Meridional flow of source driven abyssal currents

The equatorward flow of source driven deep western boundary currents within a stratified basin with variable topography is examined. The model corresponds to the two-layer quasi-geostrophic equations, describing the overlying ocean, coupled to the planetary geostrophic equations, describing the abyssal layer, on a midlatitude beta-plane. The model retains important sub-approximations such as classical Stommel-Arons theory, the Nof abyssal dynamical balance, the so-called "planetary shock wave" balance (describing the finite amplitude beta-induced westward propagation of abyssal anomalies) and the Swaters's baroclinic instability mechanism between the abyssal current and the overlying ocean. A new steady state balance is identified which connects source-driven equatorward flow (as predicted by the Sverdrup vorticity balance, i.e., Stommel-Arons theory) and the inertial topographically steered deep flow described by abyssal Nof dynamics. In addition, the baroclinic instability characteristics for meridional grounded abyssal flow over sloping topography with beta present are described. Numerical simulations of the fully coupled model exhibit distinct interannual varaibility.