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5 December 2013 11:26 am ,
Vol. 342 ,
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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El Niño Fills Its Bath
29 December 1998 5:00 pm
The El Niño of 1997 hit many regions hard--toasting Texas, practically drowning parts of California, and burying much of New England under a fierce ice storm. But the pernicious weather phenomenon also had a much more pervasive, if easily overlooked, impact. Scientists announced earlier this month that the El Niño--a sharp warming of the tropical Pacific Ocean--had pumped up global sea level by 2 centimeters, on average. This is the first time that such a rise has been detected in oceans around the world.
In the past century, researchers tried to track the ocean's ups and downs by gauging the tides off a few scattered islands. But these measurements were often misleading--simultaneous local swells in tidal levels, for instance, could be mistaken for a global sea level rise. Since 1992, however, the TOPEX/Poseidon satellite has been drafting extremely detailed ocean maps every 10 days by bouncing radar signals off the surface water. These maps have allowed Steve Nerem, an aerospace engineer at the University of Texas, Austin, and his colleagues to average out tides and waves and determine the sea level with unprecedented precision.
In March 1997, the level of the tropical Pacific, southern Pacific, and Indian Ocean started rising independently of other oceans; it reached about 2 centimeters above normal in November 1997. By July, the oceans had subsided back to normal. To check on the source of the change, the team monitored sea surface temperatures for the same period. The rise and fall of sea level matched the warming and cooling in the Pacific and other oceans. "We know that the oceans retain heat during an El Niño," says Nerem, which apparently caused the water to expand, pushing up sea levels.
This kind of satellite observation could pick up sea level change from global warming, says Lee-Lueng Fu, an oceanographer at NASA's Jet Propulsion Laboratory in Pasadena, California. But radar-ranging satellites alone won't be able to tell an ocean rise due to melting ice from one due to heat expansion. To tease apart these variables, he says, "we need an integrated ocean observation system, for example, floats in the ocean that can measure its temperature and salinity," along with the satellite data.