Polar Biology 30:1395-1405. Kochnev, A. A. 2006. Research on polar bear autumn aggregations on Chukotka, 1989-2004. Pages 157-165 in J. Aars, N.J. Lunn, and A.E. Derocher, eds. Polar Bears: ...

The polar ice sheets are the key to climate tipping points—thresholds in Earth's systems that, when breached, lead to large and often irreversible environmental change. They have some of the ...