Closing the North Atlantic Meridional Overturning Circulation: Mixing in the Southern Oceans


OCCI Project Funded: 2002

Proposed Research

The meridional overturning circulation refers to the flow of dense and bottom water away from their high-latitude sources and the compensating return flow of less dense upper-ocean water. Production of dense water in the northern Atlantic results in a prominent high salinity, relatively cold water mass, the North Atlantic Deep Water (NADW), that penetrates southward into the South Atlantic. NADW can be traced circumpolarly around the Southern Ocean and into the subtropical Indian and Pacific Oceans. Diapycnal fluxes of mass, heat, salt and other properties close the NADW circulation by upwelling across isopycnals somewhere in the southern oceans (Southern Ocean and subtropical South Atlantic, South Pacific and Indian Oceans). The diapycnal fluxes are therefore a key element of the NADW overturning circulation. This proposal will determine deep mixing rates in the Southern Ocean and adjacent subtropical Ocean basins using recent hydrographic data. The deep mixing estimates will elucidate the circulation route of NADW in the southern oceans and conversion of deep water to intermediate water which closes the North Atlantic meridional overturning circulation.