No abstract

[1] Circulation in the north Indian Ocean is influenced by both local and remote wind forcing. So far, however, determining the contribution of these two forcing mechanisms at a location has been possible only in numerical experiments. Here we separate remote and local forcing in observations. Using field measurements (current, sea level, and wind) for a month during March-April 2003 off Goa in the near-coast regime of the West India Coastal Current (WICC), we show that the current was driven by local winds only at periods less than $10 days, with remote forcing contributing at longer periods. The high-passed (HP; period less than 10 days) component of the along-shore current was strongly correlated with the HP component of the along-shore wind, the current lagging the wind by half a day. The low-passed (LP) components of the wind and current were not correlated: the former was unidirectional, but the latter reversed during the period of observation. The relationship between the HP wind and current was used to estimate the locally forced LP current, permitting an estimate of the remote current, the LP residual. This separation of locally forced and remotely forced currents showed that remote forcing contributed as much as local forcing to the WICC. The local current behaved like a classical eastern boundary current forced by local winds. The reversal in the remote current was due to winds 700 km farther south along the coast; frictional damping had an impact only at periods less than 10 days, there being no remotely forced HP current.

Abstract:An oil spill occurred off Goa, west coast of India, on 23 March 2005 due to collision of 2 vessels. In general, fair weather with weak winds prevails along the west coast of India during March. In that case, the spill would have moved slowly and reached the coast.

The Gulf of Kachchh is a funnel shaped, macrotidal water body located in the arid region of northwestern India with ~ 50 cm annual rainfall and insignificant fluvial input. The Gulf waters, however, have high-suspended matter. Time series measurements of total suspended matter (TSM) and synchronous, validated hydrodynamic modeling have been used to decipher the dispersal pathways and the sources of the high turbidity. Contrary to the prevalent offshore reducing trend for most of the Indian Coast, the Gulf is anomalous for having an enhanced turbidity at the mouth with lower concentrations in the inland areas. The hydrography of the Gulf is dominated by strong, alongshore currents at the mouth which move in (out) during flood (ebb), and undergo cyclic, dynamic changes with tidal phases. The flood tidal currents amplify inland with propagating tides, pulling in the offshore waters and acting as a feeder of high saline, turbid offshore waters into the Gulf, most of which are trapped inland due to time lag of ebb and flood between the outer and the inner Gulf. Based upon the distribution maps of TSM and clays in the water column, it is deduced that a large segment of the Gulf is nourished by contributions from the Indus River.