26 August 2011

UN Climate Report Fails to Capture Arctic Ice Thinning Reality: MIT

The United Nations' most recent global climate report "fails to capture trends in Arctic sea-ice thinning and drift, and in some cases substantially underestimates these trends," says a new research from MIT.

The Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report, released in 2007, forecasts an ice-free Arctic summer by the year 2100.

However, the Arctic sea ice may be thinning four times faster than predicted, according to Pierre Rampal and his research team of MIT'S Department of Earth, Atmosphere, and Planetary Sciences (EAPS).

The research team's findings will be published in the Journal of Geophysical Research-Oceans.

After comparing IPCC models with actual data, Rampal and his collaborators concluded that the forecasts were significantly off. IPCC models focused on changes in temperature, which are one way to lose or gain ice. However, Rampal said that the report underestimates mechanical forces that contributed to ice-melting.

Mechanical forces like wind or ocean currents batter the ice causing it to break up. Ice in small pieces behave differently than ice in one large mass and are more susceptible to thinning due to temperature changes.

Wind and currents also play a significant role in winter, when they can cause "drastic effects" on the ice's shape and movement, said Rampal.

Since the Arctic Ocean's winter ice-cover has grown thinner over the years, it breaks up more easily under the influence of winds and currents. This leads to even more ice break up in the summer. The study states that smaller pieces of ice are more likely to escape from the Arctic basin and move to warmer waters in the south where the ice would melt, which would mean more Arctic ice thinning.

On the other hand, large cracks in winter's ice cover help create new ice, since the extremely cold air in contact with the liquid ocean promotes refreezing.

Because "everything is coupled" in these intricate feedback loops, "it's hard to predict the future of Arctic sea ice," Rampal says.

Rampal believes that it is necessary to improve the accuracy of the Arctic ice thinning predictions by considering mechanical forces and other ice phenomena that have taken a back seat in IPCC models.

Rampal is working on a project with researchers at MIT and NASA's Jet Propulsion Laboratory to combine models and observations which will produce a more accurate picture of what's happening.

Rampal and his research team aren't the only ones contemplating the fate of the Arctic ice.

Scientists at the National Center for Atmospheric Research (NCAR) published a study in the journal Geophysical Research Letters, stating 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.

Computer simulations showed that the level of Arctic sea ice loss was not wholly the result of warming, but ran hand in hand with climate variability.

"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. The computer simulations suggest that we could see a 10-year period of stable ice or even a slight 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," said NCAR scientist Jennifer Kay, the lead author.

Despite the thinning of Arctic ice getting a short reprieve in the next decade, even Kay admitted that the long term trend did not bode well.

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

Studies show that ice in the Arctic has shrunk by about a third since 1979. Arctic ice cover hit a new monthly record low, this July.

Scientists have warned that Arctic summer ice could soon be a thing of the past.

IPCC predicts that this could happen by 2100. But MIT researchers seem to disagree, saying that it could be sooner. It is still uncertain when we might see an Arctic summer devoid of ice.

The most important thing to do is to start "with the interventions even earlier. Now," Rajendra Pachauri, IPCC chair, said in an interview reported by The New York Times.

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