3/10/2016 6:51:54 PM
Warm and Weird Arctic Winter
This winter may go down in the history books as the winter when things got weird in the Arctic. Temperatures rose more than 4° Celsius (7.2° Fahrenheit) above the 1951-1980 average. Winter sea ice reached record lows in January and February. And age-old patterns were threatened for wildlife from seals to walruses and polar bears.
"The record warmth in the Arctic this winter is simply bizarre," said Dr. Andrew Derocher of the University of Alberta. "In the 30+ years I've studied polar bears, I've never seen anything like this."
Derocher noted that while some polar bear populations live in areas that have experienced relatively little sea ice loss, others have been hard hit.
"This year, it seems that the Barents Sea polar bears have been particularly affected by changing sea ice," he said. "Many of the places where I studied bears in Svalbard, Norway, no longer have sea ice—and this is changing the rules that polar bears have learned to live with. "
Dr. Michael Mann, director of the Earth System Science Center at Pennsylvania State University, said the warmth seen this winter in the Arctic is unprecedented, bringing with it unprecedented low levels of winter sea ice recovery.
"El NiÌ±o may have played a small role here," he said, "but it is human-caused climate change that is propelling the Arctic climate into uncharted territory."
On February 24, for example, there were only 14.2 million square kilometers of sea ice across the Arctic. Since record keeping began, the average sea ice coverage hasn't shrunk that low until the end of April, when spring temperatures begin to thaw the Arctic region.
Dr. Jonny Day, a climate scientist with the University of Reading, said it's difficult to say exactly how unusual these temperatures are in the Arctic due to a sparseness of direct surface temperature observations over sea ice.
"But global average temperatures are currently the warmest on record, " he said, "and the Arctic sea ice extent—which can be observed from satellite—has been the lowest on record for this time of year."
Reading explained that the reduction in sea ice due to climate change allows the ocean to absorb more heat in summer and subsequently release it, leading to increased temperatures in winter months. "High Arctic winter temperatures are exactly what we'd expect to see in as a result of climate warming," he said.
What does that mean for polar bears? For mothers and cubs emerging from their dens in regions like Svalbard, the lack of ice will affect hunting during the seal pupping season—a time when female bears typically pack on the fat after months of fasting in the den. And for polar bears seeking mates during the spring breeding season, more fragmented ice drifts may make it harder for males to locate females.
"Males follow the tracks of females in breeding condition, but when the ice is drifting and breaking up, it makes it a lot more difficult to keep on the tracks," Derocher said.
He added that, taken as a whole, the signs are worrisome.
"Scientists tend to be conservative in what they say, but the unofficial chatter amongst polar bear scientists is shifting to increased concern," Derocher said. "As scientists, we'll continue to collect data to gain better insights about how the bears are faring—but we already know enough to understand the problem. The perils of not acting on climate change are abundantly clear. It's a societal issue now. The effects on polar bears are well understood."