Indian Ocean: Encyclopedia II - Indian Ocean - Environment

Indian Ocean - Environment

The African, Indian, and Antarctic crustal plates converge in the Indian Ocean. Their junctures are marked by branches of the Mid-Oceanic Ridge forming an inverted Y, with the stem running south from the edge of the continental shelf near Mumbai, India. The eastern, western, and southern basins thus formed are subdivided into smaller basins by ridges. The ocean's continental shelves are narrow, averaging 200 km (125 mi) in width. An exception is found off Australia's western coast, where the shelf width exceeds 1,000 km (600 mi). The average depth of the ocean is 3,890 m (12,760 ft). Its deepest point, in the Java Trench, is estimated to be 7,450 m (24,442 ft). North of 50° south latitude, 86% of the main basin is covered by pelagic sediments, of which more than one-half is globigerina ooze. The remaining 14% is layered with terrigenous sediments. Glacial outwash dominates the extreme southern latitudes.

Indian Ocean - Climate

The climate north of the equator is affected by a Monsoon wind system. Strong northeast winds blow from October until April; from May until October south and west winds prevail. In the Arabian Sea the violent monsoon brings rain to the Indian subcontinent. In the southern hemisphere the winds generally are milder, but summer storms near Mauritius can be severe. When the monsoon winds change, cyclones sometimes strike the shores of the Arabian Sea and the Bay of Bengal.

Indian Ocean - Hydrology

Among the few large rivers flowing into the Indian Ocean are the Zambezi, Arvandrud/Shatt-al-Arab, Indus, Ganges, Brahmaputra, and Irrawaddy. Currents are largely controlled by the monsoon. Two large circular currents, one in the northern hemisphere flowing clockwise and one south of the equator moving counterclockwise, constitute the dominant flow pattern. During the winter monsoon, however, currents in the north are reversed. Deepwater circulation is controlled primarily by inflows from the Atlantic Ocean, the Red Sea, and Antarctic currents. North of 20°south latitude the minimum surface temperature is 22°C (72°F), exceeding 28°C (82°F) to the east. Southward of 40°south latitude, temperatures drop quickly. Surface water salinity ranges from 32 to 37 parts per 1,000, the highest occurring in the Arabian Sea and in a belt between southern Africa and southwestern Australia. Pack ice and icebergs are found throughout the year south of about 65°south latitude. The average northern limit of icebergs is 45°south latitude.

Adapted from the Wikipedia article "Environment", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki