The Big Thaw

From Greenland to Antarctica, the world is losing its ice faster than anyone thought possible. Can humans slow the melting?

:From National Geographic:

Even in better times, the Chacaltaya ski area was no competition for Aspen. Set in a bleak valley high in the Andes mountains of Bolivia, it offered a half-mile (one kilometer) swoop downhill, a precarious ride back up on a rope tow, and coca-leaf tea for altitude headaches. At 17,250 feet (5,260 meters), after all, Chacaltaya was the highest ski area in the world. "It gave us a lot of glory," says Walter Laguna, the president of Bolivia's mountain club. "We organized South American championships—with Chile, with Argentina, with Colombia."

The glory days are over. Skiing at this improbable spot depended on a small glacier that made a passable ski run when Bolivia's wet season dusted it with snow. The glacier was already shrinking when the ski area opened in 1939. But in the past decade, it's gone into a death spiral.

By last year all that remained were three patches of gritty ice, the largest just a couple of hundred yards (200 meters) across. The rope tow traversed boulder fields. Laguna insists that skiing will go on. Perhaps the club can make artificial snow, he says; perhaps it can haul in slabs of ice to mend the glacier. But in the long run, he knows, Chacaltaya is history. "The process is irreversible. Global warming will continue."

From the high mountains to the vast polar ice sheets, the world is losing its ice faster than anyone thought possible. Even scientists who had monitored Chacaltaya since 1991 thought it would hold out for a few more years. It's no surprise that glaciers are melting as emissions from cars and industry warm the climate. But lately, the ice loss has outstripped the upward creep of global temperatures.

Scientists are finding that glaciers and ice sheets are surprisingly touchy. Instead of melting steadily, like an ice cube on a summer day, they are prone to feedbacks, when melting begets more melting and the ice shrinks precipitously. At Chacaltaya, for instance, the shrinking glacier exposed dark rocks, which sped up its demise by soaking up heat from the sun. Other feedbacks are shriveling bigger mountain glaciers ahead of schedule and sending polar ice sheets slipping into the ocean.

Most glaciers in the Alps could be gone by the end of the century, Glacier National Park's namesake ice by 2030. The small glaciers sprinkled through the Andes and Himalaya have a few more decades at best. And the prognosis for the massive ice sheets covering Greenland and Antarctica? No one knows, if only because the turn for the worse has been so sudden. Eric Rignot, a scientist at NASA's Jet Propulsion Laboratory who has measured a doubling in ice loss from Greenland over the past decade, says: "We see things today that five years ago would have seemed completely impossible, extravagant, exaggerated."

The fate of many mountain glaciers is already sealed. To keep skiing alive in Bolivia, Walter Laguna will need to find a bigger, higher ice field. And the millions of people in countries like Bolivia, Peru, and India who now depend on meltwater from mountain glaciers for irrigation, drinking, and hydropower could be left high and dry. Meanwhile, if global warming continues unabated, the coasts could drown. If vulnerable parts of the ice that blankets Greenland and Antarctica succumb, rising seas could flood hundreds of thousands of square miles—much of Florida, Bangladesh, the Netherlands—and displace tens of millions of people.

The temperature threshold for drastic sea-level rise is near, but many scientists think we still have time to stop short of it, by sharply cutting back consumption of climate-warming coal, oil, and gas. Few doubt, however, that another 50 years of business as usual will take us beyond a point of no return.


ANCIENT CORAL HEADS, white and dead, record an earlier time when the climate warmed and the seas rose. Found just inland in the Florida Keys, Bermuda, and the Bahamas, they date from roughly 130,000 years ago, before the last ice age. These corals grew just below the sea surface, and are now marooned well above it. When they flourished, sea level must have been 15 to 20 feet (five to six meters) higher—which means that much of the water now in Greenland's ice was sloshing in the oceans.

All it took to release that water was a few degrees of warming. Climate back then had a different driver: not fossil-fuel emissions but changes in Earth's tilt in space and its path around the sun, which warmed summers in the far North by three to five degrees Celsius (5° to 9°F) compared with today. At the rate the Arctic is now warming, those temperatures could be back soon—"by mid-century, no problem," says Jonathan Overpeck of the University of Arizona, who has studied the ancient climate. "There's just unbelievable warming in the Arctic. It's going much faster than anyone thought it could or would."

Computer models that forecast how ice sheets will react to the warming tend to predict a sluggish response—a few thousand years for them to melt, shrink, and catch up to the reality of a warmer world. If the models are right, rising seas are a distant threat.

Yet what is happening on the Greenland ice sheet is anything but leisurely. For the past 15 years, Konrad Steffen of the University of Colorado at Boulder has spent each spring monitoring the ice from a camp deep in the interior. Back again in the coastal village of Ilulissat last summer, the Swiss-born climate researcher, lean and weathered from wind and glacial glare, sits with colleagues in a waterfront hotel, waiting out fog that has grounded their helicopter. "Things are changing," he says. "We see it all over."

Offshore, flotillas of icebergs drift silvery in the half-light—tangible evidence of the change. Their voyage began nearby in a deep fjord, where a glacier called Jakobshavn Isbræ flows to the sea.

Ice seems rock hard when you crunch an ice cube or slip on a frozen puddle. But when piled in a great mass, ice oozes like slow, cold taffy. On Greenland, it flows outward from the heart of the ice sheet, a dome of ice the size of the Gulf of Mexico, and either peters out on land or follows fast-flowing ice streams all the way to the ocean. Four miles (six kilometers) wide and several thousand feet thick, Jakobshavn is an icy Amazon, disgorging more ice than any other Greenland glacier.

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