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Ocean currents Ocean currents
The waters of the oceans are not still, but are continually moving. The patterns of this movement are the ocean currents.
Water moves in the oceans because it is driven by the winds. Water also moves because some regions are more dense (saltier) than others.
The warmest parts of the oceans are in the tropics, and the coldest are near the poles.
The saltiest parts of the oceans are at the same latitudes as the world’s great deserts. Between about 15° and 20° of latitude there is almost no rain, but the sea is continually losing water by evaporation.
In contrast, near the equator, where rain falls every day, and
in high latitudes where there are storms, fresh water is continually added to the sea, and the water is less salty.
As water moves to balance
out differences in the heat and saltiness, it is affected by the spinning of the Earth. The spinning of the Earth causes the ocean currents to turn clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. As a result, ocean currents tend to move in circles around the edges of the oceans.
The movements of the currents become concentrated in some parts of the oceans. One of the most noticeable currents is called the North Atlantic Drift, or the Gulf Stream. It begins in the Gulf of Mexico, flows up the East Coast of the United States, and then heads off across the North Atlantic Ocean to reach the western shores of Europe. The heat that this current carries is enormous and accounts for the fact that the winter climate
in western Europe is much milder than on the eastern seaboard of North America.
In other places cold currents rise to the surface and cool the air. This is very noticeable in places such as the coast of California. (See also: El Niño.)
Ocean life
 Ocean currents—Ocean currents change position during the year, but much more slowly than changes in the atmosphere. You can see the changes in the pattern off the coast of North America between February (top) and August (bottom).
The oceans contain more life than anywhere else on Earth. Indeed,
it is believed that life began in the world’s oceans.
The oceans are full of plant life. However, unlike on land where the plant life is easy to see and makes up a striking part of the landscape, the plant life in the oceans may
go unnoticed. That is because it is mainly composed of microscopic living organisms called plankton that drift near the surface of the ocean waters. They absorb sunlight just like land plants and use it, along with the carbon dioxide dissolved in the water, to make
Cold ocean current Warm ocean current
February
Labrador Current
Gulf Stream
North Pacific Current
North Equatorial Current
North Atlantic Drift
North Equatorial Current
North Pacific Current
North Atlantic Drift
August
Labrador Current
Gulf Stream
North Equatorial Current
North Equatorial Current
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