Wind-driven oceanic circulation

From Glossary of Meteorology

wind-driven oceanic circulation

That part of the large-scale circulation of the ocean driven by and associated with the stress (force per unit area) applied by the wind at the ocean surface.

The main principles of wind-driven ocean circulation are as follows.
Wind stress causes transport of water in a thin Ekman surface layer
If there is a curl to the wind stress, the Ekman layer transport will converge or diverge, causing downwelling or upwelling
The downwelling or upwelling motions cause fluid columns to squash or stretch vertically, and this causes slow southward or northward flow due to conservation of potential vorticity.
The southward or northward flow is determined by the Sverdrup relationship, which links the N-S transport of water with the curl of the wind stress. In order to conserve mass, the water returns to its original position via a relatively thin boundary layer adjacent to the western edge of the basin.