Note on the beam structure in step-trapped internal tides

Abstract

The along-slope propagation of sub-inertial trapped internal tides is studied for the configuration of a simple step. It is revealed that they form a beam structure in the along-slope direction that is evanescent above the top of the step; these beams lack strict periodicity in the along-slope direction. As in classical internal Kelvin waves, they become less sharp away from the step, as higher modes decay more rapidly in the cross-slope direction. We discuss implications for abyssal mixing and outline the necessary ingredients for their generation.