Maintaining the inshore shear of continental boundary currents

It is suggested that the large inshore shear of Western Boundary Currents, such as is observed on the continental slope of the Florida Current, can be maintained by instability waves which produce a downgradient potential vorticity flux and an upgradient flux of relative vorticity. This is shown for a non-inflected barotropic shear layer above continuously varying bottom topography, and also for a ‘ 1 1 2 layer’ quasi-geostrophic current bounded below by a density interface. The linear eigenfunctions are substituted into the nonlinear potential vorticity equation to obtain the mean vorticity tendency, and then the quantitative increase (in the case of the barotropic model) is computed by a pseudo-spectral calculation of the nonlinear equation.