A Modeling Study of the Episodic Cross-Frontal Water Transport over the Inner Shelf of the South Atlantic Bight

Physical processes that control the episodic cross-frontal transport over the inner shelf of the South Atlantic Bight were examined using a 3D primitive turbulent closure equation model. The model results showed that significant cross-frontal water exchange occurred under upwelling-favorable wind conditions through the detachment of isolated low-salinity lenses at the outer edge of the front. The formation of isolated lenses was a 3D feature associated with complex nonlinear processes. It depended on 1) the amount of multiple river discharges, 2) direction and magnitude of the wind, and 3) tidal mixing. As the total amount of river discharges increased, stronger winds were required to form the isolated lenses. When the river discharges were larger, tidal mixing tended to delay the occurrence of isolated lenses through 1) increasing the cross-shelf gradients of density and surface elevation and thus enhancing the along-shelf current and reducing the along-shelf variation of salinity, and 2) streng...