The connection between Southern Ocean winds, the Atlantic Meridional overturning circulation, and Indo-Pacific upwelling

Abstract

Coupled GCM simulations are analyzed to quantify the dynamic effect of Southern Ocean (SO) winds on transports in the ocean. It is found that the closure for skew diffusivity in the non-eddy-resolving ocean model does not allow for a realistic eddy saturation of the zonal transports in the SO in response to the wind changes and that eddy compensation of the meridional transports in the SO is underestimated too. Despite this underestimated eddy compensation in the SO, however, and in contrast to previous suggestions, the Atlantic meridional overturning circulation (AMOC) strength is almost insensitive to SO winds. In the limit of weak SO winds the AMOC waters upwell not in the SO but rather in the tropical Indo-Pacific. Through their effect on sea ice, weaker SO winds also lead to less production of Antarctic Bottom Water and therefore a deeper and stronger AMOC.