EMERGENCE OF INERTIAL GYRES IN A 2-LAYER QUASI-GEOSTROPHIC OCEAN MODEL

The emergence of Fofonoff-like flows over a wide range of dissipative parameter regimes is explored in a wind-driven two-layer quasigeostrop hic model. Two regimes are found in which Fofonoff-like circulations e merge as a direct consequence of the baroclinic nature of the system, since the wind forcing used in these experiments has been shown to inh ibit the formation of Fofonoff flows in the barotropic case. The first regime is one in which the magnitudes of the frictional coefficients (viscosity and bottom dissipation) are extremely small. The experiment s clearly illustrate the transition of the numerical solution from a c onventional wind-driven circulation to an inertial Fofonoff-like regim e. The latter circulation first appears in the lower layer and then sp reads throughout the water column via barotropization. The second regi me, surprisingly, is obtained with very high bottom friction. This res ult indicates that entropy can be maximized independently in each laye r, depending on the distribution of forcing and dissipation. This shed s a new perspective on the common assumption that forcing and dissipat ion are disruptive effects that prevent the system from displaying a F ofonoff state.