text: An ocean current is any more or less permanent or continuous, directed movement of ocean water that flows in one of the Earth's oceans.\n\nSurface ocean currents are generally wind driven and develop their typical clockwise spirals in the northern hemisphere and counter-clockwise rotation in the southern hemisphere due to the imposed wind stresses. In wind driven currents the Ekman spiral effect results in the currents flowing at an angle to the driving winds. The areas of surface ocean currents move somewhat with the seasons, this is most notable in equatorial currents.\n\nDeep ocean currents are driven by density and temperature gradients. Thermohaline circulation, also known as the ocean's conveyor belt, refers to the deep ocean density-driven ocean basin currents. These currents that flow under the surface of the ocean, and are thus hidden from immediate detection, are called submarine rivers. These are currently being researched by floating devices, which maintain their depth according to slightly differing densities of waters. Upwelling and downwelling areas in the oceans are areas, where significant vertical movement of ocean water is observed.