Vertical migration in tidal currents

Abstract

A simple model which employs linear velocity shear in the vertical, and sinusoidal vertical migration, is used to establish the fundamental ideas. For linear shear, only when tidal and migration periods exactly match is long-term unidirectional transport possible. For non-linear forms of velocity shear, unidirectional transport is also possible for migration periods which are exact multiples of the tidal period. -from Author