Abstract

This data documentation discusses the procedures and methods used to measure total carbon dioxide concentration (TCO₂) and partial pressure of CO₂ (pCO₂) in discrete water samples collected during three expeditions of the Research Vessel (R/V) Knorr in the South Pacific Ocean. Conducted as part of the World Ocean Circulation Experiment (WOCE), the first cruise (WOCE Section P16A/P17A) began in Papeete, Tahiti, French Polynesia, on October 6, 1992, and returned to Papeete on November 25, 1992. The second cruise (WOCE Section P17E/P19S) began in Papeete on December 4, 1992, and finished in Punta Arenas, Chile, on January 22, 1993. The third expedition (WOCE Section P19C) started in Punta Arenas, on February 22 and finished in Panama City, Panama, on April 13, 1993. During the three expeditions, 422 hydrographic stations were occupied. Hydrographic and chemical measurements made along WOCE Sections P16A/P17A, P17E/P19S, andP19C included pressure, temperature, salinity, and oxygen [measured by conductivity, temperature, and depth (CTD) sensor], as well as discrete measurements of salinity, oxygen, phosphate, nitrate, nitrite, silicate, chlorofluorocarbons (CFC-11, CFC-12), TCO₂, and pCO₂ measured at 4 and 20°C. In addition, potential temperatures were calculated from the measured variables.

The TCO₂ concentration in 4419 seawater samples was determined with a coulometric analysis system; the pCO₂ in 4419 discrete water samples was determined with an equilibrator/gas chromatograph system. At 114 stations, complete vertical profiles from the surface to the ocean floor were obtained, whereas at the remainder of stations only surface mixed layer samples were taken. In addition, 758 coulometric measurements for the Certified Reference Material (CRM) (batch nos. 12 and 13) were made. The shipboard analyses of CRM agreed with the Scripps Institution of Oceanography (SIO) manometric values within 1.2 µmol/kg. The overall precision of TCO₂ measurements is estimated to be ~±2 µmol/kg. The shipboard TCO₂ measurements listed in this data report have not been corrected for the differences with the SIO manometric values.

The data set is available free of charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center. The NDP consists of six oceanographic data files, two FORTRAN 77 data-retrieval routine files, a documentation file, and this printed report, which describes the contents and format of all files and the procedures and methods used to obtain the data.

Keywords: total carbon dioxide; partial pressure of carbon dioxide; World Ocean Circulation Experiment; South Pacific Ocean; hydrographic measurements; carbon cycle; carbonate chemistry; coulometer; equilibrator

Reference

• Rubin, S., J. G. Goddard, D. W. Chipman, T. Takahashi, S. C. Sutherland, J. L. Reid, J. H. Swift, L. D. Talley, and A. Kozyr. 1998. Carbon Dioxide, Hydrographic, and Chemical Data Obtained in the South Pacific Ocean (WOCE Sections P16A/P17A, P17E/P19S, and P19C, R/V Knorr, October 1992-April 1993. ORNL/CDIAC-109, NDP-065. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee. 186 pp. doi: 10.3334/CDIAC/otg.ndp065