Frontal Eddy

A frontal eddy is a mesoscale to submesoscale vortex that forms along a sharp ocean front, where a strong horizontal density and velocity gradient becomes baroclinically or barotropically unstable and rolls up into a coherent swirl. Frontal eddies are common on the cyclonic shoreward edge of western boundary currents such as the Gulf Stream, with diameters of tens of kilometers and lifetimes of days to weeks. They pump cold, nutrient-rich water upward, drive cross-frontal exchange of heat, salt, and biota, and locally distort the surface current field. For ship routing they create patchy surface currents and surface-temperature contrasts that satellite altimetry and sea-surface-temperature imagery resolve.