Modelling the depth of penetration of the wind's momentum at super-inertial frequencies due to non-linear effects in frontal regions
A numerical model with a coast and density front is used to examine the influence of the front upon the depth of penetration of the wind's momentum. We find that non-linear processes associated with spatial variations in vorticity play an important role in driving wind-induced currents at depth. Internal wave generation and propagation also occur in the frontal region. For a bottom front, the downward propagation of internal waves in the frontal region is inhibited by the presence of sloping isotherms and a region of enhanced current magnitude develops at depth at the front's edge on the stratified side. For a surface front the presence of enhanced surface vorticity on the well mixed side of the front, means that the wind's energy is trapped in the surface layer. These calculations help to explaining the large spatial variability of wind forced energy found in observations.