Satellite comparison of the seasonal circulation in the Benguela and California current systems

Abstract

Satellite surface height and surface temperature fields are used to examine the seasonal surface circulation in the Benguela and California Current systems. In the California Current system, an equatorward jet develops in spring and summer near to the coast, with a latitudinal structure that responds to the equatorward longshore winds. This jet moves offshore from spring to autumn and contributes eddy kinetic energy to the deep ocean. In the Benguela system north of 32°S, winds are upwelling-favourable and currents are equatorward all year, but stronger in summer. The current strengthens in summer, when water parcels with high steric heights move into the region offshore of the jet from the Agulhas Retroflection area at the same time that steric heights next to the coast drop as a result of coastal upwelling. Off the Cape (32–34°S), winds and currents are more seasonal. The Geosat altimeter fields do not resolve the equatorward flow along the SST front next to the coast in spring and summer, but pick up strong equatorward flow off the Cape in autumn and winter, after the front moves offshore.