Suggested mechanism for the chronic pollution by oil of beaches east of Cape Agulhas,South Africa

The distribution of tar balls over the Agulhas Bank during 1977 and 1978, although variable, was consistent with the oceanography of the region. Mesoscale patches of tar-ball concentrations appeared to move onto the Agulhas Bank from the south between 20 and 21°E, under the influence of prevailing winds and currents. Substantial concentrations were observed inshore and offshore in the region east of Cape Agulhas. Data of a hydrological and meteorological nature, on ship's drift and from drift cards have shown the existence of a zone of surface divergence extending southwards from Cape Agulhas. Surface water east of Cape Agulhas (20°E) tends to move slowly eastwards and northwards and water west of the same longitude has a predominantly westerly component. The surface currents east of Cape Agulhas would tend to move the tar balls, which accumulate in eddies in the area, on shore, whereas west of Cape Agulhas on-shore flow is less pronounced. The residence time of tar balls on the Agulhas Bank appears to be substantial, in the range 2—8 weeks. It is concluded that the beaches between Cape Agulhas and Mossel Bay are highly susceptible to pollution by oil and tar balls.