley, 1979; Dickson and Millero, 1987): pH(SWS) = pH(T) - log{(l + [S04^(2-)]/K(HSO4) + [F]/K(HF))/ (1 + [SO4^(2-)]/K(HSO4)} - log(1 - 1.005 x 10^(-3)S) (8) where the total concentration of fluoride, [F^-] = 0.000067 x 35/S, and K(HF) is the dissociation constant for hydrogen fluoride (Dickson and Riley, 1979). The seawater pH(SWS) scale was used here since the carbonate constants used are on this scale (Dickson and Millero, 1987; Millero et al., 1993b). The absorbance measurements were made using a HP™ Diode Array 8452 A spectrophotometer. The temperature was controlled to 20°C with an Endocal™ RTE 8DD refrigerated circulating temperature bath that regulates the temperature to ±0.01°C. The temperature was measured using a Guildline™ 9540 digital platinum resistance thermometer. TOTAL ALKALINITY MEASUREMENTS, TAlk TITRATION SYSTEM The titration systems used to determine TAlk consisted of a Metrohm™ 665 Dosimat titrator and an Orion™ 720A pH meter that is controlled by a personal computer (Millero et al., 1993c). Both the acid titrant in a water- jacketed burette and the seawater sample in a water-jacketed cell were controlled to a constant temperature of 25 ±0.1°C with a Neslab™ constant temperature bath. The Plexiglass™ water jacketed cells used during the cruise were similar to those used by Bradshaw and Brewer (1988) except a larger volume (about 200 mL) was used to increase the precision. This cell had a fill and drain valve, which increased the reproducibility of the cell volume. A GWBASIC™ program used to run the titration records the volume of the added acid and the emf of the electrodes using RS232 interfaces. The titration is made by adding HCl to seawater past the carbonic acid end point. A typical titration records the emf reading after the readings become stable (±0.09 mV) and adds enough acid to change the voltage to a pre-assigned increment (13 mV). In contrast to the delivery of a fixed volume increment of acid, this method gives data points in the range of a rapid increase in the emf near the endpoint. A full titration (25 points) takes about 20 minutes. Using three systems a 24-bottle station cast was completed in 3.5 hours. ELECTRODES The electrodes used to measure the emf of the sample during a titration consisted of a ROSS™ glass pH electrode and an Orion™ double junction Ag, AgCl reference electrode. STANDARD ACIDS The HCl used throughout the cruise was made, standardized, and stored in 500 mL glass bottles in the laboratory for use at sea. The 0.2526 M HCl solutions were made from 1 M Mallinckrodt™ standard solutions in 0.45 M NaCl to yield an ionic strength equivalent to that of average seawater (~0.7 M). The acid was standardized using a coulometric technique by Millero's group (RSMAS) and Dickson's group (Taylor and Smith, 1959; Marinenko and Taylor, 1968). Both results agree to ±0.0001 N. VOLUME OF THE CELLS The volumes of the cells were determined in the laboratory by making weight titrations of Gulf stream seawater (S - 36). The TAlk of this water was determined by making a number of titrations. The volume was determined by comparing the values of TAlk obtained for Gulf stream seawater with open (weighed amount of seawater) and closed cells NMI = Talk x V(HCl)(open) / V(HCl)(closed)). The density of seawater at the temperature of the measurement (25°C) was calculated from the international equation of state of seawater (Millero and Poisson, 1981). The nominal volume of all cells is approximately 200 mL. If the cells were modified during the cruise, adjustments were made to the volumes using the daily titrations on low nutrient surface seawater and CRMs. VOLUME OF TITRANT The volume of HC1 delivered to the cell is traditionally assumed to have small uncertainties (Dickson, 1981) and equated to the digital output of the titrator. Calibrations of the burettes of the Dosimats were done with Milli-Q™ water at 25°C. Since the titration systems are calibrated using standard solutions, this error in the accuracy of volume delivery will be partially canceled and included in the value of cell volumes assigned. EVALUATION OF THE CARBONATE PARAMETERS The total alkalinity of seawater was evaluated from the proton balance at the alkalinity equivalence point, pH(equiv) = 4.5, according to the exact definition of total alkalinity (Dickson, 1981) TAlk = [HCO(3)^-] + 2[CO(3)^(2-)] + [B(OH)(4)^-] + [0H^-] + [HP0(4)^(2-)] + 2[PO(4)^(3-)] + [SiO(OH)(3)^-1] (9) + [HS^-] + [NH(3)] - [HSO(4)] - [H(3)PO(4)] At any point of the titration, the total alkalinity of seawater can be calculated from the equation (V(0) x Talk - V x N)/(V(0) + Y) = [HCO(3)^-] + 2[CO(3)^(2-)] + [B(OH)(4)^-] + [OH^-] + [HPO(4)^(2-)] + 