10 Dec 09
The water at the ocean surface is moved primarily by winds that blow in certain patterns because of the Earth’s spin and the Coriolis Effect. Winds are able to move the top 400 meters of the ocean creating surface ocean currents.
Surface ocean currents form large circular patterns called gyres. Gyres flow clockwise in Northern Hemisphere oceans and counterclockwise in Southern Hemisphere oceans because of the Coriolis Effect. creating surface ocean currents. Near the Earth’s poles, gyres tend to flow in the opposite direction.
Surface ocean currents flow in a regular pattern, but they are not all the same. Some currents are deep and narrow. Other currents are shallow and wide. Currents are often affected by the shape of the ocean floor. Some move quickly while others move more slowly. A current can also change somewhat in depth and speed over time.
Surface ocean currents can be very large. The Gulf Stream, a surface current in the North Atlantic, carries 4500 times more water than the Mississippi River. Each second, ninety million cubic meters of water is carried past Chesapeake Bay (US) in the Gulf Stream.
Surface ocean currents carry heat from place to place in the Earth system. This affects regional climates. The Sun warms water at the equator more than it does at the high latitude polar regions. The heat travels in surface currents to higher latitudes. A current that brings warmth into a high latitude region will make that region’s climate less chilly.
Surface ocean currents can create eddies, swirling loops of water, as they flow. Surface ocean currents can also affect upwelling in many places. They are important for sailors planning routes through the ocean. Currents are also important for marine life because they transport creatures around the world and affect the water temperature in ecosystems.
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- 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.
- North & South Equatorial Current
- Equatorial Counter Current
- North Atlantic Drift
- Gulf Stream
- Kuroshio Current (off of Japan)
- Antarctic Circumpolar Current
- East Australian current
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 (please see illustration for a more complete listing):
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