GENERATION OF MESOSCALE FLOWS OVER THE SHELF AND SLOPE BY SHELF WAVE SCATTERING IN THE PRESENCE OF A STABLE, SHEARED MEAN CURRENT

A linearized barotropic model is used to investigate the scattering of barotropic shelf waves by variations of the shelf width in the presen ce of a sheared but stable mean along-shelf current located over the c ontinental slope. The mean current is chosen to eliminate all backward propagating waves, so no energy is reflected from the scattering regi on. In addition, the mean current shear severely limits the number of forward propagating waves which carry energy downstream from the scatt ering region. For a narrowing shelf this tends to increase the strengt h of the scattering and, more importantly, generates large-amplitude e vanescent modes which dominate the velocity fields within and slightly upstream and downstream of the scattering region. When viewed in comb ination with the mean current, the wave scattering forms intense mesos cale flows between the mean current and the coast. This mechanism may be partially responsible for the highly variable and energetic flows o ften associated with along-shelf currents found over many continental slopes.