Background Information

The World Ocean Circulation Experiment (WOCE) expeditions in the high-latitude South Pacific Ocean surrounding the Antarctic continent were designed to increase knowledge about an area of the World Ocean that has not been investigated extensively due to its remoteness and difficult ice and weather conditions. Acquiring oceanographic information from the South Pacific Ocean is extremely important because the Southern Ocean is known to be an area of formation for deep and intermediate water masses. These water masses provide a direct link between the atmosphere and global deep oceans through water-mass formation and ventilation processes (Chipman et al. 1996).

According to Tans et al. (1990), the Southern Ocean (south of 50° S) should be a moderate net source of carbon dioxide (CO₂) (0.5 Gt of carbon per year) to the atmosphere to account for the observed meridional gradient of the atmospheric CO₂ concentration. However, the available data suggest that the South Pacific Ocean is a net sink, at least during the summer period. To resolve the controversy, more measurements are needed. The DOE Global Ocean CO₂ Survey is taking advantage of the sampling opportunities provided by the WOCE cruises in the South Pacific Ocean.

This report presents hydrographic and CO₂-related measurements obtained during the 51-day expedition of the Russian Research Vessel (R/V) Akademik Ioffe along the WOCE Section S4P, which is located in the Pacific sector of the Southern Ocean along ~67° S, between ~73° W and 172° E (Fig.1).

The parameters measured during the cruise and listed in this report include the following: total CO₂ (TCO₂) concentration; discrete partial pressure of CO₂ (pCO₂) measured at 4°C; pressure, temperature, salinity, and oxygen measured by the conductivity, temperature, and depth (CTD) sensor; bottle salinity, bottle oxygen, and nutrients.

The CO₂ investigation along WOCE Section S4P was supported by a grant (No. DE-FGO2-92-ER61397) from the U.S. Department of Energy.