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Accelerating Arctic Melt Worries Experts

AP
Posted: 2007-12-12  07:13:53
Filed Under: _Science News_ (http://news.aol.com/science) 
 
WASHINGTON (Dec. 11) - An already relentless melting of  the Arctic greatly 
accelerated this summer, a warning sign that some scientists  worry could mean 
global warming has passed an ominous tipping point. One even  speculated that 
summer sea ice would be gone in five years.

Greenland's  ice sheet melted nearly 19 billion tons more than the previous 
high mark, and  the volume of Arctic sea ice at summer's end was half what it 
was just four  years earlier, according to new NASA satellite data obtained by 
The Associated  Press.



 
 
 
Photo Gallery: Effects of Global Warming

 
 
 

John McConnico, AP  


A record amount of  Greenland's ice sheet melted this summer -- 19 billion 
tons more than the  previous high mark. And for the first time on record, the 
Northwest Passage was  open to navigation. 
 
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"The Arctic is screaming," said Mark Serreze, senior  scientist at the 
government's snow and ice data center in Boulder,  Colo.

Just last year, two top scientists surprised their colleagues by  projecting 
that the Arctic sea ice was melting so rapidly that it could  disappear 
entirely by the summer of 2040.

This week, after reviewing his  own new data, NASA climate scientist Jay 
Zwally said: "At this rate, the Arctic  Ocean could be nearly ice-free at the end 
of summer by 2012, much faster than  previous predictions."

So scientists in recent days have been asking  themselves these questions: 
Was the record melt seen all over the Arctic in 2007  a blip amid relentless and 
steady warming? Or has everything sped up to a new  climate cycle that goes 
beyond the worst case scenarios presented by computer  models?

"The Arctic is often cited as the canary in the coal mine for  climate 
warming," said Zwally, who as a teenager hauled coal. "Now as a sign of  climate 
warming, the canary has died. It is time to start getting out of the  coal mines."

It is the burning of coal, oil and other fossil fuels that  produces carbon 
dioxide and other greenhouse gases, responsible for man-made  global warming. 
For the past several days, government diplomats have been  debating in Bali, 
Indonesia, the outlines of a new climate treaty calling for  tougher limits on 
these gases.

What happens in the Arctic has  implications for the rest of the world. 
Faster melting there means eventual sea  level rise and more immediate changes in 
winter weather because of less sea  ice.

In the United States, a weakened Arctic blast moving south to  collide with 
moist air from the Gulf of Mexico can mean less rain and snow in  some areas, 
including the drought-stricken Southeast, said Michael MacCracken, a  former 
federal climate scientist who now heads the nonprofit Climate Institute.  Some 
regions, like Colorado, would likely get extra rain or snow.

More  than 18 scientists told the AP that they were surprised by the level of 
ice melt  this year.

"I don't pay much attention to one year ... but this year the  change is so 
big, particularly in the Arctic sea ice, that you've got to stop  and say, 
'What is going on here?' You can't look away from what's happening  here," said 
Waleed Abdalati, NASA's chief of cyrospheric sciences. "This is  going to be a 
watershed year."

2007 shattered records for Arctic melt in  the following ways:

• 552 billion tons of ice melted this summer from the  Greenland ice sheet, 
according to preliminary satellite data to be released by  NASA Wednesday. 
That's 15 percent more than the annual average summer melt,  beating 2005's record.

• A record amount of surface ice was lost over  Greenland this year, 12 
percent more than the previous worst year, 2005,  according to data the University 
of Colorado released Monday. That's nearly  quadruple the amount that melted 
just 15 years ago. It's an amount of water that  could cover Washington, D.C., 
a half-mile deep, researchers calculated.

•  The surface area of summer sea ice floating in the Arctic Ocean this 
summer was  nearly 23 percent below the previous record. The dwindling sea ice 
already has  affected wildlife, with 6,000 walruses coming ashore in northwest 
Alaska in  October for the first time in recorded history. Another first: the 
Northwest  Passage was open to navigation.

• Still to be released is NASA data  showing the remaining Arctic sea ice to 
be unusually thin, another record. That  makes it more likely to melt in 
future summers. Combining the shrinking area  covered by sea ice with the new 
thinness of the remaining ice, scientists  calculate that the overall volume of ice 
is half of 2004's total.

•  Alaska's frozen permafrost is warming, not quite thawing yet. But 
temperature  measurements 66 feet deep in the frozen soil rose nearly four-tenths of a 
degree  from 2006 to 2007, according to measurements from the University of 
Alaska.  While that may not sound like much, "it's very significant," said 
University of  Alaska professor Vladimir Romanovsky.

- Surface temperatures in the  Arctic Ocean this summer were the highest in 
77 years of record-keeping, with  some places 8 degrees Fahrenheit above 
normal, according to research to be  released Wednesday by University of 
Washington's Michael  Steele.

Greenland, in particular, is a significant bellwether. Most of  its surface 
is covered by ice. If it completely melted — something key  scientists think 
would likely take centuries, not decades — it could add more  than 22 feet to 
the world's sea level.

However, for nearly the past 30  years, the data pattern of its ice sheet 
melt has zigzagged. A bad year, like  2005, would be followed by a couple of 
lesser years.

According to that  pattern, 2007 shouldn't have been a major melt year, but 
it was, said Konrad  Steffen, of the University of Colorado, which gathered the 
latest  data.

"I'm quite concerned," he said. "Now I look at 2008. Will it be  even warmer 
than the past year?"

Other new data, from a NASA satellite,  measures ice volume. NASA 
geophysicist Scott Luthcke, reviewing it and other  Greenland numbers, concluded: "We are 
quite likely entering a new  regime."

Melting of sea ice and Greenland's ice sheets also alarms  scientists because 
they become part of a troubling spiral.

White sea ice  reflects about 80 percent of the sun's heat off Earth, NASA's 
Zwally said. When  there is no sea ice, about 90 percent of the heat goes into 
the ocean which then  warms everything else up. Warmer oceans then lead to 
more melting.

"That  feedback is the key to why the models predict that the Arctic warming 
is going  to be faster," Zwally said. "It's getting even worse than the models 
 predicted."

NASA scientist James Hansen, the lone-wolf researcher often  called the 
godfather of global warming, on Thursday was to tell scientists and  others at the 
American Geophysical Union scientific in San Francisco that in  some ways 
Earth has hit one of his so-called tipping points, based on Greenland  melt data.

"We have passed that and some other tipping points in the way  that I will 
define them," Hansen said in an e-mail. "We have not passed a point  of no 
return. We can still roll things back in time — but it is going to require  a quick 
turn in direction."

Last year, Cecilia Bitz at the University of  Washington and Marika Holland 
at the National Center for Atmospheric Research in  Colorado startled their 
colleagues when they predicted an Arctic free of sea ice  in just a few decades. 
Both say they are surprised by the dramatic melt of  2007.

Bitz, unlike others at NASA, believes that "next year we'll be back  to 
normal, but we'll be seeing big anomalies again, occurring more frequently in  the 
future." And that normal, she said, is still a "relentless decline" in  ice.





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