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Map of ocean current circulation.
The map shows a generalized pattern of ocean currents. In each ocean basin there is a roughly circular current flow called a gyre.

The world's oceans travel in well-defined circular patterns called currents which flow like rivers. When the atmosphere pushes over the surface of the ocean some of the energy goes to forming waves while the rest goes to pushing the water in the direction of the wind. North of the equator currents bend to the right; south of the equator, they bend to the left. This is called the Coriolis effect. Winds, continents and the Coriolis effect make currents flow around the oceans in huge loops called gyres.

Energy from the sun also causes currents to flow. Water near the equator is heated more than water at middle latitudes causing a surface flow toward the poles. Where two currents meet, the colder water sinks pushing warmer water up to the surface.

The Gulf Stream
Historical map of the Gulf Stream.

Each current has its own characteristic salinity, density and temperature. The Gulf Stream, which was first mapped by Benjamin Franklin, runs along the east coast of the United States and is one of the strongest currents known. It is a warm, salty current up to 37 miles wide, 2600 feet deep and in some places it may travel more than 60 miles in a day. The importance of currents can be seen when they change. On the west coast of South America, the Humboldt current normally brings cold water to the surface. With it come minerals and other nutrients that feed huge schools of fish. During an El Niño event, trade winds diminish and warm water flows down western South America. This stops nutrient-rich cold water from rising up and causes plankton and fisheries to fail.

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Water Currents

The movement of ocean currents is influenced by changes in water density. In this experiment you will examine how temperature and salinity affect water density.

Learn more about El Niño

NOAA's El Niño Page
Detecting El Niño
El Niño Facts

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