2[P0(4)^(3-)] (10) + [Si0(OH)(3)^-] + [HS^-] + [NH(3)] - [H^+] - [HS0(4)^-] - [HF] - [H(3)PO(4)] where V(0) is the initial volume of the cell or the sample to be titrated, N is the normality of acid titrant, and V is the volume of acid added. In the calculation all the volumes are converted to mass using the known densities of the solutions. A FORTRAN computer program has been developed to calculate the carbonate parameters (pHs, E*, TAlk, TCO2, and Pk(4)) in Na(2)CO(3), TRIS, and seawater solutions. The program is patterned after those developed by Dickson (1981), Johansson and Wedborg (1982) and Dickson (DOE, 1991). The fitting is performed using the STEPIT routine (J.P. Chandler, Oklahoma State University, Stillwater, OK 74074). The STEPIT software package minimizes the sum of squares of residuals by adjusting the parameters E*, TAlk, TCO2 and Pk(1). The computer program is based on equation (10) and assumes that nutrients such as phosphate, silicate and ammonia are negligible. This assumption is valid only for surface waters. Neglecting the concentration of nutrients in the seawater sample does not affect the accuracy of TAlk, but does affect the carbonate alkalinity. The pH and pK of the acids used in the program are on the seawater scale, [H+](SW) = [H+] + [HS0(4)^-] + [HF] (Dickson, 1984). The dissociation constants used in the program were taken from Dickson and Millero (1987) for carbonic acid, from Dickson (1990a) for boric acid, from Dickson and Riley (1979) for HF, from Dickson (1990b) for HS0(4)^- and from Millero (1995) for water. The program requires as input the concentration of acid, volume of the cell, salinity, temperature, measured emf (E), and volume of HCl WHO. To obtain a reliable TAlk from a full titration at least 25 data points are collected (9 data points between pH=3.0 to 4.5). The precision of the fit is less than 0.4 μmol/kg when pK(1) is allowed to vary and 1.5 μmol/kg when pK(1) is fixed. Our titration program has been compared to the titration programs used by others (Johansson and Wedborg, 1982; Bradshaw et al.,1981; Bradshaw and Brewer, 1988) and the values of TAlk agree to within ±1 μmol/kg. The performance of our three titration systems has been monitored by titrating CRM Batch #16 that have a known TCO2 and constant TAlk. The precision of the values of TAlk on these CRMs was ±2 μmol/kg throughout this cruise. All measured values of TAlk were normalized to the CRM value (2303 μmol/kg) obtained in the laboratory. 2.3 UNDERWAY MEASUREMENT METHODS 2.3.1 Underway fCO2 Measurements Underway fCO2 measurements were performed quasi-continuously whenever the MALCOLM BALDRIGE was out at sea, and out of territorial waters if no science clearance was obtained. The survey department of the BALDRIGE maintained the instrument during the cruise. The data shown here include the transects from Miami to Fortaleza (Leg 0) and from Iceland to Miami (Leg 3). SYSTEM DESCRIPTION AND PROCEDURES The underway system used during the cruise is described in detail in Wanninkhof and Thoning, (1993). The shipboard automated underway fCO2 system runs on an hourly cycle during which three gas standards, a headspace sample from the equilibrator, and an ambient air sample are analyzed using a LI-COR™ infrared analyzer. The IR analyzer/detector's voltage output is measured once per second with a Keithley™ (model 195 A) digital multimeter, 1-minute averages are calculated and stored on the hard disk of an MS-DOS™ computer. The mass flow controllers (MFCs) connected to the reference and sample inlet of the IR, the mass flow meter's (MFM's) measurement of the intake rate of ambient air and recirculation rate of the headspace of the equilibrator, the back pressure in the air and equilibrated air lines, and two thermistors readings of the water temperature in the equilibrator are all logged at 1-minute intervals as well. Compressed gas standards with nominal mixing ratios of 300, 350, and 400 ppm flow through the IR analyzer for 5 minutes each hour at 75 mL/min for calibration. The 300 ppm standard flows continuously at 50 mL/min through the reference side of the IR analyzer (detector) as well. All reference tanks undergo a pre- and post-cruise calibration at NOAA's Climate Monitoring and Diagnostics Laboratory (CMDL) against standards certified by the World Meteorological Organization (WMO). The equilibrator, which was designed by R. Weiss of SIO, is made from a large (58 cm H x 23 cm ID) Plexiglas™ chamber. The equilibrator has a shower head in the top through which surface seawater is forced at a rate of 15-20 L/min. The water spray through the 16 L head space and the turbulence created by the jets impinging on the surface of 8 L of water, cause the gases in water and headspace