Polar bear and cub, arctic

Courtesy NOAA Photo Library

A polar bear and cub traverse floating Arctic sea ice in search of prey.

Arctic Melt Shrinks Polar Bears’ Chances

Increasing loss of Arctic sea ice is cutting back the platform of life on which all polar bears rely for successful feeding and breeding

The world of the polar bear is shrinking—everywhere. New research by scientists in the U.S. confirms that each of the 19 known populations of Ursus maritimus is increasingly affected by the earlier sea ice melt in the Arctic spring, and the later arrival of ice every autumn.

The finding is hardly a shock, as there have been warnings from conservationists about such things for years, with the polar bear becoming an icon of climate change concerns. And in most cases of species threat there are winners as well as losers.

But the latest study—published in The Cryosphere, a journal of the European Geosciences Union—confirms that there are no winners. The ice is in retreat for all polar bear populations.

The 25,000 or so surviving Arctic bears rely on the ice for their feeding and breeding success. A few stay on the ice all year round, but southerly populations survive ashore in the summer, and it is the seasonal winter feast upon seals and other sea mammals that gives them the nourishment to make it to the next breeding season.

Arctic Concentrations

“Sea ice really is their platform for life,” says Kristin Laidre, principal scientist at the University of Washington’s Polar Science Centre (PSC). “They are capable of existing on land for part of the year, but the sea ice is where they obtain their main prey.”

She and her co-author, Harry Stern, principal mathematician at the PSC, used 35 years of satellite data to examine sea ice concentrations around the entire Arctic.

The total number of ice-covered days fell at the rate of seven to 19 days per decade between 1979 and 2014. Sea ice in the summer months—when polar bears are often forced to fast on land—also declined in all regions, by between one percent and nine percent per decade.

“We expect that if the trends continue,
polar bears will experience another six to seven weeks
of ice-free periods by mid-century”

And they found that the trend toward an earlier spring melt and a later autumn freeze was consistent everywhere.

Dr Laidre and other scientists reported last year that all Arctic marine mammals could be at risk because of habitat loss. The catch was that biologists did not know enough about them to be sure.

Spring Melt

Another group of researchers has established that things look bleak for Canada’s polar bears, but this is just a subset of the species.

The PSC scientists have now established that spring melt has begun on average three to nine days earlier per decade, and the freeze similarly later each decade. Effectively, that added up to seven weeks’ total loss of good habitat—that is, firm ice upon which the bears can stalk seals.

“These spring and fall transitions bound the period when there is good ice habitat available for bears to feed,” Dr Laidre says. “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.”

Originally published on Climate News Network on September 25, 2016. Reprinted with permission under a Creative Commons license.

Comments are closed.

Credit Card Identification Number

This number is recorded as an additional security precaution.

americanexpress

American Express

4 digit, non-embossed number printed above your account number on the front of your card.
visa

Visa

3-digit, non-embossed number printed on the signature panel on the of the card immediately following the card account number.
mastercard

MasterCard

3-digit, non-embossed number printed on the signature panel on the back of the card.

Enter Your Log In Credentials

Send this to friend

Hi,
I thought you might find this interesting:
Arctic Melt Shrinks Polar Bears’ Chances

URL: https://indiancountrymedianetwork.com/news/environment/arctic-melt-shrinks-polar-bears-chances/