Ocean currents can be generated by wind, density differences in water masses caused by temperature and salinity variations, gravity, and events such as earthquakes.
Currents are cohesive streams of seawater that circulate through the ocean. Some are short-lived and small, while others are vast flows that take centuries to complete a circuit of the globe. There are two distinct current systems in the ocean—surface circulation, which stirs a relatively thin upper layer of the sea, and deep circulation, which sweeps along the deep-sea floor.
