Some polar bears in Greenland survive on surprisingly little sea ice

“Pihoqahiak” means “ever-wandering one,” and is an Inuit name for the polar bear, a creature known to roam vast expanses of sea ice, sometimes plodding thousands of kilometers a year in search of seals.

But along the fjord-cut coastline of southeast Greenland, where the sea freezes over for just a few months of the year, some isolated polar bears are surviving as homebodies.

Unlike most polar bears, these bears don’t follow the sea ice during its annual recession or move onto land to hunt. Instead, the crafty ursids stalk seals on nearby glacial mélange — a floating mishmash of icebergs, sea ice fragments and snow that persists year-round near the front of glaciers in the fjords, researchers report in the June 17 Science.

“They’re residents in fjords that are sea ice–free for more than eight months of the year,” says Kristin Laidre, a biologist at the University of Washington in Seattle. “Normally, a polar bear wouldn’t be able to survive without sea ice for that long.”

For polar bears (Ursus maritimus), sea ice isn’t just frozen seawater; it’s the platform they usually use to hunt their preferred prey — seals. But as human-caused climate change raises Earth’s global temperature, that ice is disappearing. The number of polar bears that live on sea ice in the Beaufort Sea in the Arctic Ocean and Canada’s Hudson Bay is already declining. Researchers estimate that most other subpopulations of the bears will collapse by 2100 unless greenhouse gas emissions are curbed. The International Union for Conservation of Nature classifies the species as “vulnerable.”

The fjords of southeast Greenland and similar, limited areas could become a last, temporary refuge for a small number of bears, though only curbing climate change can save the ice-dependent species, Laidre and her colleagues say. Glacial mélange isn’t widespread in the Arctic, and what exists could disappear if temperatures rise too much.

Laidre and her colleagues estimate that several hundred bears may dwell in the fjords of southeast Greenland, though further work is needed to obtain a more precise count.

The southeast Greenland group came to the researchers’ attention while they were studying polar bears along east Greenland’s coast to provide advice to the Indigenous peoples who hunt the bears for subsistence. An analysis of 83 receiver-tagged polar bears from 1993 to 2021 revealed that, for the most part, bears living south of about 64° N latitude don’t interact with bears to the north, and vice versa.

Southeast Greenland bears may be mostly isolated by Greenland’s ice sheet to the west and a rapid current to the east, which could sweep seafaring bears south and stifle northward movement, the researchers say.

In northeast Greenland, the median distance traveled by tagged bears was 40 kilometers every four days. But in the southeast region, the median distance traveled was just 10 kilometers every four days, with bears sometimes traveling between neighboring fjords and sometimes remaining in the same fjord all year.

“For a polar bear, that’s nothing,” says Steven Amstrup, a zoologist and chief scientist of the conservation organization Polar Bears International, based in Bozeman, Mont., who was not involved in the study. “Apparently they’re finding enough resources there that they don’t have to make these huge, big movements.”

Southeast Greenland bears hunted on sea ice when it was present during a few months in winter and spring, the researchers found. For the rest of the year, the ursids used the glacial mélange that packed the fjords as hunting grounds.

“They use it just like sea ice,” Laidre says. “They’re able to walk [and hunt] on the mélange … and they can swim around between the pieces of ice and ambush seals.”

A polar bear mother and two cubs move across glacial mélange in southeast Greenland in September 2016.NASA OMG

It’s not entirely surprising that polar bears have settled at the fronts — or toes — of glaciers in the fjords, Amstrup says. “Oftentimes, the toes of these glaciers are very productive areas,” he says, because glacial meltwater can flush nutrients from deeper in the ocean up toward the water’s surface. “You might expect that they would have seal populations [that] could support bears.”

The researchers also analyzed rare genetic variations in the southeast Greenland bears. That work revealed that the sampled animals shared a common ancestor about 200 years ago and have essentially kept to themselves since. “They’re the most genetically isolated polar bears in the world,” Laidre says. Conserving the distinctive bears will be important for protecting the species’ genetic diversity, which is already low, she says.

But for all their peculiarity, even southeast Greenland polar bears will perish without human climate action, Laidre and Amstrup agree (SN: 12/15/10). “Loss of Arctic sea ice is still the primary threat to all polar bears,” Laidre says. “This study does not change that.”