Interaction of high frequency internal waves and the boundary layer on the continental shelf

Intermittent, shoreward propagating packets of high frequency firstmode internal waves are common on the continental shelf when the watercolumn is stratified and may induce large fluctuations in near bottomvelocity. Simple theoretical considerations here lead to an approximatemethod for estimating those quantities of most interest for the bottomboundary layer interaction problem. Examination of data from the pilotCoastal Ocean Dynamics Experiment (CODE I) shows that near bottomvelocity fluctuations in the high frequency internal wave band weredominated by shoreward propagating, intermittent mode 1 internal events.Predictions of CODE I internal wave characteristics using the aboveapproximate method are shown to be good.A boundary layer model is developed, which allows for the nonlinearinteraction of surface waves, internal waves, and a steady current over arough bottom. Modeling results suggest that internal waves willsignificantly enhance the stress felt by the steady current, and canincrease the variability and decrease the reliability of boundary layermeasurements by the "log profile" technique, when the waves are present.Theoretical dissipation of internal wave energy in the bottom boundarylayer is found to be significantly enhanced in the presence of surfacewaves and currents, and may be important to the overall internal waveenergy balance on the shelf.

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution August 1984

My doctoral work was supported for the first three years by an NSFGraduate Fellowship and has been supported since under NSF grantOCE-8014938.