This illustration shows the circulation of the ocean’s surface water. Names of the major ocean currents are noted. Warm currents are noted in the color red and cold currents are noted in the color blue. Click on image for full size (260K JPEG) Windows Original

There are two main sections of ocean water: the surface layer and the the deep waters. The surface layer is the layer at the top of the ocean that is well mixed by waves, tides, and weather events like rain or a hurricane. The surface layer sits on top of the deep water because the surface layer is less dense. The depth of the surface layer varies depending on location and season, but the depth is typically a couple hundred meters. There is a boundary layer between the surface layer and the deep waters that is called the the pycnocline (meaning rapid change of density). The pycnocline is caused by rapid changes of temperature and salinity.Surface water movement takes place in the form of currents. Currents move ocean water horizontally at the ocean’s surface. Surface currents are driven mainly by the wind. Other forces such as the Coriolis effect and the location of land masses do affect surface current patterns. In fact, huge circular patterns called current gyres can be seen when looking at the world’s ocean currents. From the equator to middle latitudes, the circular motion is clockwise in the Northern Hemisphere and counterclockwise in the Southern hemisphere. Near the poles of the Earth, there is a tendency for the gyres to flow in the opposite direction. This circulation of water helps spread energy from the Sun. The Sun warms water at the equator and then water and heat are transported to higher latitudes.

Major ocean currents of the world include :

• North & South Equatorial Current
• Equatorial Counter Current
• North Atlantic Drift
• Gulf Stream
• Kuroshio Current (off of Japan)
• Antarctic Circumpolar Current
• East Australian current

source:http://www.windows.ucar.edu

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