Brennan Linsley, Associated Press
ON JAKOBSHAVN GLACIER, Greenland — The pilot eased his five-ton helicopter toward the glacier's rumpled surface, aiming for the lightest of setdowns atop one of the fastest-flowing ice streams on Earth.
David Holland's voice suddenly broke in on the intercom.
"Carl doesn't like this!" the scientist shouted. "Carl says it's snow bridges!" — drifts that can hide a deep crevasse.
The chopper pulled up sharply and veered off over the chaotic icescape of white knobs and pinnacles and bluish glints of meltwater, on to another, safer landing spot where Carl Gladish, Holland's lanky, ponytailed assistant, stepped cautiously off the skid and onto the ice, under the thudding rotor blades, to swiftly carry out his assigned task.
It was one of eight 2-minute touchdowns on which the New York University research team positioned instruments to measure the movement and internal cracking of Jakobshavn Glacier, a risky operation meant to shed light on one more tiny piece of the giant puzzle called Greenland.
Other scientists elsewhere were working on their own pieces, on demanding and often dangerous missions, sometimes in subfreezing temperatures and high winds, sleeping in tents on the ice, isolated for weeks at a time, linked tenuously by satellite phone.
On this same July day, Alun Hubbard was on a solitary trek to the north coast's spectacular, remote Petermann Glacier. Liz Morris was in the first hours of a monthlong research traverse along the hump of Greenland's vast, 3-kilometer-thick (2-mile-thick) ice sheet. Asa Rennermalm and her colleagues, at the ice's western fringe, were in their fourth summer of meticulous, tedious sampling of the meltwater flow from the interior.
Scattered across the world's largest island, as big as Alaska and California combined and 80 percent covered by ice, small bands of specialists tended to GPS sites and automatic weather stations, drilled down into the island's frozen cap, and analyzed the air and clouds overhead, working long hours under the midnight sun.
All this is to help begin answering a crucial question: How much of Greenland's ice will melt, and how quickly, in a world growing warmer and warming fastest in the Arctic?
If all the ice eventually slipped into the ocean, it would be enough to raise global sea levels by 7 meters (23 feet). Even a fraction of that would inundate Bangladesh and south Florida, drown small islands, threaten cities as widely dispersed as Shanghai and New York.
But as temperatures rise from greenhouse gases in the atmosphere, the answer isn't coming easily. The challenge — scientific, logistical — appears greater than the resources devoted to it.
This Greenland puzzle, and uncertainty over Antarctica's ice, led the U.N.-sponsored Intergovernmental Panel on Climate Change to essentially disregard the impact on oceans of an accelerating polar melt. In its 2007 global warming report, the IPCC projected a sea-level rise of only 18 to 59 centimeters (7 to 23 inches) this century, mostly from water expanding when warmed.
But researchers have since determined that Greenland lost ice in the 2004-2009 period four times faster than in 1995-2000. This May, the eight-nation Arctic Monitoring and Assessment Program forecast a much higher global sea-level rise — of 90 to 160 centimeters (35 to 63 inches) by 2100.
To those best informed, like Cambridge University's Morris, a polar research veteran, melt is inevitable in a place where temperatures over the ice sheet have risen 2.2 degrees C (4 degrees F) in just 20 years.
"There's no way that you put greenhouse gases into the atmosphere and it won't warm and the ice won't melt," she said before setting out on her snowmobile expedition. "The uncertainty is when."
The "when" hinges on a web of variables in what Morris called Greenland's "massively complex" ice system.
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