Vast and white, easily visible from space, Earth’s Arctic ice cap seems such a permanent fixture—a frozen country at the top of the world—that the idea that it could ever vanish almost defies comprehension. But by the middle of the century most of it will in fact vanish, thanks to our burning of fossil fuels. The North Pole and most of the ocean around it will be free of sea ice in summer for the first time in thousands of years.
Will we ever bring the ice back?
That’s the question a team of researchers from Columbia University pondered in a presentation last week at the annual meeting of the American Geophysical Union in San Francisco. It’s not as academic as it sounds. Most climate models suggest that our efforts to limit carbon dioxide emissions—starting with the steps agreed to in Paris on December 12—will not be enough to keep Earth from warming more than 2 degrees Celsius. To prevent even worse impacts than the loss of Arctic ice, by late in this century we’ll have to not only shut down emissions, but find a way to clean up massive amounts of carbon dioxide that we’ve already put in the atmosphere.
That technology, once developed, would give us the ability to cool the planet—which would put the future of the Arctic in play again. “The basic message,” says oceanographer Stephanie Pfirman of Columbia, “is that we will be able to bring the ice back as long as we bring the [planet’s] temperature down.”
The question is, will future generations, accustomed to a warmer world and an open Arctic, want to cover it with ice again?
A Two-Way Street
The Arctic Ocean still freezes over most of its surface every winter, but an increasing area of that ice is so thin that it melts again the following summer. Since the first satellite measurements in 1979, the extent of the ice in September, when it reaches its annual minimum, has shrunk by more than 11 percent per decade. (Read about a research ship that locked itself in the ice last winter.)
The ice helps cool the Arctic by reflecting most incoming sunlight back to space— so as it shrinks, the warming and the melting accelerate. That feedback is one reason the Arctic is warming twice as fast as the rest of the globe. (Check out a graphic that explains the loss of ice.)
If we pull carbon dioxide out of the atmosphere—if the planet cools in a global sense—the sea ice ought to rebound almost instantly, certainly within a few years.
And because of that feedback, many researchers have assumed that once the perennial sea ice was gone, it wouldn’t come back. “People thought if we got rid of the sea ice and had this big black ocean surface up there absorbing a lot of sunlight, we would never be able to restore the ice cover,” Pfirman says. The warmer sea surface would still freeze in winter, but the ice would never get thick enough to survive the summer.
But research cited by Pfirman and her colleagues indicates that Arctic ice could prove to be more resilient, and the loss of ice more reversible, than some models have predicted. Ice-free water absorbs more sunlight, but it also radiates away more heat. There doesn’t seem to be a temperature threshold that’s a point of no return.
“Both from the paleontological records and from the [computer] model runs going forward, it does seem that the ice responds very quickly to the surface air temperature,” says Robert Newton, an oceanographer at Columbia and one of Pfirman’s coauthors. “If we pull carbon dioxide out of the atmosphere—if the planet cools in a global sense—the sea ice ought to rebound almost instantly, certainly within a few years.”
To Chill or Not To Chill
The Paris climate agreement aims to keep global warming below 2 degrees Celsius. But even if the world meets that ambitious goal, the Arctic is still likely to warm by at least 4 degrees.
The impact on the region’s people and wildlife, from Inuit hunters to polar bears to ice algae, will be enormous. Many ice-dependent species may not survive in the new, blue Arctic. But researchers don’t expect all the ice to disappear by mid-century. In the "last ice" area off northernmost Canada and Greenland, a small remnant of a few hundred thousand square miles may linger into the 2070s or 2080s. Enric Sala, a National Geographic Explorer-In Residence, is leading an effort to protect the region.
The survival of that last ice will be important later in this century, says Pfirman, “because around that time is when we're thinking that we might be able to turn the temperature around and start regrowing ice.” The last-ice area could become a kind of refuge that would permit polar bears and other species to survive—assuming, that is, we eventually figure out how to cool the planet by sucking hundreds of billions of tons of carbon dioxide back out of the atmosphere.
And assuming our descendants decide they want to do that. The loss of sea ice will have dire consequences, but it’s also expected to open the Arctic to shipping, resource development, and tourism. Will future generations of Inuit want to return to the icy norm of their ancestors? Will powerful economic interests allow it? Or will dreams of bringing back the polar bear seem as quixotic then as talk of repopulating the Great Plains with buffalo does now?
“The changes we’re seeing are a by-product, an unintended consequence of human economic activity,” says Newton. “But to go back in the other direction is not going to be unintended. It’s only going to happen through concerted action. And we think it’s worth thinking through ahead of time.”
One strategy, he says, would be “to draw a line around the late 20th century perennial ice pack, as a kind of warning sign to people in the extraction industries or fishing or tourism. To say, ‘Come up, develop these resources, but this is a temporary situation.’” Because one day we might want to bring the ice back.
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