During low ice seasons, some polar bears turn to glacier ice
Holes in the sea ice provide the perfect hunting ground for polar bears looking to catch their primary food source: seals. So when rising temperatures melt the sea ice, the existence of polar bears is threatened, making them the poster child for many climate change reports and documentaries. While every population of polar bears is threatened by the loss of this sea ice, some have developed adaptations to survive low ice seasons. In southeast Greenland, researchers have discovered a unique subpopulation of polar bears that have found a way to live in an area with low sea ice by hunting on glacial mix – a floating mix of icebergs that have calved glaciers, pack ice and snow that forms at the base of glaciers and survives the warm season.
The discovery was published in June in the journal Science by an international team of Arctic scientists. The population is isolated and genetically distinct from other groups of polar bears and survives in fjords free of sea ice for more than two-thirds of the year.
The Arctic Ocean is a mixture of liquid and frozen seawater at the North Pole. This area and the adjacent seas surrounding it are critical and declining habitat for polar bears. Polar bears use the sea ice to travel long distances and hunt ringed seals, their favorite prey, or other seals and marine mammals. Typically, polar bears wait near holes in the sea ice for their prey to come to the surface for air so they can snatch them out of the water.
As sea ice in the Arctic Ocean regained the mass it had lost in the summer during the cold, dark winter months, it has been steadily shrinking for decades. It has lost an average of 27,000 square miles of ice per year since 1979. That’s bad news for species that depend on sea ice, like polar bears, who are now forced to spend more time on land and to fast for longer periods. . With sea ice breaking up and retreating earlier in the summer, many polar bears have little or no access to food during the warmer months, affecting both their physical and reproductive health.
According to the new study, an isolated population of polar bears on the southeast coast of Greenland supplement the low-ice season by relying on glacier ice for hunting when the sea ice has disappeared. Unlike sea ice, glaciers form on land, while sea ice forms and melts in the ocean. Glacial mixing is a floating mixture of icebergs from glaciers, snow and freshwater ice that forms at the base of glaciers that end in lakes and rivers in fjords, narrow valleys carved out by the movement of ancient ice. Since glaciers do not melt completely in summer, they provide a hunting ground for this subpopulation when sea ice is not available.
Lead author Kristin Laidre, an associate professor in the School of Aquatic and Fisheries Sciences at the University of Washington, was conducting a decade-long survey of polar bears on the east coast of Greenland with her team when they realized that they could be looking at two subpopulations rather than one. “We were assessing what we thought was a single subpopulation on the 1,800-mile-long east coast of Greenland when we made this totally unexpected discovery,” Laidre said in an interview with GlacierHub. The decade-long survey tracked the movements, genetics and demographics of polar bears along the east coast of Greenland. They also interviewed indigenous subsistence hunters in East Greenland and incorporated their traditional ecological knowledge into the study.
Using genetic and behavioral data, Laidre and his team realized they had found a new subpopulation of polar bears on the southeast coast of Greenland – the “world’s most genetically isolated polar bears”, according to Ugly. In other words, although these bears are still the same species as other polar bears, they are genetically and demographically different from other subpopulations. Genetic diversity is important for species because it allows them to adapt to changing environments. While more research needs to be done on the population, a combination of genetic diversity and behavioral adaptation has allowed these bears to hunt on glacier ice during low sea ice seasons to supplement their diet.
Laidre stressed that this research does not mean bears are not at risk from sea ice loss. is not available to the vast majority of polar bears,” she explained. In the long term, she notes the importance of studying this population and other polar bears to understand where Arctic polar bears might survive and how genetic diversity can help other species threatened by climate change.