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Bay of Bengal

In Bangladesh, the Ganges River flows in from the west and meets up with the Brahmaputra River flowing in from the east. The two rivers join and flow out to the Bay of Bengal through the Mouths of the Ganges. At top are the Himalaya Mountains in Nepal. (Photo: Jacques Descloitres, MODIS Rapid Response Team, NASA/GSFC)

The Bay of Bengal is the northeastern part of the Indian Ocean, located between the Indian peninsular in the west and Burma (Myanmar) to the east. The bay receives many large rivers forming fertile and heavily populated deltas.


The enormous sediment input from the rivers made the interior bay a rather shallow sea, and the drained waters significantly reduce the surface salinity along the coast. The Ganges cone spreads far out into the Bay of Bengal and gently slopes towards greater depths, while the narrow continental shelf slopes rather steeply break to the deep sea.


The central surface circulation of the Bay of Bengal is characterized by a large cyclonic gyre surrounded by anti cyclonic cells influenced from fresh water. Northward currents along the eastern Indian coast during spring and summer are replaced by southward flow in fall and winter. This current reversal is due to the prevailing wind directions during southwest and northeast Monsoons (see: ”Story”). During transition periods the oceanographic situation becomes more complicated.


The climate of the Bengal region varies from tropical to subtropical conditions. High precipitation rates during the hot summer make the coastal areas fertile arable land.


The major export fish is prawn. Other important fisheries include several tuna species. Fishing by local fishermen from surrounding coastal countries is largely artisanal, representing roughly 60 to 90 percent of the entire catch. Conventional species are nearly over-exploited, but non-traditional and off shore species are rather under exploited.


Much of the coastal mangroves already died and multi-species communities were reduced towards single-species domination. Along few coastal areas, the prawn catches significantly declined due to agricultural pollution and industrial waste drained by the rivers. High levels of pollutants exceeding permitted limits were traced in the coastal waters, with even extreme levels near cities and ports.


The surrounding coasts of the Bay of Bengal were strongly colonized by the Portuguese. One of the main installations was the town of Sao Tomé de Melipore near today’s Madras. In 1522, the Portuguese constructed a church at that site and in 1523 a new city was born. At the beginning of 1600, Sao Tomé had grown considerably. Although Europeans certainly played an important role in the development of the Bengal region, they were rather followers than initiators. Today scientists believe that the impact of ancient European trade was overemphasized; it could be shown that the share of Asian merchants in regional import and export of e.g. textiles and raw silk in the Bay of Bengal even in the mid-eighteenth century was larger than that of the Europeans.





The Bay of Bengal is influenced by the wet southwest summer Monsoon and the colder, dryer continental northeast Monsoon during winter.


The southwest Monsoon dominates from June through September with southwest maritime winds bringing strong rainfall to most of the area. The normal onset of the southwest Monsoon is about 1 June. Because of the critical importance of Monsoon rainfall to agricultural production in the coastal wetlands, predictions of the monsoon's arrival date are eagerly watched by government planners and agronomists who need to determine the optimal dates for plantings.


The precipitation can reach as much as 25 millimeter per day in certain zones. Monsoon rains and coincident destructive cyclone storms recurrently cause great loss of life along the bay's northern coast. On the average, four to six Monsoon depressions form in the Bay of Bengal during the southwestern Monsoon season.


By early October the southwest Monsoon has withdrawn from most parts of the area and the dry, continental Monsoon winds from northeasterly directions prevail during November and December.


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