The Role of Boundary Layers in the Large-scale Ocean Circulation

Understanding the mechanisms governing the ocean circulation is a challenge for geophysicists, but also for mathematicians who have to develop tools to analyze these complex models (involving a large number of time and space scales). A particularly important mechanism for the large-scale circulation is the boundary layer phenomenon, which accounts for a macroscopic part of the energetic fluxes. We will show here using a very simplified model that it explains in particular the Western intensification of currents. We will then exhibit the mathematical difficulties arising in more complex geometries.