to equilibrate. A drain 20 cm from the bottom of the equilibrator discharges excess water from the system over the side of the ship. Air in the equilibrator head space is circulated with an AIR CADET™ pump (model 7530-40) at 6 L/min in a closed loop through a MFM and back pressure regulator. During 23 minutes of each hour, 75 mL/min is teed off upstream of the back pressure regulator through a MFC and into the 12 mL sample cell of a LICOR™ (model 6251) non-dispersive infrared (IR) analyzer. The air removed from the equilibrator through the IR analyzer is replaced with ambient air through an intake/vent line that runs to the outside of the ship. The introduction of the ambient air into the equilibrator chamber during sampling of the headspace results in an error in the determination of the equilibrated head space composition which is a function of water flow rate. Tests performed during the cruise showed that an appreciable bias (~ 1 μatm towards ambient air values) could be introduced when water now rates were greater than 20 L/min. The headspace equilibration time, as determined by return to equilibrium after perturbation by adding nitrogen to the head space, is approximately 2.5 minutes. The vent line on the equilibrator is necessary to assure that the pressure in the head space of the equilibrator remains at atmospheric value. During underway sampling operations ambient air is drawn through 100 m of 0.37 cm OD Dekoron™ tubing from the bow mast of the ship at a rate of 6 to 8 L/min. During 22 minutes of each hour, ambient air mixing ratios are measured in the IR analyzer by teeing off the air line at a flow rate of 75 mL/min. UNDERWAY ƒCO2 CALCULATIONS The mixing ratios of ambient air and equilibrated headspace air are calculated by fitting a second-order polynomial fit through the response of the detector versus mixing ratio of the standards. Due to the need for sufficient time to flush the sample cell and lines leading to the IR from the previous gas, the first three minutes of each analysis run are not used in the calculations. The subsequent one-minute readings for each analysis are averaged, yielding one 19-minute average ambient air mixing ratio and one 20- minute average equilibrated headspace mixing ratio per hour. Typical standard deviations for air values are ±0.1 ppm and ±0.3 ppm for equilibrated headspace. Mixing ratios of dried equilibrated headspace and air must be converted to Fugacity of CO2 in water and water saturated air in order to determine the driving force for the air-sea CO2 flux. For ambient air, assuming 100% water vapor content, the conversion is: ƒCO(2a) = XCO(2a) (P - pH20) exp(B(11) + 2δ(12)) P/RT(SW) (11) where pH20 is the water vapor pressure at the sea surface temperature (T(SW)), P is the atmospheric pressure, R is the ideal gas constant and T(SW) is the sea surface temp (in K) as measured at the bow intake with a thermosalinograph. The exponential term is the fugacity correction where B(11) is the second virial coefficient of pure CO2 (B(11) = -1636.75 + 12.0408T - 0.0327957 T^2 + 3.16528 x 10^-5 T^3) and δ(12) (= 57.7 - 0.118 T) is the correction for an air-CO2 mixture (Weiss, 1974). The calculation for the fugacity in water includes an empirical temperature correction term for the increase of WO, due to heating of the water from passing through the pump and through 5 cm. ID PVC tubing within the ship. The water in the equilibrator is typically 0.2°C warmer than intake temperature. First the fugacity of the air in equilibrium in the headspace (W02eq) is calculated according to: ƒCO(2eq) = XCO(2eq)(P - pH20(eq))exp(B(11) + 2σ(l2)) P/RT(eq) (12) where pH2O(eq) is the water vapor pressure at the temperature of the water in the equilibrator and T(eq) is the temperature of the water in the equilibrator (in °K). The CO(2eq) is converted to the fugacity in surface seawater ƒCO(2w) by applying an empirical correction suggested by Weiss et al., (1982): Δln(ƒCO2)/ Δt(SW) = 0.03107 - 2.785 10^(-4t) - 1.839 10^(-3) ln(ƒCO2) (13) where t is the SST in °C. COMMENTS ON DATA The cruise track is shown in Figure 1 and the data are presented in graphical format for each segment in Figures 21 to 25. The data are plotted either versus latitude or longitude depending if the track trended north-south or east-west. Figures 21 though 24 have a top panel with ƒCO(2W) (filled circles with dashed line) and ƒCO(2a) (empty circles) and a bottom panel with a double Y graph depicting SST (empty circles), and salinity (filled circles dashed line) as determined from the thermosalinograph at the bow intake. The figures show the large scale features along the track. Between Miami and Fortaleza the waters are on average supersaturated by