This report summarizes the measurements of the total CO2 concentration and pCO2 in discrete water samples made by the LDEO group during the expeditions for the WOCE sections P-16S, P-17S, P-17A, P-17E, P-19C and P-19S conducted from October 1992, through April 1993, in the South Pacific Ocean. The methods employed for the measurements of these two quantities as well as the computational schemes used for obtaining the alkalinity and the apparent oxygen utilization are described. These data are listed along with the standard hydrographic data provided by the WOCE Hydrographic Project Office.
During this investigation, hydrographic and chemical measurements were repeated at five locations about a month to a year apart. An analysis of these repeat station data for total CO2 and pCO2 indicates that the expedition-to-expedition precision is about twice as large as the precision estimated for a single station. The expedition-to-expedition precision for oxygen measurements is excellent and is comparable to the single station precision. While the single station precision for the nutrient data is excellent, the data suffer from systematic offsets from one expedition to another due likely to calibration problems.
The meridional sections drawn for the total CO2 concentration in the South Pacific show the presence of a CO2 maximum centered around a depth about 2600 meters, representing a southward return flow from the North Pacific. The flow patterns of this high CO2 water are affected by the sea floor topography, namely the East Pacific Rise and Tuamotu Archipelago. This return water from the north is undercut by northward flowing Southern Ocean waters which have lower CO2 concentrations. The surface water pCO2 data indicate that, in austral summer, the eastern half of the South Pacific is a source for atmospheric CO2, whereas the western half is a sink. Since the sea-air pCO2 difference in the eastern half has a similar magnitude as that in the western half but has an opposite sign, the source flux tends to cancel with the sink flux. Hence, the South Pacific as a whole appears to have a small net CO2 flux.