evidence: A new study finds that an area of the Arctic Ocean critical for the survival of polar bears is fast becoming vulnerable to climate change. [...] Polar bears in the area use the ice to hunt for seals who build dens to raise their young on the frozen water. [...] According to the researchers, unusually strong winds moved much of the sea ice out of the area - but this was enhanced by a thinning trend, related to warming, that's been going on for years.