The ‘last ice zone’ may be more vulnerable to climate change than previously thought – .

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The ‘last ice zone’ may be more vulnerable to climate change than previously thought – .


TORONTO – It was long believed that the area considered to be the “last ice zone” – an area of ​​the Arctic covering the summit of Greenland and Canada – would remain safe for glacial creatures thanks to the still strong ice, though neighboring areas were becoming inhospitable.

But recent research revealing a record sea ice concentration in part of the region last summer suggests the last area of ​​ice is more vulnerable to climate change than we previously thought.

“Current thinking is that this area could be the last refuge for ice-dependent species,” said Axel Schweiger, polar scientist at UW’s Applied Physics Laboratory and lead researcher, in a press release. .

“So if, as our study shows, it may be more vulnerable to climate change than people have assumed, that’s important. “

The study, published in the journal Communications Earth and Environment last week, focused on a region of the last area of ​​ice just above Greenland, called the Wandel Sea.

The Wandel Sea is normally almost completely covered with ice which has survived for several years and remains thick all year round, even during the summer.

But when a German icebreaker called Polarstern attempted to cross the region in August 2020, mapping the route with satellite imagery, images showed their path was less obstructed than usual.

Researchers say satellite images found only 50% sea ice concentration in the region on August 14, a record high.

“Sea ice moves in the Arctic, it has a particular pattern, and it naturally ends up building up against Greenland and the northern coast of Canada,” said Schweiger. “In climate models, when you take them forward over the next century, this area tends to make summer ice survive the longest. “

Although sea ice has thinned in these areas in recent years as part of a long-term trend, the numbers have come as a surprise. The researchers note that in early 2020 the ice thickness in the region was slightly thicker than in previous years, and by early summer levels were near normal, suggesting that temporary gains in ice thickness do little to slow down the overall ice. loss.

“During the winter and spring of 2020, you had patches of older, thicker ice drifting there, but there was enough thinner, newer ice that melted to expose the open ocean.” , said Schweiger. “It started a cycle of absorbing thermal energy to melt more ice, despite the fact that there was thick ice. So, the years that you replenish the ice cover in this area with older, thicker ice, it doesn’t seem to help as much as you might expect. “

Not all sea ice disturbances in the region are caused by climate change; in 2018, unexpected winds pushed sea ice away from the coast of Greenland and created vast expanses of ocean surrounded by ice.

Much of this recent loss of ice concentration observed in the study is believed to be largely caused by unusual weather conditions. The researchers modeled the period from June 1 to August 16, 2020 and found that 80% of the record low was caused by weather factors, including winds that break and push ice.

However, a fifth of the damage was caused by long-term thinning of the ice due to global warming. The researchers are concerned about the impact of climate change, saying it “contributed significantly to the lowest record” in the study.

« [Winds] transported sea ice out of the region and allowed heat to build up due to absorption of solar radiation in the ocean, ”the study said. “This heat was mixed with the rise and contributed to rapid melting during high winds. “

Climate change is one of the factors behind the growing trend towards thinner ice and freer water. The study also points out that extreme weather events such as storms, heat waves or floods are heightened by the effect of climate change, showing how it can exacerbate existing weather patterns or problems.

“Given the long-term thinning trend and the high interannual variability in atmospheric forcing, it seems reasonable to expect that summer sea ice conditions in the [Wandel Sea] will likely become more variable in the future, ”the study explained.

While the researchers only looked at the Wandel Sea, this new data raises questions for the future of the last ice area.

The final ice zone includes vast expanses of ice that connect the islands in the northernmost regions of Canada, above Baffin Island. It is home to many species of arctic marine animals, such as polar bears, bearded seals, ringed seals and walruses.

“This area has long been considered the primary refuge for ice-dependent species, as it is one of the last places we expect summer sea ice to survive in the Arctic,” co- Author Kristin Laidre, senior scientist at the UW Applied Physics Laboratory, said in the release.

The effect that open water could have on these species is unknown.

“We know very little about the marine mammals in the last ice area,” Laidre said. “We have almost no historical or current data, and the reality is that there are many more questions than answers about the future of these populations. “

So is the last area of ​​ice in danger? We can’t tell yet. But more research needs to be done.

“Our work suggests a re-examination of climate model simulations in this area, as most do not predict the low level of summer 2020 [sea ice thicknesses] up to several decades or more in the future, ”the study says.

” While the [Wandel Sea] is only part of the LIA, our results should give us pause for thought when making assumptions about the persistence and resilience of summer sea ice in the LIA.

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