Arctic ice might win short reprieve

The Greenland ice sheet has lost 1,500 billion tons of ice since 2000. Declines like this have made it possible for a long-lost species of plankton to return to the North Atlantic. Getty Images

The retreat of Arctic ice might get a short reprieve in the next decade, a new study finds, but the long-term trend is still toward a complete summer melt.

A new model predicts that Arctic ice, which has been declining for roughly three decades, may stabilize in the next 10 years or so, meaning no additional melting, or even expand.

"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," study researcher Jennifer Kay, a scientist at the National Center for Atmospheric Research (NCAR), said in a statement. "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."

Kay added that "the fate of sea ice over the next decade depends not only on human activity but also on climate variability that cannot be predicted."

But while temporary weather conditions could boost Arctic ice, the long-term trend is not so rosy.

"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, telling LiveScience that "the long-term fate is basically sealed if we continue to increase greenhouse gas concentrations in the atmosphere."

Ice retreat

The extent of summertime ice in the Arctic has shrunk by about a third since 1979, studies show. This July set a new monthly record low in Arctic ice cover, and scientists have warned that Arctic summer ice could be a thing of the past within decades or by the end of the century.

"Once you initiate the process you accelerate the whole thing," said Josefino Comiso, a senior scientist at the cyrospheric sciences branch of NASA Goddard Space Flight Center who was not involved in the new study. "If the area becomes warmer that means that the ice doesn't have as much time to grow. And in the process it's generally thinner every year than the previous year, and if it's thinner then it's more vulnerable to melt in the following summer."

A temporary expansion due to a particularly icy year will do little to halt the overall trend, Comiso told LiveScience.

"You'd have to have a sustained change in temperature, a sustained cooling in the region, so then your ice cover gets a chance to get thicker," he said.

Ice ups and downs

The new study confirmed that the losses of Arctic ice in the late 20th century can't be explained by natural climate variability alone, the researchers write Thursday (Aug. 11) in the journal Geophysical Research Letters. They used a computer model called the Community Climate System Model and verified that the model can indeed capture the ice ebbs and flows already observed in the real world. About half of the summer ice loss between 1979 and 2005 can be explained by natural variability, the researchers found, while the other half is due to human greenhouse emissions.

Next, the researchers simulated possibilities for future climate, plugging in different levels of greenhouse gases under varied natural conditions. They found that under current climate conditions Arctic ice is just as likely to expand as it is to contract over the next decade, depending on wind patterns and other difficult-to-predict variability. A warming climate muddles that short-term picture.

"The changing Arctic climate is complicating matters," Kay said. "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 results are in line with what Arctic scientists would expect, said Julienne Stroeve, a researcher at the National Snow and Ice Data Center in Boulder, Colo. Sea ice ups and downs happen, Stroeve told LiveScience, but in a 20-year timeframe, the ice cover trend is inescapably downward.

"You might get more variability for awhile until the ice gets thin enough that it just all goes away," Stroeve said. "But this doesn't in any way contradict the long-term sea ice loss."

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