[Mb-civic] Antarctic Ice Sheet Is Melting Rapidly - Washington Post

[William Swiggard]

Antarctic Ice Sheet Is Melting Rapidly
New Study Warns Of Rising Sea Levels

By Juliet Eilperin
Washington Post Staff Writer
Friday, March 3, 2006; A01

The Antarctic ice sheet is losing as much as 36 cubic miles of ice a 
year in a trend that scientists link to global warming, according to a 
new paper that provides the first evidence that the sheet's total mass 
is shrinking significantly.

The new findings, which are being published today in the journal 
Science, suggest that global sea level could rise substantially over the 
next several centuries.

It is one of a slew of scientific papers in recent weeks that have 
sought to gauge the impact of climate change on the world's oceans and 
lakes. Just last month two researchers reported that Greenland's 
glaciers are melting into the sea twice as fast as previously believed, 
and a separate paper in Science today predicts that by the end of this 
century lakes and streams on one-fourth of the African continent could 
be drying up because of higher temperatures.

The new Antarctic measurements, using data from two NASA satellites 
called the Gravity Recovery and Climate Experiment (GRACE), found that 
the amount of water pouring annually from the ice sheet into the ocean 
-- equivalent to the amount of water the United States uses in three 
months -- is causing global sea level to rise by 0.4 millimeters a year. 
The continent holds 90 percent of the world's ice, and the disappearance 
of even its smaller West Antarctic ice sheet could raise worldwide sea 
levels by an estimated 20 feet.

"The ice sheet is losing mass at a significant rate," said Isabella 
Velicogna, the study's lead author and a research scientist at Colorado 
University at Boulder's Cooperative Institute for Research in 
Environmental Sciences. "It's a good indicator of how the climate is 
changing. It tells us we have to pay attention."

Richard Alley, a Pennsylvania State University glaciologist who has 
studied the Antarctic ice sheet but was not involved in the new 
research, said more research is needed to determine if the shrinkage is 
a long-term trend, because the new report is based on just three years 
of data. "One person's trend is another person's fluctuation," he said.

But Alley called the study significant and "a bit surprising" because a 
major international scientific panel predicted five years ago that the 
Antarctic ice sheet would gain mass this century as higher temperatures 
led to increased snowfall.

"It looks like the ice sheets are ahead of schedule" in terms of 
melting, Alley said. "That's a wake-up call. We better figure out what's 
going on."

Velicogna acknowledged that it is hard to predict how fast the ice sheet 
will melt in the future but said, "I don't expect it's going to stop in 
the next couple of years."

Scientists have been debating whether the Antarctic ice sheet is 
expanding or shrinking overall, because the center of the sheet tends to 
gain mass through snowfall whereas the coastal regions are more 
vulnerable to melting.

Velicogna and her co-author, University of Colorado at Boulder physics 
professor John Wahr, based their measurements on data from the two GRACE 
satellites that circle the world more than a dozen times a day at an 
altitude of 310 miles. The satellites measure variations in Earth's mass 
and gravitational pull: Increases or decreases in the Antarctic ice 
sheet's mass change the distance between the satellites as they fly over 
the region.

"The strength of GRACE is that we were able to assess the entire 
Antarctic region in one fell swoop to determine if it was gaining or 
losing mass," Wahr said.

But some scientists remain unconvinced. Oregon state climatologist 
George Taylor noted that sea ice in some areas of Antarctica is 
expanding and part of the region is getting colder, despite computer 
models that would predict otherwise.

"The Antarctic is really a puzzle," said Taylor, who writes for the Web 
site TSCDaily, which is partly financed by fossil fuel companies that 
oppose curbs on greenhouse gases linked to climate change. "A lot more 
research is needed to understand the degree of climate and ice trends in 
and around the Antarctic."

At the other end of the temperature spectrum, two South African 
researchers are reporting today in Science that their computer models 
indicate that by 2100 climate change may rob the south and west of 
Africa and areas in the upper Nile region of a significant portion of 
their current water supply. Warming may reduce the rainfall needed to 
replenish up to 25 percent of Africa's surface water, said Maarten de 
Wit and Jacek Stankiewicz at the University of Cape Town in Rondebosch, 
South Africa.

"Water is essential to human survival," they wrote, "and changes in its 
supply can potentially have devastating implications, particularly in 
Africa, where much of the population relies on local rivers for water."

Congressional Democrats, including Sen. John F. Kerry (Mass.) and Rep. 
Henry A. Waxman (Calif.) said yesterday that the two new papers show 
that the United States must act quickly to impose mandatory limits on 
carbon dioxide and other greenhouse gases. The Bush administration 
opposes such curbs on the grounds that they could hurt the country's 
economy and has instead invested money on new technology to limit 
greenhouse emissions and further climate science research.

"Climate change is not just someone else's concern but a very real 
threat to the lives and livelihood of people across the globe," Kerry said.

http://www.washingtonpost.com/wp-dyn/content/article/2006/03/02/AR2006030201712.html?nav=hcmodule
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