Ocean currents act as conveyer belts of warm and cold water, sending heat toward the polar regions and helping tropical areas cool off, thus influencing both weather and climate. Download image jpg, KB. The majority of radiation from the sun is absorbed by the ocean, particularly in tropical waters around the equator, where the ocean acts like a massive, heat-retaining solar panel.
The currents then bend to the right, heading north. At about 30 degrees north latitude, a different set of winds, the westerlies, push the currents back to the east, producing a closed clockwise loop. The same thing happens below the equator, in the Southern Hemisphere, except that here the Coriolis effect bends surface currents to the left, producing a counter-clockwise loop.
Large rotating currents that start near the equator are called subtropical gyres. These surface currents play an important role in moderating climate by transferring heat from the equator towards the poles.
Subtropical gyres are also responsible for concentrating plastic trash in certain areas of the ocean. In contrast to wind-driven surface currents, deep-ocean currents are caused by differences in water density.
It all starts with surface currents carrying warm water north from the equator. The water cools as it moves into higher northern latitudes, and the more it cools, the denser it becomes.
In the North Atlantic Ocean, near Iceland, the water becomes so cold that sea ice starts to form. The salt naturally present in seawater does not become part of the ice, however.
It is left behind in the ocean water that lies just under the ice, making that water extra salty and dense. The denser water sinks, and as it does, more ocean water moves in to fill the space it once occupied. This water also cools and sinks, keeping a deep current in motion. These currents circulate around the globe in a thousand-year cycle. The Coriolis effect makes storms swirl clockwise in the Southern hemisphere and counterclockwise in the Northern Hemisphere.
The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited. Tyson Brown, National Geographic Society. Wind is not the only factor that affects ocean currents. The Earth is a sphere that spins on its axis in a counterclockwise direction when seen from the North Pole. The further towards one of the poles you move from the equator, the shorter the distance around the Earth.
This means that objects on the equator move faster than objects further from the equator. While wind or an ocean current moves, the Earth is spinning underneath it. As a result, an object moving north or south along the Earth will appear to move in a curve, instead of in a straight line.
Wind or water that travels toward the poles from the equator is deflected to the east, while wind or water that travels toward the equator from the poles gets bent to the west. The Coriolis Effect bends the direction of surface currents. The third major factor that determines the direction of surface currents is the shape of ocean basins Figure When a surface current collides with land, it changes the direction of the currents.
Imagine pushing the water in a bathtub towards the end of the tub. When the water reaches the edge, it has to change direction.
Figure Currents are created by wind, and their directions are determined by the Coriolis effect and the shape of ocean basins. Surface currents play a large role in determining climate.
These currents bring warm water from the equator to cooler parts of the ocean; they transfer heat energy. The Gulf Stream is an ocean current that transports warm water from the equator past the east coast of North America and across the Atlantic to Europe. You can see on the map of the major surface ocean currents that the surface ocean currents create loops called gyres Figure below. The Antarctic Circumpolar Current is unique because it travels uninhibited around the globe.
Why is it the only current to go all the way around? The ocean gyres. Why do the Northern Hemisphere gyres rotate clockwise and the Southern Hemisphere gyres rotate counterclockwise? Even though the equator and poles have very different climates, these regions would have more extremely different climates if ocean currents did not transfer heat from the equatorial regions to the higher latitudes.
The Gulf Stream is a river of warm water in the Atlantic Ocean, about kilometers wide and about a kilometer deep. Water that enters the Gulf Stream is heated as it travels along the equator. London, U. Because air traveling over the warm water in the Gulf Stream picks up a lot of water, London gets a lot of rain. In contrast, Quebec is much drier and receives its precipitation as snow. In a satellite image of water temperature in the western Atlantic it is easy to pick out the Gulf Stream, which brings warmer waters from the equator up eastern North America.
Deep Currents Thermohaline circulation drives deep ocean circulation. Thermo means heat and haline refers to salinity. Differences in temperature and in salinity change the density of seawater. So thermohaline circulation is the result of density differences in water masses because of their different temperature and salinity. What is the temperature and salinity of very dense water?
Lower temperature and higher salinity yield the densest water. When a volume of water is cooled, the molecules move less vigorously so same number of molecules takes up less space and the water is denser. If salt is added to a volume of water, there are more molecules in the same volume so the water is denser. Changes in temperature and salinity of seawater take place at the surface.
Water becomes dense near the poles. Cold polar air cools the water and lowers its temperature, increasing its salinity.
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