Wave-induced upper-ocean mixing and climate modelling

In air-sea interaction models, the wind stress is usually parameterised to directly drive the dynamics of the upper ocean, that is the wind stress provides a momentum flux to the ocean surface and the flux is then diffused down by means of turbulence. The dominant part of the wind stress, however, is supported by the flux of momentum from the wind to waves. This means that, before the momentum is received by the upper ocean in the form of turbulence and mean currents, it goes through a stage of surface wave motion. This motion can directly affect or influence the upper-ocean mixing and other processes, and thus disregarding the wave phase of momentum transformation may undermine accuracy of such parameterisations. There are at least two processes in the upper ocean which can deliver turbulence directly to the depths of the order of 100m instead of diffusing it from the top. First process is Langmuir circulation. Another mechanism is the wave-induced turbulence (in absence of breaking). The concept of this turbulence, its estimates and measurements, as well as implications of such turbulence for ocean circulation models, will be discussed.