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Physical oceanography of the Bay of Bengal and Andaman Sea
Varkey, M.J.; Murty, V.S.N.; Suryanarayana, A. (1996). Physical oceanography of the Bay of Bengal and Andaman Sea. Oceanogr. Mar. Biol. Ann. Rev. 34: 1-70
In: Oceanography and Marine Biology: An Annual Review. Aberdeen University Press/Allen & Unwin: London. ISSN 0078-3218, more
Peer reviewed article  

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  • Varkey, M.J.
  • Murty, V.S.N.
  • Suryanarayana, A.

Abstract
    Physical oceanography of the Bay of Bengal and Andaman Sea is reviewed for the first time. All available information for over 50 years is consolidated in this review. To begin with, information on peripheral or related aspects of climate of the hinterland, such as pressure, rainfall, storms, winds, sunshine etc., are presented. The Bay of Bengal and Andaman Sea are divided into two regions, viz., the coastal belt and the open ocean areas, on the basis of large differences in water properties. Considerable variation in salinity and density exists all over the coastal areas due to abundant freshwater discharges, especially during the rainy months. The coastal circulation is mainly driven by river runoff and wind thrust and is influenced by branches of the Equatorial Current system. Strong wind-driven upwelling and sinking are seen along the eastern Indian coast. The surface circulation system in the Bay of Bengal and Andaman Sea can be divided into three gyres, viz., (a) the northwestern gyre, (b) the large gyre in the southern Bay of Bengal and (c) the Andaman gyre. Gyres are noted also at 500m and 1000m. The net water exchanges [Evaporation (E) + Precipitation (P) + Runoff (R)] at surface, for the whole area north of 5°N are -11.5 cm and + 63.7 cm during the winter monsoon and summer monsoon, respectively. The net water transports across 6°N between surface and 1250m, are found to be -79 x 1012m³ and + 129 x 1012m³ for winter monsoon and summer monsoon periods, respectively. High salinity water masses from the Red Sea, Persian Gulf and eastern and southern Arabian Sea flow into the Bay of Bengal and play an important role in its water structure. A strong gradient of surface temperature is observed during winter (25.5 to 28.5°C) from the head of the Bay to 5°N; similarly for salinity (21.0 to 34.5ppt) during summer. Variation in mixed layer thickness is greater during summer (about 25 to 100m) and less during the winter (60 to 100m). Abyssal water flows and properties are least studied in the Bay of Bengal.

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