Abstract

This data documentation discusses the procedures and methods used to measure total carbon dioxide (TCO₂), total alkalinity (TALK), and radiocarbon (delta ¹⁴C), at hydrographic stations, as well as the underway partial pressure of CO₂ (pCO₂) during the R/V Thomas G. Thompson oceanographic cruise in the Pacific Ocean (Section P10). Conducted as part of the World Ocean Circulation Experiment (WOCE), the cruise began in Suva, Fiji, on October 5, 1993, and ended in Yokohama, Japan, on November 10, 1993. Measurements made along WOCE Section P10 included pressure, temperature, salinity [measured by conductivity, temperature, and depth sensor (CTD)], bottle salinity, bottle oxygen, phosphate, nitrate, nitrite, silicate, chlorofluorocarbons (CFC-11 , CFC-12), TCO₂, TALK, delta ¹⁴C, and underway pCO₂.

The TCO₂ was measured by coulometry using a Single-Operator Multiparameter Metabolic Analyzer (SOMMA). The overall precision and accuracy of the analyses was ±2 µmol/kg. Samples collected for TALK were measured by potentiometric titration; precision was ±4 µmol/kg. Small volume samples collected for ¹⁴C were sent to shore and measured by use of an accelerator mass spectrometry technique. Underway xCO₂ was measured by infrared photometry with a precision of ±1 µatm. The CO₂-related measurements aboard the R/V Thomas G. Thompson were supported by the U.S. Department of Energy.

P10 is the western most section of the U.S. WOCE survey of the North Pacific Ocean. It is important for understanding the dynamics of the far western equatorial Pacific. The results from this cruise can be used to infer the relative magnitude of various tracers to the North Pacific from the South China Sea and the Sea of Japan. WOCE Section P10 also provides a transect across the Kuroshio Current which can be used to better understand the northward transport of heat, salt, and other important ocean tracers.

The underway surface measurements show a small outgassing of CO₂ at the equator. The TCO₂, TALK, and radiocarbon values show profiles typical for the North Pacific. TALK correlates strongly with salinity. ¹⁴C correlates strongly with silicate. Deflection of the isolines of all parameters at the northern end of the cruise results from the Kuroshio Current.

The WOCE Section P10 data set is available free of charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center. The NDP consists of four oceanographic data files, four FORTRAN 90 data-retrieval routine files, a documentation file, and this printed report, which describes the contents and format of all files as well as the procedures and methods used to obtain the data. Instructions on how to access the data are provided.

Keywords: carbon dioxide; coulometry; World Ocean Circulation Experiment; Pacific Ocean; hydrographic measurements; alkalinity; partial pressure of carbon dioxide; radiocarbon; carbon cycle

Reference

• Sabine, C. L., R. M. Key, M. Hall, and A. Kozyr (ed.). 1999. Carbon Dioxide, Hydrographic, and Chemical Data Obtained During the R/V Thomas G. Thompson Cruise in the Pacific Ocean (WOCE Section P10, October 5 - November 10, 1993). ORNL/CDIAC-122, NDP-071 Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, U.S.A. doi: 10.3334/CDIAC/otg.ndp071.