Surface frontogenesis and thermohaline intrusion in a shelfbreak front

Surface frontogenesis and thermohaline intrusion are examined in a submesoscale eddy-resolving primitive-equation model simulation of an idealized summer shelfbreak front of the Middle Atlantic Bight (USA). The initial front evolves into fully developed geostrophic turbulence characterized by large Rossby number, strong vortical asymmetry, and k−3 eddy kinetic energy and density spectra (k is the horizontal wavenumber). The baroclinic eddies are trapped in the upper 20 m, and their growth is limited by conversion from the eddy to mean kinetic energy. The surface frontogenesis drives vigorous thermohaline intrusions of density-compensated temperature and salinity anomalies. Warmer saltier slope waters are subducted in the wave troughs, while colder fresher shelf waters are upwelled in the wave crests. The model results compare well with the observed distribution of subsurface salinity maxima. The total eddy induced onshore salt flux is comparable to the estimated salt budget in the Mid-Atlantic shelf.

► Submesoscale eddy-resolving O(1 km), primitive-equation.
► Surface frontogenesis drives vigorous thermohaline intrusion.
► Surface eddy kinetic energy and density variance follow a k−3 slope.