Interactions between sea surface temperature over the South Atlantic Ocean and the South Atlantic Convergence Zone

Interactions between the sea surface temperature (SST) over the South Atlantic Ocean ( 40 degreesS-Equador) and the South Atlantic Convergence Zone (SACZ) were studied through numerical experiments with an atmospheric general circulation model (AGCM) and an ocean general circulation model (OGCM). The AGCM experiments showed that warm SST anomalies over the South Atlantic tend to intensify the SACZ and shift it northward, while cool SST anomalies over the South Atlantic tend to weaken the SACZ. The OGCM experiments, on the other hand, showed that the intensification of the SACZ contributes to cool the underlying ocean through the reduction of incident shortwave solar radiation, causing the appearance of cold SST anomalies or the weakening of pre-existing warm SST anomalies. The most important finding in this work was the predominance of the cloud/shortwave - SST negative thermodynamic feedback between the atmosphere and the ocean over the southwest tropical Atlantic, this is one order of magnitude larger than the dynamic feedback associated with Ekman pumping. The latter was verified only during strong SACZ events. The results suggest that negative SST anomalies often observed underlying the SACZ represent an ocean response to atmospheric forcing.