FTV 2/16/12 Currents

Large masses of moving water are called currents. In the oceans there are major surface currents, subsurface currents, and tidal currents. Each of these mass movements of seawater is slightly different. Local areas have more complicated current patterns but in this lesson the global currents will be explained.

Winds are the primary force causing seawater movement at the surface of the ocean. These surface winds are responsible for the major ocean currents and waves. The causes of the winds are almost completely due to the energy from the sun in the form of heat. As the sun heats the air it becomes less dense and rises. Since the greatest amount of heat is centered at the equator there is a large mass of rising air there. As this heated air rises it cools and spreads out near the top of our atmosphere.

Earth's surface winds are influenced by the rotation of Earth and the Coriolis effect. As Earth rotates there is a drag on the surface wind. This drag makes moving masses veer right in northern hemisphere and left in southern hemisphere in relation to the surface of Earth. Imagine a giant at the North Pole who prepares to jump to an island in the middle of the Pacific Ocean (say Hawaii). Now, imagine yourself, standing in Hawaii, viewing this giant as it leaps into the air and flies toward you. You see the giant coming right toward you at first but the Earth is rotating and you move with the Earth toward the east. As you watch the giant it appears to you that the giant veers to its right and falls into the ocean (missing Hawaii) - all due to the rotation of Earth. This effect is the Coriolis Effect (in simple form) and affects all moving masses going over long distances.

In addition to the Gulf Stream here is a list of other important surface currents:

California Current: This flows from the Arctic waters of the North Pacific down the western coast of Canada, Washington, Oregon and California. The beach and coasts north of Point Conception, located just north of Santa Barbara, generally are chilly all year long because the California Current runs close to shore in these regions.

South of Point Conception the California Current veers offshore because the California coast south of Point Conception curves eastward and a warmer eddy flows up the coast from the south, warming southern California.

 Kuroshio Current: This major surface current flows north along the western side of the North Pacific basin, warming Japan and Korea far to the north of the tropics. Antarctic Current: This is the largest surface current of all in terms of volume of water transported per year. This enormous current system circulates without interruption from west to east around the continent of Antarctica, driven by the violent West Wind Drift, the wind system that circles Antarctica.

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