Wave-Induced Turbulence and Upper-Ocean Mixing
Alexander Babanin
Swinburne University of Technology, Melbourne, Australia
Ocean surface waves are routinely treated as irrotational and therefore not able to
generate turbulence other than that caused by the breaking. This is, however, only true
in non-viscous approximation of the water motion, and real water waves produce
turbulence which, unlike the breaking turbulence concentrated near the surface, is
distributed through the water column and can facilitate the mixing and other dynamic
processes in the upper ocean.
In the presentation, concept of the wave-induced non-breaking turbulence will be
discussed first. Laboratory and field measurements of such turbulence will be
demonstrated. They allow us to estimate intensity of the turbulence, rate of mixing of
stratified fluid due to non-breaking turbulence, response of the depth of the mixed
layer to the passage of an ocean storm. Including such turbulence into ocean-mixing
schemes brings about very significant effects and essentially, sometimes critically
improves agreement between the models and observation. This will be demonstrated
by estimating swell propagation across the ocean, modelling sediment suspension in
finite-depth seas, sea-temperature distributions, as well as climate with a model of
intermediate complexity. Finally, fully nonlinear wave model coupled with turbulence
model will be presented.