Molines, 2007: Southern Ocean overturning across streamlines in an eddying simulation of the Antarctic Circumpolar current

Abstract. An eddying global model is used to study the characteristics of the Antarctic Circumpolar Current (ACC) in a streamline-following framework. In the upper layers, the meridional circulation across streamlines agrees with the theoretical view: an equatorward mean flow partially can-celled by a poleward eddy mass flux. The same calculation in a zonal average gives a completely different view and un-derestimates the eddy effects. Two model simulations, in which the buoyancy forcing above the ACC changes from positive to negative, suggest that the relationship between the residual meridional circulation and the surface buoy-ancy flux is not as straightforward as assumed by some re-cent theoretical studies: even the sign of the residual circu-lation cannot be inferred from the buoyancy forcing. Heat and salt transports by the time-mean flow are important even in the streamline framework. Streamline-averaged, two-dimensional models cannot account quantitatively for the complex three-dimensional structure of the ACC. Heat and salt are balanced in the ACC, the model drift being small, but the nonlinearity of the equation of state cannot be ignored in the density balance.