Unsteady Ekman–Stokes dynamics: implications for surface-wave induced
drift of floating marine litter
Abstract
We examine Stokes drift and wave-induced transport of floating marine
litter on the surface of a rotating ocean with a turbulent mixed layer.
Due to Coriolis–Stokes forcing and surface wave stress, a second-order
Eulerian-mean flow forms, which must be added to the Stokes drift to
obtain the correct Lagrangian velocity. We show that this wave-driven
Eulerian-mean flow can be expressed as a convolution between the
unsteady Stokes drift and an ‘Ekman–Stokes kernel’. Using this
convolution we calculate the unsteady wave-driven contribution to
particle transport. We report significant differences in both direction
and magnitude of transport when the Eulerian-mean Ekman–Stokes velocity
is included.