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Seasonal Mean Circulation in the Indian Ocean

The Somali current, monsoon currents (coastal currents), Wyrtki jets and ITF are the major current systems affecting the north Indian Ocean. Somali current is closely associated with the Findlater jet and the resultant coastal upwelling. The strong upwelling brings down the seasonal mean SST to below 26 °C off Somalia and the Arabian Peninsula. This further undergoes significant intraseasonal (Roxy and Tanimoto, 2007; Vialard et al. 2012) and interannual (Schott et al. 2009) variability, making it an important process in this part of the Indian Ocean. The monsoon currents are the pathways for the interbasin mass transport between Arabian Sea and Bay of Bengal. This plays an important role in the salt balance in the Bay of Bengal and Arabian Sea. This interbasin mass and salt transport displays strong interannual variability through changes in the circulation patterns of Bay of Bengal (e.g. Thompson et al. 2006; Jensen 2007). The equatorial Indian Ocean is characterized by strong eastward surface currents (Wyrtki jets, Wyrtki 1973) during boreal spring and fall, driven by the prevailing westerlies. The Wyrtki jets are closely related to the heat budget of the tropical Indian Ocean. They deepen the thermocline in the east and raise it in the west (Wyrtki 1973), inducing an east-west thermocline (and temperature) gradient (Gnanaseelan et al. 2012). The ITF links Pacific and Indian Oceans by providing a pathway and modifies the stratification within each of these oceans. In addition to the heat and freshwater balance in the Indian Ocean, ITF plays a significant role in the global circulation (Godfrey and Golding 1981). ITF also displays intraseasonal to decadal variability (Valsala et al. 2010).

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