A new study documents the formation of a 3,000 square kilometer hole in the oldest and thickest ice in the Arctic, an area also known as “The last ice zone”.
This region, located north of Greenland and Ellesmere Island (northern Canada), is considered the North Pole region that will lose its permanent sea ice and the last refuge for species in this ecosystem.
According to the document published on Thursday, October 14 in the scientific journal Geophysical Research Letters, the hole formed in May 2020 near Ellesmere. It is another sign of the rapid changes taking place in the Arctic.
It is estimated that this opening of the sea ice, called polynya, remained for two weeks, which puzzled scientists because in this part of the “last ice zone”, the layer is up to five meters thick.
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“No one had seen a polynya in this area before. North of Ellesmere Island, it is difficult to move the ice or even melt it because it is thick and there is a lot of it, ”Kent Moore, an Arctic researcher at the University of Toronto-Mississauga, who was the lead author of the study, said in a statement. .
The polynya formed during extreme wind conditions in a persistent anticyclone or a high-pressure storm with strong, clockwise winds, Moore found.
The researcher reviewed sea ice images and atmospheric data for decades. Through this, he discovered that polynyas formed there at least twice before, under similar conditions in 2004 and 1988, but no one had noticed.
Extreme wind conditions can create a gap by pushing ice aside, “explained David Babb, a sea ice researcher at the University of Manitoba who was not involved in the study,” but it is unusual for such a thick layer, as in the last ice area, move especially away from the coast, where the winds tend to be weaker than near it.
Therefore, the new study shows that the region may not be as resilient to climate change as previously thought.
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“The formation of a polynya in this area is really interesting. It is like a crack in the shield of this solid ice sheet. This event also highlights how the Arctic is changing, “said Babb.
Given the Arctic ice gets thinner every year, polynyas could form more frequently, triggering a feedback loop of ice loss.
“The thing about thinning ice is that it’s easier to move it. As the ice thins, it is easier to create these polynyas with less extreme forcing, so there is some evidence that these may become more common or larger than in the past, “said Moore.
On the other hand, warmer temperatures mean lost ice is unlikely to be replaced.
Polynyas are mainly formed in two ways: the ice is pushed out of the region or it melts, generating the hole. They tend to form in the same places year after year. They generally grow near the shoreline, where the landscape can channel the winds along the shoreline, blowing steadily in the same spot.
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Meanwhile, polynyas are not necessarily bad for their local ecosystem on short timescales. Snow-covered ice does not let much light into the water below it, limiting the amount of photosynthesis in marine vegetation, slowing productivity higher in the food chain. When the ice breaks, the ecosystem becomes animated, that is, fish fills up and predators such as birds, seals and polar bears arrive.
“There is a transitional time in which if we start to lose ice, there could be a net gain because it would be more productive. But in the long run, as the ice melts and moves out to sea and species like walruses and seabirds lose access to it, we lose that benefit. And finally, it is so hot that species cannot survive, “said Moore.