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Observed mixed standing-wave signatures in Cochin Estuary on the southwest coast of India

DRS at CSIR-National Institute of Oceanography

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Title Observed mixed standing-wave signatures in Cochin Estuary on the southwest coast of India
 
Creator DineshKumar, P.K.
Srinivas, K.
Muraleedharan, K.R.
Thottam, T.J.
 
Subject standing waves
estuarine dynamics
water level
water currents
 
Description Study of the characteristics of currents and water-level variations in the Cochin estuary reveals, for the first time, unique signatures of mixed standing-waves in the southern region. Analysis of the simultaneous water-level data generated at the mouth of the estuary, located about 45 km upstream, showed very little dissipation had taken place in the tidal amplitudes, implying that tides are amplified because of a physical barrier. The amplitudes of the major tidal constituents O sub(1), K sub(1), M sub(2), and S sub(2) were 87, 87, 83, and 79%, respectively, of the values close to the sea. The M sub(2) tide was found to be the maximum, followed by the K sub(1), S sub(2), and O sub(1) constituents. Sea level was found to be largely forced by the astronomical tides at both the locations. The nontidal time series at the two locations correlated strongly, with the percentage of the variance explained by the relationship being about 82.3%. Currents and their displacements were found to be of low magnitude but revealed significant spatial variability, even though they were closely spaced. As compared with the cross-shore currents, the alongshore currents were highly coherent, with clear signatures of tidal forcing. Further, tidal analysis of synchronous data on various parameters-water level, alongshore and crossshore currents, temperature, and salinity-revealed the relative dominance of the various tidal constituents. The water temperature peaked during late afternoon, suggesting solar forcing, whereas salinity variation, though quite low in range, showed signatures of tidal forcing. A scatter plot of water level and spatial average of alongshore currents revealed correlations of minima in overtide velocity amplitudes. The magnitude of the currents was very small and not proportional to the tidal heights observed. Intense mixing is closely related to the horizontal velocity shear, which causes mixing sufficient to destratify the water column. Resonance of the M sub(2) tidal wave may be possible because of the length and depth relation in the estuary, and the results suggest overtides are the causative factor
 
Date 2009-12-18T11:43:07Z
2009-12-18T11:43:07Z
2009
 
Type Journal Article
 
Identifier Journal of Coastal Research, vol.25(5); 1106-1113
http://drs.nio.org/drs/handle/2264/3478
 
Language en
 
Rights Copyright [2009] Coastal Research Foundation. All efforts have been made to respect the copyright to the best of our
knowledge. Inadvertent omissions, if brought to our notice, stand for correction and withdrawal of document from this repository.
 
Publisher Coastal Research Foundation