Making Sense Of Melting Ice

Every year, the cap of sea ice floating atop the North Pole dwindles from about 14 million to 7 million square kilometers—a number that would panic scientists if it weren't a normal occurrence, courtesy of nature. Most of the summer shrinkage is caused by melting, and the pack ice grows again once winter arrives, freezing the choppy water back into solid sheets. Because it's a recurring cycle, scientists have never found this phenomenon worrisome. Until this year, when Ronald Kwok of NASA's Jet Propulsion Laboratory rang the alarm. He'd noticed that in 2005, little of the ice that had formed the previous winter had gone on to survive the summer—making the Arctic cap the smallest it had been in five decades.

The polar regions are notorious shape-shifters. Complex ecosystems, they can be swayed by factors from wind to water to warming, and their forbidding climate makes on-site research difficult. As a result, they're a bit of a mystery to scientists, and their future is hard to predict. But with ever more omens foretelling the death of the ice caps—possibly, in some models, by the year 2040—researchers are launching a major effort to make such a prediction. Mark Serreze of the University of Colorado's National Snow and Ice Data Center says the 2040 doomsday forecast "has gotten thrown around too loosely." We might have more time than that, he says: it could be 2060, 2070, 2080. On the other hand, it could be sooner. "We may already have had a kick to the system that has sent it over the edge," says Serreze. Either way, he adds, most researchers agree it's a question of "when," because it's too late for "if."

That worry is driving many scientists' current projects. From now until March 2009, as part of the International Polar Year, 63 nations will funnel $1.7 billioninto polar research, aiming to determine which changes in the frozen landscape are natural, which are man-made and which, if any, are preventable. "There's been a rallying cry," says Ted Scambos of the University of Colorado. "We have to figure out how to tell policymakers, and the public, where and when to expect a big change."

So far, the studies don't look good. In mid-March, the journal Science devoteda section to the polar regions that was uniformly depressing: lower latitudes pollute pristine pole, read one headline. Another paper warned that Greenland and Antarctica are shedding 125 gigatons of ice per year, and though the southern continent has picked up some new ice from increased snowfall, it's not enough. The journal's only positive study about an ice cap concerned the south pole—of Mars.

The IPY projects may help explain how the situation got so grim. Scientists are boring deep into the ice, looking for molecular clues that can illustrate the history of the world's climate going back as far as 500,000 years. Then they're setting recent events against that background. Scambos says some lessons can already be learned from the aftermath of the 2002 Larsen B Ice Shelf collapse in Antarctica. Glaciers that surrounded the shelf are now "dumping five or six times as much ice into the ocean" as they did when the shelf was stable, says Scambos. The thick ice, it turned out, had been holding that flow back.

Some researchers worry that their ability to gather real-time data is in jeopardy. Despite the publicity around the IPY, scientists still have limited access to the technology they need. The U.S. Arctic Research Commission recently published a wish list of monitoring equipment, topped by icebreakers (America rents some ships from Russia and Sweden), a better sensor network of buoys and river gauges, and satellites. Alas, by the next polar satellite launch, in 2015, much of the current U.S. equipment will be verging on breakdown. A new Canadian satellite called radarsat-2 will also be key. The United States paid to launch radarsat-1 and has had a "free ticket" for its data over the last 12 years, says Mead Treadwell, the ARC's chairman. But it didn't help with the launch of radarsat-2, and Treadwell says he's "not aware that any federal agency has a budget to buy" its data after 2009, says Treadwell.

Without that knowledge, the polar ice caps may melt away before we can understand how. It was satellite data, after all, that formed the basis of Kwok's research. As a morbid joke, he says, he sometimes ponders a solution: icebreakers, like all the king's horses and all the king's men, putting the Arctic ice cover together again. But in real life, he adds, "it's not clear that we can do anything about it." Our only option, it seems, is to study the ice caps—before there's far less of them to study.

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