Topographic generation of residual circulation by oscillatory (tidal) currents

Abstract

It is shown that an irregular bottom topography acts as a catalyst for transferring vorticity from the oscillating tidal velocity field to the mean (residual) field. A small scale vorticity field is produced by the Coriolis and frictional torques over an irregular bottom topography and subsequently transferred to the mean field by (nonlinear) advection. The transfer is such as to make the energy density of the mean field largest if the length scale of the bottom topography is of the order of the amplitude of tidal displacement.