With Record Low Sea Ice Extent, Polar Bears Persevere on Marginal Ice -- or on Land

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On Saturday, 15 September -- the day before the Arctic sea ice extent reached its record low -- a scientist aboard the USGS Healy spotted a polar bear struggling across thin ice.  Her photos capture a situation facing growing numbers of polar bears as sea ice extent declines, and the ice grows thinner, in response to warming conditions. The bears must persevere on marginal ice or swim in search of suitable sea ice -- both far from preferred coastal waters; or they must abandon the ice altogether and swim to land.

Lisa Robbins, a Principal Investigator at the St. Petersburg Coastal and Marine Science Center (St. Petersburg, Florida), was on board the Coast Guard icebreaker Healy when the polar bear was sighted on the sea ice over the Arctic Ocean far north of Alaska.  The photos were posted on the center's ocean acidification blog (Sliding on Thin Ice: Another Polar Bear Sighting!, 17 September 2012).  According to the blog:  "The polar bear was observed having trouble walking on the thin ice.  The bear’s paws were breaking through the ice,  so it got on its belly, distributed the weight, and slid!"

Above: Polar bear walking on thin sea-ice.  Photo: Lisa Robbins, USGS.

 Above: Polar bear distributes its weight across the ice -- and initially
avoids breaking through the ice -- by sliding across the ice on its belly. 
Photo: Lisa Robbins, USGS.

  Above: The polar bear partially breaks through the ice and
into the water below, as it struggles to reach thicker ice. 
Photo: Lisa Robbins, USGS.

  Above: The polar bear again finds itself on ice thick
enough to support its weight.
Photo: Lisa Robbins, USGS.

At the time Lisa Robbins took the photos from the USGC Healy, the icebreaker was in the Arctic Ocean north of Alaska in the area of Latitude 80 06.8 N,  Longitude 161 10.2W (see image  below).

 

Above: The view from the USCGC Healy on 15 September 2012, the day before Arctic sea ice extent reached the lowest level on record.  Source: U. S. Coast Guard.

Like the bear in the photos above, many polar bears this year likely have found enough ice to survive.  Many others, however, probably have been less fortunate. As we reported last year (Melting Sea Ice is Forcing Polar Bears to Swim Longer, Increasing Cub Mortality, WWF Climate Blog, 18 Sep 2011), bears are being forced to swim long distances in search of better ice conditions or swim to land. “Climate change is pulling the sea ice out from under polar bears’ feet, forcing some to swim longer distances to find food and habitat,” said Geoff York, a WWF Polar Bear expert, last year.

Large Numbers of Polar Bears Sighted on Land

Reporting on an aerial survey along the coast of the southern Beaufort Sea from Barrow, Alaska, to the U.S.-Canada border conducted 24-27 August 2012, U.S. Fish and Wildlife Service scientists reported "two polar bears on barrier islands that were alive but unable to move, possibly due to exhaustion after a long-distance swim."  In all, the researchers spotted 137 bears along the coast.  "The number of bears observed this year was high relative to similar surveys conducted over the past decade," they reported.

Several weeks later, on the mainland, a record number of polar bears were reported in Kaktovik, Alaska.  According to the Alaska Dispatch (Record number of polar bears flock to whale remains in Kaktovik, 22 September 2012), researchers counted 80 bears on 13 September in and around Kaktovik, well over the previous daily record of 65 bears.  The bears were attracted there by food -- in this case a whale carcass.  "While the whale carcass is one reason for the polar bear bonanza, scientists wonder if there isn’t another reason," says the Alaska Dispatch.  "Namely, the record retreat of Arctic sea ice from the northeast coast of Alaska into the Beaufort Sea." 

In 2008, scientists reported in the journal Ecological Complexity (Effects of sea ice extent and food availability on spatial and temporal distribution of polar bears during the fall open-water period in the Southern Beaufort Sea, by S. Schliebe et al., March 2008):

"The number of bears on land both within and among years increased when sea-ice was retreated furthest from the shore... Our results suggest that long-term reductions in sea-ice could result in an increasing proportion of the Southern Beaufort Sea polar bear population coming on land during the fall open-water period and an increase in the amount of time individual bears spend on land."

While spending more time ashore can be benign for short durations and in remote locations, longer periods on land for an increased number of polar bears may decrease their overall body condition as we have seen documented in Hudson Bay (Canada), expose them to new vectors for disease, and increase the risk of negative human-bear interactions. While some communities may benefit from increased tourism opportunities from this new phenomenon, they are also trying to manage numerous large predators directly in their backyards.

Online Resources:

Record number of polar bears flock to whale remains in Kaktovik, Alaska Dispatch, 22 September 2012.  Do not miss the spectacular Photos: Polar bears of Kaktovik, by Loren Holmes.

Record Arctic ice low drives urgent global action. Press release (19 Sep 2012) from WWF International.

WWF

WWF Climate Change Blog > Regions > Arctic:

 

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