Laboratory simulations of coastally trapped waves with rotation, topography and stratification

Abstract

We describe observations of the generation and propagation of coastally trapped waves in the laboratory and their comparison with theory, over a range of values of several experimental parameters. The topography and stratification used consisted of a sloping continental shelf and vertical continental slope with three-layer stratification that could be approximated by an extended version of the Gill and Clarke model [Gill, A.E., Clarke, A., 1974. Wind-induced upwelling, coastal currents and sea level changes. Deep Sea Res. 21, 325-345]. The latter was modified to accommodate a central mixed layer, curved geometry, and friction on the shelf. This configuration represents coastal geometry with large Burger number. The experiments were successful in realizing coastally trapped waves that were consistent with the theoretical expectations. However, the waves propagated more slowly, and for narrow shelves were damped more rapidly than predicted by the theory. The first was attributed to: (i) the effect of stratification on fluid on the shelf, reducing the topographic Rossby wave effect; (ii) the parameterization of the viscosity. The second difference was attributed to the mechanism of generation: the paddle used did not always generate sinusoidal waves, and the subsequent dispersion resulted in a net loss of amplitude.

Tidal currents in the St. Lawrence Island region

“…The dynamics of diurnal tides can be described using the major constituent K 1 . K 1 wave has a maximum amplitude of approximately 40 cm in the region of the shelf break and this amplitude decreases from the shelf break to about 7 -8 cm in the St. Lawrence Island region, thus indicating the presence of trapped shelf waves [Baines et al, 2005]. Mofjeld [1984] suggested that such behavior of the K 1 tidal wave on the Bering Sea shelf resembles a Sverdrup wave generated by an incident wave from the deep Bering basin.…”