Figure 5.11 Ocean currents. Ocean currents circulate as a result of unequal heating, Coriolis effects, predominant wind directions, and the topography of the ocean basins. Each of the five major ocean basins contains a gyre. These gyres are driven by the trade winds in the tropics and the westerlies at mid-latitudes. This produces a clockwise circulation pattern in the Northern Hemisphere and a counterclockwise circulation pattern in the Southern Hemisphere. Along the west coasts of many continents, currents diverge and cause the upwelling of deeper and more fertile water.