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Lack of ice causing major problems for female polar bears

In April the Norwegian Polar Institute observed unusually many female bears with cubs. The cause was record amount of new ice last winter. This year the situation is completely different. The picture was taken April 25 in Wahlenbergfjorden. FOTO: Jon Aars, Norwegian Polar Institute

Climate:

Lack of ice causing major problems for female polar bears

The polar bears are sleeping, but where? That is a mystery. A near-record absence of sea ice is destroying access to the traditionally important denning areas in Svalbard.

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27.12.2015 kl 13:17

The winter ice cover in the Arctic is so far one of the worst since satellite measurements began nearly 40 years ago, according to the U.S. National Oceanic and Atmospheric Administration (NOAA). The sea ice minimum in October was the sixth-lowest ever.

Ice charts for Svalbard show small narrows with open sea in all directions. Such conditions stretch across the archipelago to Kong Karls Land and Hopen, the most important denning areas for polar bears in the archipelago.

The deadline for pregnant females to hibernate is here. In about one month they will begin to give birth.

"When ice is as it is now, we are certain that there will be few bears that hibernate in these places," said Jon Aars, a polar bear researcher at the Norwegian Polar Institute.
"At Hopen there are virtually no lairs because of the ice conditions now. By comparison, there can be more than 30 in good years."

"There will be almost none that come to Hopen if the ice is not settled by Dec. 1," he said.

Se bildet større

2015 ice charts for Svalbard on 30 November. With the exception of some ice in a few fjords, it is open sea in all directions. It prevents the polar bear in achieving its main denning areas on Kong Karls Land and Hopen. FOTO: Meteorological Institute

Where are the sleeping bears?

At Kong Karls Land there will "always be some females who are left on land" for the summer season But during a bad ice year there will be far fewer than normal able to hibernate there.

"Polar bears are good at swimming, but it doesn't seem like they're doing it mainly to reach denning areas," Aars said.

Where does a bear go if she can't get to her planned den site?
That's one of many unanswered questions surrounding the mysterious life of the bears, Aars said.

"We don't know," he said. "There are two possibilities. Either she goes and hibernates somewhere else, or she skips giving birth for one year. How much energy will she use looking for a worse alternative?"

An opportunity exists for some to follow the ice edge eastward to Franz Josef Land and hibernate there, instead of pointing their snouts south toward solid ground in Svalbard. But data for such movement is too thin to conclude anything.

"Another question is how much we understand about the probability that there is good ice in and around those areas," Aars said. "Why if a female bear, standing up on ice edge and realizing that there is little ice in the fjords of Svalbard, would she therefore choose to go to Franz Josef Land instead?"

Aars said there are indications females prefer to go back to the same denning areas year after year.

"There are also genetic studies that suggest cubs will use the same location as their mothers," he said.

Se bildet større

2014: This is how it looked like one year ago. The contitions was exceptionally good with thick drift ice along the east coast of Svalbard and all the way to Hopen. FOTO: Meteorological Institute

Affects survival rates

There are many indications the problematic conditions have an effect on the survival of cubs, which weigh only about half a kilo at birth. In March or April, when they typically leave the den with their mother, they are fortunate if they weigh about ten kilos and are well-fed on nutritious milk. But that requires the mother having good fat reserves.

"There are studies showing the years in which female bears came late in to the den that the cubs had lower weights," Aars said. "For every week she uses to look for a new place, she loses energy."

Bountiful last year

While this winter's ice extent is currently near a record low, last year's season was one of the best in a long time (see map). The ice began solidifying southward in October – first to Nordaustlandet and then to Kong Karls Land, the east coast of Spitsbergen, Barentsøya, Edgeøya and Hopen.

The consequences were apparent during this year's field work, according to the polar institute.

"Overall, we handled 63 polar bears in the spring. Of these…19 were cubs from this year. The proportion of females for the year was above normal and probably reflects a good ice year from 2014-2015, and that the year before was bad so many females were without cubs and mated in 2014," stated a report submitted by the institute to The Governor of Svalbard.

"The ice was also present for a long time, meaning that many bears going into this winter are in good shape," Aars said. "It will be interesting to see how next spring will be. It changes all the time between good and bad ice years, but lately it has become mostly poor."

The ice is disappearing

According to the Norwegian Meteorological Institute's ice center, one must go back to 1991 to find less at this time of year around Svalbard.

"On Dec. 1 there was an area on the ice charts of 202,155 square kilometers," a report from the agency states. "That is 125,544 square kilometers below the average from 1981 to 2010."

While there can be huge variations from year to year and many different factors that come into play, the trend is still evident. During the past half century there has been less ice in the Arctic, both in extent and thickness.

"The sea ice extent for October is on average going down by 6.73 percent each year," the National Snow and Ice Data Center (NSIDC) wrote in its most recent update.

It is not fully known how the reduction has affected polar bears, and what the consequence will be if they keep getting smaller hunting grounds and poorer access to good denning areas in the future.

Based on the latest figures and calculations, the International Union for Conservation of Nature (IUCN) issued a warning a couple of weeks ago that the population will probably decline sharply.

"Climate change will continue to threaten polar bears," IUCN General Director Inger Andersen told Reuters. "There is a high probability that the global population will fall by more than 30 percent during the next 35 to 40 years."

The result of this year's polar bear count in the Norwegian portion of the Barents Sea region will not be ready until later in December.

The project, which initially was supposed to include Franz Josef Land, were hampered by uncooperative Russians and bad weather.

"We are working overtime with the data now and hope to have something clear closer to Christmas," Aars said. "The work is quite difficult."


Translated by Mark Sabbatini

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