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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, C05014, doi:10.1029/2007JC004310, 2008

On the modification of tides in shallow water regions by wind effects

J. Eric Jones

Proudman Oceanographic Laboratory, Liverpool, Merseyside, UK


Alan M. Davies

Proudman Oceanographic Laboratory, Liverpool, Merseyside, UK


Abstract

The influence of non-linear effects upon tides in shallow coastal regions, due to the presence of a significant storm surge is examined using a two-dimensional model of the west coast of Britain. The model has an unstructured grid, designed to have a high resolution mesh in the near coastal region of the eastern Irish Sea, the area chosen as the focus of this study. The influence of tide-surge interaction upon the M2, M4 and M6 components of the tide, due to surges produced by steady uniform wind stresses is examined in detail. Calculations show that in deep regions the tide is unaffected by the surge. However, in shallow coastal regions there is significant modification of tidal elevations and currents. This arises because of changes in bottom stress, and the non-linear interaction term in the hydrodynamic equations. In addition the locations of regions that “wet and dry” are changed during the tidal cycle due to the influence of the surge. This gives rise to significant spatial variations and changes in magnitude of the tide and its higher harmonics depending upon wind stress direction and water depth. These results explain why tidal energy remains in the surge residual in shallow water when it is computed by de-tiding the total signal using a tide only calculation; an effect often found in observed surge residuals.

Received 1 May 2007; accepted 2 January 2008; published 10 May 2008.

Keywords: Finite element; storm surge; U.K. West Coast.

Index Terms: 4504 Oceanography: Physical: Air/sea interactions (0312, 3339); 4534 Oceanography: Physical: Hydrodynamic modeling; 4560 Oceanography: Physical: Surface waves and tides (1222); 4546 Oceanography: Physical: Nearshore processes; 4562 Oceanography: Physical: Topographic/bathymetric interactions.

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 7365310 bytes)

Citation: Jones, J. E., and A. M. Davies (2008), On the modification of tides in shallow water regions by wind effects, J. Geophys. Res., 113, C05014, doi:10.1029/2007JC004310.