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indonesian throughflow

The Indonesian Throughflow (ITF) transfers heat and freshwater from the Pacific to the Indian Ocean. The ITF therefore exerts a control on regional environments through the Asian and Australian monsoons, and probably also on global climate through its effect on the global thermohaline circulation. Today, the bulk of the mass transport through Indonesia occurs at subsurface levels in the thermocline, hence having a net cooling effect on the tropical Indian Ocean (Gordon, 2005). The flux rate and hydrographic structure of the ITF are, and have been, variable on all timescales, from seasonal through ENSO to geologic. The major inflow passage to Indonesian archipelago waters is Makassar Strait, leading into Lombok Strait and the eastern Indonesian seas (Banda Sea). The main exit passages of ITF into the eastern Indian Ocean are Ombai Strait and Timor Passage. The geometry, hydrography and atmospheric dynamics of the pathways control the ITF intensity.

At 3-5 Myr ago, when Australia and Papua lay 2°-3°S of their present position, there was also a seaway between the Pacific and Indian Oceans as wide and deep as the Makassar Strait. The changing geometry of the Indonesian seaway could be responsible for remote climate changes, e.g., the aridification of Africa approx. 5 Myr ago. Around that time, the northward displacement of Papua may have switched the source of flow through Indonesia from the warm tropical Pacific to relatively cooler North Pacific waters. This may have decreased the SST in the Indian Ocean, leading to reduced rainfall over eastern Africa (Cane and Molnar, 2001).



References:

Cane, M.A. and P. Molnar (2001), Closing of the Indonesian seaway as a precursor to east African aridification around 3-4 milion years ago, Nature, 411:157-162.