Polar bears on thin ice

Polar bears need sea ice to hunt and breed. But a study published last week in the journal The Cryosphere by University of Washington researchers using satellite data found earlier sea ice melt in the spring and later ice growth in the fall (autumn) diminishes feeding and breeding across all 19 polar bear subpopulations.

The researchers found that on average, spring melting was three to nine days earlier per decade, and fall freeze-up was three to nine days later per decade. That corresponds to a roughly 3.5-week shift at either end — and seven weeks of total loss of good sea ice habitat for polar bears.