Oceanic current systems of planetary scale driven by the global wind system. The subtropical gyres are driven by the trade winds and by the westerlies of the temperate regions, the subpolar gyres by the westerlies and the polar easterlies. Gyres consist of a narrow, swift-flowing western boundary current, an eastward-flowing zonal current, a broad and slow-moving eastern boundary current, and a westward flowing zonal current. Eight gyres are distinguished in the World Ocean: In the Atlantic, the Brazil, South Atlantic, Benguela, and South Equatorial Currents form the subtropical gyre of the Southern Hemisphere; the Gulf Stream, Azores, Canary, and North Equatorial Currents form the subtropical gyre in the Northern Hemisphere; the Labrador, North Atlantic, Irminger, and East Greenland Currents form the subpolar gyre. In the Pacific, the East Australian, South Pacific, Peru/Chile, and South Equatorial Currents form the subtropical gyre of the Southern Hemisphere; the Kuroshio, North Pacific, California, and North Equatorial Currents form the subtropical gyre of the Northern Hemisphere; the Oyashio, Aleutian, California, and Alaskan Currents and the Alaskan Stream form the subpolar gyre; a second subpolar gyre exists in the Bering Sea. In the Indian Ocean, the Agulhas, South Indian, West Australian, and South Equatorial Currents form the only subtropical gyre.