Post-tsunami impact study on thermohaline structure in the Bay of Bengal

Temperature and salinity profiles measured on-board ORV Sagar Kanya, during 18 January-17 February 2005, in the vicinity of the Chennai coast and west of the Andaman (AN) Islands, have been employed to assess and quantify the post-tsunami impact on the upper-ocean thermohaline structure, by comparing these with previous year's data. In the vicinity of the AN Islands, the sea surface temperature increased by 0.5°C and surface salinity decreased from 33.5 to 32 psu, between 90°E and 92°E along 10°N. This freshening has been attributed to westward geostrophic flow from the AN Sea facilitated by a sea surface height gradient inferred from the merged multi-mission satellite data. Significant temperature variations exceeding 1°C were observed between 50 and 250 m, west of the AN Islands. Near the Chennai coast (10°N, 80.9°E), influx of freshwater from the northern Bay of Bengal reduced salinity by 0.8 psu and stratification in the upper 100 m was observed. Upward shift in the 20°C isotherm was observed at all locations, suggesting a vertical entrainment. In general, this study reveals that considerable thermohaline variability has occurred in the upper 300 m water column, which is expected to have a significant impact on primary production and fisheries