Climate scientists track young, thin Arctic ice

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Sea ice mingles with icebergs off the coast of Greenland during the peak of the 2015 melt season. @bberwyn photo.

Remarkable changes with huge planetary implications

Staff Report

Earth’s climate control system — the Arctic — is changing so fast that researchers are having a hard time keeping up. In an effort to understand how the region is shifting toward a new state, a team of scientists spent nearly six months examining the younger and thinner sea ice that’s become ubiquitous in the past few years. They discussed their findings this week at the fall meeting of the American Geophysical Union in San Francisco.

“Many things we experienced took us by surprise,” said Mats Granskog, a research scientist at the Norwegian Polar Institute and chief scientist of the Norwegian young sea ICE, or N-ICE2015 project. “We saw that the new Arctic, with much thinner sea ice only three to four feet thick, functions much differently from the Arctic we knew only 20 years ago, when the ice was much thicker.”

One of the biggest concerns is that the reduced sea-ice coverage and thickness will lead to even more melting, the so-called Arctic amplification. Most of the solar energy that reaches Arctic snow and sea ice gets reflected back into space. But when the snow and ice is replaced by darker, open water, most of the energy gets absorbed and in turn helps melt more ice.

The thin ice that remains is particularly vulnerable. It moves faster, breaks up more easily and is more vulnerable to winds and storms.

Von Walden, a Washington State University professor of civil and environmental engineering, documented how winter storms affect the surface energy balance of the young, thinner sea ice.

One winter storm raised the surface temperature from  minus 40 degrees Fahrenheit to 32 degrees in less than 48 hours, while the moisture in the air increased tenfold. These storms also bring clouds. All of these factors significantly warm the surface at a time when there is no sunlight, he said.

Amelie Meyer, an oceanographer at the Norwegian Polar Institute, saw how storms can move the ice so fast that warm, 40 degree Fahrenheit water rises tens to hundreds of feet to melt the underside of the ice. In the summer, as much as 10 inches of ice can melt in one day.

At one point, the scientists saw vast stretches of ice break up in a few hours, forcing them to scramble and even wade through frozen water to retrieve their equipment.

The researchers also observed the first phytoplankton bloom under snow-covered ice as additional light passing through leads, or cracks, triggers its early growth. Traditional Arctic under-ice blooms tend to sink to the deep ocean, sequestering carbon in a sort of “carbon pump.” But this bloom did not sink as much as expected due to a different algae that grew in it. Such changes could have significant implications for Arctic ecology and the movement of carbon, the researchers said.

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