Transient coastal currents and inertio-gravity waves

Abstract

Solutions are found for the flow field generated near a coast by the sudden application of an alongshore wind stress. Alongshore geostrophy is not assumed, and so the near-inertial oscillations are retained. The model is alongshore independent, hydrostatic, continuously stratified, has a well-mixed surface layer, and admits vertical diffusion in the anterior. The asymptotic form of the solution for large time and fixed position shows that the inertial oscillations decay like t −1/2, leaving behind an accelerating coastally trapped baroclinic jet and a steady upwelling circulation. Calculations for up to 5 days show coastal inhibition of the inertial oscillations within the Rossby radius, outside which they increase in large parts of the ocean interior. The increase is due in part to the downward leakage of coastal inertial energy from the mixed layer and in part to the offshore leakage near the bottom. Several weeks may be needed to obtain significant decay everywhere in the flow field. Estimates of certain properties of the inertial oscillations in the model are in fair agreement with observations.