approximately 20 μatm, except in the region with very low salinity (caused by Amazon River outflow) near 10°N and 55°W which is undersaturated (Figure 21). The irregularities between 50°W and 40°W are caused by the ship steaming in a grid pattern in a region with significant gradients. Figure 22 is the transect from 5°S to Iceland. The ocean is supersaturated up to 40°N at which point the N. Atlantic turns into a strong sink. The low salinity region at 8°N, caused by excess precipitation and perhaps river outflow, is a CO2 sink as well. The transect from Iceland to Miami shows undersaturation from Iceland to 50°E, the region from 50°E to 40°E is close to saturation while the region further to the southwest is a source for CO2. During the cruise segment from Fortaleza to 3°N, 25°W the air analyses drifted significantly during the 20-minute sampling period and were above the expected seasonal values for the region. This behavior was also observed for several other cruises with this system. Replacement and/or cleaning of nearly all the components in the air line (tubing to the bow, mass flow meters, and solenoids) eliminated the problem. We hypothesize that sea salt aerosols coated the air intake lines and that CO2 was gradually released from the carbonate and bicarbonate salts due to heating of the lines and acidic air. The air mixing ratios for the region were extrapolated based on values before and after the problem arose. Stations of the NOAA/CMDL flask network (Ascension Island, and Key Biscayne, FL) were too far removed to improve the extrapolation. The thermistors in the equilibrator were calibrated before the cruise and compared to 6-hourly readings of a mercury thermometer in the equilibrator throughout the cruise. Based on the pre-cruise calibrations the resistances of the thermistor were converted to temperatures using a second order polynomial fit. The agreement with the shipboard thermometer readings was reasonable (Figure 25) except for SST < 12°C because the laboratory calibration was only performed down to 12°C. A secondary correction was applied to the thermistor based on the comparison between the Teqand the 6- hour thermometer readings. A fifth-order least squares best fit polynomial was applied to the difference in T(eq) and T(thermometerversus) T(eq) (Figure 25). This correction was subsequently applied to the T(eq) values used to calculate the ƒCO(2eq). The air XCO2 values were compared at 6 locations with duplicate flask samples obtained from the bow of the ship during the cruise and analyzed at CMDL. Table 4 shows that the results agree to better than 1 ppm, suggesting good accuracy of the calibrated infrared analyzer used during the cruise. TABLE 8. Dependence of headspace mixing ratio on water flow rate through equilibrator (from Chen, et al. 1995). ______________________________________________________ FLOW MIXING RATIO(a) EQUIL. CORR.X(b) %EQUIL.(c) ---- --------------- ------ --------- ---------- 20 389.57 ±0.06 24.05 389.57 96.7 15 390.72 ±0.25 24.05 390.72 99.6 10 391.54 ±0.35 24.09 390.87 15 389.75 ±0.12 24.04 389.91 97.6 20 388.28 24.00 389.10 95.6 ______________________________________________________ Comments: a: The air mixing ratio during the test was 351.0 ± 0.2 ppm. b: Corr. X is the ratio normalized to 24.05°C using δX(CO2)/δT=0.0423. c: percent equilibration is defined as: (X(CO2)water-air)@xL/min/(X(CO2)water-air)@10L/min * 100 TABLE 9. Comparison of in situ air values vs. flask samples analyzed at CMDL _______________________________________________________________ J.D. Lat Long AIR CO2 s.d. CMDL 1 2 diff. ------ ----- ------ ------- ---- ------ -------- ----- 190.83 -1.29 -25.02 356.99 0.12 357.2 356.98 -0.1 198.08 13.4 -28.89 355.93 0.19 355.94 356.85 -0.47 202.83 22.8 -22.53 53.78 0.07 354.1 354.05 -0.3 217.63 26.64 -25.41 355.39 0.09 355.76 0.37 221.92 15.91 -29 353.61 0.1 353.88 353.83 -0.25 225.83 28.57 -24.36 353.54 0.07 353.83 54.06 -0.39 240.54 61.84 -19.75 348.39 0.09 347.57 347.46 0.88 -------- ----- Average -0.14 St. Dev. 0.46 _______________________________________________________________ Comments: J.D. = fractional Julian day (GMT) Lat = Latitude (fractional degrees) Long = Longitude (fractional degrees) Air CO2 = air mixing ratio obtained ship board s.d. = standard deviation of 19 consecutive 1-minute averages CMDL I = results of analysis of flask #1 performed at NOAA/CMDL 2 = results of analysis of flask #2 performed at NOAA/CMDL diff. = difference between air CO2 value and average of the two CMDL analyses 3. ACKNOWLEDGMENTS The dedication and assistance of the officers and crew of the NOAA ship MALCOLM BALDRIGE is gratefully appreciated and hereby acknowledged. In particular, we would like to thank the Survey Department under the direction of Chief Survey Tech Dennis Sweeney for their capable assistance with the CTD and underway systems. 