Water Seeps To Base of Icecap of Greenland Glacier
Melting glaciers point to overheated globe.
WATER SEEPS TO BASE OF ICECAP IN GREENLAND GLACIER
Glaciers' melt rate surprises scientists
by Robert Lee Hotz
LOS ANGELES TIMES
JAKOBSHAVN GLACIER, Greenland - The Greenland ice sheet -- two miles thick and broad enough to blanket an area the size of Mexico -- shapes the world's weather, matched in influence only by Antarctica in the Southern Hemisphere. In its heart, snow that fell a quarter of a million years ago is preserved.
Should all of the ice sheet ever thaw, the meltwater could raise sea level 21 feet and swamp the world's coastal cities, home to a billion people. It would cause higher tides, generate more powerful storm surges and, by altering ocean currents, drastically disrupt the global climate.
Climate experts have started to worry that the icecap is disappearing in ways that computer models had not predicted.
By all accounts, the glaciers of Greenland are melting twice as fast as they were five years ago, even as the ice sheets of Antarctica also are shrinking, researchers at NASA's Jet Propulsion Laboratory and the University of Kansas reported in February.
Researchers have focused on a delicate ribbon -- the equilibrium line, which marks the fulcrum of frost and thaw in Greenland's seasonal balance. The zone rims the icecap like a drawstring. Summer melting, on average, offsets the annual accumulation of snow.
But across the icecap, the area of seasonal melting was broader last year than in 27 years of record-keeping, University of Colorado climate scientists reported. In early May, temperatures on the icecap some days were almost 20 degrees above normal, hovering just below freezing.
From cores of ancient Greenland ice extracted by the National Science Foundation, researchers have identified at least 20 sudden climate changes in the last 110,000 years, in which average temperatures fluctuated as much as 15 degrees in a single decade.
The increasingly erratic behavior of the Greenland ice has scientists wondering whether the climate, after thousands of years of relative stability, might again start oscillating.
For those assessing the effect of global warming, there may be no more perfect natural laboratory. Here, the theoretical effects seen in computerized climate models take tangible form.
University of Colorado climatologist Konrad Steffen set up Swiss Camp 155 miles north of the Arctic Circle in 1990 to study the weather along the equilibrium line. As a precaution, Steffen, 54, built the camp on a plywood platform to keep it afloat when the ice turns into summer slush and open lakes before refreezing in the fall.
NASA glaciologist Jay Zwally joined his colleagues there on May 8 in the regular spring migration of scientists to the arctic. He has been coming to Swiss Camp every year since 1994 and has been studying the polar regions since 1972, monitoring the polar ice through satellite sensors. Eventually, he realized he had to study the ice firsthand.
The ice sheet seemed such a stolid reservoir of cold that many experts had been confident of its taking centuries for higher temperatures to work their way thousands of feet down to the base of the icecap and undermine its stability.
By and large, computer models supported that view, predicting that as winter temperatures rose, more snow would fall across the dome of the icecap. Thus, by the seasonal bookkeeping of the ice sheet, Greenland would neatly balance its losses through new snow.
Indeed, Zwally and his colleagues in March released an analysis of data from two European satellites showing that the amount of water locked in the ice sheet had risen slightly from 1992 to 2002.
Then the ice sheet began to confound computer-generated predictions.
By 2005, Greenland was beginning to lose more ice volume than anyone had anticipated -- an annual loss of up to 52 cubic miles a year -- according to more recent satellite gravity measurements released by JPL. The volume of freshwater ice dumped into the Atlantic Ocean has almost tripled in a decade.
There was even a period of melting in December. "We have never seen that," Steffen said.
In an influential paper published in the journal Science, Zwally surmised that the ice sheets had accelerated in response to warmer temperatures, as summer meltwater lubricated the base of the ice sheet and allowed it to slide faster toward the sea.
In a way no one had detected, the warm water made its way through thousands of feet of ice to the bedrock -- in weeks, not decades or centuries.
University of Texas physicist Ginny Catania pulled an ice-penetrating radar in a search pattern around the camp, seeking evidence of any melt holes or drainage crevices that could so quickly channel the hot water of global warming deep into the ice.
To her surprise, she detected a maze of tunnels, natural pipes and cracks beneath the unblemished surface. "I have never seen anything like it, except in an area where people have been drilling bore holes," Catania said.
No one knows how much of the ice sheet is affected. In all, 12 major outlet glaciers drain the ice sheet the way rivers drain a watershed.
© 2006 Lexiton Herald-Leader
All rights reserved. Used with permission.
The following sources were used in the creation of this Kentroversy Paper . . .
Water Seeps To Base of Icecap in Greenland (June 25, 2006)
U.S. Weather Service