OCEAN CURRENTS. Currents. Surface currents in the oceans are driven by winds. The major surface circulation patterns at sea are the result of the prevailing winds in the atmosphere. Prevailing winds in the atmosphere drive surface currents in the oceans in predictable patterns.
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Wind-driven transport and resulting surface currents in an ocean bounded by land to the east and west
Currents form large oceanic gyres that rotate clockwise in the north and counterclockwise in the south
Satellite view of solar reflection of off eddies in the Mediterranean
a)Normal conditions January 1997b) El Niño conditions November 1997c) End of El Niño and the beginning of a normal cycle in March 1998
El Niño’s effects: (1) Huge areas of warm water drift east. (2) Storms then follow, drenching California and more of South America’s west coast. (3) The jet stream sometimes splits in two, leaving the Pacific Northwest dry, with mild temperatures, and the Northeast warm.
Some scientists even link the recent onslaught of El Niños to the specter of global warming. In the last 20 years, the world has experienced five El Niños—well above the historical norm of one every four to seven years. Might the greenhouse effect be responsible?
El Niño acts as a kind of distributor of global warming. When carbon dioxide in the atmosphere absorbs radiation from space, Graham’s global warming theory goes, it transfers this extra energy to the oceans in the form of heat. As the equatorial Pacific warms, the extra energy accelerates the “hydrologic cycle” of convection and precipitation—and speeds up the El Niño rhythm by throwing more heat and moisture into the atmosphere. El Niño, in turn, spreads that heat virtually across the globe, upsetting weather patterns in ways ranging from mildly amusing (January sellouts of Bermuda shorts in the Northeast) to devastating (African droughts and famine).
For nine straight days in 1995, row after row of sodden, gray clouds marched from the Pacific Ocean into normally sunny California. They deluged Los Angeles, San Francisco, and every town in between with as much as 16 inches of rain—more than the average annual total for some locations. The devastation was widespread: 11 dead, hundreds of homes destroyed, and $1.3 billion in damages.
The 1982-’83 El Niño, the so-called El Niño of the Century, wreaked an estimated $8.1 billion of damage and destruction across five continents. It wiped out delicate coral reefs and drove an estimated 17 million island nesting birds from their homes in the Pacific; caused drought that devastated crops in India and led to paralyzing dust storms and brushfires in Australia; spawned a rash of cyclones that left 25,000 Tahitians homeless; and dumped an incredible 100 inches of rain in six months in some areas of Ecuador, creating inland lakes where previously there had been desert.