GENERATION OF INTERNAL LEE WAVES TRAPPED OVER A TALL ISOLATED SEAMOUNT

A primitive equation numerical model is used to study the generation o f internal lee waves in a steady, rotating, uniformly stratified flow past an isolated seamount. We find that large-amplitude internal lee w aves can form over the seamount even when the imposed steady flow is t oo weak to support the internal lee waves away from the seamount (i.e. low Froude and Rossby numbers). These internal lee waves are trapped over the flank of the seamount where nonlinear advection of momentum l eads to a large local acceleration of the flow. As the flow decelerate s downstream of the seamount, the internal lee wave amplitude and wave length are reduced to the point where parameterized subgridscale mixin g quickly dissipates the waves. This contrasts with the traditional ca se of internal lee waves in rapid background flows where the local acc eleration over the seamount is relatively unimportant and the waves co ntinue well downstream of the seamount. The model results also indicat e that the trapped internal lee waves form within a few days following flow initiation, suggesting that they may be excited by more realisti c temporally varying oceanic flows.