Post-tsunami oceanographic conditions in southern Arabian Sea and Bay of Bengal

Physical oceanographic conditions along the east and west coasts of India immediately after the recent devastating tsunami are presented here. The thermocline in the southeast coast exhibited trivial downward tilt towards north. A mixed layer deepening (> 50 m) associated with low-salinity (< 34 psu) and relatively colder water is noticed in the Gulf of Mannar region and along east coast of India. The low-salinity waters observed are apparently from the Bay of Bengal, driven along the coast into the Arabian Sea by north equatorial current between equator and 10 degrees N, and the southward-flowing east India coastal current. A high-salinity tongue (> 36.0 psu) was identified as the Arabian Sea high salinity water mass along the west coast of India around 100 m depth up to 10 degrees N. The heat content changes closely followed similar changes in the depth of the 20 degrees C isotherm. Turbidity measurements using light scattering sensor showed the existence of two layers of high-scattering, one around 40 m and the other around 250 m. The shallow high-scattering layer is associated with high chlorophyll a concentration, but the deeper high-scattering layer noticed at shallow stations off the west and east coasts of India may be due to the resuspension of the sea-floor sediments due to turbulence generated by the tsunami.