Current measurements over the western continental shelf of India

Abstract

Current meter observations obtained from a site off Goa (15 degrees 08'N, 73 degrees 16'E) over the western continental shelf of India are presented. Data were collected from the site during three different months in a water column of depth about 100 m. The nature of flows are describEd. by means of visual display, linear regression and spectral analysis. The flows are a result of the superimposition of oscillations of wide-ranging frequencies over a weak mean flow. The mean flow was towards south during May and March and towards north during November. The spectral analysis indicates that the inertial and semidiurnal frequency motions are the major contributors to the current structure. The inertial currents were concentrated near the surface with a rapid decay towards the bottom. The analysis also indicates that the diurnal and semidiurnal motions are mainly due to baroclinic internal tides rather than due to barotropic surface tides. Above the semidiurnal frequencies the currents were composed mainly of high-frequency oscillations of comparatively low magnitudes. These motions are strongly time-dependent and they may be related to internal waves in coastal waters.