High-frequency internal waves generated by Langmuir motions over stratified water may be an important source of turbulent mixing below the surface mixed layer. Large eddy simulations of a developing mixed layer and inertial current are employed to investigate this phenomena. Uniform surface wind stress and parallel Stokes drift wave forcing rapidly establishes a turbulent mixed-layer flow, which ( as the inertial motion veers off the wind) generates high-frequency internal waves in the stratified fluid below. The internal waves evolve such that their vector phase velocity matches the depth-averaged mixed-layer velocity that rotates as an inertial oscillation. The internal waves drain energy and momentum from the mixed layer on decay time-scales that are comparable to those of near-inertial oscillations. The high-frequency waves, which are likely to be trapped in the transition layer, may significantly contribute to mixing there and thus provide a potentially important energy sink for mixed-layer inertial motions.
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