Thinning sea ice bodes ice-free North Pole summers

Is this drastic reduction the result of natural variability superimposed on a general declining trend, or is Arctic sea ice cover shifting into a different climatic state characterized by completely ice-free summers? To help answer this, Haas et al. study the Arctic's Transpolar Drift, a current that carries ice from Siberia across the North Pole to the east coast of Greenland.

Through helicopter-borne electromagnetic measurements, the authors calculate sea ice thicknesses over the Transpolar Drift during the late summers of 2001, 2004, and 2007, adding to a ground-based data set that extends to 1991. They find that average ice thickness has reduced by 44 percent since 2001. A model of ice ages shows that the area of older, thicker ice has decreased due to changed drift patterns.

The authors suggest that the shift to younger and thinner ice could soon result in an ice-free North Pole during summer.-American Geophysical Union