Interactions between near-inertial and geostrophic modes in the double gyre problem

The ocean midlatitude double gyre problem is revisited to examine effects of near-inertial modes on the (geostrophic) gyre energetics. This is done in the context of a homogeneous hydrostatic fluid. Generally one also assumes the flow to be depth-independent; however, this assumption is relaxed here. That is, (unstratified) vertical modes, which correspond to inertial oscillations in the linear limit, are retained. We consider the effect of their interaction with the barotropic circulation and describe regimes of oceanographic relevance in which energy transfer from the gyres to the forward energy cascading 3d modes constitute the primary energy dissipation mechanism ---with the more traditional Rayleigh drag playing a lesser role.