Old snow stays in Rockies, adds to glaciers’ size
November 1, 2011
CHEYENNE, Wyo. – Scientists who monitor the effects of global warming are watching glaciers shrink all over the world, but this year could be an exception in parts of the Rocky Mountains.
Snow is already piling up in the high country, but not all of the unusually deep snow from last winter has melted. As a result, some glaciers and snowfields are actually gaining volume this year.
Scientists have measured new ice in Montana’s Glacier National Park and atop Colorado’s Front Range mountains. In northwest Wyoming, there is photographic evidence of snowfield growth after Bob Comey, director of the Bridger-Teton National Forest Avalanche Center, compared photos of peaks from year to year.
His images taken before snow started falling again this autumn show what appears to be significantly more ice in the Teton Range compared with two years ago.
Last spring, record snow depths and avalanches around Jackson Hole gave way to concern about possible flooding, but fairly cool weather kept much of the snow right where it was. The flooding that did occur, at least in Wyoming, was less severe than feared.
“I’ve never seen a season with a gain like we’ve seen this summer,” Comey said.
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The new ice isn’t nearly deep enough to much offset the huge volumes that have melted off the Rocky Mountains in recent years.
On Arikaree Glacier, near the Continental Divide about 20 miles west of Boulder, Colo., scientist Nel Caine said he measured between 2 and 3 feet of snow from last winter and spring still remaining in late September.
While that might seem like plenty, it’s no more than the average ice loss he has measured on the glacier each year since 1998.
Caine, a professor emeritus of geography at the University of Colorado at Boulder, said the glacier didn’t lose any ice volume, on average, from 1965 to 1997. As much as 9 feet of ice melted off the glacier in 2002.
“If that rate had continued uninterrupted, we might have lost all by 2012-2013. Fortunately, it did not,” Caine wrote in an email from England, where he spends part of the year.
He cautioned that his data for this year was still preliminary and needed verification.
In northwest Montana, scientists have measured a “very modest” increase on Sperry Glacier in Glacier National Park. They were expecting a much bigger increase after last winter’s heavy snow, said Dan Fagre, climate change research coordinator for the U.S. Geological Survey’s Northern Rocky Mountain Science Center.
“It was not nearly what we thought it would be because we had an extended warm and dry September,” Fagre said Tuesday. “This year we basically had summer extend into September. So the glaciers continued to lose their seasonal snow.”
Scientists in Glacier National Park have measured such increases two or three times in the past seven or eight years, each one more than offset by the losses in the negative years, Fagre said.