Summer sea ice in the Arctic has plunged 46 percent since accurate observations began 40 years ago, but one region has remained relatively immune. Known as the Last Ice Area, this zone north of Greenland and parts of Canada is seen as crucial for the prospects of endangered polar species. However, in the face of record-breaking temperatures in Canada and Arctic Siberia it's not surprising scientists have found even this refuge is threatened by a rapidly heating world.
"Current thinking is that this area may be the last refuge for ice-dependent species,” said Dr Axel Schweiger of the University of Washington in a statement. “So if...it may be more vulnerable to climate change than people have been assuming, that's important," Examples include polar bears and walruses, which need ice to hunt, and some seals that use it to protect their young.
Schweiger is lead author of a paper in Communications Earth and Environment that suggests this is indeed the case. The paper focuses on the Wandel Sea, the easternmost portion of the Last Ice Area, and probably indicative of the whole region's fate. The Wandel lies to the north of eastern Greenland. Two immense fjords open into it, feeding ice from Greenland interior into the Arctic Ocean.
"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."
The first sign the Last Ice Area might not be as impregnable as previously thought came in spring 2018, when unusual northward winds caused a large ice-free area to open up.
This might have been dismissed as a freak event, but on August 14, 2020 satellites show just 50 percent of the Wandel sea was ice covered, despite near-normal levels a few months earlier. Schweiger and co-authors modeled this event in detail, trying to separate transitory and long-term drivers.
Temporary factors such as strong winds causing ice to break up were the dominant cause. However, the authors concluded, 20 percent of the lost ice was a consequence of long-term ice thinning as a result of worldwide rising temperatures. For the Arctic as a whole 2020 saw the second lowest summer ice on record.
With global causes accounting for only one-fifth of the forces driving last year's extreme conditions the lack of Wandel sea ice may not return this year, particularly soon. However, barring a dramatic turnaround in human activity, years with even less ice coverage are inevitable, with disastrous consequences for local mammals, and even birds.
The situation has parallels elsewhere. “Flooding in New York City in response to Superstorm Sandy was on the order of 20% more extreme owing to long-term sea level rise,” the paper notes.
Most of the paper's authors are based in Seattle, so publication coincides with them suffering under the heat dome, another phenomenon caused primarily by unusual local conditions, but greatly exacerbated by rising carbon dioxide and methane concentrations. They're unlikely to have any shortage of further examples to study.