Ekman layer

Summary

An Ekman layer is a thin boundary layer in a rotating fluid in which friction is balanced by the Coriolis force. It forms at the bottom of the ocean and the atmosphere, and below the sea surface where the wind drags the water. Inside it the velocity turns with depth along a spiral, and the net transport of fluid is at right angles to the surface stress. The convergence and divergence of this transport drive upwelling, downwelling and the spin-down of rotating flows.