Using ocean models of different complexity we show that opening theIndonesian Passage between the Pacific and the Indian oceans increases theinput of Indian Ocean water into the South Atlantic via the Agulhas leakage.In a strongly eddying global ocean model this response results from anincreased Agulhas Current transport and a constant proportion of Agulhasretroflection south of Africa. The leakage increases through an increasedfrequency of ring shedding events. In an idealized two-layer and flat-bottomeddy resolving model, the proportion of the Agulhas Current transport thatretroflects is (for a wide range of wind stress forcing) not affected by anopening of the Indonesian Passage. Using a comparison with a linear model andprevious work on the retroflection problem, the result is explained as abalance between two mechanisms: decrease retroflection due to large-scalemomentum balance and increase due to local barotropic/baroclinicinstabilities.
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