Wacky weather from the bottom of the sea.
If you think that's odd, check out the wacky weather in other regions: Parts of Australia recently went a full year without rain; huge dust clouds hung over cities and dead cattle littered the fields. Meanwhile, in Ecuador, south America, almost three meters (nine feet) of rain fell in six months-over a desert!
What periodically turns the world's weather upside down? Daniel Walker, a geophysicist at the University of Hawaii, thinks he's found an explanation-volcanoes on the floor of the Pacific Ocean!
"There are times'" says Walker, "when the volcanoes just go berserk," spewing hot lava and gases from Earth's interior into the sea. And those eruptions, he says, often precede weird weather events.
The connection? "There's a tremendous amount of energy in the form of heat being released [from volcanoes] on the ocean floor," Walker explains. That heat might be enough to warm parts of the Pacific, he says. The warm water, in turn, could heat up the air, churn up the atmosphere, and mess with the world's weather (see diagram, right).
THE VOLCANO HYPOTHESIS
What evidence does Walker have? Well, scientists recently found thousands of active volcanoes on the floor of the Pacific Ocean (see SW 10/8/93, p. 8). These volcanoes lie directly beneath an area of the ocean where scientists and fishermen have noticed the regular appearance of a warm-water current.
This current, called El Nino (meaning "the child" in Spanish), appears off the west coast of South America around December every year. During some years, the waters are abnormally warm and extend over a vast portion of the tropical Pacific. Scientists now commonly refer to these episodes of abnormal warming as El Nino.
Most climate scientists agree that the abnormal warming has drastic effects on the world's weather. El Nino's warm water heats the air above, which lowers the air pressure. Clouds and rainfall from farther west in the Pacific rush into the low-pressure zone. So in effect, El Nino "steals" weather (for example, rain) from the western Pacific (places like Australia) and carries it to the eastern Pacific-say, Ecuador.
In addition, the thunderclouds formed and carried by El Nino reach high up into Earth's atmosphere. There, they disrupt the jet stream--bands of wind that normally blow steadily west to east around the globe.
The predictable movement of the jet stream is what normally carries storms and other weather patterns west to east across the U.S. (see "Talkin' 'bout the weather," right, and SW 10/22/93, p. 10). But El Nino's thunderclouds act like giant boulders in a river: They make the jet stream take a northern turn here or a southern twist there. The result: weird weather patterns.
Though climate scientists agree on El Nino's ultimate effects, many say the idea that volcanoes start the whole cycle is full of hot air.
"It's nonsense," says Gerry Bell, a climate researcher at the National Oceanic and Atmospheric Administration (NOAA) in Maryland. "I don't know anybody who knows anything about El Nino who thinks [volcanoes are the cause.]"
Most climate researchers think El Nino is simply part of a natural swing in ocean temperatures. Water that is always warm near the equator in the western Pacific, they say, sometimes flows farther eastward, depending on changes in air pressure and temperature.
In fact, says Allan Clarke, an oceanographer at Florida State University, scientists have predicted the intensity of El Nino currents based on surface-water temperatures and wind and air-pressure data. So far, says Clarke, the predictions have been pretty accurate-without volcano data.
Besides, the climate researchers say, no one has ever found a warm-water current rising from deep in the ocean. "We've got millions of observations [of ocean temperatures]," Clarke says, referring to data collected over decades by ships, buoys, and satellites. If there are warm upwellings from undersea volcanic eruptions, why hasn't anyone observed them?
A CLOSER LOOK
Maybe because no one has been looking for them, says Steve Hammond, a NOAA scientist in Oregon who studies undersea volcanoes. He thinks scientists should keep an open mind about Walker's volcano/El Nino hypothesis--at least until we learn more.
"The bottom of the ocean is not a quiet, dark, uninteresting place," Hammond says. "There's a lot going on down there." The volcanoes themselves were only recently discovered, he adds. No one can fully understand them or the roles they might play in the world's weather ... yet.
Meanwhile, back on the surface, scientists say the latest El Nino episode--which began in 1991--seems to be dying down. That means the world's weather may soon return to normal: Australian farmers can plant their wheat again, kids in Vermont may look forward to skiing, and Californians (we hope!) won't have to get in canoes to travel down Main Street next spring.
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|Title Annotation:||volcanoes erupting under the sea may cause climatic changes|
|Date:||Oct 20, 1995|
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