Boundary Processes in the Ocean: Some Interesting Effect of Stratification and Rough Slopes

School of Oceanography
University of Washington

Abstract-
At the margins of all ocean basins there is a common boundary condition: stratification along a gently sloping sidewall. Here diapycnal mixing is greatly enhanced, nutrients are brought to the surface, and polluted urban water is injected. In the last decade oceanographers have made great progress in the observation, theory, and modeling of this complicated region.

I will focus on the fluid mechanics of how rotating, stratified flow interacts with a sloping boundary. The basic boundary layer solution is the "Arrested Ekman Layer" in which the standard Ekman layer is strongly modified by cross-slope advection of the stratification, leading to a rapid decrease in boundary stress. Another topic of great interest with sloping boundaries is their potential contribution to the mixing of buoyancy across density surfaces: mixing which is required for the global "conveyor belt" or overturning circulation. A major unanswered question is how, and how fast, mixed fluid is exchanged between sloping boundaries and the interior. Tidal currents interacting with kilometer-scale roughness on the continental slope is a prime candidate for forcing this exchange. I present recent research results from this regime.

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