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Greenland's Ice Sheet Is Slip-Sliding Away



June 25, 2006|Robert Lee Hotz | Times Staff Writer

University of Colorado climatologist Konrad Steffen set up Swiss Camp 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.

Even so, Steffen and Zwally often spent days chiseling out tables and chairs had frozen in floodwater into a single block of ice.

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 it taking centuries for higher temperatures to work their way thousands of feet down to the base of the ice cap 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 ice cap. 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 remote-sensing satellites showing the amount of water locked up in the ice sheet had risen slightly between 1992 and 2002.

Then the ice sheet began to confound computer-generated predictions.

By 2005, Greenland was beginning to lose more ice volume than anyone expected -- an annual loss of up to 52 cubic miles a year -- according to more recent satellite gravity measurements released by JPL.


"We are clearly seeing the effects of climate change starting to kick in," Zwally said.

Since Steffen started monitoring the weather at Swiss Camp in 1991, the average winter temperature has risen almost 10 degrees. Last year, the annual melt zone reached farther inland and up to higher elevations than ever before.

There was even a period of melting in December.

"We have never seen that," Steffen said, combing the ice crystals from his beard. "It is significantly warmer now, and it happened quite suddenly. This year, the temperatures were warmer than I have ever experienced."

At this time of year, the sun never sets, and at Swiss Camp, the pace of field work slackens only for dinner.

Layered in fleece, the field researchers gathered around a makeshift plywood table littered with heels of whole grain bread, pots of raspberry jam and crumbs of granola. A ridge of ice 6 inches high encased an electrical cable running between their feet.

Their cheeks were coarse with stubble. Their hair rose in waxy spikes. Their eyes had reddened from insomnia and too much midnight sun.

While one researcher spooned out the first course -- pasta in a sauce of sun-dried tomatoes -- another opened the last bottle of the 2003 Cotes du Rhone.

Zwally tended the pot on the stove.

The Greenland ice sheet was in the same predicament as his frozen lobsters, steaming in meltwater.

Getting Into the Ice

The pilot refused to land. There were too many crevasses.

Steffen waved him on to fly farther inland. He checked their position by satellite every few hundred yards.

After 34 years in the Arctic, Steffen was attuned to its subtleties. Where a novice could only see a monochromatic plain stretching to the horizon, Steffen could discern the undulating outlines left by seasonal lakes and riverbeds.

Clear of the hazard, the Otter touched down and glided on its skis to a halt on an inviting featherbed of snow.

Steffen and his crew unloaded crates of equipment and began drilling into the ice. Zwally, stripping wires with bare fingers in the biting wind, hooked up a satellite receiver.

Within the hour, they erected a tall mast festooned with monitoring instruments.

They continued to hopscotch by air across the ice sheet, planting sensors at every stop.

As spring comes earlier each year, alpine glaciers recede, hurricanes gather power and other signs of climate change accrue, the research team tries to understand how the Greenland ice sheet can respond so quickly to rising temperatures.

"How does climate change get into the ice?" Zwally asked.

Most of the computer models on which climate predictions are based did not take the dynamics of the glaciers into account.

Contrary to appearances, the monolith of ice is constantly on the move, just as Southern California, driven by plate tectonics, inches every year toward Alaska.

In that sense, the Swiss Camp is a measure of shifting property values.

The camp has been rafting on the ice stream toward the sea, on average, at about 1 foot every day. Since Steffen pitched the main tents, the camp has moved about a mile downhill.

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