Generation and Separation of Mesoscale Eddies from Surface Ocean Fronts

Motivated by observations of sub-mixed layer eddies in the Arctic Ocean, eddy formation is explored through high resolution numerical simulations of the instability of a surface ocean front. Results show that fronts with configurations similar to those observed in the Arctic Ocean are baroclinically unstable and lead to the development of eddies. Most eddies form as dipoles and hence have the potential to self-propagate away from the front; this can explain why the observed Arctic eddies appear at great distances from their assumed frontal formation region. Most dipoles, however, consist of a dominating surface cyclone and a weaker anticylone below, and thus propagate on a curved trajectory with eventual recirculation back to the front. An idealized quasi-geostrophic model of potential vorticity conservation is developed to provide an analytical prediction of the factors (such as frontal parameters) that control dipole trajectories. Theory guided analysis of numerical results shows that within the simulated range of frontal configurations there is a small probability of frontal instabilities leading to the formation of dipoles that can propagate large distances from the front.