The World Ocean Circulation Experiment (WOCE) Hydrographic Program (WHP) was a major component of the World Climate Research Program (WCRP), whose overall goal was to obtain a better understand of the ocean's role in climate and climatic changes resulting from both natural and anthropogenic causes. The need for this experiment arose from serious concern over the rising atmospheric concentration of carbon dioxide (CO2) and their effect on the heat balance of the global atmosphere. The increasing concentrations of these gases may intensify the earth's natural greenhouse effect and alter the global climate in ways that are not well understood. Carbon in the oceans is unevenly distributed because of poorly characterized and complex circulation patterns and biogeochemical cycles. Although total carbon dioxide (TCO2) was not an official WOCE measurement, a coordinated effort, supported in the United States by the Department of Energy (DOE) and National Oceanic and Atmospheric Administration (NOAA), was made on WOCE cruises through 1998 to measure the global spatial and temporal distributions of TCO2 and other related parameters. Goals were to estimate the meridional transport of inorganic carbon in a manner analogous to the estimates of oceanic heat transport (Bryden and Hall 1980; Brewer et al. 1989; Holfort et al. 1998; Roemmich and Wunsch 1985) and to build a database suitable for carbon-cycle modeling and the estimation of anthropogenic CO2 increase in the oceans. The CO2 Survey took advantage of the sampling opportunities provided by the WHP cruises during this period, and the final data set is expected to cover on the order of 23,000 stations. Wallace (2001) has recently reviewed the goals, conduct, and initial findings of the Joint Global Ocean Flux Study (JGOFS)/WOCE Global CO2 Survey.
This report discusses carbonate system parameters TCO2 and the partial pressure of CO2 (pCO2) measured aboard the research vessel (R/V) Knorr on the three legs comprising WOCE Zonal Section P6. The section began in Valparaiso, Chile, on May 2, and ended in Sydney, Australia, on July 20, 1992, (Fig. 1), with stops at Easter Island, Chile, and Auckland, New Zealand. The P6 Section was divided into three legs (P6E, P6C, and P6W) and scientists from Brookhaven National Laboratory (BNL) were responsible for the carbonate system measurements on all of these legs. The Chief Scientists, scientific crew, and CO2 measurement groups from BNL were exchanged after each leg. Based on the measurements from these sections and the data from other Pacific sections occupied during the WOCE Survey (Lamb et al. 2001), the large-scale three-dimensional distribution of temperature, salinity, and chemical constituents including the carbonate system parameters will be mapped. Knowledge of these parameters and their initial conditions will allow determination of heat and water transports as well as carbon transport. An understanding of these transports will contribute to the understanding of processes that are relevant for climate change.
The work aboard the R/V Knorr was supported by the U.S. DOE under contract DE-ACO2-76CH00016. The authors are grateful to the Sonderforschungsbereich 460 at the University of Kiel, which was lead by Dr. F. Schott, and funded by the Deutsche Forschungsgemeinschaft, for their support and assistance in completing the written documentation. The authors would also like to acknowledge the invaluable assistance of the members of the CO2 measurement group with whom they have lost contact in the years intervening since the P6 section was done. Without the help of Victoria (Nee) Coles, David Hunter, and Kevin Wills this work could not have been completed.