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Greenland glaciers could be particularly hard-hit by global warming |
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April 7, 2000
UNDATED, APR 5 (AP) -Worried about the effects of global warming, scientists who have been watching the West Antarctic ice sheet for years for signs of melting now say the bigger threat comes from glaciers in Greenland.
Scientists fear that a rise in the Earth's average temperature could make the oceans rise and swamp low-lying coastal cities in the coming century.
New research suggests that Antarctica's second-largest ice sheet is more stable than had been believed. The glaciers of Greenland, more than 14,500 kilometers (9,000 miles) to the north, are more likely to melt with dire consequences as Earth warms up, said Kurt M. Cuffey, a geographer at the University of California, Berkeley.
"If nothing is done to stabilize our climate and sea levels rise as much as 6 meters (20 feet), you'll flood the southern half of Florida, the southern half of Louisiana. A two-degree Fahrenheit global warming doesn't sound like much, but you have to realize the consequences can be really quite disastrous," said Cuffey, the study's co-author.
The findings are reported in Thursday's issue of the journal Nature.
A United Nations-sponsored panel predicts that average global temperatures will rise two to six degrees in the next 100 years if current greenhouse gas emissions are not curtailed.
For their study, Cuffey and colleagues extracted ice cores from Greenland's ice sheet to look for clues to the last "interglacial period" - a warm period 110,000 to 130,000 years ago that preceded the last ice age.
They found evidence that much of Greenland's ice melted during that balmy interlude, and calculated that the massive Greenland melt off accounted for nearly all of the rise in sea levels around the globe during that time. They concluded that the melt from the West Antarctic ice sheet was comparatively negligible.
Greenland covers 2.14 million square kilometers (840,000 square miles) - 85 percent of which is covered by ice up to 3 kilometers (2 miles) thick. Its ice sheet is particularly vulnerable to ice melt because it is closer to the equator than the West Antarctic ice sheet at the South Pole.
Cuffey and co-author Shawn Marshall of the University of British Columbia estimate that Greenland's melt water raised ocean levels 4 to 6 meters (13 to 20 feet) and inundated coastal regions worldwide during the last interglacial period.
The researchers also dropped thermometers into the holes created by their ice drilling operations and took the temperature of the ice sheet's deep interior.
They found that temperatures in central Greenland during the last interglacial period were 8 to 15 degrees Fahrenheit warmer than had been estimated, offering additional evidence that much of the ice sheet melted during that period.
The team's findings fit in well with other evidence, including a lack of old ice near the bottom of some parts of Greenland's ice sheet, said Richard Alley, a professor of geosciences at Pennsylvania State University.
"I think this accounts for most or all of the high sea levels during the previous warm period," Alley said.
Although the findings suggest that the West Antarctic ice sheet was stable during Earth's last warm period, scientists can't predict what will happen now that human activity has disrupted Earth's natural cycles and accelerated atmospheric warming, said Jim White, a professor of geological sciences at the University of Colorado. He agrees that Greenland could be the more immediate threat but says the possible long-term role of melting in Antarctica is still unclear.
"This makes it that much more important that we understand the long-term history of the West Antarctic ice sheet," he said. "If you have to look for a piece of ice that has nasty future implications, that's the piece."
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