Tidally induced turbulent mixing at Irving Seamount—Modeling and measurements

Abstract

The relationship of tidal currents and turbulence over Irving Seamount is examined by model and measurement. Surface tides are partially scattered into internal tides and, particularly over the seamount summit, current strength and shear greatly increase. Current shear causes the model's turbulent mixing. At Irving, modeled turbulent mixing, as represented by vertical diffusivity, is largest O(10−3 m2 s−1) in the bottom boundary layer and in a turbulent column rising to the sea surface directly above the seamount. Pockets of less intense mixing occur within the turbulent column, but their locations are highly variable. Field measurements confirm a turbulent mixing column atop Irving of comparable intensity. Increased model diffusivity (average of 7 × 10−5 m2 s−1) also occurs to a distance of several hundred kilometers from the seamount flanks in a band vertically centered at ∼800 m depth.