TOP STORIES 'Completely unexpected': These polar bears can survive without sea...

‘Completely unexpected’: These polar bears can survive without sea ice


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Scientists have identified a distinct subpopulation of polar bears in southeast Greenland, which, in an area with little sea ice, survive by hunting off ice that has broken away from glaciers.

The discovery suggests that a small number of bears may survive as warming continues and much of the sea ice they normally depend on disappears. But researchers and other polar experts have warned that serious risks to the general polar bear population in the Arctic remain and will only be reduced by reducing greenhouse gas emissions to curb global warming.

The subpopulation, believed to number several hundred animals, was identified in a multi-year survey of what was thought to be the only bear population along the entire 1,800-mile-long east coast of Greenland. Through analysis of satellite-tracked movements, tissue samples and other data, bears in the southeast have been found to be isolated both physically and genetically from others.

“This was a completely unexpected discovery,” said Christine Leidre, a biologist at the University of Washington who has been studying marine mammal ecology in Greenland for two decades. Dr. Laidre is the lead author subpopulation article published Thursday in the journal Science.

Southeast Greenland is particularly remote, with narrow fjords surrounded by steep mountains. At the inner end there are often glaciers that end in water; at the other end is an open ocean with a strong southerly current. “These bears are very geographically isolated,” Dr. Laidre said. “They really turned into residents because that’s the only way to live there.” Researchers estimate that this subpopulation has been isolated for at least several hundred years.

General. There are an estimated 26,000 polar bears in the Arctic, belonging to 19 officially designated subpopulations. The animals live on the seasonal sea ice, preying on their main prey, seals, as the seals bask on the ice or exhale through breathing holes. But the rapid warming of the Arctic, associated with anthropogenic greenhouse gas emissions, has reduced the extent and duration of sea ice cover.

Some subpopulations, especially in the southern Beaufort Sea off the coast of Alaska and Canada, are already declining because the ice doesn’t persist long enough for the bears to hunt for enough food for themselves and their young. Polar bear experts say that if the world continues to warm, polar bears could almost disappear by the end of the century.

Southeast Greenland is relatively warm, and the fjords there have less sea ice than many other areas with polar bears – on average, about 100 days a year of ice is enough for them to live and hunt. “We know that this is too little for the polar bear to survive,” Dr. Laidre said. It is these conditions that may become widespread in other parts of the Arctic at the end of this century.

Dr Laidre and her colleagues have discovered that the bears of southeast Greenland hunt from the ice as long as he is around. But when it’s gone, the bears have another ice to hunt: freshwater ice that breaks off glaciers in the fjords in icebergs and smaller pieces, and that lasts most of the year.

Bears hunt from this floating mixture of ice called glacial melange, just like they hunt from sea ice. “This gives them an extra and unusual ice platform that bears don’t have in many other places,” Dr. Laidre said, allowing them to catch enough seals so that they and their offspring can survive and thrive.

But such habitats are rare, says Twila Moon, a scientist at the National Snow and Ice Data Center in Boulder, Colorado, who analyzed sea ice and fjord ice sheets as part of the study.

“There are a limited number of places in the Arctic where we are seeing significant and consistent production of glacial mélange,” Dr. Moon said. In addition to some areas of Greenland, the Norwegian archipelago of Svalbard has glaciers that end in water.

So while these special conditions may allow some bears to survive as sea ice continues to shrink, overall the bears will continue to be threatened by climate change.

“We expect a significant decline in the number of polar bears in the Arctic under the current warming trajectories,” Dr. Laidre said. “And this study doesn’t change that.”

Steven Amstrup, chief scientist at conservation group Polar Bears International, who was not involved in the study, said the study was “really thorough” and “points to a very distinct group of bears.”

Whether this is the 20th official subpopulation is decided by a panel of experts under the auspices of International Union for Conservation of Nature. “It’s not clear to me whether this will benefit this group of bears in terms of their safety or their overall well-being in the future,” Dr. Amstrup said.

He said he agreed with the researchers that, in his words, “this is not some kind of salvation for polar bears.” First, according to him, warming leads to the retreat and disappearance of all types of ice, including glaciers. Thus, the glaciers in the fjords of Greenland will not go into the water forever and produce glacial mélange. The study, he says, “shows a temporary advantage for these bears.”

“Now they can survive even though there are too many ice-free days in terms of sea ice,” added Dr Amstrup. “But that will change in the future if we don’t stop the global rise in greenhouse gases.”

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