Arctic's First Ice-Free Summer Possible Even This Year

A polar bear by water's edge, Arctic National Wildlife Refuge, Alaska, USA. An increase in thin, young ice raises the possibilities that the polar bear's Arctic home may one day be ice free.

(Johnny Johnson/Getty Images )

The distinct possibility that this summer -- for the first time in recorded history -- the North pole could be free of sea ice, is now a common subject of discussion among the world's climate experts.

The Arctic's thick, resilient multiyear sea ice (frozen sea surface), which accumulates and usually lasts through the annual melting season, has started to give way to thinner, vulnerable first-year ice.

Satellite data gathered by the University of Colorado's National Snow and Ice Data Center showed that young sea ice, which is no more than about 60 inches deep and much more susceptible to melting away, now makes up 72 percent of the Arctic ice sheet. Using that estimate, scientists at the center see a 50 percent chance that ice at the Earth's highest point will melt by the summer's end.

Andy Mahoney, a center researcher, has pinpointed this year in particular as having the "greatest chance" of being ice-free.

By TUAN C. NGUYEN and BILL BLAKEMORE