Greenland’s polar bears are learning to get around in a less icy world

Greenland’s polar bears are learning to get around in a less icy world

A newly discovered subpopulation of polar bears in remote southeastern Greenland have found a way to eke out a living under warm conditions similar to those forecasted for much of the Arctic later this century, scientists reported on June 16 in Science.

Increasing temperatures are causing sea-ice, which is vital for survival of polar bears, to shrink. The Southeast Greenland bears, however, use freshwater glaciers from the coast to hunt seals all year. Researchers believe that these glaciers could provide polar bears with a “climate refugia” previously unknown to them.

“Our study provides evidence that a highly isolated and previously undocumented subpopulation of polar bears off the southeast coast of Greenland is surviving in a special manner,” Kristin L. Leidre, a University of Washington marine biologist, stated in an email. “These bears may be able to tell us a little more about the future of the species .”

Although the glacier ice allows bears to live in fjords where there is no sea ice for more than eight months, this habitat is uncommon for the Arctic. Laidre acknowledged that glacier ice may be beneficial to a small number of polar bears, but not for the vast majority.

She and her collaborators identified the unique group while surveying polar bears along Greenland’s east coast, which is about 1,800 miles long. The data gathered from subsistence hunters and captured polar bears was used by the team for more than three decades. Researchers tracked the movements of bears with GPS collars and analysed DNA to determine the region’s demographics.

To their surprise, researchers discovered that bears in Southeast Greenland were not able to interact with bears on the northern coast. They found that these southerly bears were genetically distinct from the 19 other previously recognized polar bear subpopulations. Laidre noted that they are the most genetically distinct polar bears anywhere in the world.

an ice covered landscape of mountains and a valley of fast ice cutting through
A Southeast Greenland fjord is covered in fast ice, or sea ice that is connected to the coast, for about four months of the year, between February and late May. This photo was taken in April 2016. The open water seen on the horizon confines these polar bears, believed to be a 20th subpopulation, to a small region along the coast. Kristin Laidre/University of Washington

Researchers estimated that this subpopulation had been isolated for hundreds of decades. One reason is the difficult terrain, which is characterized by steep fjords that separate mountains from narrow glaciers. The Greenland Ice Sheet to west and the open water in the Denmark Strait to east keep the bears inside. The East Greenland Coastal Current, which is fast-moving, may also cut the bears off from their northern neighbors. The barricading terrain and rugged landscape may have made it harder for the Southeast Greenland bears find mates, leading to fewer cubs than other subpopulations.

[Related: For polar bears contending with climate change, it’s ‘survival of the fattest’]

Sea Ice frozen to the shore, also known as fast ice in this region of Greenland, usually persists from February through May. This means that the bears are left without sea ice for more than 250 days of the year–over 100 days longer than they can go without feeding.

Elsewhere, polar bears can move to land or northwards when the Arctic sea ice melts during the warmer months. The freshwater ice from Greenland Ice Sheet that flows into the sea allowed the Southeast Greenland bears, also known as glacial melange to stay put and capture prey all year.

Some bears were found in the same fjord over many years. On 11 occasions, the researchers observed polar bears carried southwards on drift ice caught in the East Greenland Coastal Current. The bears returned to their home fjords within a month or so after swimming ashore.

Researchers estimated that there are several hundred polar bears living in Southeast Greenland. It’s not clear if their numbers are increasing, decreasing or staying steady. Laidre stated that this is an important fact to monitor and that it requires more monitoring.

a far away picture of a lone polar bear on an iceberg
A polar bear stands on a snow-covered iceberg that is surrounded by fast ice, or sea ice connected to the shore, in Southeast Greenland in March 2016. Kristin Laidre/University of Washington

She and her colleagues concluded that it is crucial to conserve this subpopulation in order to preserve the genetic diversity and understand how climate change will affect polar bears. Although glacial melanges don’t occur often, they are found in Greenland and the Norwegian archipelago Svalbard. They are home to ring seals which are the main prey for polar bears. These conditions could provide a buffer for bears in other parts of Southeast Greenland, which is a possibility.

Laidre stated that “loss Arctic sea ice remains the primary threat to all Polar bears.” “This study does not change that.” Even the freshwater ice havens may be transformed as the Arctic heats up and the Greenland Ice Sheet melts.

“Climate change is the single most important thing that will ensure the survival of polar bears,” Laidre stated.

[Related: Record-breaking heat is bombarding the North and South poles]

Robert Newton, a geochemist at Columbia University’s Lamont-Doherty Earth Observatory who studies Arctic sea ice, praised the wealth of information that Laidre and her team analyzed to discover the new subpopulation.

” The article is optimistic in the sense that polar bears could survive without sea ice, provided they have an alternative platform to hunt.” He said, noting that glaciers can retreat for hundreds of years. “It is possible that the Arctic sea ice loss will not affect the polar bear species, even if they are forced to extinction or forced onto the land where they will merge with the brown bear population.”

Newton said that future research should examine how organisms lower down the food chain (e.g. fish, crustaceans and seals) will adapt to shrinking sea ice. The findings suggest that glacial melanges may offer a refuge for polar bears while conditions stabilize.

” If we can control global warming and greenhouse gasses, and we can return to historical temperatures at the Arctic surface, all of our modeling shows that sea ice will soon return to its former state. “If we can create refugia and protect animals there, we are really conserving something .”

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