The Southern Boundary of the South Atlantic

Abstract

The boundary region between the South Atlantic and Southern Ocean is discussed making use of results from the FRAM model and hydrographic sections. Although, at first, the system appears to be a simple one, with a sub-tropical gyre to the north abutting a zonal jet to the south, the detailed structure is more complex. Part of the complexity is well known and arises from the large scale thermohaline circulation, water being transported north in the surface Ekman layer and at depth, and returning south at intermediate levels. More recent work has shown that, in addition, the sub-tropical gyre and the Antarctic Circumpolar Current combine to form the Deacon Cell which transforms surface stress due to the wind down to mid-depths. Further complications arise from the Agulhas eddies which pass through the regions and the constraints on the circulation due to the bottom topography.