The Mediterranean Outflow as an Example of a Deep Buoyancy-Driven Flow

Abstract

Motivated by the Mediterranean outflow into the North Atlantic, a simple diffusive layer model of a deep buoyancy-driven circulation driven by a middepth inflow from the eastern boundary is developed. Cross-interfacial velocities are allowed and are related to the stratification through a density equation. The horizontal circulation, cross-interfacial (vertical) velocities, and density stratification are all coupled and are determined by the model as part of the solution. The importance of water masses injected into the ocean interior in driving the deep circulation is demonstrated. The inflow from the eastern boundary turns northward before reaching the western boundary current region and flows along the eastern boundary. The westward distance traveled by the inflow before turning northward can be derived by considering the dissipation of long westward traveling Rossby waves by the vertical density diffusion. Layers above and below the inflow are also set in motion, and their circulation is southward along the eastern boundary, opposite to the direction of the circulation in the inflow layer. The vertically integrated circulation of the model is similar to that in a Stommel-Arons model with the mass source on the eastern boundary: Most of the inflow flows to the western boundary current region, spreads there along the boundary, and reenters the interior as a broad northward current.