Arctic ice 'is at tipping point'

By Richard Black
Environment correspondent, BBC News website

Arctic sea ice has shrunk to the second smallest extent since satellite records began, US scientists have revealed.

The National Snow and Ice Data Center (NSIDC) says that the ice-covered area has fallen below its 2005 level, which was the second lowest on record.

Melting has occurred earlier in the year than usual, meaning that the iced area could become even smaller than last September, the lowest recorded.

Researchers say the Arctic is now at a climatic "tipping point".

"We could very well be in that quick slide downwards in terms of passing a tipping point," said Mark Serreze, a senior scientist at the Colorado-based NSIDC.

"It's tipping now. We're seeing it happen now," he told the Associated Press news agency.

Under covered

The area covered by ice on 26 August measured 5.26 million sq km (2.03 million sq miles), just below the 2005 low of 5.32 million sq km (2.05 million sq).

But the 2005 low came in late September; and with the 2008 graph pointing downwards, the NSIDC team believes last year's record could still be broken even though air temperatures, both in the Arctic and globally, have been lower than last year.

Last September, the ice covered just 4.13 million sq km (1.59 million sq miles), the smallest extent seen since satellite imaging began 30 years ago. The 1980 figure was 7.8 million sq km (3 million sq miles).

The 2008 graph shows a steeper decline than at the same time last year

Most of the cover consists of relatively thin ice that formed within a single winter and melts more easily than ice that accumulated over many years.

Irrespective of whether the 2007 record falls in the next few weeks, the long-term trend is obvious, scientists said; the ice is declining more sharply than even a decade ago, and the Arctic region will progressively turn to open water in summers.

A few years ago, scientists were predicting ice-free Arctic summers by about 2080.

Then computer models started projecting earlier dates, around 2030 to 2050; and some researchers now believe it could happen within five years.

Global Warming Puts the Arctic on Thin Ice

1. Why are global warming specialists watching the Arctic so closely?
The Arctic is global warming's canary in the coal mine. It's a highly sensitive region, and it's being profoundly affected by the changing climate. Most scientists view what's happening now in the Arctic as a harbinger of things to come.
2. What kinds of changes are taking place in the Arctic now?Average temperatures in the Arctic region are rising twice as fast as they are elsewhere in the world. Arctic ice is getting thinner, melting and rupturing. For example, the largest single block of ice in the Arctic, the Ward Hunt Ice Shelf, had been around for 3,000 years before it started cracking in 2000. Within two years it had split all the way through and is now breaking into pieces.

The polar ice cap as a whole is shrinking. Images from NASA satellites show that the area of permanent ice cover is contracting at a rate of 9 percent each decade. If this trend continues, summers in the Arctic could become ice-free by the end of the century.

3. How does this dramatic ice melt affect the Arctic?

The melting of once-permanent ice is already affecting native people, wildlife and plants. When the Ward Hunt Ice Shelf splintered, the rare freshwater lake it enclosed, along with its unique ecosystem, drained into the ocean. Polar bears, whales, walrus and seals are changing their feeding and migration patterns, making it harder for native people to hunt them. And along Arctic coastlines, entire villages will be uprooted because they're in danger of being swamped. The native people of the Arctic view global warming as a threat to their cultural identity and their very survival.

4. Will Arctic ice melt have any effects beyond the polar region?

Arctic Ice: Going, Going...

The chances for a total meltdown at the pole are higher than ever because the layer of ice coating the sea is thinner than ever, he said.

"A large area at the North Pole and surrounding the North Pole is first-year ice," Serreze said. "That's the stuff that tends to melt out in the summer because it's thin."

Preliminary February and March data from a NASA satellite shows that the circle of ice surrounding the North Pole is "considerably thinner" than scientists have seen during the five years the satellite has been taking pictures, NASA ice scientist Jay Zwally said Friday. He thinks there is slightly less than a 50-50 chance the North Pole will be ice-free.

Last year was a record year for ice melt all over the Arctic and the ice band surrounding the North Pole is even thinner now.

There is nothing scientifically significant about the North Pole, Serreze said. But there is a cultural and symbolic importance. It's home to Santa Claus, after all. Last August, the Northwest Passage was open to navigation for the first time in memory.

A more conservative ice scientist, Cecilia Bitz at the University of Washington, put the odds of a North Pole without ice closer to 1 in 4. Even that is far worse than climate models had predicted, which was 1 in 70 sometime in the next decade, she said.

But both she and Serreze agree it's just a matter of time.

North Pole May Be Ice Free for First Time This Summer

Aalok Mehta aboard the C.C.G.S. Amundsen
National Geographic News

June 20, 2008

Arctic warming has become so dramatic that the North Pole may melt this summer, report scientists studying the effects of climate change in the field.

"We're actually projecting this year that the North Pole may be free of ice for the first time [in history]," David Barber, of the University of Manitoba, told National Geographic News aboard the C.C.G.S. Amundsen, a Canadian research

Firsthand observations and satellite images show that the immediate area around the geographic North Pole is now mostly annual, or first-year, ice—thin new ice that forms each year during the winter freeze.

Such ice is much more prone to melting during the summer months than perennial, or multiyear, ice, which is thick and dense ice that has lasted through multiple cycles of thawing and refreezing.

"I would say the ice in the vicinity of the North Pole is primed for melting, and an ice-free North Pole is a good possibility," Sheldon Drobot, a climatologist at the Colorado Center for Astrodynamics Research at the University of Colorado, said by email.