4.REFERENCES Armstrong, F. A. J., Stearns, C. R. and Strickland, J. D. H., 1967. The measurement of upwelling and subsequent biological processes by means of the Technicon Auto-Analyzer@ and associated equipment. Deep-Sea Research, 14, 381-389. Atlas, E. L., Callaway, J. C., Tomlinson, R. D., Gordon, L. I., Barstow, L. and Park, P. K., 1971. A practical manual for use of the Technicon Auto- Analyzer for nutrient analysis, revised. Oregon State University Technical Report 215, Reference No 71-22. Bradshaw, A. L. and Brewer, P. G., 1988. High precision measurements of alkalinity and total carbon dioxide in seawater by potentiometric titration- 1. 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NOAA Technical Memorandum ERL AOML-85. Chipman, D. W., Marra, J. and Takahashi, T., 1993. Primary production at 47°N and 20°W in the North Atlantic Ocean: A comparison between the ^(14)C incubation method and the mixed layer carbon budget. Deep-Sea Research 11, 40, 151-169. Clayton T. D. and Byrne, R. H., 1993. Spectrophotometric seawater pH measurements: total hydrogen ion concentration scale calibration of m- cresol purple and at-sea results. Deep-Sea Research 1, 40, 2115-2129. Cunnold, D. M., Fraser, P. J., Weiss, R. F., Prinn, R. G., Simmonds, P. G., Miller, B. R., Alyea, F. N. and Crawford, A. J., 1994. Global trends and annual releasesof CC1(3)F and CC1(2)F(2) estimated from ALE/GAGE and other measurements from July 1978 to June 1991. Journal of Geophysical Research, 99, 1107-1126. DOE, 1994. Handbook of methods for the analysis of the various parameters of the carbon dioxide system in sea water; version 2. A. G. Dickson and C. Goyet, eds. ORNL/CDIAC-74. Dickson, A. G., 1981. An exact definition of total alkalinity and a procedure for the estimation of alkalinity and total inorganic carbon from titration data. Deep-Sea Research A, 28, 609-623. Dickson, A. G., 1984. pH scales and proton-transfer reactions in saline media such as sea water. Geochimica et Cosmochimica Acta, 48, 2299-2308. Dickson, A. G., 1990a. Thermodynamics of the dissociation of boric acid in synthetic seawater from 273.15 to 318.15 K. Deep-Sea Research A, 37, 755- 766. Dickson, A. G., 1990b. Standard potential of the (AgCl + 1/2 H2= Ag + HCI(aq)) cell and the dissociation of bisulfate ion in synthetic sea water from 273.15 to 318.15 K, Journal of Chemical Thermodynamics, 22, 113-127. Dickson, A. G., 1993. pH buffers for sea water media based on the total hydrogen ion concentration scale. Deep-Sea Research 1, 40, 107-118. Dickson, A. G. and Riley, J. P., 1979. The estimation of acid dissociation constants in seawater media from potentiometric titrations with strong base. I. The ionic production of water-Kw. Marine Chemistry, 7-8, 89-99. Dickson, A. G. and Millero, F. J., 1987. A comparison of the equilibrium constants for the dissociation of carbonic acid in seawater media. Deep- Sea Research A, 34, 17331743. Doney, S. C. and Bullister, J. L., 1992. A chlorofluorocarbon section in the eastern North Atlantic. Deep-Sea Research, 39, 1857-1883. Forde, E. B., Hendee, J. C. and Wanninkhof, R., 1994. Hydrographic, carbon dioxide, nutrient, and productivity measurements from the South Atlantic during July and August of 1991. NOAA Data Report ERL AOML-24. Friederich, G. E., Sherman, P. and Codispoti, L. A., 1984. A high p*recision automated Winkler titration system based on an HP-85 computer, a simple colorimeter and an inexpensive electromechanical buret. Bigelow Lab. For Ocean Sciences, Tech. Report 42. Grasshoff, K., 1965. Automated determination of fluoride, phosphate, and silicate in seawater. In Technicon Fifth International Symposium, Automation in Analytical Chemistry, held in London, October 13, 1965. No.65-P76E, p. 304-307. Hansson 1., 1973. A new set of acidity constants for carbonic acid and boric acid in sea water. Deep-Sea Research, 20, 461-478. Johansson, 0. and Wedborg, M., 1982. On the evaluation of potentiometric titrations of seawater with hydrochloric acid. Oceanologica Acta, 5, 209- 218. Johnson, K. M., 1992. Operator's manual; Single operator multiparameter metabolic analyzer (SOMMA) for total carbon dioxide (CT) with Coulometric detection. Brookhaven N.Y. Johnson, K. M., Wills, K. D., Butler, D. B., Johnson, W. K. and Wong, C. S., 1993. Coulometric total carbon dioxide analysis for marine studies: maximizing the performance of an automated gas extraction system and coulometric detector. Marine Chemistry, 44, 167-189. Lantry, T., Lamb, M. F., Hendee, J. C., Wanninkhof, R., Feely, R. A., Millero, F. J., Byrne, R., Peltzer, E. T., Wilson, D. and