Thermal field and oceanic circulation along the east coast of India

Abstract

From the bathythermographic data, collected during the first 19 cruises of the Andhra University during the period October 1952 to April 1953 along the east coast of India, thermal fields at surface, 40, 100, 200 and 400 feet levels have been constructed for the three seasons,viz., Post-Monsoon, Winter and Summer seasons. The present study is confined to the coastal region between latitudes 13° N. to 18° N. and longitudes 80° E. to 84° E. In addition to this area, during winter season, the study has been extended to an area over theSwatch of No Ground. From the above, circulation has been deduced and the current directions have been entered on the charts. The limitations and the validity of the method in entering the current directions is discussed and further it is shown, from a consideration of the current boundaries, that the method yields a fairly good representation of the oceanic circulation at various depths. Seasonal variation in the thermal structure and the associated circulation is presented.

In the Post-Monsoon and Hot Weather seasons the current pattern indicates turbulence in the surface layers as a consequence of sinking and upwelling. Greater turbulence occurs off Visakhapatnam than off Madras. At a level at which thermocline forms, currents are opposing to those found above and below that level. A nearly isothermal water mass which forms over the continental shelf during the Hot Weather season appears as a semi-permanent feature, keeping its position due to the existing north-easterly current.