Earth's Polar Ice Melting Less Than Thought

Nearly 230 billion tons of ice is melting into the ocean from glaciers, ice caps, and mountaintops annually—which is actually less than previous estimates, according to new research by scientists at the University of Colorado, Boulder.

If the amount of ice lost between 2003 and 2010 covered the United States, the whole country would be under one-and-a-half feet of water, or it'd fill Lake Erie eight times, researchers say. Ocean levels worldwide are rising about six hundredths of an inch per year, according to researcher John Wahr.

While vast quantities of ice melting into the ocean is not exactly good news, Wahr says, according to his team's estimates, about 30 percent less ice is melting than previously thought.

The team used data from the Gravity Recovery and Climate Experiment satellite, which was launched as a joint project between NASA and Germany in 2002. The GRACE satellite measures gravity, which is related to mass, in 20 distinct regions worldwide. Wahr says that gives the team more accurate estimates, because previous teams had to measure ice loss at "a few easily accessible glaciers" and then extrapolate it to the 200,000 glaciers worldwide.

"It's tough to get an estimate [with previous methods]," he says.

With GRACE, the team can measure wide swaths of the earth, giving them a more complete picture. "It was time to do a complete global inventory," he says. Although the team used eight years of GRACE's data, Wahr says it's important to realize that melting patterns are hard to predict.

"Even with an eight-year estimate, it's not clear how far into the future you can project," he says. "A lot of people want to predict into the end of the century, but I think it's too dangerous to do that … We don't have enough info to know what'll happen. There's some ebb and flow to these things."

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jkoebler@usnews.com

Twitter: @jason_koebler

Corrected 2/8/12: An earlier version of this article misidentified the rate at which global sea levels are rising.

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