On the Influence of Stratification and Continental Shelf and Slope Topography on the Dispersion of Subinertial Coastally Trapped Waves

Open Access
Publisher Website
Google Scholar
Abstract
The behavior of subinertial, coastally trapped free waves in a continuously stratified ocean is examined using a two-slope topography in which the continental shelf and slope are each represented by a single uniform slope. Surface-intensified stratification is assumed in which the squared buoyancy frequency profile is of the form N2eβz, where N is the buoyancy frequency at the surface (z = 0) and β the vertical decay scale normalized by the deep-sea depth. The continental slope is typically assumed to be steeper than the shelf. Two qualitatively different types of dispersive behavior are distinguished. When (N/f)a2>eβh/2, where f is the Coriolis parameter, a2 the bottom slope of the continental slope, and h the shelf-break depth normalized by the deep-sea depth, then free waves may occur at any subinertial frequency, and each dispersion curve rises to f at some finite alongshore wavenumber (as in the case of baroclinic Kelvin waves). If (N/f)a2<eβh/2, then all of the free-wave dispersion curves are limited to frequencies below some subinertial maximum, but are unlimited in wavenumber. This result is independent of the shelf width or shelf slope. Furthermore, for realistic shelf-break depths (h≲0.2), the result is only weakly dependent on β, and if (N/f)a2≳3 then the lowest-mode dispersion curve generally reaches f at a relatively small alongshore wavenumber (less than or equal to the wavenumber at which the corresponding fiat-bottom, baroclinic-Kelvin-wave dispersion curve crosses f). Thus, because realistic values of (N/f)a2 are typically of order 1 or greater, even seemingly weak stratification may be sufficient to cause the dispersion curves to go to f, and the stratification effects may be crucial for accurately modeling coastally trapped wave behavior, especially when short waves are important as in scattering or resonant interaction calculations.

This publication has 0 references indexed in Scilit: