The U.S. Geological Survey and the University of Wyoming have published a new study showing that polar bears are having to expend more energy to keep up with faster drifting sea ice.
The study, titled "Increased Arctic sea ice drift alters polar bear movements and energetics," came out in the June 5 issue of Global Change Biology.
UW Zoology and Physiology professor Merav Ben-David is one of the authors of the report. Because of sea ice floats, it drifts in the direction of currents and wind, which in the North go from Canada to Russia. As the climate warms, the ice gets thinner and more prone to breaking and drifting faster. Ben-David said polar bears have always had to walk in the opposite direction of ice drift to keep up with their food and not be stranded.
“However, more recently, basically the last couple decades or last 15 years or so, we’ve lost so much of the old heavy multi-year ice. The current ice, which is mostly annual, it freezes every year again, is very thin. And that ice drifts faster,” said Ben-David.
To keep up, Ben-David said solitary female polar bears have to walk faster and females with cubs have to walk longer hours in a day – and all of this limits the energy and time they have to hunt. She said the polar bear population is feeling the impacts of this.
“We see smaller sized bears, they have lower skull size, lower body mass. And we see lower survival, especially of these younger cubs and yearlings. And in general, at least in the Southern Beaufort Sea population, we see a population decline,” said Ben-David.
The study looked at 77,000 bear locations from 1987 to 2013, and Ben-David said it is one of the most extensive studies on ice drift ever done.