Agulhas current variability and inshore structures off the Cape Province, South Africa

Abstract

Satellite imagery over a 3‐year period is used to provide statistical data on the position of the Agulhas Current, frontal features, and meanders off the southeast coast of South Africa. Data recorded during a cruise undertaken over the continental shelf off Algoa Bay in May 1987 provided subsurface temperature data of a large frontal feature and is used to correlate in situ measurements with satellite imagery. It is found that the inshore thermal front of the Agulhas Current lay, on average, at the shelf break northeast of Algoa Bay and seaward of it to the west. Its thermal core was about 26 km further out. The Agulhas Current influences the ocean structures over the shelf area by longer‐term Natal Pulses and shorter term warm surface frontal plume fluctuations. A case study of a rapidly propagating meander (average speed, 42 km/day) showed that an inshore plume formed a thin wedge over the cooler shelf water, and it illustrated that the surface signature as seen by satellite imagery does not necessarily correspond to the subsurface structure. The formation of a large shear‐edge eddy could also be followed and was possibly accentuated by a severe storm.