The air at the top of the world is warming at twice the rate as in the lower latitudes, with resulting melting of ice on land and sea in Arctic regions affecting polar bears and the migrations of fish, a report indicates.
An Arctic Report Card issued by the National Atmospheric and Oceanic Administration for the year says Alaska has seen temperatures almost 20 degrees above the state's January average as warmer air flowed north.
Meanwhile, record low snow levels were recorded earlier this year in the high latitudes of Europe, Asia and North America, says Jacqueline A. Richter-Menge, a senior research engineer for NOAA's Cold Regions Research and Engineering Laboratory.
The report, released in San Francisco at t meeting of the American Geophysical Union, highlights disruption in weather, the disappearance of snow and high-latitude lands turning green with warming temperatures.
The impacts are greatest in Arctic marine ecosystems, the report authors say, with warm air coming up from the tropics and white sea ice -- which reflects heat back into the atmosphere -- being replaced with darker, heat-absorbing water.
In addition, new flows of warm water have been detected entering the Arctic through the Bering Strait on the Pacific side and through the Norwegian Sea on the Atlantic side, all adding to the warming of the region.
"We not only have the solar radiation, but we have these currents to bring water in laterally," says NOAA oceanographer Kathy Crane.
The warming could have dramatic impacts on the region's marine life, experts say, as elevated water temperatures and increasingly acid waters could kill off many species.
Changes in fish migrations have countries in the region worried, as scientists have noted cod and other northern Atlantic fish moving north from existing Barents Sea fisheries into the Arctic Ocean.
"It's very much a concern in Norway and among the Russians, who worry the fish may be leaving fisheries," says Crane, who was a leader in preparing the NOAA report card with contributions from 63 scientists in 13 countries.
The warming is also affecting polar bears, with reports the population of bears in Canada's Hudson Bay area declined from around 1,200 in 1987 to 800 in 2011.
Sea ice, which the bears depend on to travel, hunt and mate, has been breaking up earlier and freezing later, shortening the season when it is available to the animals.
Overall, the Report Card paints a worrisome picture of the future of the Arctic region, says Craig McLean, the acting assistant administrator for NOAA research.
"Arctic warming is setting off changes that affect people and the environment in this fragile region and has broader effects beyond the Arctic on global security, trade and climate," he says.