On Thin Ice
What will the future hold if Arctic glaciers continue to melt at an accelerating rate?

When UNH glaciologist Mark Fahnestock heads north to conduct field research on the Greenland ice sheet, he travels 2,300 miles up and 10,000 years back. Dropped by helicopter to camp in tents on the rocky shoreline near the Jakobshavn Isbrae glacier outside the town of Ilulissat, Fahnestock and his colleagues are on the edge of a 630,000-cubic-mile sheet of ice that blankets the world's largest island in all directions--a living remnant of Earth's last ice age.

A mere fraction of the massive ice sheet, Jakobshavn fills a Grand Canyon-sized chasm with ice over a mile and a half thick. It gives birth to 35 billion tons of icebergs every year as its 4-mile-wide front "calves" chunks into the Jakobshavn Icefjord. Some of the icebergs are so large that one laid on its side would squash the UNH campus end to end under thousands of feet of ice. Five years ago this great wall of ice, which had moved at a stately 65 feet per day for half a century, suddenly quickened its slide towards the sea. Today, Jakobshavn moves 130 feet, or nearly half a football field, per day. Other Greenland glaciers, including two as large as Jakobshavn, have also doubled their speed, and no one knows exactly why.

DOUBLE TIME: Glaciologist Mark Fahnestock hopes to find out why Greenland's glaciers have begun melting at a rapid pace.

To shed light on this phenomenon and determine what it might mean for our planet's future, Fahnestock and his fellow scientists make two annual, month-long pilgrimages to Jakobshavn, deploying Global Positioning System receivers to gauge its movement. Fahnestock will return in May to retrieve data collected by the instruments, which were strategically placed to travel a year on the flowing river of ice without--it is hoped--pitching into a crevasse or getting drowned in a surface lake along the way.

Fahnestock, who relishes getting back on the ice, will be right at home--in a primordial sort of way. "The area around Jakobshavn is a rocky, treeless coastline that looks exactly like New Hampshire's would have after the ice sheet retreated 10,000 years ago," he says. It is a pristine landscape of stark beauty with a palpable connection to the "deep time" of Earth's glacial history, which goes back millions of years through a series of major ice ages.

Fahnestock himself has a keen sense of this deep time--it's in his blood. He spent virtually every summer of his childhood camped out in remote regions across North America while his father studied glacial deposits and streams. Glacial till was the boy's sandbox, and when Fahnestock describes the immense flowing, grinding, cracking, calving, sky-blue rivers of ice that are now his quarry, you sense that these are indeed living organisms.

But despite our planet's long glacial history and its extraordinary load of ice, which still covers more than one-tenth of its surface, the earth's "cryosphere" is about as tangible in most people's minds as the ice-laden surfaces of Neptune. "It's hard for people to connect to the ice, I think, because it's so far away," Fahnestock says before pausing and adding, "Well, it seems like it's so far away."

In fact, what's happening to Jakobshavn and other glaciers worldwide is as close as the waves lapping at our coastlines. Jakobshavn is an "outlet glacier," meaning that it drains a portion (6.5 percent) of the massive Greenland ice sheet. Jakobshavn and its sister outlet glaciers dump vast quantities of icebergs and freshwater into their fjords and, thus, the world's oceans. The end result of this dribbling away of Earth's glaciers will be a slow rise in sea levels and a change in ocean circulation patterns due to lower water salinity and density.

Jakobshavn's current rate of melting is a fraction of a percent of the potential decay of the entire Greenland ice sheet: if it completely melted, it would raise the global sea level by 23 feet. Today's rate, however, is no match for the past. At the end of the last ice age, so much of the earth's ice melted that sea levels rose 300 feet in just 3,000 to 4,000 years. But in addition to not knowing why the Greenland glaciers have suddenly doubled their speed, scientists are unclear if this behavior represents a periodic, controlled release or is the beginning of a massive "dam" failure. "We don't have a way to predict how large these changes are going to be," Fahnestock says. "We have no way of knowing if the whole glacial system near the coast will have the capacity of holding back all the ice that's behind it. But we do know that there is no reason these systems have to be stable, and there's good reason to think they can change fairly quickly. What's to keep them from tripling their speed?"

Ten years ago, Fahnestock says, had any reputable scientist stood up at a scientific meeting and predicted that three of Greenland's largest outlet glaciers would suddenly, inexplicably make a dash for the sea, they would have been hooted from the hall. And while he's concerned that human-induced climate warming may have triggered a runaway break in the dam, he is enthralled, from a scientific point of view, by the challenge of trying to hit a moving target.

"Almost all the ice on earth is on the move in one way or another." With a smile he adds, "We live in interesting times."

Fahnestock's office within the Complex Systems Research Center at the UNH Institute for the Study of Earth, Oceans, and Space appears to have undergone its own epoch of glacial retreat, leaving an "outwash plain" of debris behind. Stratified stacks of papers flow across desk surfaces, buttes of cardboard boxes rise from the floor, and a melange of computer gadgetry, power cords and hardware sprawl like glacial till in a jumble of comfortable disaster. A small pathway snakes through the rubble to his desk chair.

Inside his office, Fahnestock's long, bony frame hunches in front of one of several laptops and computer monitors as he puzzles over satellite imagery from polar regions or cobbles together videos from a profusion of digital photographs taken in the field. In one video he's created, an iceberg the size of four city blocks rolls on its side and spawns a 1,000-foot-high wave.

That his office resembles glacial chaos is, perhaps, testament to Fahnestock's desire not to be holed up inside but rather perched atop Jakobshavn or camped out at its base--preferably with his wife, Judy, and their two young sons. But, alas, times have changed from days of yore when scientists could take their families with them into the field for a summer of research.

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