Numerical Studies of Coastal Internal-Wave Mixing

Away from surface and bottom boundary layers turbulent mixing is primarily driven by breaking internal waves. While internal wave energy is generated mostly in the form of large-scale waves (typically internal tides), it is the smallest-scale internal waves that break through shear or convective instabilities to produce turbulence. When waves are reasonably linear (as opposed to, for example, strongly nonlinear solitons or bores), the rate of small-scale wave breaking is controlled by and equal to the rate at which energy is transferred from large to small-scale waves through wave-wave interactions. In the open ocean, theories have been developed that use concepts of wave-wave interaction to predict turbulent mixing rates in terms of larger-scale shear and stratification. Such theories, in particular the class known as Gregg-Henyey parameterizations, compare well to observed turbulent dissipation rates.