The Deacon Cell and the Other Meridional Cells of the Southern Ocean

Abstract

The meridional circulation cells of the Southern Ocean are investigated using the results from a fine-resolution primitive equation model. Zonal integration along depth levels shows the classical series of meridional cells but integration along density layers shows a number of differences, including the virtual disappearance of the Deacon cell. To investigate the differences, the meridional transport is calculated as a function of both density and depth. The results show that the Deacon cell is associated with systematic changes in the depth of density surfaces between the western boundary current region off South America and the return flow in the interior of the ocean. Water flowing on each density surface produces a meridional cell with a vertical excursion of a few hundred meters. Thew cells combine, without water crossing density surfaces, to produce a single integrated Deacon cell extending from the surface to below 2000 m. The results also show that, at each latitude, water on each of the density surfaces in the upper layers of the ocean systematically transfers angular momentum from the shallowest depths at which it is found to deeper depths. In this way the torque, due the wind acting on the surface of the ocean, is transferred downward, in a series of steps between water masses of increasing density, until it is finally lost as a pressure torque acting on the ocean bottom topography.