'Last Ice Area' may be more vulnerable to climate change than thought

A polar bear is perched on a thick chunk of sea ice north of Greenland in March 2016. These thicker, older pieces of sea ice don't fully protect the larger region from losing its summer ice cover. (Kristin Laidre/University of Washington)

TORONTO -

It’s long been thought the area deemed the “Last Ice Area” — a region of the Arctic spanning the top of Greenland and Canada — would remain safe for ice-dwelling creatures through consistently strong ice even if neighbouring areas became inhospitable.

But recent research finding a record low of sea-ice concentration in part of the region last summer is suggesting that the Last Ice Area is more vulnerable to climate change than we previously thought.

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

“So if, as our study shows, it may be more vulnerable to climate change than people have been assuming, that's important.”

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The study, published in the journal Communications Earth and Environment last week, focused on a region of the Last Ice Area right above Greenland, called the Wandel Sea.

The Wandel Sea normally is almost entirely covered by ice that has survived for multiple years and remains thick year-round, even during the summer.

But when a German icebreaker called Polarstern was attempting to sail through the area in August 2020, mapping the route with satellite images, the images showed that their path was less obstructed than usual.

Researchers say the satellite images found just 50 per cent sea ice concentration in the area on August 14, a record low.

"Sea ice circulates through the Arctic, it has a particular pattern, and it naturally ends up piling up against Greenland and the northern Canadian coast," Schweiger said. "In climate models, when you spin them forward over the coming century, that area has the tendency to have ice survive in the summer the longest."

While sea ice has been thinning in these regions in recent years as part of a long-term trend, the numbers came as a surprise. Researchers note that at the start of 2020, the ice thickness in the area was slightly thicker than previous years, and that at the start of the summer the levels were close to normal, suggesting that temporary gains in ice thickness do little to slow overall ice loss.

"During the winter and spring of 2020 you had patches of older, thicker ice that had drifted into there, but there was enough thinner, newer ice that melted to expose open ocean," Schweiger said. "That began a cycle of absorbing heat energy to melt more ice, in spite of the fact that there was some thick ice. So in years where you replenish the ice cover in this region with older and thicker ice, that doesn't seem to help as much as you might expect."

Not every disruption of sea ice in the region is caused by climate change; in 2018, unexpected winds pushed sea ice away from the coast of Greenland and created wide stretches of ocean hemmed in by ice.

The majority of this recent loss in ice concentration observed in the study is thought to be largely caused by unusual weather. Researchers modelled the period from June 1 to August 16, 2020, and found that 80 per cent of the record low was caused by weather-related factors, including winds that break up ice and push it around.

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

“[Winds] transported sea ice out of the region and allowed the accumulation of heat from the absorption of solar radiation in the ocean,” the study stated. “This heat was mixed upward and contributed to rapid melt during high wind events.”

Climate change is one of the driving factors behind the growing trend of thinner ice and more open water. The study also points out that extreme weather events such as storms, heat waves or floods are increased by climate change’s effect, showing how it can exacerbate existing weather patterns or issues.

“Given the long-term thinning trend and strong 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 researchers only looked at the Wandel Sea, this new data does bring up questions for the future of the Last Ice Area.

The Last Ice Area includes wide swathes of ice that connects islands in the northernmost parts of Canada, above Baffin Island. It supports numerous species of Arctic marine animals, such as polar bears, bearded seals, ringed seals and walruses.

"This area has long been expected to be the primary refuge for ice-dependent species because it is one of the last places where we expect summer sea ice to survive in the Arctic," co-author Kristin Laidre, a principal scientist at the UW Applied Physics Laboratory, said in the release.

What affect more open water could have on these species is unknown.

"We know very little about marine mammals in the Last Ice Area,” Laidre said. “We have almost no historical or present-day data, and the reality is that there are a lot more questions than answers about the future of these populations.”

So is the Last Ice Area at risk? 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, since most do not predict summer 2020-level low [sea ice thicknesses] until several decades or more into the future,” the study said.

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