This data documentation discusses the procedures and methods used to measure total carbon dioxide (TCO2) and partial pressure of carbon dioxide (pCO2) at hydrographic stations during the research vessel (R/V) Knorr oceanographic cruises 138-3, -4, and -5 in the South Pacific Ocean (Section P6). The work was divided into three legs designated as P6E, P6C, and P6W which correspond to cruises 138-3, -4, and -5, respectively. Conducted as part of the World Ocean Circulation Experiment (WOCE), the P6 section began in Valparaiso, Chile, on May 2, 1992, and ended 81 days later in Sydney, Australia, on July 30, 1992. Measurements made along WOCE Section P6 included pressure, temperature, salinity [measured by a conductivity, temperature, and depth sensor (CTD)], bottle salinity, bottle oxygen, silicate, nitrate, nitrite, phosphate, radiocarbon (14C), TCO2 ,and pCO2.
TCO2 was measured coulometrically by use of two Single-Operator Multiparameter Metabolic Analyzers (SOMMAs). The precision and accuracy of the measurements was ±1.65 µmol/kg. The pCO2 in discrete samples was measured using a headspace-equilibration technique and gas chromatography with precision of ~1 to 2 %. The CO2-related measurements aboard the R/V Knorr were supported by the U.S. Department of Energy.
The P6 data set is available free of charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center. The NDP consists of three oceanographic data files, three station inventory files, two FORTRAN 90 data retrieval routine files, a readme file, and this web documentation that describes the contents and format of all files as well as the procedures and instructions for accessing the data.
Keywords: carbon dioxide; TCO2;
pCO2; coulometry; gas chromatography; World Ocean
Circulation Experiment; Pacific Ocean; hydrographic measurements; carbon cycle.