Berberian, G., 1995. Chemical and hydrographic measurements from the Equatorial Pacific during boreal spring 1992. NOAA Data Report ERL AOML-27. Marinenko, G. and Taylor, J. K., 1968. Electrochemical equivalents of benzoic and oxalic acid. Analytical Chemistry, 40, 1645-165 1. Michisaki, R. P., Chavez, F. P. and Buck, K. R., 1995. Primary Productivity and Chlorophyll from the North Atlantic. MBARI Technical Report. Monterey Bay Aquarium Research Institute, Pacific Grove, California. Millard, R. C. and Yang, K., 1993. CTD Calibration and processing methods used at Woods Hole Oceanographic Institution. Technical Report WHOI-93- 44, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts. Millero, F. J. and Poisson, A., 1981. International one-atmosphere equation of state of seawater. Deep-Sea Research A, 28, 625-629. Millero F. J., Zhang, J.-Z., Fiol, S., Sotolongo, S., Roy, R., Lee, K. and Mane, S., 1993a. The use of buffers to measure the pH of seawater. Marine Chemistry, 44, 143-152. Millero, F. J., Byrne, R. H., Wanninkhof, R., Feely, R. A., Clayton, T., Murphy, P. and Lamb, M. F., 1993b. The internal consistency of CO2 measurements in the Equatorial Pacific. Marine Chemistry, 44, 269- 280. Millero F. J., Zhang, J.-Z., Lee, K. and Campbell, D. M., 1993c. Titration alkalinity of seawater. Marine Chemistry, 44, 153-16. Murphy, J. and Riley, J. P., 1962. A modified single solution method for the determination of phosphate in natural waters. Analytica Chimica Acta 27, 30. Peng, T.-H., Takahashi, T., Broecker, W. S. and Olafsson, J., 1987. Seasonal variability of carbon dioxide, nutrients and oxygen in the northern North Atlantic surface water: observations and a model. Tellus, 39B, 439-458. Ramette, R. W., Culberson, C. H. and Bates, R. G., 1977. Acid base properties of Tris (hydroxymethyl) aminomethane (Tris) buffers in seawater from 5 to 40°C. Analytical Chemistry, 49, 867-870. Saunders, P. M. and Fofonoff, N. P., 1976. Conversion of pressure to depth in the ocean. Deep-Sea Research, 23(l), 109-111. Taylor, J. K. and Smith, S. W., 1959. Precise coulometric titration of acids and bases. Journal of Research of the National Bureau of Standards, 63A, 153-159. Tsuchiya, M., Talley, L. D. and McCartney, M. S., 1992. An eastern Atlantic section from Iceland southward across the equator. Deep-Sea Research, 39, 1885-1917. Wanninkhof, R. and Thoning, K., 1993. Measurement of fugacity of CO2 in surface water using continuous and discrete sampling methods. Marine Chemistry, 44, 189205. Weiss, R. F., 1974. Carbon dioxide in water and seawater: the solubility of a non-ideal gas. Marine Chemistry, 2, 203-215. Weiss, R. F., Jahnke, R. A. and Keeling, C. D., 1982. Seasonal effects of temperature and salinity on the partial pressureof CO2 in seawater. Nature, 300, 511-513. Whitledge, T. E., Malloy, S. C., Patton, C. J. and Wirick, C. D., 1981. Automated nutrient analyses in seawater. Technical Report 51398, Brookhaven National Laboratory, Upton, New York. APPENDIX A: Contour Plots (See PDF file) This appendix contains contour plots of all hydrographic and chemical parameters, plots of underway measurements (see Section 2.3 for explanation), and plots comparing AOML and U.W. nutrient values. Figures 2 through 20 were generated using Surfer™ for Windows™ version 6.04. Only values with a qc flag value of 2 (good) were used in gridding the data. Gridding was accomplished using the built in Kriging algorithm with an anisotropy of four and no smoothing. The 0-6000 db plots were created from 140 column by 81 row grids and the 0-1000 db plots were created from 140 column by 34 row grids. Hachures in enclosed contours mark relative minima in the plot. Each contour plot includes a scale bar showing the contour levels used. Nutrient plots (Figures 9 through 14) were done in two ways for each individual nutrient. Plots labelled "U.W. & AOML" use University of Washington nutrient values for Leg 1 (to about 15°N) and AOML values for all other stations. The plots labelled "AOML" use AOML nutrients for all stations. Figures 26 through 28 show a comparison of AOML and U.W. nutrients with the difference (U.W. value - AOML value) on the Y-axis and the U.W. value on the X-axis. DATA PROCESSING NOTES DATE CONTACT DATA TYPE EVENT SUMMARY ---------- ---------- ------------- ------------------------------------------ 1999-10-01 Bartolacci CTD/BTL/SUM sent to S.Anderson for reformatting 2000-01-11 Wanninkhof CTD Submitted needs reformatting 2000-05-06 Wanninkhof CTD Data are Public I did not realize that the data were in non-public status. Feel free to release it to the community at large (recognizing that not all data meets WOCE specifications). Don't hesitate to contact us if there are further questions. 