Arctic ice pack losing ground
HYPERLINK "http://www.news-miner.com/Stories/0" \t "linkWin" http://www.news-miner.com/Stories/0,1413,113~7244~3286890,00.html#
By CHRIS TALBOTT
Staff Writer
Fairbanks Daily News-Miner
Monday, April 10, 2006 - The Arctic Ocean ice pack has not rebounded from record minimums recorded last summer, causing scientists to worry that the planet's global warming "canary in the coal mine" is in a tightening spiral of decline.
Abnormally high temperatures across the Arctic basin most of this winter have slowed the production of new ice, according to Mark Serreze of the National Snow and Ice Data Center at the University of Colorado. The ice pack lost an area the size of Alaska in 2005 and has thinned dramatically in the last four years.
Serreze said conditions are now right for another record-breaking minimum following this summer's melt, provided there isn't a cold snap.
"It's just not recovering this winter," Serreze said. "And the basic reason it's not recovering is the Arctic Ocean has been so darn warm."
Weather data shows surface temperatures across much of the Arctic were 4 to 5 degrees above normal September through December. The pack has been at or near record minimums every month this winter and Serreze said Wednesday the latest data for March also shows a record minimum.
Satellite images of the sea ice date back to 1978. By using other data, Serreze and his fellow researchers believe the sea ice is at its smallest in more than a century.
The ice pack covered more than 3 million square miles in the mid-1970s. That figure had been whittled down to about 2 million square miles by September, according satellite observations. More than 500,000 square miles of ice disappeared last summer alone, according to Serreze.
"In the past four years or so, we've really seen the bottom drop out of the system," he said.
He and his Colorado colleagues now predict the summer ice pack could disappear by the end of the century. Canadian researchers in a 2005 Canadian Broadcasting Corp. report predicted ice-free summers in no more than 15 years.
Loss of the ice would have dramatic impacts locally and globally. Some, such as unfettered shipping across the top of the world, might be considered positives. Other impacts--the loss of wildlife dependent on the ice pack and the accompanying traditional subsistence hunting opportunities--will be considered negatives.
The melting will also change some of the globe's natural systems, accelerating climate change in ways that can be anticipated but not predicted with certainty.
A growing number of scientists believe changes in temperature, currents, water salinity and other variables have altered the Arctic's natural rhythms so much that they are now the driving force. Change begets change.
These changes--manmade or not--have knocked the system into a state of decline with a loss of ice mass now at about 8 percent a year, according to multiple researchers. Like a wobbly top, each successive spin becomes more erratic.
Sea ice, for instance, is reflective and sends much of the sun's radiation back into space. Remove the ice and the sun's heat is absorbed by the darker ocean water, raising the Arctic's average temperature and hampering future ice growth.
"And the next loop may bring even more change," said Igor Polyakov, a research professor at the University of Alaska Fairbanks' International Arctic Research Center.
Point of no return
The acceleration of sea ice decline has some scientists hypothesizing that the Arctic system has crossed a "tipping point," and a state of decline is the new normal.
Ronald W. Lindsay and Jinlun Zhang of the University of Washington's Polar Science Center wrote in a 2003 paper: "It is quite possible that the large changes ... of the early 1990s have forced the system into a new state in which very large extents of summer open water and winter first-year ice are the norm. ... The gradually increasing winter air temperatures may reflect a global warming signal that will preclude a return to the old regime."
That the sea ice is declining is as clear as the blue ocean seen by satellites from above. What's causing that decline remains up to debate.
The ice has been steadily declining for decades, researchers have found. But it has done so in halting steps, Serreze said. A low year might be followed by a high year, but the cumulative average still dwindled over time.
Serreze said he believes evidence shows a "greenhouse forcing effect" is evident in the Arctic. Manmade gases have accumulated in the atmosphere over the decades. Large quantities of carbon dioxide have helped change the weather, warming some areas and cooling others.
In the Far North, Serreze said, a warming of temperatures was the first domino in a chain reaction that has brought us to the point where his canary sits unsteadily upon its high-latitude perch.
"It just looks more and more like what we're going to see," Serreze said of the effect.
"You're forcing it to warm up with greenhouse gases. And a significant signal of that is sea ice."
Others aren't ready to lump the blame on man and greenhouse gases. Many agree that temperature deserves to be considered, but point to another increase in temperature during the 1930s had little effect on the sea ice.
This led some scientists to look at other mechanisms that could cause changes. As it turns out there are several possible culprits. And all might play their own little part in the ice pack's decline.
Ignatius Rigor, a professor at Washington's Polar Science Center, said wind and its effects upon current have had more to do with Arctic change than temperature. Only time can prove him right.
"If it's purely temperature-driven, then it's toast, it's gone," Rigor said. "If the wind does play a bigger role, then there's a chance."
Rigor said his research showed circulation changes in the Arctic Ocean in the late 1980s and early '90s drastically changed the composition of sea ice.
"Most of the older, thicker sea ice got flushed out of the Arctic Ocean," he said. "So what you're left with is younger, thinner ice.
"The younger, thinner ice doesn't have enough mass to withstand a summer melt."
A matter of time
There are basically two kinds of sea ice: first-year ice and multi-year ice.
Cold temperatures each winter create first-year ice. It measures no thicker than 2 yards, is fragile and lately has tended to melt each summer barring a cold snap.
Multi-year ice accumulates with the help of successive cold winters and storms, which Rigor said cause ridging and rafting. As ice floes pile upon one another, the pack's thickness grows and adds to a central pack that can withstand short-term weather variability.
Rigor created an animation clip that showed what he believes are the dramatic effects of a change in what climate researchers refer to as Arctic Oscillation, the system of currents that control polar water flow. Those current changes pushed most of the Arctic's multi-year ice through Fram Strait east of Greenland and into the Atlantic Ocean where it melted.
So the Arctic is now dominated by first-year ice, which is much more susceptible to the ravages of temperature.
"I associate a lot of the climate change we're seeing in the Arctic right now with the fact we had a high Arctic Oscillation event in the '90s and we're kind of seeing the memory of that," Rigor said.
Others view water temperature as a possible culprit. Polyakov said his research shows warmer Atlantic water has been entering the Arctic. And he pointed to the studies of others who think Pacific Ocean water is also infiltrating the Arctic, increasing the warming trend.
"What we found in 2004 and one year later in 2005 is the Arctic Ocean is becoming warmer and warmer," he said.
Lindsay and Zhang in their tipping point paper tied most of these variables together:
* The ice pack was "preconditioned" by gradually increasing fall, winter and spring temperatures over the past six decades. The warmth hindered the growth of first-year ice, which no longer survived through the summer.
* The multi-year ice that remained was then flushed into the Atlantic. Current changes that caused this have reverted to normal.
* These changes have caused a feedback: Reduced ice cover leads to warmer water, which further reduces ice coverage.
Lindsay and Zhang call their ideas a hypothesis, but Rigor can see a future in which all of these variables are blended together to create a complete picture.
"It may sound like we disagree and have these different biases, but I really think when it comes down to it and we figure it out 20 years from now, we're going to make those puzzle pieces fit together," he said.
Chris Talbott can be reached at 459-7575 or HYPERLINK "http://farns9.iserver.net/imanager/wizards/mm_compose.cgi?mbox=&mpos=1&send_to=ctalbott@newsminer.com" \t "linkWin" ctalbott@newsminer.com .