ONR Science & Technology Focus
               Oceanography       Space Sciences       Blow the Ballast!       Teachers' Corner   
Ocean in Motion Ocean Habitats Ocean Life Ocean Water Ocean in Regions Research Vessels Resources

Ocean in Motion: Currents - Characteristics

Driven by forces such as wind, tides, and gravity, currents keep our oceans in constant motion. Currents move large amounts of water great distances. Countless currents have been named, but the seven major ones are the West Wind Drift (or the Antarctic Circumpolar Current), East Wind Drift, the North and South Equatorial currents, the Peru Current, the Kuroshio Current and the Gulf Stream. These currents flow in large rotating loops called gyres. In the Northern Hemisphere, gyres spin in a clockwise direction, and in the Southern Hemisphere, gyres spin in a counterclockwise direction. This is because of Earth's spinning rotation and is called the Coriolis Effect.

Diagram of the seven major currents

Large surface currents are mainly driven by winds that blow year round. The winds at the equator are called the northeast and southeast trade winds. At the mid-latitudes, the winds are called the westerlies, and at the highest latitudes, the winds are called the polar easterlies. These winds blow in one direction all year.

Two of the largest currents are the Antarctic Circumpolar Current and the Kuroshio Current. The Antarctic Circumpolar Current, sometimes called the West Wind Drift, circles eastward around Antarctica. The Kuroshio Current, which is located just off Japan's coast, travels up to 75 miles a day at a speed of up to 3 miles per hour.

The Gulf Stream is a current with a strong influence on the East Coast of the United States. Actually, the Gulf Stream is part of a larger current system, which includes the North Atlantic Current, the Canary Current and the North Equatorial Current. From the Yucatan Peninsula in Mexico, the Gulf Stream flows north through the Straits of Florida and along Florida's East Coast. When it reaches North Carolina, around Cape Hatteras, it begins to drift off into the North Atlantic towards the Grand Banks near Newfoundland. The Gulf Stream usually travels at a speed of 3 or 4 knots.

next page