Researchers led by the University of Washington have discovered that polar bears in the high Arctic are sustaining ice-related injuries due to climate change. The study reveals unprecedented damage to bear paws, emphasizing the broader impact of a warming world.
In a stark reminder of the impacts of climate change, researchers have discovered polar bears in the high Arctic suffering from severe ice-related injuries to their feet. Due to shifting sea ice conditions, the bears are experiencing unprecedented levels of lacerations, hair loss and skin ulcerations.
The study, published in the journal Ecology, represents the first documentation of such injuries in polar bears.
Lead author Kristin Laidre, a senior principal scientist at the University of Washington’s Applied Physics Laboratory and a professor in the UW School of Aquatic and Fishery sciences, revealed that the bears are being affected due to more frequent freeze-thaw cycles and wet snow tied to climate warming.
“As strange as it sounds, with climate warming there are more frequent freeze-thaw cycles with more wet snow, and this leads to ice buildup on polar bears’ paws,” Laidre said in a news release.
The research team, including wildlife veterinarian Stephen Atkinson, studied two polar bear populations between 2012 and 2022.
They found that 31 of 61 bears in the Kane Basin population and 15 of 124 bears in East Greenland had injuries consistent with ice buildup. Two bears in Greenland even had massive ice blocks, up to one foot in diameter, stuck to their feet, making it nearly impossible for them to walk.
“The two most affected bears couldn’t run — they couldn’t even walk very easily,” Laidre added. “When immobilizing them for research, we very carefully removed the ice balls. The chunks of ice weren’t just caught up in the hair. They were sealed to the skin, and when you palpated the feet, it was apparent that the bears were in pain.”
The study has garnered attention because these injuries have not been previously observed despite extensive research on these polar bear populations since the 1990s. Lifetime Indigenous subsistence hunters and a survey of scientific literature also pointed to this being a recent phenomenon.
Polar bears possess small bumps on their foot pads designed to provide traction on slippery surfaces. These bumps, while helping with movement, now exacerbate the problem by allowing wet snow to freeze more easily onto their paws.
The researchers have likened this issue to one that also affects sled dogs in the North.
The study proposes three primary mechanisms through which climate change may be causing these injuries:
- Increased rain-on-snow events leading to slushy snow that clumps and freezes on paws.
- Warm spells causing surface snow to melt and refreeze into a hard crust, resulting in cuts from sharp edges.
- Thinner sea ice from warming enabling seawater to seep into the snow, which then clumps and freezes on polar bears’ feet.
While the individual bears are clearly suffering, the researchers are cautious about making broader assertions regarding the health of the populations.
Melinda Webster, a research scientist also at UW’s Applied Physics Laboratory who published a separate study on Arctic snow cover, explained the risks posed by climate change to polar bears.
“The surface of Arctic sea ice is transforming with climate change. The sea ice has less snow in late spring and summer, and the snow that does exist is experiencing earlier, episodic melt and more frequent rain. All these things can create challenging surface conditions for polar bears to travel on,” she said in the news release.
To help, “[w]e can reduce greenhouse gas emissions and try to limit climate warming,” added Webster.