Generation of internal lee waves trapped over a tall isolated seamount

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Abstract
A primitive equation numerical model is used to study the generation of internal lee waves in a steady, rotating, uniformly stratified flow past an isolated seamount. We find that large-amplitude internal lee waves can form over the seamount even when the imposed steady flow is too 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 leads to a large local acceleration of the flow. As the flow decelerates downstream of the seamount, the internal lee wave amplitude and wavelength are reduced to the point where parameterized subgridscale mixing quickly dissipates the waves. This contrasts with the traditional case of internal lee waves in rapid background flows where the local acceleration over the seamount is relatively unimportant and the waves continue well downstream of the seamount. The model results also indicate that the trapped internal lee waves form within a few days following flow initiation, suggesting that they may be excited by more realistic temporally varying oceanic flows.