A study of currents south of Africa using Geosat satellite altimetry

Geosat altimeter data were used to study a region to the south and east of South Africa, which includes the Agulhas Current System and the Antarctic Circumpolar Current (ACC). The sea surface height variability was determined from 2 years of Geosat altimeter data by collinear techniques. Strong association was found between variability and changes in topography, even at scales of 100–200 km. The height anomaly profiles were used to determine geostrophic current speeds of the order of 20 cm s −1 for the ACC and up to 138 cm s −1 for the Agulhas Current System. Correlation length scales of the height anomalies were found to agree with the first internal Rossby radius of deformation. Differences appear to be related to physical mechanisms such as wind forcing and topographic stretching which alter the vorticity balance of the Agulhas Current System.