Abstract

This data documentation discusses the procedures and methods used to measure total carbon dioxide (TCO₂), total alkalinity (TALK), and discrete partial pressure of CO₂ (pCO₂) during the Research Vessel (R/V) Thomas Washington TUNES Leg 2 Expedition in the central South Pacific Ocean. Conducted as part of the World Ocean Circulation Experiment (WOCE), the cruise began in Papeete, Tahiti, French Polynesia, on July 16, 1991, and returned to Papeete on August 25, 1991. WOCE Zonal Sections P17S along 135^oW and P16S along 150^oW were completed during the 40-day expedition. A total of 97 hydrographic stations were occupied. Hydrographic and chemical measurements made along WOCE Sections P17S and P16S included pressure, temperature, salinity, and oxygen measured by conductivity, temperature and depth sensor; bottle salinity; oxygen; phosphate; nitrate; nitrite; silicate; CFC-12; CFC-11; TCO₂; TALK; and pCO₂ measured at 20^oC.

The TCO₂ concentration in 1000 seawater samples was determined with a coulometric analysis system, the TALK concentration in 139 samples was determined on shore at the laboratory of C. Goyet of Woods Hole Oceanographic Institution with an alkalinity titration system, and the pCO₂ in 940 water samples was determined with an equilibrator/gas chromatograph system. In addition, 156 coulometric measurements for the Certified Reference Material (Batch #6) were made and yielded a mean value of 2303.2 ± 1.5 µ mol/kg. This mean value agrees within a standard deviation of the 2304.6 ± 1.6 µ mol/kg (N=9) value determined with the manometer of C. D. Keeling at Scripps Institution of Oceanography (SIO). Replicate samples from 11 Niskin bottles at 4 stations were also collected for later shore-based reference analyses of TCO₂ and TALK by vacuum extraction and manometry in the laboratory of C. D. Keeling of SIO.

The R/V Thomas Washington TUNES-2 Expedition data set is available free-of-charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center. The NDP consists of two oceanographic data files, two FORTRAN 77 data-retrieval routine files, a readme file, and printed documentation, which describes the contents and format of all files and the procedures and methods used to obtain the data.

Keywords: carbon dioxide; carbon cycle; total alkalinity; World Ocean Circulation Experiment; South Pacific Ocean; hydrographic measurements; nutrient measurements

Reference

• Takahashi, T., J. G. Goddard, S. Rubin, D. W. Chipman, S. C. Sutherland, and C. Goyet. 1995. Carbon Dioxide, Hydrographic, and Chemical Data Obtained in the Central South Pacific Ocean (WOCE Sections P17S and P16S) During the TUNES-2 Expedition of the R/V Thomas Washington, July-August, 1991. ORNL/CDIAC-86, NDP-054. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee. doi: 10.3334/CDIAC/otg.ndp054.