A new study finds that earlier sea ice melt in the spring and later ice growth in the fall is hurting the feeding and breeding capabilities of polar bear populations all across the the Arctic.
Polar bears are among the animals most affected declines in Arctic sea ice. The bears spend their winters and springs roaming and hunting on the ice. Polar bears have evolved mainly to eat seals, which provide the fats and nutrients they need in in the harsh Arctic environment. Bears can’t outswim their prey, so instead they perch on the ice as a platform and ambush seals at breathing holes or break through the ice to access their dens. Kristin Laidre of the University of Washington’s Polar Science Center is a study co-author. She said in a statement:
Sea ice really is their platform for life. They are capable of existing on land for part of the year, but the sea ice is where they obtain their main prey.
The study, published September 14, 2016 in The Cryosphere looked at all of the 19 separate polar bear populations living throughout the Arctic, and showed declining sea ice for all the of them. The most striking result, the 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. Laidre said:
These spring and fall transitions bound the period when there is good ice habitat available for bears to feed. 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.
According to a statement from the University of Washington:
Across all 19 polar bear populations, the researchers found that 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.
Bottom line: A study published September 14, 2016 in The Cryosphere finds that earlier sea ice melt in the spring and later ice growth in the fall is hurting the feeding and breeding capabilities of polar bear populations all across the the Arctic.
Eleanor Imster has helped write and edit EarthSky since 1995. She was an integral part of the award-winning EarthSky radio series almost since it began until it ended in 2013. Today, as Lead Editor at EarthSky.org, she helps present the science and nature stories and photos you enjoy. She also serves as one of the voices of EarthSky on social media platforms including Facebook, Twitter and G+. She and her husband live in Tennessee and have two grown sons.