On Oceanic Heat and Freshwater Fluxes at 30°S

Abstract

A simple box model based on mass, heat and salinity conservation combined with existing estimates of ocean?atmosphere heat and freshwater exchanges is used to calculate the oceanic mean meridional volume fluxes of three water masses at 30°S. Model results lead to relatively large volume fluxes and questionable flow directions in the South Pacific Ocean. It is shown that although solutions are sensitive to changes in the mean temperature and salinity of each water mass, changes of these properties within realistic limits cannot lead to large changes in the mass fluxes or flow reversals. The effect of changes in the ocean?atmosphere fluxes north of 30°S on the oceanic mass transports is evaluated. In the South Atlantic Ocean, reduction of the excess evaporation would significantly reduce the required volume fluxes whereas in the South Pacific Ocean, reduction of the volume fluxes and reversing the flow direction in the Antarctic Intermediate Water requires reduction of both heat and freshwater fluxes into the ocean. The role of a possible flow of Pacific Ocean waters into the Indian Ocean at equatorial latitudes, through the Southeast Asian Seas, and its effects on the Pacific and Indian Oceans' mass, heat and freshwater budgets are evaluated. Such a flow would strongly relax the requirement of southward freshwater flux at 30°S in the South Pacific Ocean.