Surface oceanic currents are sometimes wind driven and develop their typical clockwise spirals in the northern hemisphere and counterclockwise rotation in the southern hemisphere because of 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.
Ocean basins generally have a non-symmetric surface current, in that the eastern equatorward-flowing branch is broad and diffuse whereas the western poleward flowing branch is very narrow. These western boundary currents (of which the Gulf Stream is an example) are a consequence of the rotation of the Earth.
Deep ocean currents are driven by density and temperature gradients. Thermohaline circulation is also known as the ocean's conveyor belt (which refers to deep ocean density driven ocean basin currents). These currents, called submarine rivers, flow under the surface of the ocean and are hidden from immediate detection. Where significant vertical movement of ocean currents is observed, this is known as upwelling and downwelling. Deep ocean currents are currently being researched using a fleet of underwater robots called Argo.
https://en.wikipedia.org/wiki/Ocean_current
https://www.reddit.com/r/gifs/comments/3l2jxu/ocean_currents/
Video: https://www.youtube.com/watch?v=oA1sphuyazY
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