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Last August, scientists boarded an icebreaker ship that was drifting along the Arctic Ocean with the ice. annual research expedition He decided to go to the North Pole.
They needed to get there quickly, so they used satellite data to find a route where the sea ice concentration was low enough for the icebreaker Polarstern to pass easily. They found him in an unexpected place, in the Wandel Sea, just north of Greenland.
“This area used to be filled with this old, thick sea ice,” said researcher Melinda Webster of the University of Alaska Fairbanks, who was on this part of the mosaic expedition. “This is not what we encountered as we passed by.”
Dr. Instead, the ice was thin and there was plenty of open water, Webster said.
Scientists have now shown why ice conditions in the Wandel Sea were so different last summer. The warming Arctic climate thinned the ice, and an unusual change in winds pushed most of the ice out of the sea.
“There is an underlying component to climate change, as is typically the case with extreme events,” said Axel J. Schweiger, a climate scientist at the University of Washington and lead author of the study. article describing the research It was published Thursday in Communications Earth & Environment magazine.
The findings have potentially troubling implications for the Wandel Sea, a region often referred to as the “last ice zone,” and the near waters in northern Canada. Because the Beaufort Cycle, a circular ocean current, tends to trap ice there, climate models predict it will likely retain ice over the next few decades as warming will cause the rest of the Arctic Ocean to become ice-free. .
If this area remains ice-filled, it could become last summer’s refuge for polar bears and other Arctic wildlife dependent on sea ice. But new research suggests the region may be less resistant to warming, and similar lower ice concentrations are expected.
“This region is not as stable as we thought,” said Luisa von Albedyll, an ice dynamics researcher at the Alfred Wegener Institute in Germany, who was in Polarstern when the route was chosen. Neither he nor Dr. Webster was not involved in the new research.
Dr. Schweiger and other researchers have seen and studied thinning ice in the Wandel Sea in recent years, including when a large open water area called polynya opened up in 2018. The Polarstern experience also helped Dr. Schweiger was intrigued. “It wouldn’t normally be an icebreaker captain’s first choice,” Rota said.
Using satellite imagery and computer models simulating sea ice, he and his colleagues showed that much of the impact on ice at Wandel in 2020 could be linked to natural variability in winds in the region.
These winds normally blow from the north and tend to hold the ice in place with the coasts of Greenland and Canada in the south. They were displaced to blow in the opposite direction in August 2020, causing most of the ice to leave the sea and drift elsewhere.
But simulations have also shown that, as elsewhere in the Arctic Ocean in recent years, climate change is playing a role by melting and thinning ice. While the world in general is warming as a result of man-made emissions of carbon dioxide and other heat-trapping gases, the Arctic is warming two and a half times faster than average, much faster than other regions.
Using data starting in 1979, when modern satellite imagery of the Arctic began, the researchers also examined what might have happened in previous years under the same wind conditions that existed last summer.
The analysis showed that if the same variable winds had occurred in 2018 and 2019, similar low ice conditions would have arisen. Dr. “But the probability of this happening with ice from 1979 is much smaller,” Schweiger said, because the area wasn’t that warm at that point, and the ice was thicker.
Dr. Webster said the study provides a “very plausible explanation” for what happened last summer. And he said it illustrates an important point about the effects of climate change in the Arctic.
“As sea ice gets thinner and more seasonal, it becomes more sensitive to what’s going on in the atmosphere and ocean,” he said. “So windy conditions will play a bigger role.”
Dr. “What we experienced last summer was unprecedented,” Webster added. “But it will probably be the norm for decades to come.”
“This is how the North Pole changes.”
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