The Indonesian throughflow has stimulated a lot of oceanographic research due to its important role in the global thermohaline circulation. The sealevel difference between the Pacific and the Indian Ocean was identified by Wyrtki (1987) as the basic force driving the flow. Several research programs have been devoted to estimate the magnitude of the throughflow and understand how it is regulated. It has become obvious that there are large variations in the flow, both on interannual, annual and shorter time scales.
Using a simple model of the Indonesian archipelago described as a number of basins connected by straits, we describe an attempt to understand the mechanisms regualting the throughflows. We find that the flow resistance in the straits is too small to control the magnitude of the flow. Instead we find that the sea level difference across the archipelago almost vanishes due to the build up of a pool of Pacific water in the North Australian Basin, just west of the archipelago. The sea level difference between the Pacific and the Indian Oceans is thereby essentially concentrated to the sealevel difference between this pool and the Indian Ocean. We propose that this pool is drained by baroclinic flow and that the control of the throughflow is excerted by the pool.
Regional winds lead to variations in the drainage of the pool which effects both volume and depth of the pool which in turn give effects on the throughflow as measured in the straits of the archipelago. In accordance with previous research we find that the throughflow is maximum during boreal summer and minimum during boreal winter with a mean flow of about 10 Sv. |
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