Hydrophysical manifestations of the Indian ocean tsunami

Abstract

The horrendous destruction caused by the tsunami waves due to the earthquake in the west coast of northern Sumatra (3.307 degrees N; 95.947 degrees E) at 30 km depth with a magnitude of 9.3 on Richter scale at 00.59 UTC on 26 December 2004, has been described in detail by several authors. This chapter summarises the results of our investigations on the hydrophysical manifestations (salinity and temperature, coastal currents, internal waves, etc.) of the tsunami on the coastal environments in India. The National Institute of Oceanography (NIO), Goa, its Regional centre at Visakhapatnam and the National Centre for Antarctica and Ocean Research (NCAOR), Goa, jointly organised two cruises on board ORV Sagar Kanya during 3-15 January and 16 January-21 February 2005, to study the impact of tsunami in the Bay of Bengal and Andaman region. From the post-tsunami cruise on board Sagar Kanya during 16 January-21 February 2005, from Chennai to Andamans, it was observed that the sea surface temperature (SST) was 27 degrees C off Chennai. The mixed layer depth (MLD) varied from 50 to 100m between 80 degrees 52 minutes E and 87 degrees E and thereafter it decreased to 70m towards Andamans. Salinity varied from 32.8 to 33.9 psu along the west-east section (13 degrees N) and the low salinity (31.7 psu) was observed near the Andaman Islands. High values of salinity (35.2 psu) and temperature (29 degrees C) were observed around 100m depth in the region, 83-84 degrees E. The Visakhapatnam Centre organised a short cruise on board CRV Sagar Sukthi during 3-10 January 2005, to study the impact of tsunami on temperature, salinity and currents in the coastal waters off Visakhapatnam coast. The effect of the tsunami waves on internal waves, acoustic losses and propagation are also studied.