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Study: 'Surprise' As Computer Simulation Says Arctic Ice Melt Could Pause For Several Years, Then Resume Again

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BOULDER, Colorado -- Although Arctic sea ice appears fated to melt as the climate continues to warm, the ice may temporarily stabilize or somewhat expand at times over the next few decades, new research indicates.

The computer modeling study, by scientists at the National Center for Atmospheric Research, reinforces previous findings by other research teams that the level of Arctic sea ice loss observed in recent decades cannot be explained by natural causes alone, and that the ice will eventually disappear during summer if climate change continues.

But in an unexpected new result, the NCAR research team found that Arctic ice under current climate conditions is as likely to expand as it is to contract for periods of up to about a decade.

"One of the results that surprised us all was the number of computer simulations that indicated a temporary halt to the loss of the ice," says NCAR scientist Jennifer Kay, the lead author. "The computer simulations suggest that we could see a 10-year period of stable ice or even an increase in the extent of the ice. Even though the observed ice loss has accelerated over the last decade, the fate of sea ice over the next decade depends not only on human activity but also on climate variability that cannot be predicted."

Kay explains that variations in atmospheric conditions such as wind patterns could, for example, temporarily halt the sea ice loss. Still, the ultimate fate of the ice in a warming world is clear.

"When you start looking at longer-term trends, 50 or 60 years, there's no escaping the loss of ice in the summer," Kay says.

Kay and her colleagues also ran computer simulations to answer a fundamental question: why did Arctic sea ice melt far more rapidly in the late 20th century than projected by computer models? By analyzing multiple realizations of the 20th century from a single climate model, they attribute approximately half the observed decline to human emissions of greenhouse gases, and the other half to climate variability.

These findings point to climate change and variability working together equally to accelerate the observed sea ice loss during the late 20th century.

The study appears this week in Geophysical Research Letters. It was funded by the National Science Foundation, NCAR's sponsor.

Rapid melt

Since accurate satellite measurements became available in 1979, the extent of summertime Arctic sea ice has shrunk by about one third. The ice returns each winter, but the extent shrank to a record low in September 2007 and is again extremely low this year, already setting a monthly record low for July. Whereas scientists warned just a few years ago that the Arctic could lose its summertime ice cover by the end of the century, some research has indicated that Arctic summers could be largely ice-free within the next several decades.

To simulate what is happening with the ice, the NCAR team used a newly updated version of one of the world's most powerful computer climate models. The software, known as the Community Climate System Model, was developed at NCAR in collaboration with scientists at multiple organizations and with funding by NSF and the Department of Energy.

The research team first evaluated whether the model was a credible tool for the study. By comparing the computer results with Arctic observations, they verified that, though the model has certain biases, it can capture observed late 20th century sea ice trends and the observed thickness and seasonal variations in the extent of the ice.

Kay and her colleagues then conducted a series of future simulations that looked at how Arctic sea ice was affected both by natural conditions and by the increased level of greenhouse gases in the atmosphere. The computer studies indicated that the year-to-year and decade-to-decade trends in the extent of sea ice are likely to fluctuate increasingly as temperatures warm and the ice thins.

"Over periods up to a decade, both positive and negative trends become more pronounced in a warming world," says NCAR scientist Marika Holland, a co-author of the study.

The simulations also indicated that Arctic sea ice is equally likely to expand or contract over short time periods under the climate conditions of the late 20th and early 21st century.

Although the Community Climate System Model simulations provide new insights, the paper cautions that more modeling studies and longer-term observations are needed to better understand the impacts of climate change and weather variability on Arctic ice.

The authors note that it is also difficult to disentangle the variability of weather systems and sea ice patterns from the ongoing impacts of human emissions of greenhouse gases.

"The changing Arctic climate is complicating matters," Kay says. "We can't measure natural variability now because, when temperatures warm and the ice thins, the ice variability changes and is not entirely natural."

The University Corporation for Atmospheric Research manages the National Center for Atmospheric Research under sponsorship by the National Science Foundation. Any opinions, findings and conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Views expressed in this article do not necessarily reflect those of, its staff or its advertisers.

Reader Comments

5 people have commented so far. cloud add your comment

Brought to you by the Al Gore Propaganda league.
   comment# 1   - Jason · El Dorado USA · Aug 12, 2011 @ 7:52pm

Meteorologists got away with the percentage forecast.This created the startling tolerance amongst the public. Andy Byar has more status for his predictions. After these industrious scientists got millions of dollars in grants and spent millions of hours of graduate students' time they arrived at this alarming conclusion: The ice cap might shrink or expand. You can bank on this,and you can keep sending those climate warming checks to all those non-profit protectors of the environment and polar bears. Next year the polar bears will be purchasing new coats from LL Bean.
   comment# 2   - barbara cormeny · san luis obispo,california · Aug 13, 2011 @ 6:57am

Did a majority of US residents fail basic science classes in grade & high school ? Why do so people attack scientific research with neither evidence nor credibility ? " Arctic Ice Retreating More Quickly Than Computer Models Project; 'Thirty Years Ahead Of Schedule' Study: Melting Sea Ice A Major Cause Of Warming In Arctic; 'Like A Shiny Lid On The Arctic Ocean' " Study: Melt Water Flowing Through Ice Sheets Accelerates Warming, Could Speed Up Ice Flow Arctic Ice At Low Point Compared To Recent Geologic History; 'Unmatched Over At Least The Last Few Thousand Years'
   comment# 3   - Ron Renkoski · Blooming Grove, USA · Aug 13, 2011 @ 2:37pm

ok so only three precent of greenhouse gas is made up of carbon dioxide, water vapor which occurs naturally makes up 95% of greenhouse gas. man made emmissions make up less than 1% of all greenhouse gasses. major eruptions of volcanoes over the centuries have repeatedly spewed more gas into the atmosphere than all of man kind has ever done yet even with volcanic winters the results were not drastic and only temporary. The thinking skeptic asks why are climatists so insistent that we are the cause of global warming to the point of changing numbers to favor their opinions and to out and out lie about what is ocurring today? Its about money and more importantly it's about power. Most climatists are exreme left wing idealogs who despise big business, America, and what they stand for. By demonizing them they have the power through regulation to control them and empower themselves. this is vial and should be exposed at every opportunity until even the most apathetic amongst us says no more! no more lies! no more ridiculous regulation! no more goverment intrusion into our personal lives.
   comment# 4   - joe t. · cantania sicily · Aug 16, 2011 @ 3:58pm

it is disgusting
   comment# 5   - Ana Florano Santoyo · Japan · Jul 27, 2012 @ 9:58pm
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