Associated Press: The polar bear has become an icon of global warming vulnerability, but a new study found an Arctic mammal that may be even more at risk to climate change: the narwhal. The narwhal, a whale with a long spiral tusk that inspired the myth of the unicorn, edged out the polar bear for the ranking of most potentially vulnerable in a climate change risk analysis of Arctic marine mammals. The study was published this week in the peer-reviewed journal Ecological Applications. Polar …