Oceanography (2+1)

Water mass of Indian Ocean

 The characteristics of water masses of Indian ocean are different from those of the other oceans because of its geographic position, climatic conditions, its separation from other regions and the nature of its current pattern.

The important factor which influences the water masses are the air temperature and the differences in precipitation from one region to another region.

There is a large difference in precipitation between the eastern and the western regions in the north. The annual mean precipitation in the North Indian Ocean is about 10cm/yr in the west on the Arabian coast and about 300cm/yr in the east near Sumatra. This is opposite to the situation usually seen on the easten side and heavy precipitation on the western side occurs in the South Indian ocean.The southwestern Australia receives precipitation less than 50cm/yr and Madagascar gets 200cm/yr. The influence of the Asian rivers in bringing fresh water into the Indian Ocean is magnified by the monsoonal climate. The summer monsoon fresh-waters which the Ganges, the Brahmaputra, the Mahanadi, the Godavari and the Krishna rivers brings into the Bay of Bengal; the Indus, the Narmada and the Tapti rivers into the Arabian Sea and the Irrawady and the Salween rivers into the Andaman Sea greatly influence the salinity of the waters in the North Indian ocean.

 The Indian ocean is closed on the northern side by the landmass of Asia at subtropical latitude. As a result, the ocean is separated from deep reaching vertical convection areas in the northern hemisphere and a unique atmospheric circulation known as monsoon circulation is developed, which influences the ocean southwards up to 10°S. The surface current pattern in the North Indian Ocean which changes with the seasonal reversal of monsoon winds influence its water masses. The waters from the Red Sea and Persian Gulf greatly influence the water masses of the Indian Ocean.

 In general, the water masses in the south Indian ocean between subtropical convergence (40°S) and 10°S are similar to those in the South Atlantic because of the similarly of the two regions with respect to latitudinal extent and climatic conditions,