2000-06-12 Bartolacci CTD Website Updated: data are public 2000-07-24 Huynh Cruise Report Website Updated: txt version online 2001-02-12 Muus CTD Update Needed Notes Feb 12, 2001 D. Muus AR21 EXPOCODE Data to be reformatted taken from: /usr/export/html-public/data/repeat/atlantic/ar21/ar21_b/original/ ar21.csv ar21.des ar21_93_ctd.zip CTD file taken from web Feb 2, 2001: ar21_bct.zip dated 000612 diff indicates ar21_bct.zip same as ar21_93_ctd.zip No quality codes in CTD files. No bottom depths. CTD Cast numbers consecutive through cruise, not by station. Used CTD cast numbers in file names. Station numbers are in comments. No Bottle Number from originator but Bottle quality code is included. Sample Number appears to be Rosette Cast # and Bottle #. Rosette Cast Numbers are different sequence from CTD cast numbers and are also consecutive for the cruise not just each station. Missing rosette cast number probably other event not connected to Rosette and CTD work. TCARBN was listed in original data as TCO2. PCO2 is PCO2 at 20 deg C. In-situ PCO2 is in original data file but not in exchange file. Can be calculated from data available in exchange file. PH is spectrophotometric pH at 20 deg C 2001-02-25 Bartolacci CTD/BTL Website Updated: btl encrypted, ctd public 2001.02.25 DMB Reformatted exchange bottle and zipped ctd files were copied from Dave Muus' directory to this subdirectory and put online. No WOCE formatted files exist to date. The CTD and BOTTLE exchange files should be read into OceanAtlas as a check before making them available to anyone outside WHPO. They are now in ~dave/DANIE/AR21b/ar21_b_ct1.zip/ar21_b_hy1.csv D. Muus Feb 12, 2001 Feb 14, 2001, successfully read into OceanAtlas by Jim Swift. dm DATE CONTACT DATA TYPE EVENT SUMMARY ---------- ---------- ------------- ------------------------------------------ 2002-05-01 Bartolacci CTD/BTL Update Needed Exchange BOT & CTD online need WOCE fmttd files. BOT CTD NONPUB. Create WOCE fmttd files. Create SUM. Email Wanninkhov for PUB status. 2005-01-04 Key BTL Data are Public The data for this cruise have been public for quite some time so it may be worthwhile to check that the version you have is current. The NOAA people routinely refer to this cruise as OACES93 or A16N with the EXPOCODE you have in the table. This is one of their repeat sections, but the timing of the repeat is further apart than a typical WOCE repeat cruise. 2005-01-05 Key Cruise Report Submitted scanned, pdf doc 2005-01-05 Key DELC13/DELC14 Submitted Updated data files With this message I've attached myAR21b (1993 Baldrige occupation of A16N) files even though you didn't ask. I'm certain that my file is the only copy anywhere that has C14 data and may be the only one with QCed C13. I've also attached my README file for this cruise. The files currently at AOML and CDIAC were built from my reworking of their original files as part of GLODAP so I can answer any questions that arise. The only thing that will need to be fixed to create formal exchange format are:column labels, column order and number of decimal places (my code drops trailing decimal 0s and/or prints too many decimal places. I included calculated values (depth, theta, aou, sigmax), which you may want to drop and recalculate in case of minor function differences. Other than the information that is included in my README, you already have posted all the metadata I know about other than a final report (also attached) which I found on the AOML CO2 web site as a pdf file. 2005-04-13 Key OXY/PHS/SIL Update Needed: Add 7.5 µmol/kg to oxy values On 1/5/05 I submitted to you a copy of the data from the 1993 NOAA occupation of A16N (Malcolm Baldridge, NOAA called it OACES93). I mentioned that the carbon community used this cruise rather than 32OC202_1,2 as the WOCE era occupation of this line (the Oceanus cruise did not have carbon measurements). In the final data report for that cruise the participants suggested that 7.5 µmol/kg should be added to the oxygen values. The version of the data i sent you included that oxygen adjustment. The need for an adjustment to the oxygen data was confirmed by V. Gouretski's objective analysis of Atlantic data. He derived an adjustment of 5.05 µmol/kg (.116ml/l) for stations 32-83 (no adjustment for stations 1-31). Gouretski also estimated that the phosphate and silicate values needed minor adjustment. None of the Gouretski adjustments were in what I sent. I don't know the WHPO policy for such situations. It is easy enough to back out the adjustment I made if required. Regardless, a footnote to the oxygen data for this cruise is required (or at least desirable). This cruise has not yet