Observational evidence for remote forcing of the West India Coastal Current

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.

Influence of El Niño and Indian Ocean Dipole on sea level variability in the Bay of Bengal

“…These coastal Kelvin waves influence the east India coastal current and west India coastal current (Shetye et al, 2008;Shenoi, 2010). The intraseasonal variability in the pathways and intensity of BoB coastal Kelvin waves and associated radiated Rossby waves are reported in Rao et al (2010).…”

Inhibition of mixed-layer deepening during winter in the northeastern Arabian Sea by the West India Coastal Current

“…4). The other key process is advection by the WICC, whose seasonal cycle is not locally forced [as realised by Banse (1984) and Shetye and Shenoi (1988)], but has been shown to be primarily forced remotely from the east coast of India (McCreary et al 1993;Shankar and Shetye 1997;Shankar et al 2002), with the alongshore winds off southwest India also playing a role (Shetye et al 2008;Amol et al 2012Amol et al , 2014. These two processes are not necessarily correlated, implying the possibility of considerable interannual variability in the evolution and extent of these deep mixed layers in the NEAS.…”

An appraisal of biological responses and network of environmental interactions in non-mining and mining impacted coastal waters

“…The wind blows from Southwest during May-September and from Northeast during November-February (Luis and Kawamura 2004 and references therein). Moreover, the currents are driven by local winds having periods <10 days (Shetye et al 2008). Taking into account the above discussion, it is possible that there is perhaps movement from anthropogenically less impacted RAT waters (Table 1) to GOA during the sampling season.…”