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

摘要

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 degree C and surface salinity decreased from 33.5 to 32 psu, between 90 degree E and 92 degree E along 10 degree 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 degree C were observed between 50 and 250 m, west of the AN Islands. Near the Chennai coast (10 degree N, 80.9 degree 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 degree 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.