Scientists say they now have unambiguous evidence that the warming in the Arctic is accelerating.MORE >
Computer models have long predicted that decreasing sea ice should amplify temperature changes in the northern polar region.
Julienne Stroeve, from the US National Snow and Ice Data Center, told a meeting of the American Geophysical Union that this process was under way.
Arctic ice cover in summer has seen rapid retreat in recent years.
The minimum extents reached in 2007 and 2008 were the smallest recorded in the satellite age.
"The sea ice is entering a new state where the ice cover has become so thin that no matter what happens during the summer in terms of temperature or circulation patterns, you're still going to have very low ice conditions," she told the meeting.
As a result, there can no longer be any doubt that polar bears and other species (beluga whales, seals, the arctic fox, etc.) are at grave risk.