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A polar bear is perched on a thick chunk of sea ice north of Greenland. These thicker, older pieces of sea ice don’t fully protect the larger region from losing its summer ice cover.Handout

The part of the Arctic Ocean that is permanently covered in sea ice is more vulnerable to climate change than previously thought, according to an international study.

The result carries implications for species that depend on the ice as a habitat – and for policy makers trying to understand how much time countries have to shift to low-carbon energy sources before the region reaches a point of no return.

Researchers in the United States and Canada set out to analyze the conditions that led to the record low in sea-ice extent that occurred last summer in the Wandel Sea, north of Greenland. The region is part of what has been dubbed the Last Ice Area because it includes the thickest, most enduring sea ice in the Arctic.

Last year, there was enough open water in the Wandel Sea to allow the German research icebreaker Polarstern to cut directly across it as part of a one-year expedition. Kent Moore, a professor of atmospheric physics at the University of Toronto Mississauga and a co-author on the study, said the ship’s passage through an area known for thick ice cover that persists year-round may indicate that the ice is more varied and subject to change than previously appreciated.

“While the ice is quite thick in general, it’s important to look at the distribution of thick and thin ice, [not just the average thickness],” Dr. Moore said.

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In previous studies, Dr. Moore and colleagues have shown that the thin areas can result from winds that push on the ice, forcing cracks to open. That effect was in play last summer, when atmospheric circulation in the region was particularly strong owing to a large, high-pressure system north of Siberia.

The researchers investigated whether a longer-term climate shift also played a role through rising temperatures acting on the ice. After using a computer model to simulate different climate scenarios, they determined that warming owing to climate change is responsible for about 20 per cent of the conditions that led to the Wandel Sea opening up last year, over and above any variations in wind patterns.

“That’s a pretty important signal,” Dr. Moore said. “It means that as the ice continues to thin we’ll see a more pronounced response even under less extreme natural variability.”

The Last Ice Area extends westward from the Wandel Sea toward the Canadian Artic archipelago, where similar forces are at work on the ice, though with some regional differences, Dr. Moore said. As climate change continues to transform the Arctic, conservationists have looked to the area as a last refuge for species that depend on a permanent ice ecosystem, including polar bears and seals, while the world works to eliminate carbon emissions by mid-century.

The new research, published Thursday in the journal Communications Earth & Environment, shows that the Last Ice Area may be less resilient than hoped.

Julienne Stroeve, a climatologist at the University of Manitoba and senior scientist at the U.S. National Snow and Ice Data Center in Colorado who was not involved in the study, said the results from the modelling lend quantitative support to the changes researchers are seeing in the region – though she added that she saw no surprises given what is already known about sea ice loss in the Arctic.

“I do agree that we will also lose this last remnant ice in the future,” she said.

Open this photo in gallery:

Sea ice on the Wandel Sea north of Greenland seen from the German icebreaker Polarstern, which passed through the area as part of the year-long MOSAiC Expedition. This area used to remain fully covered in ice throughout the year.Handout

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