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Polar bears negatively affected as Arctic sea ice break-up and freeze-up timings change


Polar bears have become the poster child of the negative effects of climate change and global warming and showing how these bears will face further problems is a new study that reveals that change in the Arctic sea ice break-up and freeze-up timings will negatively affect the polar bears.

Published in the Cryosphere is a new study by University of Washington scientists wherein scientists have found a trend toward earlier sea ice melt in the spring and later ice growth in the fall across all 19 polar bear populations, which can negatively impact the feeding and breeding capabilities of the bears. Scientists have, for the first time, been able to quantify the sea ice changes in each polar bear subpopulation across the entire Arctic region.

Through their findings, scientists show that the critical timing of the sea ice break-up and sea ice freeze-up is changing in all areas in a direction that is harmful for polar bears.

Why is sea ice so important for these polar bears? The simple answer to this question is that the sea ice is like a platform of life for these polar bears. The primary food source of these bears in the harsh Arctic weather are seals. Because the bears can’t outswim these seals, their best bet is ambush. The bears perch on the ice as a platform and ambush seals at breathing holes or break through the ice to access their dens.

The study was able to show that across all 19 polar bear populations in the Arctic, the total number of ice-covered days declined at the rate of seven to 19 days per decade between 1979 and 2014. Sea ice concentration during the summer months — an important measure because summertime is when some subpopulations are forced to fast on land — also declined in all regions, by 1 percent to 9 percent per decade.

The most striking result, researchers said, is the consistent trend across all polar bear regions for an earlier spring ice melt and a later fall freeze-up. Arctic sea ice retreats in the springtime as daylight reappears and temperatures warm. In the fall months the ice sheets build again as temperatures drop.

“These spring and fall transitions bound the period when there is good ice habitat available for bears to feed,” said co-author Kristin Laidre, a researcher at the UW’s Polar Science Center. “Those periods are also tied to the breeding season when bears find mates, and when females come out of their maternity dens with very small cubs and haven’t eaten for months.”

“We expect that if the trends continue, compared with today, polar bears will experience another six to seven weeks of ice-free periods by mid-century,” said co-author Harry Stern, a researcher with the UW’s Polar Science Center.