The melt would be mostly symbolic—thicker ice, pushed against the Canadian continental shelf by weather and Earth's rotation, would still survive the summer.

Recent models suggest that the Arctic won't see its first completely ice-free summer until somewhere between 2013 and 2030.

But this summer's forecast—and unusual early melting events all around the Arctic—serve as a dire warning of how quickly the polar regions are being affected by climate change

Massive Melt

Scientists are particularly interested in the North and South Poles because they are expected to show the most dramatic effects of global warming.

Models predict that the regions will see temperature increases roughly three times as quickly as the rest of the globe because of an effect known as ice albedo feedback, which occurs when highly reflective ice gives way to dark water.

The water absorbs much more of the sun's energy, increasing temperatures and causing further ice melting.

Arctic sea ice melt 'even faster'

By Richard Black
Environment correspondent, BBC News website
Arctic sea ice is melting even faster than last year, despite a cold winter.

Data from the US National Snow and Ice Data Center (NSIDC) shows that the year began with ice covering a larger area than at the beginning of 2007.

But now it is down to levels seen last June, at the beginning of a summer that broke records for sea ice loss.

Scientists on the project say that much of the ice is so thin that it melts easily, and the Arctic may be ice-free in summer within five to 10 years. We had a bit more ice in the winter, although we were still way below the long-term average," said Julienne Stroeve from NSIDC in Boulder, Colorado.

"So we had a partial recovery. But the real issue is that most of the pack ice has become really thin, and if we have a regular summer now, it can just melt away," she told BBC News.

In March, Nasa reported that the area covered by sea ice was slightly larger than in 2007, but much of it consisted of thin floes that had formed during the previous winter. These are much less robust than thicker, less saline floes that have already survived for several years.
GraphA few years ago, scientists were predicting ice-free Arctic summers by about 2080.

Then computer models started projecting earlier dates, around 2030 to 2050.

Then came the 2007 summer that saw Arctic sea ice shrink to the smallest extent ever recorded, down to 4.2 million sq km from 7.8 million sq km in 1980.

By the end of last year, one research group was forecasting ice-free summers by 2013.

"I think we're going to beat last year's record melt, though I'd love to be wrong," said Dr Stroeve.

"If we do, then I don't think 2013 is far off any more. If what we think is going to happen does happen, then it'll be within a decade anyway."

Rising tide

Countries surrounding the Arctic are eyeing the economic opportunities that melting ice might bring.

Canada and Russia are exploring sovereignty claims over tracts of Arctic seafloor, while just this week US President George Bush has urged more oil exploration in US waters - which could point the way to exploitation of reserves off the Alaskan coast.

Summer ice cover in the Arctic has declined sharply

But from a climate point of view, the melt could bring global impacts accelerating the rate of warming and of sea level rise.

"This is a positive feedback process," commented Dr Ian Willis, from the Scott Polar Research Institute in Cambridge.

"Sea ice has a higher albedo (reflectivity) than ocean water; so as the ice melts, the water absorbs more of the Sun's energy and warms up more, and that in turn warms the atmosphere more - including the atmosphere over the Greenland ice sheet."

Greenland is already losing ice to the oceans, contributing to the gradual rise in sea levels. The ice cap holds enough water to lift sea levels globally by about seven metres (22ft) if it all melted.

Natural climatic cycles such as the Arctic Oscillation play a role in year-to-year variations in ice cover. But Julienne Stroeve believes the sea ice is now so thin that there is little chance of the melting trend turning round.

"If the ice were as thin as it was in the 1970s, last year's conditions would have brought a dip in cover, but nothing exceptional.

"But now it's so thin that you would have to have an exceptional sequence of cold winters and cold summers in order for it to rebuild."

Richard.Black-INTERNET@bbc.co.uk

Climate change hitting Arctic faster, harder

A new study by WWF warns that climate change is having a greater and faster impact on the Arctic than previously thought.

The new report, called Arctic Climate Impact Science � An Update Since ACIA, represents the most wide-ranging reviews of arctic climate impact science since the Arctic Climate Impact Assessment (ACIA) was published in 2005.

The report shows that the melting of Arctic sea ice and the Greenland Ice Sheet is severely accelerated, prompting concerns that both may be close to their 'tipping point'; the point where, because of climate change, natural systems may experience sudden, rapid and perhaps irreversible change. "The magnitude of the physical and ecological changes in the Arctic creates an unprecedented challenge for governments, the corporate sector, community leaders and conservationists to create the conditions under which arctic natural systems have the best chance to adapt," said Dr Martin Sommerkorn, one of the report�s authors and Senior Climate Change Adviser at WWF International's Arctic Programme. According to last year's reports from the Intergovernmental Panel on Climate Change (IPCC), if the entire Greenland Ice Sheet were to melt, sea levels would rise 7.3m, making its status a global concern.

While it is currently impossible to accurately predict how much of the ice sheet will be melting, and over what time, the new report shows there has been a far greater loss of ice mass in the past few years than had been predicted by scientific models.

Likewise, the loss of summer Arctic sea ice has increased dramatically. In September 2007, the sea ice shrank to 39 per cent below its 1979-2000 average, the lowest since satellite monitoring began in 1979 and also the lowest for the entire 20th century based on monitoring from ships and aircraft.