Seasonal Currents In The Bay Of Bengal

The advances in satellite oceanography and ocean observation provide new knowledge of circulation patterns and their variability in the Indian Ocean.The Bay of Bengal is the northeastern part of the Indian Ocean.It is surrounded by Sri Lanka and India in the west,Bangladesh in the north and Myanmar in the east,further followed by the Andaman and Nicobar Islands in the east and separates the coast from the Andaman Island.The most striking characteristic is the seasonal reversal of the monsoon winds in the bay.The absence of a temperate and polar region is another peculiarity.The bay exhibits the changes in seasonal circulation with monsoon cycles,heavy cyclonic depressions,and storms on the subcontinent.The western areas partially receive the recirculation of water flow at a high flow rate with intensive western currents and changes in direction twice a year,resulting in far-reaching consequences for the circulation and hydrology.The recently-advanced satellite altimetry data are available for determining currents and changes of circulation patterns.However,there are still limited studies that have carried out on seasonally-changing circulation patterns in this field.The purpose of the study is to find the seasonal changes regarding to the currents,flow patterns and their affecting parameters with changes in time.The observational study is based on the data from the satellite'Doppler',the observational data from buoys,hydrographic cruise data,and satellite-tracked drifter buoys collected during the past 10 years.These data were obtained from newly advanced observations and exhibits an enormous data points to describe the changes in intra-seasonal current patterns.With a difference from the past observations,they explain the intra-seasonal currents qualitatively.As implicated by the observations,the northern part of the bay is one of the highly dynamic areas for the development of internal tides over the shelf slope region.Winds over this area reverse twice a year with the southwesterly winds during summer monsoon and the northeasterly winds during winter monsoon.The bay is affected by the wind stress associated with these winds,leading to upwelling and down-welling separately near the east coast of India.According to the observational studies in the Bay of Bengal,there are significant and apparent changes in the surface circulation and mesoscale variability.Seen from the collected datasets and previous rudimentary observations,there is a minimal change in the estimated velocity in the coastal sea areas.The new observation data have shown that the local along-shore winds and Ekman pumping are the main factors of changes in the currents.Near surface currents as large as 2.25 m/s were observed from Jan 2014-2016,and the currents stronger than 0.4-0.8 m s-1 were confined in the upper 150-200 m depths.Scaled simulations based on local winds also indicated that local currents affect the coastal sea area.This clearly showcases that the change of these patterns appears from the east of Andaman where water is warmer and highly saline in May.The change occurring from South consists of the mixing between cool deep layers and warm surface layer.This clarifies that heavy rapidly-changing river run-off affect salinity level in November and December,which is steady towards the coast.In addition to the coastal Kelvin waves,the westward propagating Rossby wave modulates the eastern and central bay.This observational study also investigated temporal variability of sea surface temperatures affecting seasonally averaged wind speed and significant wave altitude.The patterns analyzed from new observations exhibited complicated currents with seasonal changes in the north eastern part of the Indian Ocean.The new advanced oceanographic observation techniques reveal the inside character of the mean changes.They presented the newly recorded changing patterns of seasonal currents with the help of re-analyzing and computing the combined datasets.Variability in the Bay of Bengal was observed,with some practical implications on changes of coastal processes in a seasonal changing climate scenario.