Oceanic rings and jets as statistical equilibriums states

Equilibrium statistical mechanics of freely evolving two-dimensional and geophysical flows provides an explanation and a prediction for the self-organization of large scale coherent structures. We apply this theory to the description of oceanic rings and jets, in the framework of a $1.5$ layer quasi-geostrophic model.

We explain the spontaneous formation of regions where the potential vorticity is homogenized, with strong and localized jets at their interface.

Mesoscale rings are shown to be close to a statistical equilibrium: the theory accounts for their shape, their drift, and their ubiquity in the ocean, independently of the underlying generation mechanism.

At basin scale, inertial states presenting mid basin eastward jets (and then different from the classical Fofonoff solution) are described as marginally unstable states. In that case, considering a purely inertial limit is a first step toward more comprehensive out of equilibrium studies that would take into account other essential aspects, such as wind forcing.