Atlantic deep circulation controlled by freshening in the Southern Ocean

Abstract

Numerical simulations with a climate model of intermediate complexity are used to illustrate the effect of meridional moisture transport in the Southern Hemisphere mid-latitudes on the meridional overturning circulation (MOC) and heat transport in the Atlantic. A novel feature of the model is a diapycnal mixing scheme in the ocean, which ensures low values of diffusivity (about 10-5 m2s 1) in the pycnocline. It is shown that the Atlantic MOC, northward oceanic heat transport and the associated air-sea heat flux anomalies are all proportional to the southward moisture transport from subtropical to subpolar regions in the Southern Hemisphere. The effect of the intensified ocean circulation on sea surface temperature and salinity is also illustrated.