Abstract

Previous idealized investigations of Southern Ocean circulation have omitted its connection with the Antarctic continental shelves, including its important role in bottom water formation. The contribution of mesoscale eddies in setting the stratification and overturning circulation in the Antarctic Circumpolar Current (ACC) is well established, yet their role in cross-shelf exchange of water masses remains unclear. We propose a residual -mean theory that elucidates the connection between Antarctic cross-shelf exchange and overturning in the ACC , and the contribution of mesoscale eddies to the export of Antarctic Bottom Water (AABW). We motivate and verify our theory using an eddy-resolving process model of a sector of the Southern Ocean. The strength and pattern of the simulated overturning circulation strongly resemble those of the real ocean, and are closely captured by our residual-mean theory. Over the continental slope baroclinic instability is suppressed, and so transport by mesoscale eddies is reduced. This results in a strong sensitivity of the deep overturning strength to changes in near-shore winds.