Subtropical ocean gyres are large-scale, wind-driven circulation systems whose forcing arises from the pattern of prevailing surface winds across their latitudinal extent: equatorial (trade) easterlies drive westward surface currents near the equatorial edge of the gyre, while subtropical (mid-latitude) westerlies drive eastward surface currents near the poleward edge of the gyre, and the resulting wind stress curl between these two wind belts drives the characteristic anticyclonic (in terms of Ekman pumping/convergence) gyre circulation via Sverdrup dynamics.