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When you stand on Greenland ice, solid ground is a mile or more below you. The surface appears flat as the Kansas prairie, but dips and rises undulate across the white expanse, corresponding to a topography that hasn't seen daylight in at least 100,000 years. It rises imperceptibly toward the island's southern interior, where the sheet is nearly 2 miles thick.
A team of University of Utah geographers has spent the past two springs traveling this part of the world's largest island by snowmobile, poking the ice with a drill and prodding it with ground-penetrating radar in an effort to understand year-to-year changes in Greenland's wettest region: the east slope just below the Arctic Circle.
"All the models show this has the highest accumulation rate, but no one has gone to measure," said project leader Richard Forster, a professor of geography. "We want a better estimate of how much mass it's losing. This will decrease our uncertainty."
Funded by a three-year, $400,000 National Science Foundation grant, the U.'s Arctic Circle Traverse wrapped up its second field season last week when Forster's crew, including graduate students Clement Miege and Evan Burgess and Utah climber Brian Ballard, were flown out of the interior to a staging base at Kangerlussuaq on the west coast. They had spent a month on the ice sheet, riding about 400 miles with thousands of pounds of instruments, equipment and camping gear in tow.
"It's like being at sea. From horizon to horizon your landscape doesn't change," said Forster, who stayed home this season. "Last year we camped on the ice sheet for three weeks. There were several days we had white-out conditions. It's really disorienting. All you can see is the next tent or a fuel barrel, with no contrast behind sky and the ground."
Teams drilled three cores that spring, and four earlier this month, up to depths of 60 meters. Extracted in one-meter lengths, the cores will help Forster and colleague Joe McConnell, of the Desert Research Institute in Reno, reconstruct accumulation layers of firn, the snow that remains from one winter to the next, going back 30 to 40 years.
Scientists suspect Arctic warming could be causing greater precipitation over Greenland, which would complicate models used to predict how the massive ice sheet will respond to climate changes. Forster's team is trying to get a picture of how much ice Greenland is gaining at its wettest spots, and check their findings against radar data NASA is gathering from space.
Greenland ice is closely studied, but the area where Forster's team has extracted cores is not well understood because the ice is so deep, up to 2 miles. The ice sheet might actually be thickening here, while it is melting near the coasts and calving icebergs into the sea. Back in the 1990s, NASA estimated Greenland shed 12 cubic miles of ice each year.
"The rate of this mass loss is increasing yearly," Forster wrote in his blog. "This lost mass eventually all ends up as water in the global oceans and is one of the contributors to present-day sea level rise."
While scientists have a handle on how much ice Greenland loses, they aren't sure how much it gains each year. The U. research hopes to answer that question.
This season's trip got off to a late departure out of Kangerlussuaq, an old military site once used as a refueling stop. Temperatures dropped to 40 degrees below and 40-knot winds scoured the ice.
The U. team hitched a ride on a military transport 110 miles inland to Raven, where the military maintains an airstrip on the ice at the site of a radar station once used to detect potential Soviet missile strikes during the Cold War.
The team snowmobiled to the easternmost drill location, and worked its way back to Raven.
Despite a colder than usual April, the team struck a water layer 10 meters down at the first drill site, a sign of internal warming, according to Forster. His goal was to extract samples from a variety of elevations between the coast and the interior, so he chose six locations. The unanticipated water forced the team to drill a seventh spot.
Using a special drill borrowed from the University of Wisconsin, the team spent 18 hours to sink the 50-meter holes the study required. The cores came out in one-meter segments, which they measured, bagged and labeled. They inserted them in tubes and left them on the ice in insulated cardboard boxes. Contract pilots later picked up the samples and flew them to Kangerlussuaq. Later this summer, they will be shipped aboard an Air National Guard plane to New York and trucked to McConnell's lab in Reno.
McConnell, a research professor of hydrology and an expert in ultra-trace chemistry, will slice them in half lengthwise. His halves will undergo chemical analysis to map the annual snow-accumulation layers. The other halves will be delivered to Forster, who keeps his cores in a walk-in freezer in the U.'s Kennecott Building.
The team will analyze data for a year before publishing its results.
Greenland ice
Greenland lies mostly above the Arctic Circle. It is 10 times the size of Utah, and 80 percent of its land is covered by glacial ice. Climate scientists closely study this ice sheet to predict the effects of global warming, which has a greater effect in upper latitudes.
Eight percent of the world's freshwater is locked in the Greenland ice sheet, which would raise sea levels 23 feet if it all melted. NASA has estimated that Greenland shed 12 cubic miles of ice each year in the 1990s. That's enough water to fill three Great Salt Lakes, but the rate of ice loss has since accelerated, according to U. geographer Richard Forster.