Mass, heat, oxygen and nutrient fluxes at 30°S and their implications for the Pacific-Indian through flow and the global heat budget

Abstract

Six hydrographic basinwide sections, two in each of the three major ocean basins, are employed in a set of inverse calculations to determine the extent of exchange between the Pacific and Indian Oceans through the Indonesian Archipelago and the net global oceanic heat flux at 30°S. Using a model which combines the data for the South Pacific and South Indian Oceans, it is found that even the largest existing estimates of Indonesian Passage through flow (20 Sv) are consistent with the data. However, the available information cannot limit the extent of the exchange, i.e. both smaller and larger through flows produce physically reasonable circulation patterns. The seasonal and interannual variations which have been found by other investigators and which we are incapable of resolving, lead us to conclude that in the long term mean an estimate of ~10 Sv for the through flow is most reasonable. Globally, at 30°S, we find a net oceanic heat flux of -1.1 ± 1.7 PW, which is not significantly different from zero. It is dominated by a large (>1 PW) southward heat flux in the Indian Ocean. Large equatorward (~0.8 PW) heat flux values in the South Atlantic Basin are not consistent with our data. We therefore conclude that although our data are consistent with some water following the warm water return path for NADW (Gordon 1986), the cold water path must play the dominant role in the maintenance of the global thermohaline cell associated with the formation process of NADW.