Mix of Factors Led to Record Arctic Ice Melt in 2007

Summertime ice in the Arctic Ocean has been in quick retreat. There's a lot of uncertainty about how quickly it will melt away entirely in the summertime. Estimates range from 2013 to beyond 2100. The uncertainty is explained by the science behind the phenomenon of melting.

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This is ALL THINGS CONSIDERED from NPR News. I'm Melissa Block.

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And I'm Robert Siegel.

NASA scientists announced today that 2007 tied the record for the second hottest year in a century. A lot of that warm air was near the North Pole, so it's no coincidence that 2007 was also the worst year on record for melting sea ice in the Arctic. But air temperature is only part of the story, as NPR's Richard Harris reports.

RICHARD HARRIS: Every winter, the Arctic Ocean freezes over with a bed of ice that stretches from Canada to Siberia. Every summer, a lot of that ice melts back, exposing open ocean. Melting sea ice doesn't change sea level, but it does change the environment for polar bears and other wildlife. And for the past decade, the melt back has been getting bigger and bigger. 2007 was a doozie, eclipsing all previous records.

That trend has led Wieslaw Maslowski, at the Naval Postgraduate School in Monterey, to make a bold projection. Soon, he says, virtually all the Arctic Ocean's ice will melt in the summertimes.

Prof. WIESLAW MASLOWSKI (Oceanography, Naval Postgraduate School): If the trend that we've seen through 2007 continues, we probably don't need much more than five to 10 years to actually experience ice-free summers in the Arctic.

HARRIS: At a scientific meeting in San Francisco last month, he mentioned 2013 as the date that could happen. More warming leads to more open water. Water is darker than ice, so more sunlight gets absorbed. And that warming leads to more melting.

Prof. MASLOWSKI: So, we're just pretty much like a snowball going downhill.

HARRIS: But the Arctic Ocean isn't quite so tidy. Take last year's massive ice melt off. Cecilia Bitz, at the University of Washington, says it wasn't just caused by warmer water melting more ice.

Prof. CECILIA BITZ (Department of Atmospheric Sciences, University of Washington): It's normally very cloudy in the Arctic and it was much less cloudy and that let in more sunlight and that caused a lot more sea ice to melt.

HARRIS: And not only do icebergs melt, wind also blows them out of the Arctic Ocean.

Prof. BITZ: We know there's a stream of ice moving out. Something like 10 percent of the ice leaves every year.

HARRIS: Last year, Bitz says odd weather pattern shoved a lot more ice out into the North Atlantic, and that also contributed significantly to the loss of Arctic ice.

Dr. JIM MASLANIK (Research Associate, University of Colorado, Boulder): 2007 was very unique. You had all kinds of situations that came together to make it almost a perfect storm year for lost sea ice.

HARRIS: Jim Maslanik, from the University of Colorado, says next year will almost certainly be not so dramatic, but the long-term trend is still worrisome. He has an article in the latest issue of Geophysical Research Letters, "Looking at What Happened to the Arctic Ice as it Melted."

Dr. MASLANIK: The big change that we targeted was, what's happening to the ice that's remained.

HARRIS: He and his colleagues found that the ice that manages to survive summer is getting thinner and thinner. There's a lot of variation, but in general, ice that used to be 10 feet thick is now just six feet thick.

Dr. MASLANIK: So we have greater potential to lose more and more of the surviving ice because it's thinner to start with.

HARRIS: Eventually, Maslanik says, the Arctic Ocean will probably end up looking like the ocean around Antarctica. The sea ice will form every winter and melt every summer. But because there are so many factors that contribute to ice loss, it's hard to project when that day will come.

Cecilia Bitz and colleagues have run many sophisticated climate forecasts and they show an open Arctic Ocean in the summertime as soon as 2040 and as late as some time beyond 2100.

Prof. BITZ: I will see changes in my lifetime that will be more and more remarkable. But I think it's the future generation that I worry very much for. I think that they will see a planet that we would not recognize in their lifetime.

HARRIS: That is unless we do something dramatic and soon to reduce greenhouse gas emissions. Those emissions don't explain the dramatic year-to-year changes we've seen in the Arctic, she says, but they do seem to drive a long-term trend.

Richard Harris, NPR News.

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Greenland's Mysterious Holes Speed Ice Flow to Sea

Ian Joughin uses an ice drill to sink a pole into the surface. i i

Ian Joughin from the University of Washington uses an ice drill to sink a pole into the surface. The pole will anchor his equipment, which includes an instrument that measures ice-quakes and another that tracks the movement of the ice. Richard Harris, NPR hide caption

itoggle caption Richard Harris, NPR
Ian Joughin uses an ice drill to sink a pole into the surface.

Ian Joughin from the University of Washington uses an ice drill to sink a pole into the surface. The pole will anchor his equipment, which includes an instrument that measures ice-quakes and another that tracks the movement of the ice.

