Thick spring ice due to natural causes is currently the single biggest threat to polar bears. Not declining summer sea ice – thick spring ice. That could change in the future but right now, the evidence supports that statement.
Polar bear deaths due to cyclical changes in Arctic sea ice thickness in the spring have continued despite rising CO2 emissions and declining summer sea ice extent (last major incident, 2004-2006): there is no reason to expect this will not continue. Unwarranted attention on summer ice extent has deflected attention from this major cause of local polar bear population decline.
Sea ice models do not address past or future changes in spring ice thickness and predictive models of polar bear survival blame all population declines on summer sea ice declines despite strong evidence to the contrary (Crockford 2015: The Arctic Fallacy). Continue reading