Longshore current dislocation on barred beaches

We present a numerical investigation of longshore currents driven by breaking waves on barred beaches. Alongshore inhomogeneity in the wave envelope or bathymetry leads to the generation of strong dipolar structures when the waves are breaking. The dynamics of these structures transfer momentum from the bar of the beach into the trough. This study is pursued using a new model that allows long simulation times and realistic wave amplitudes. We study two idealized settings that are expected to produce current dislocation, as observed in field experiments. In one setting the current maximum is dislocated; in the other the current is diffused, but the maximum is not shifted.