Wave-driven vortex dynamics in the near-shore region

A longstanding problem in coastal oceanography is the prediction of the alongshore currents that are forced by breaking waves in the surf zone. Traditional models based on a 1D momentum balance for the surf zone predict that current should be strongest in regions of the strongest wave breaking. However, current on a beach with a sandbar is sometimes observed to have a maximum in the "trough" of the bar, far from the region of maximum wave breaking.

We propose a mechanism for the development of this current based on vortex dynamics and show, based on idealized studies, that it can explain the broad features of the observed current.