A clockwise/counterclockwise circulation in the northern/southern hemisphere that is forced by the wind and features western intensification in the form of a western boundary current. In the northern hemisphere the gyres span the width of the oceans and extend from about 10 to 40 °N with the boundary currents in the Atlantic and Pacific called, respectively, the Gulf Stream and the Kuroshio. There are analogous features in the southern hemisphere. The polar boundaries between these and the subpolar gyres coincide with the latitude at which the curl of the wind stress vanishes, the latter being largely the mechanism of causation.