Frontal Zone

A frontal zone is a band where water masses of contrasting temperature, salinity, or density meet, producing strong horizontal gradients and, by the thermal-wind relation, an enhanced geostrophic jet aligned with the front. Fronts mark the edges of currents and gyres: the Subantarctic Front and Polar Front organize the Antarctic Circumpolar Current, and the Brazil-Malvinas Confluence and the shelfbreak front are sharp examples. They concentrate flow, generate eddies through baroclinic instability, and aggregate nutrients and biota, making them productive and dynamically active boundaries in the ocean.