We illustrate the mechanisms controlling the spatial patterns of biological productivity in the Southern Ocean using a coupled, physical-biogeochemical-ecological model. The model captures a belt of enhanced export production, figuratively termed as the Antarctic Circumpolar Productivity Belt. As observed, there is a maximum in silica export to the south of the peak in the organic carbon export. We show that the meridional and zonal structures of the productivity belt are strongly controlled by the residual mean circulation; the net effect of the Ekman flow and the eddy-induced circulation. The belt of maximum silica export coincides with the region of residual mean upwelling which supplies silica, iron and phosphate to the surface. The peak of organic carbon export is shifted to the north and is located at the boundary between iron and phosphate limited regimes. Here the equatorward residual mean flow supplies phosphate and aeolian deposition provides iron.