Influence of the Antarctic Circumpolar Current on the Atlantic meridional circulation

Abstract

The physics of the Meridional Overturning Circulation and inter-hemispheric heat transport is explored with an emphasis on the upper and central ocean using a general ocean circulation model. The ability of the Antarctic Circumpolar Current, bathymetry, and surface temperature and wind stresses to influence the MOC and inter-hemispheric heat transport is considered. All experiments are based on an idealized model of intermediate complexity with analysis focused on the interplay between the surface heat fluxes, geometry, and the meridional transport of heat and volume. The ACC is found to have an effect comparable in magnitude to that of the mechanical and thermodynamic surface forcing upon meridional circulation and inter-hemispheric heat transport. Basin geometry also plays a comparatively minor role in the inter-hemispheric transports but is essential in creating a realistic ACC by removing some of the momentum imparted by surface wind stresses. The combination of the ACC and asymmetric surface forcing results in values of inter-hemispheric transport which are comparable to actual values. This agreement suggests that previous emphasis on deep overturning in the ocean basins and small-scale mixing as a dominant factor in the driving force behind the MOC's strength and maintenance should be reconsidered, with greater emphasis being placed on studying the roles of the upper and central ocean.