Stokes' drift: A rocking ratchet

We derive the explicit analytic expression for the Stokes' drift in one dim ension in the presence of a dichotomic Markov forcing. For small amplitudes of the forcing, the drift is enhanced, but the enhancement is reduced with increasing frequency of the forcing. On the other hand, a reduction of the drift or even a flux reversal can be induced at larger amplitudes, while t he flux is now found to be an increasing function of the perturbation frequ ency.