Photo by USFWS
A 20-year study of Alaska’s polar bears blames the steady disintegration of summer sea ice for the dramatic increase in pregnant and nursing females denning on land — where sows and their cubs may fare worse.
Landward and eastward shift of Alaskan polar bear denning associated with recent sea ice changes, published online in Polar Biology, offers yet one more confirmation that Arctic climate warming has begun to change the lives of Alaska’s polar bears by melting back their Beaufort Sea ice habitat and hunting platform.
Only a few decades ago, sea ice would start freezing close to shore by late September. Now the ice edge might be more than 125 miles out until later in the fall.
“In recent years, Arctic pack ice has formed progressively later, melted earlier and lost much of its older and thicker multi-year component,” said lead author Anthony Fischbach, in a USGS story about the research. “Together, these changes have resulted in pack ice that is a less stable platform on which to give birth and raise new cubs.
“Previous research had already shown that unstable ice can result in failures of on-ice denning attempts. Less ice that is suitable for denning apparently has led to an increased frequency of pregnant polar bears in this region choosing to den on land.”