Introduction to the “Inter-ocean exchange around southern Africa”

Abstract

Abstract This issue of Deep-Sea Research II contains 12 papers that describe results from field experiments and modeling studies concerning the Indian–Atlantic exchange of water around the Cape of Good Hope. A central theme is the important role of the mesoscale features, such as eddies and filaments, in the leakage of Indian water into the Atlantic. The papers describe new direct-velocity measurements and model simulations, which reveal information about circulation patterns and physical processes that control the inter-ocean exchange. For the first time a large array of subsurface acoustic floats was tracked at the intermediate water level. The float trajectories reveal that the Cape Basin off Cape Town is virtually filled with Agulhas Rings and cyclonic eddies, which interact intensely with each other, change shape, bifurcate, and merge. These energetic eddies dominate the velocity field in the source region of the Benguela Current; they stir the various source waters and advect the blended product westward over the Walvis Ridge. These seminal results have important and lasting implications for our conceptions of the processes involved in inter-ocean exchanges around southern Africa.