Frictional dissipation at the interface of a two-layer quasi-geostrophic flow

In two-layer ocean circulation models the possible dissipation mechanism arising at the interface between the layers is parameterised in terms of the difference between the horizontal velocities of the flow in each layer. We explain and derive such parameterisation by extending the classical Ekman theory, which originally refers to the surface and to the benthic boundary layers, to the interface of a quasi-geostrophic, two-layered flow.