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Images: Melting Ice Threatens Polar Bears' Survival

Will polar bears make the leap into the next century? Recent studies project that if Arctic sea ice continues to disappear, so will the polar bear in much of its current range. (Photo by Chris Linder, Woods Hole Oceanographic Institution)

Polar bears have a low reproductive rate. To feed themselves and their cubs, they rely on sea ice for platforms to hunt for their main source of food: seals. (Photo by Chris Linder, Woods Hole Oceanographic Institution)

In September 2005, the extent of sea ice in the Artic reached a record low (right). That record was shattered in September 2007 (left), when an area roughly the combined size of Texas and California was found to have melted. The magenta line indicates the mean September extent based on data from 1979 to 2000. (Courtesy of the National Snow and Ice Data Center)

Three years (1885, 1985 and 2085) illustrate the model-simulated trend in reduced summertime sea ice. The colors range from dark blue (ice free) to white (100 percent sea ice covered). (Courtesy of NOAA)

Mathematical ecologists Hal Caswell of WHOI (above) and Christine Hunter of the University of Alaska developed new population dynamics models that documneted for the first time the critical importance of sea ice for polar bears' survival. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)

The average Arctic Ocean sea ice extent in August has trended downward from 1979 to 2007, but the low ice extent for August 2007 stands out sharply. (Graph courtesy of National Snow and Ice Data Center)