appeared on your Atlantic web page. The CDIAC and NOAA versions of this data do NOT have the oxygen correction applied. DATE CONTACT DATA TYPE EVENT SUMMARY ---------- ---------- ------------- ------------------------------------------ 2005-04-13 Key Cruise ID Believes this should be A16N On 1/5/05 I submitted to you a copy of the data from the 1993 NOAA occupation of A16N (Malcolm Baldridge, NOAA called it OACES93). I mentioned that the carbon community used this cruise rather than 32OC202_1,2 as the WOCE era occupation of this line (the Oceanus cruise did not have carbon measurements). In the final data report for that cruise the participants suggested that 7.5umol/kg should be added to the oxygen values. The version of the data i sent you included that oxygen adjustment. The need for an adjustment to the oxygen data was confirmed by V. Gouretski's objective analysis of Atlantic data. He derived an adjustment of 5.05 umol/kg (.116ml/l) for stations 32-83 (no adjustment for stations 1-31). Gouretski also estimated that the phosphate and silicate values needed minor adjustment. None of the Gouretski adjustments were in what I sent. I don't know the WHPO policy for such situations. It is easy enough to back out the adjustment I made if required. Regardless, a footnote to the oxygen data for this cruise is required (or at least desirable). This cruise has not yet appeared on your Atlantic web page. The CDIAC and NOAA versions of this data do NOT have the oxygen correction applied. 2005-04-19 Key Cruise ID Recommends Line # change to A16N Based on the WHPO repeat cruise table, this does appear to be the same cruise. The data for this cruise have been public for quite some time so it may be worthwhile to check that the version you have is current. The NOAA people routinely refer to this cruise as OACES93 or A16N with the EXPOCODE you have in the table. This is one of their repeat sections, but the timing of the repeat is further apart than a typical WOCE repeat cruise. Presumably that is the the reason I didn't even check this area of your site. On the same page you have listed the 1991 M. Baldrige cruise. Under the data link there is no bottle data. These data are public and i have a copy of everything with WOCE flags added. I can provide a copy if you need it or alternately, it should be available from Kozyr at CDIAC. 2005-04-19 Key Cruise ID Cruise ID confusion May be A16N Under Atlantic One-Time cruises WHPO lists the 2003 Ron Brown cruise, but not the 1993 NOAA occupation of this line. Carbon people generally use the 1993 NOAA cruise for the WOCE occupation of this line rather than the 1988 Oceanus cruise (which does not have carbon data). I believe that the 1993 NOAA cruise data should be added to WHPO since the CLIVAR focus is more carbon oriented than WOCE and change is paramount. Fortunately, this is easy since Kozry has the data and cruise report online: See item number 9 at http://cdiac.esd.ornl.gov/oceans/other.html For what it's worth, GLODAP used the 1993 NOAA cruise as the official WOCE occupation of A16N. In our final data set we applied the salinity, oxygen and nutrient corrections derived by V. Gouretski. There were no corrections necessary for any of the carbon parameters. If you have any trouble at all with Alex's version of the data file, I can provide one in the normal format I send. DATE CONTACT DATA TYPE EVENT SUMMARY ---------- ---------- ------------- ------------------------------------------ 2005-04-20 Swift CDOM Submitted Data are Final 2005-12-15 Johnson CTD/BTL Data are Public aka: A16N_1993 I have indeed published a paper on LSW differences along A16N including oxygen analyses in GRL (Johnson et al. 2005) this year using A16N data. The manuscript on SPMW oxygen differences is not yet out but it will be published (someday) in Prog. Oceanogr. in a special issue. That manuscript (Johnson & Gruber) has been accepted by the special issue guest editor (I. Yashayaev) and forwarded to one of the two editors-in-chief (D. Quadfasel), but I am not sure just how far along the whole issue is at present. You can find the 1998 data at the CCHDO under the repeat data (AR21): http://whpo.ucsd.edu/data/tables/repeat/subs/ar21_table.htm which is where I got them. The 1993 data are also listed in that table as residing at the WHPO, but the bottle data are still not public. However, you can find them at this web site http://www.aoml.noaa.gov/ocd/oaces/natl93.html 2008-06-22 Kappa Cruise Report New pdf & text docs compiled Reformatted NOAA Data Report ERL AOML-32 as pdf and text documents to replace the prelilminary text report currently online for this cruise. Added data processing notes, new station track, and made text in pdf searchable.