A new model for Double Diffusion plus Turbulence

Available models of Double Diffusion (DD) processes (Salt Fingers, SF and Diffusive Convection, DC) are primarily based on laboratory experiments that do not include turbulence which is however always present in the ocean. A reliable DD model for use in OGCMs (ocean global circulation models) is therefore still lacking and a true assessment of the role of oceanic DD is yet to be made. Here, we derive and validate a new model for DD + Turbulence using a second-order closure model which differs significantly from previous ones in that the ratios of the correlation time scales to the dissipation time scales, constant in previous models, now depend on Ri and Rr, the key new feature needed to reproduce both laboratory (no shear) and oceanic (with shear) data. The model can therefore be used in OGCMs. The full mixing model includes mixed layer, internal gravity waves, DD and tides.