It is well known that warm ocean currents can affect the climate of adjacent coastal areas. It was suggested as early as the 1800s that the warm Gulf Stream moderated European weather and climate. What is less well understood is how variations in oceanic temperatures influence continental climates and rainfall. The best-known interannual atmosphere-ocean feedback system is the El Nino-Southern Oscillation (ENSO). South Africa occupies a unique geographic position in the context of the world ocean: it is influenced by a warm western boundary current system to the east and south (Agulhas) and by a cold eastern boundary current system to the west (Benguela). South African workers have linked local climate and rainfall to interannual global ENSO events. Further recent research has demonstrated that significant positive correlations exist between interannual sea surface temperature variability within the Agulhas Current system and South African summer region rainfall variability, in the absence of ENSO events. The next step in the research is to examine the detailed mechanisms (e.g. moisture fluxes, changes in winds) by which the changes in sea temperatures are linked to altered rainfall patterns. One of the most important oceanic areas identified is the Agulhas Current Retroflection region to the south of the country, which feeds large amounts of heat and moisture into the marine boundary layer. Under certain synoptic conditions, this modified marine boundary layer is available to influence the South African weather and climate directly. Correlation studies between oceanic surface temperatures and South African summer rainfall have shown the importance of the surrounding ocean to the climate and rainfall of this country, and deserve to be explored more fully.