Richard Harris, NPR

If the Greenland ice cap were to melt tomorrow, the sea level around the world would rise by more than 20 feet.

The good news is that Greenland isn't going to melt in a flash. The bad news is that Greenland is slowly starting to release its water into the ocean in response to rising air temperatures.

Scientists are now trying to figure out how quickly we could be in trouble.

Eighty percent of Greenland is covered with one enormous ice sheet, and it oozes off the edges of the island as so-called outlet glaciers. Among the biggest is the Jakobshavn glacier, on the island's west coast.

It's a sight to behold. Huge mountains of ice — icebergs — clog a narrow fjord and slowly but surely push their way out toward the open ocean.

Scientist Ian Joughin says that in the past few years, Jakobshavn's speed has doubled.

"That's putting about twice as much ice into the fjord as a decade ago ... and twice as much into the ocean," he says.

Joughin adds that Jakobshavn is by no means alone.

"Many of the glaciers, especially along the southeast coast of Greenland, are doing very similar things, and what's kind of scary is that they all started doing them roughly at the same time," he says.

Speed-Up Raises Alarms

That speed-up was triggered by a spell of unusually warm weather — and that has raised alarms about Greenland. Before the warm-up and speed-up, scientists had thought Greenland's ice would be around for at least a thousand years. Now they are not so sure.

Joughin has come to Greenland with a colleague, Sarah Das, to figure out what is going on under the ice that is contributing to its slide toward the sea. Das says that's a challenge.

"It's not like you can go up and sort of poke your head under the ice and see what's happening. It's under water in many places, completely inaccessible," she says.

The story of sliding ice starts dozens of miles inland. In summer, some of the ice there melts and forms lakes. Most of those lakes drain thorough mysterious passages called moulins, which carry the water to the bedrock below the ice. Once the water gets under the ice, it lubricates the ice sheet, and the whole sheet flows faster toward the sea.

That's what Das and Joughin have come to Greenland to study, so they fly by helicopter from the coast to the island's expansive ice cap.

Measuring the Slide to the Sea

About 50 miles from the coast, the ice appears to be riddled with holes like Swiss cheese, making the helicopter pilot nervous. But Joughin reassures him that the holes are only round puddles about a foot deep. The ice itself is a solid block, half a mile thick.

The helicopter lands near an automated research station Joughin set up the previous summer. The scientific instruments there have been recording weather, ice-quakes and more gradual movements of the ice.

The station has to be re-anchored into the ice because Greenland's entire ice sheet is moving. Joughin, from the University of Washington, pulls out his GPS unit and finds that the region has slid more than 100 yards closer to the ocean during the past year.

He also measures a length of fishing line he had sunk straight down into the ice the previous summer to see how much of the ice has melted away. A lot of the line he had buried is lying on the surface.

"Wow," he says. "It's a meter and a half of melt since last year. Almost five feet."

Constant Change

Greenland's ice sheet deforms constantly, like pancake batter flowing on a griddle. Each year, more snow piles up in the middle, and each year, more ice slides off into the sea or melts away. At the moment, Greenland's melt water increases global sea level by about a quarter of an inch per decade. If that melt increases as the world warms, a melting Greenland will eventually eat away the shorelines of the world.

Das, who is from the Woods Hole Oceanographic Institution, and Joughin are trying to figure out how quickly that could happen. They pick their way down to the shore of the lake. They side-step water-filled pockets and clamber over hummocks of ice. There are rushing streams everywhere.

A torrent brings meltwater down from the surrounding hills of ice to the startlingly blue lake. That inflow is keeping the lake full, but Das says it's only temporary.

"Lakes serve as a reservoir. They collect probably a large fraction in these areas of all the surface meltwater and pool them all together as you see in this really vast and deep, blue lake that we're standing by," she says.

When the reservoir drains, the water will flow to the bottom of the ice sheet, where it will essentially grease the underside and make the entire region slide faster toward the coast.

Hunting for a Moulin

The mystery is how the water makes its way from the lake to the bedrock below. Das and Joughin have done some reconnaissance that suggests the water is draining out from the far end of the lake, more than a mile away.

There, the water cuts down and forms a stream about 20 feet wide, then heads down a series of incredibly fast rapids. It ends up in a hidden channel that snakes around and goes down ... somewhere. The scientists follow its path, moving uphill, as the stream cuts a deeper and deeper canyon below.

They find that the deep channel contains a roaring waterfall, descending thousands of feet into the ice. The river seems to come to a stop.

"My guess is that [the water is] going to the bottom of the ice sheet. Right before it disappears from view, it takes some huge jumps down, and as far as we've dared to creep to the edge and look down, you see it cascading almost 45 degrees or even steeper downwards into the ice with this thundering roar," Das says.

This is the long-sought moulin, the link between the melting ice on the surface and the invisible world below.

"It is quite an exciting discovery," Das says.

And there are hundreds more like it across Greenland, all speeding the flow of ice toward the sea.

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