  "Eddy saturation" is the regime in which the total time-mean volume transport
of an oceanic current is relatively insensitive to the wind stress forcing and
is often invoked as a dynamical description of Southern Ocean circulation. We
revisit the problem of eddy saturation using a primitive-equations model in an
idealized channel setup with bathymetry. We apply only mechanical wind stress
forcing; there is no diapycnal mixing or surface buoyancy forcing. Our main aim
is to assess the relative importance of two mechanisms for producing eddy
saturated states: (i) the commonly invoked baroclinic mechanism that involves
the competition of sloping isopycnals and restratification by production of
baroclinic eddies, and (ii) the barotropic mechanism, that involves production
of eddies through lateral shear instabilities or through the interaction of the
barotropic current with bathymetric features. Our results suggest that the
barotropic flow-component plays a crucial role in determining the total volume
transport.
