The diabatic Deacon cell

Southern Ocean air-sea fluxes from the COADS dataset are examined for compatibility between buoyancy gain and northward Ekman transport. An analysis in density classes points to an upwelling of Upper Circumpolar Deep Water and subsequent buoyancy gain from air-sea exchange as water flows northward in the Ekman layer. The Upper Circumpolar Deep Water layer is too shallow to admit southward geostrophic flow along topography, and an eddy mass flux mechanism for southward transport in this layer to replenish the upwelling is advanced, based on observed large-scale potential vorticity gradients. Estimates of the strength and vertical structure of the meridional flow are given using repeated hydrographic sections and a new climatology.