For two weeks in May 2020, a 3,000-square-kilometre hole, known as a polynya, opened up in the ‘Last Ice Area’, a million-square-kilometre area of sea ice north of Greenland and Ellesmere Island. These are natural openings that form in places that are normally covered with ice. However, this polynya has been sighted in a region north of Canada’s Ellesmere Island, which until now was thought to be immune to such events.
The formation of this polynya was unusual because of its location off the coast of Ellesmere Island, where the ice is up to five metres thick. At its peak, the polynya was 100 kilometers long and 30 kilometers wide. As the new report points out, the polynya formed during an episode of extreme winds.
According to the new study, which was published in Geophysical Research Letters, it is “expected to be the last region to lose its perennial ice.” The ‘Last Ice Area’ is home to the thickest and oldest ice in the Arctic, which can reach over 5 metres thickness in some places. It stands in stark contrast to the rest of the Arctic, where old, thick sea ice has been almost completely wiped out by warmer temperatures.
The new study also shows that the region north of Ellesmere Island may not be as resilient to climate change as previously thought.
The fear is that this will become a recurring event. Regular polynyas in the ‘Last Ice Area’ could set off a feedback loop in which the presence of thinner ice makes it increasingly easy for polynyas to form and grow larger over time.
Polynyas are formed mainly in two ways: The ice is either blown out of the region or melts and forms the hole. They tend to form in the same places year after year and typically grow near the coast, where the landscape can channel winds along the coast and blow steadily in the same place.
“The thing about thinning ice is that it’s easier to move it. As the ice gets thinner, it is easier to create these polynyas with less extreme forces. So there is evidence that these polynyas are becoming more frequent or larger than they were in the past,” said Moore, an Arctic researcher at the University of Toronto and lead author of the study. And warmer temps mean lost ice is unlikely to be replaced.
Moore and his colleagues used true-color satellite imagery from MODIS, radar satellite imagery from RADARSAT-1, and high-resolution satellite imagery from Sentinel-1 to detect the polynya. The gap was open from May 14 to May 28, 2020.
It is worth noting that polynyas are not necessarily bad and may even have ecological benefits. These occasional gaps in the ice allow photosynthesis, which increases food production in the water. The openings in the ice sheet also attract all kinds of wildlife, including seabirds, polar bears and seals.
But the short-term boost to the local ecosystem does not outweigh the long-term and irreversible damage caused by sea ice loss.
Heiner Kubny, PolarJournal
