Impacts of SST Anomalies in the Agulhas Current System on the Regional Climate Variability

Abstract

Abstract The potential impact of the variability in the Agulhas Current system on the large-scale atmospheric state in the Southern Hemisphere is examined, using the monthly near-surface baroclinicity as the key parameter, for the period between September 1980 and August 2002. Dominant patterns of anomalous near-surface baroclinicity found from empirical orthogonal function (EOF) analyses in the region that includes most of the Agulhas Current system show a wide variety of anomaly patterns: some of which indicate spatial shifts in the position of the Agulhas Retroflection and/or Agulhas Return Current. Composited anomalies in various atmospheric fields, sea surface temperature, and the net surface heat flux at the air–sea boundary based on the signals in the EOFs suggest that sea surface temperature anomalies in the Agulhas Current system thermally force the atmosphere on the synoptic scale via modification of the near-surface baroclinicity in March and April and possibly in January and February as well.