A NUMERICAL INVESTIGATION INTO THE BOTTOM BOUNDARY-LAYER FLOW AND VERTICAL STRUCTURE OF INTERNAL WAVES ON A CONTINENTAL-SLOPE

A numerical investigation is made into the vertical structure and boun dary-layer flow of semi diurnal tidal-period internal waves. The Princ eton Ocean primitive equation Model, incorporating the Mellor-Yamada l evel 2.5 turbulence closure scheme, is used to study the flow and turb ulence associated with propagating internal waves ina stratified ocean . Effects of stratification, seabed slope and a background barotropic tide are investigated. Of particular interest is the intensification o f currents near the seabed that occurs for critical or near-critical s lopes when the topographic slope is comparable to the slope of the int ernal wave characteristics. In the absence of friction, infinite inten sification of currents is predicted near the seabed, but realistic bot tom friction and vertical eddy viscosity reduce the bottom currents to about twice the speed of the surface currents. Over critical slopes, maximum current shear and vertical eddy viscosity are achieved. Strong asymmetry occurs between upslope and downslope flows. Downslope flows near the seabed are stronger and have thinner boundary layers than th e upslope flow. Observations are presented of semi-diurnal internal ti des from around the shelf break on the Australian North West Shelf. Bo ttom intensification of currents and asymmetry between upslope and dow nslope flows are observed: in qualitative agreement with the model. 19 98 Elsevier Science Ltd. All rights reserved.