Modelling processes influencing wind-induced internal wave generation and propagation

Abstract

The importance of the oceanic lateral boundary layer mixing in the shelf edge region upon oceanic mixing and hence ocean circulation and climate is briefly reviewed with references to the literature for detail. The role of internal waves in this mixing and the various processes producing these waves is considered. References to the literature and numerical calculations using a three-dimensional model are used to demonstrate the importance of internal waves in mixing. Comparison of results from idealized cross-sectional and single point models illustrate some limitations of single point models in reproducing the mixed layer thickness and associated current profiles. In nearshore areas where the water is well mixed, calculations show that internal wave generation occurs at the front between the stratified and coastal region. Non-linear effects due to vorticity in the frontal jet, and sloping isotherms can lead to internal wave trapping with locally enhanced turbulence and mixing. The importance of using a three-dimensional model that can take account of along and across shelf internal pressure gradients in generating internal waves is demonstrated. The non-linear coupling between near-inertial motion and the internal tide in shelf edge regions is shown to be an important process in oceanic lateral boundary mixing. The need for future high resolution models that can take account of internal waves and associated mixing, together with accurate and comprehensive data sets for validation, is stressed in the final section.