SIMULATION OF THE SOUTH ATLANTIC-OCEAN CIRCULATION AND ITS SEASONAL VARIABILITY

The high-resolution Princeton Ocean Model is used to simulate the circ ulation and seasonal variability of the South Atlantic Ocean. A diagno stic calculation, using the Levitus annual mean fields and forcing con sisting of the climatological annual mean wind stress, produces a real istic steady circulation pattern. In particular, the meridional overtu rning cell shows equatorward how in the surface and intermediate water s and poleward how at depth. Associated with this circulation is a nor thward heat transport that reaches a maximum of 1 PW near 20 degrees S . The model results are improved when the density field near the ocean bottom is allowed to deviate from the Levitus values. Using forcing c onsisting of observed monthly wind stress, heat flux and a prescribed seasonally varying Antarctic Circumpolar Current (ACC), a prognostic c alculation is next carried out to study the seasonal variability in th e South Atlantic Ocean. With a realistic heat flux, the model output f or the seasonal thermal field compares well with that in the Levitus d ata. An analysis suggests that the seasonal cycle of the Brazil Curren t separation latitude, as well as the strength of the Falkland-Malvina s Current depends more strongly on the prescribed seasonal variability in the strength of the ACC than on the seasonal variations in wind an d buoyancy forcing in the South Atlantic.