Combined effects of wind stress and topography in a two-layer model of the Southern Ocean

Abstract

Abstract Recent observations for the Southern Ocean suggest that bottom topography may play an important role in the dynamics of the Antarctic Circumpolar Current. In the following paper, a two-layer model of the Antarctic Circumpolar Current is used to assess the importance of Southern Ocean bathymetry. Both barotropic and baroclinic components of the velocity field have a tendency to follow contours of constant (H/|f|) (H is the depth, f the Coriolis parameter). If the flow over an isolated ridge is considered, the zonal component is significantly increased over the northern flank, whereas a weak westerly counter-current is induced over the southern portion of the ridge, mainly in the upper layer of the ocean. Behaviour at the interface shows many similarities with the observed features of the Antarctic Polar Front. Whereas the interface in a flat-bottomed ocean rises steadily towards the south, a ridge induces the interface to rise sharply over its northern flank and to flatten out over the southern side. This is consistent with the observed behaviour of surfaces of constant density in the Southern Ocean. The importance of different wind systems, the β-effect, and the size of specific ridges are qualitatively assessed.