Abstract
A linear coastal-trapped-wave (CTW) model is used to examine the effects of large-scale winds, with time scale ranging from a few days to a few weeks, on the West India Coastal Current (WICC), particularly on the shelf off the central west coast of India. We show that unlike the seasonal cycle of WICC, which is primarily forced by the winds along the east coast of India, the high-frequency WICC is mostly driven by the west-coast winds. Nevertheless, the influence of winds as far as Sri Lanka and east coast of India cannot be neglected. Simple numerical experiments with the CTW model show that the strong current observed at Goa (15° N) compared to Bhatkal (13° N) and Jaigarh (17° N) is due to two factors: (1) the superposition of local and remote CTWs and (2) the widening of shelf width north of Goa, which decreases the amplitude of the currents poleward of Goa. If the local winds are weak, the amplitude of current decreases poleward due to friction, and the current at the south leads the north. We also note that the observed phase difference between sea level and alongshore current at Goa could be attributed to the propagation of remotely forced higher-order modes of CTWs.
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Acknowledgements
We would like to thank Dr. Shankar and Prof. Vinayachandran for their comments on the application of CTW theory. We would also like to acknowledge Dr. Sanil Kumar and colleagues from Oceanographic Mooring Group of CSIR-NIO—namely Yogesh, Khalap, Narayan, Mithun, and Prakash Tari—in various cruises of Sagar Manjusha and Sindhu Sankhalp for collection of long-term in situ current data. The CTW codes are obtained from http://www.whoi.edu/fileserver.do?id=60003&pt=2&p=35366. The QuikSCAT data was downloaded from http://www.ifremer.fr/cersat/en/data/download/download.htm. All figures were created using Generic Mapping Tools (GMT) and Ferret.
Funding
Funding for this work was provided by Council of Scientific and Industrial Research (CSIR) through Supra-Institutional Project during 2007–2012 and Ocean Finder from 2012 onwards, by ESSO-INCOIS under the Ocean Observing Systems programme of the Ministry of Earth Sciences, New Delhi, and by Science and Engineering Research Board, Department of Science and Technology. A part of this work is from the doctoral research, carried out at CSIR-National Institute of Oceanography, by P. Amol. This is CSIR-NIO contribution no. 6272.
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Amol, P., Vijith, V., Fernando, V. et al. Impact of local and remote winds on the shelf circulation off the central west coast of India. Ocean Dynamics 68, 1607–1623 (2018). https://doi.org/10.1007/s10236-018-1211-3
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DOI: https://doi.org/10.1007/s10236-018-1211-3