A huge hole opened in the Arctic's oldest, thickest ice in May 2020, a new study revealed. Scientists previously thought that this area of ice was the Arctic's most stable, but the giant rift signals that the ancient ice is vulnerable to melt.
The polynya, or area of open water, is the first ever observed north of Ellesmere Island. But in their report on the hole in the ice, published in August in the journal Geophysical Research Letters, researchers deduced from old satellite data that similar polynyas may have opened in 1988 and 2004.
"North of Ellesmere Island it's hard to move the ice around or melt it just because it's thick, and there's quite a bit of it," study lead author Kent Moore, an Arctic researcher at the University of Toronto-Mississauga, said in a statement. "So, we generally haven't seen polynyas form in that region before.
A changing Arctic
The sea ice off the northern coast of Ellesmere Island is typically more than 13 feet (4 meters) thick and has an average age of 5 years. But this "last ice" of the Arctic is proving vulnerable to the rapid warming that's occurring in the northern latitudes. In summer 2020, the Wandel Sea, or the eastern reaches of the "last ice" region, lost half of its overlying ice, a July 2021 study found. Another 2021 study showed that the ice arches that connect the stable sea ice to Greenland are forming later and melting faster each year.
Now, researchers say that the last ice area may melt completely each summer by the end of the century, spelling the end for animals that depend on year-round sea ice, such as polar bears.
The polynya is another bad sign for the last ice. Polynyas are cracks in the sea ice that often open up during storms, when the wind moves the ice. There was a strong storm north of Ellesmere Island in May 2020, and satellite imagery showed that a long narrow crack, or lead, formed on May 14. By May 15, the lead had evolved into an elliptical polynya, about 62 miles (100 kilometers) long and 18.6 miles (30 km) wide. On May 26, the polynya rapidly closed.
The researchers looked back at older satellite datasets that recorded sea ice concentration. They found that a polynya likely opened in the area in May 1988, though satellite imagery from that time was not sharp enough to discern much about the shape or size of the opening. A second polynya likely occurred in May 2004. The winds during the 2004 event were stronger than in 1988 or 2020, but the 2004 polynya was smaller than the 2020 opening, the researchers wrote in their paper. This may be because the ice has thinned since 2004, they wrote, meaning that weaker winds can create wider openings.
"The formation of a polynya in the area is really interesting," David Babb, a sea ice researcher at the University of Manitoba in Canada, who was not involved in the study, said in the statement. "It's sort of like a crack in the shield of this solid ice cover that typically exists in that area. So that this is happening is also really, really highlighting how the Arctic is changing."
In the future, polynyas might open up more frequently as the Arctic's last ice melts, Moore said. In the short term, these open areas can be oases for life: Sunlight hits the ocean water, allowing for more algal photosynthesis, which attracts fish and crustaceans. These animals, in turn, attract seabirds, seals and polar bears, he added. But this explosion of life is only temporary.
"[O]ver the long term, as ice melts and moves offshore and species like walruses and seabirds lose access to it, we lose that benefit," Moore said. "And eventually, it gets so warm that species can't survive."
Originally published on Live Science.