A previously unknown population of polar bears that adapt to limited sea ice access due to global warming by hunting from freshwater ice pouring into the ocean from glaciers have been discovered by scientists.
While most polar bears rely on sea ice to hunt seals, scientists found this distinct, isolated population uses freshwater ice at the marine terminal glacial fronts as a platform to hunt seals year-round.
The study was published in the journal Science on Thursday by scientists, including those from the University of Washington in the US.
It sheds light on this isolated population of a few hundred polar bears that are genetically distinct and uniquely adapted to this environment.
Researchers said studying this population could shed light on the future of the species in the warming Arctic.
“We wanted to survey this region because we didn’t know much about the polar bears in southeast Greenland, but we never expected to find a new subpopulation living there,” Kristin Laidre, a polar scientist and lead author of the study, said in a statement.
“We knew there were some bears in the area from historical records and indigenous knowledge. We just didn’t know how special they were,” Dr Laidre said.
In the study, scientists combined seven years of new data collected from the southeastern coast of Greenland – a region poorly studied due to unpredictable weather, jagged mountains and heavy snowfall – along with 30 years of historical data from the island’s entire east coast.
The findings revealed that this unique subpopulation of polar bears, with limited access to sea ice, used glacier ice to survive.
“Southeast Greenland bears survive in fjords that are sea-ice free more than eight months of the year because they have access to glacier (freshwater) ice on which they can hunt seals. They are the most genetically isolated polar bears in the world,” Dr Laidre tweeted.
“Polar bears are threatened by sea ice loss due to climate change. This new population gives us some insight into how the species might persist into the future,” she said.
Researchers said the genetic difference between these polar bears and their nearest genetic neighbours was greater than that observed for any of the 19 previously known populations.
“But we need to be careful about extrapolating our findings because the glacier ice that makes it possible for Southeast Greenland bears to survive is not available in most of the Arctic,” she added.
“They are the most genetically isolated population of polar bears anywhere on the planet,” Beth Shapiro, another co-author of the study, said.
“We know that this population has been living separately from other polar bear populations for at least several hundred years, and that their population size throughout this time has remained small,” Dr Shapiro added.
These bears are likely isolated as they are hemmed in on all sides by sharp mountain peaks and the massive Greenland Ice Sheet to the west, open water of the Denmark Strait to the east and a fast-flowing east Greenland coastal current posing a hazard offshore.
While other polar bear populations move on land or migrate with receding sea ice into less productive areas during the ice-free season, the adaptation seen in this new group allows the bears to succeed in an otherwise inhospitable place, researchers said.
The findings, according to the scientists, have implications for polar bear conservation.
They suggest that these marine-terminating glaciers, although of limited availability, may provide previously unrecognised climate refugia to the bears.
While these habitats are uncommon in the Arctic, researchers said they are available in places like Greenland or Svalbard.
However, scientists cautioned that longer-term monitoring is needed to know the future viability of these unique bears and to understand what happens to polar bear subpopulations as they are increasingly cut off from the rest of the Arctic.
“Preserving the genetic diversity of polar bears is crucial going forward under climate change. Officially recognising these bears as a separate population will be important for conservation and management,” Dr Laidre said.