Thawing permafrost, melting ice sheets and threats to Arctic wildlife are just some of the growing concerns about the effect of global warming at the top of the planet, according to a new U.S. government report card.
The report card notes that 2007 was the warmest year on record in the Arctic region, with sea-ice cover at record lows, less snow cover and increased effects on walruses and polar bears.
"These are clearly dynamic and dramatic times in the Arctic," said report editor Jackie Richter-Menge, a researcher with the Army Corps of Engineers Cold Regions Research and Engineering Laboratory in Hanover, N.H.
The massive ice sheet in Greenland underwent "record melting" in 2007, the report said, losing at least 24 cubic miles of ice.
That is about 100 times the amount of ice that the city of Los Angeles uses in an entire year, according to Eric Rignot, a scientist at NASA's Jet Propulsion Laboratory who was not involved in the report card.
And the length of time that the ice sheet is melting has increased: 20 more days of melting than average, researchers report, with some areas of the ice sheet seeing as many as 53 more days of melting every season.
The report, which was released today, notes that Arctic autumn temperatures for the year 2007 were 10 degrees above normal, as disappearing sea ice allows the ocean to warm at faster rates.
"The loss of sea ice allows more solar heating of the ocean, and the more the ocean heats up, the harder it is to grow sea ice," Richter-Menge said in a conference call with reporters today.
What's more, there is "justifiable concern" for Arctic wildlife, according to the report. Less sea ice means polar bears have already seen "reduced survival" in some regions, and the walrus population may be affected as "habitats are unable to sustain the needs of concentrated populations of walrus into the future," the report said.
Wild caribou and reindeer populations may already be declining, and some ocean species may not be able to adapt to warming waters, according to the report.
Researchers said there are still a number of mysteries when it comes to the Arctic.
"Unlike most of the Arctic, which is experiencing general warming, the Bering Sea is in a prolonged cold phase," Richter-Menge pointed out. "While permafrost is warming, the rate of warming is slower than in the 1990s. It is also likely that environmental changes will likely be beneficial to some species."
"This is a very complicated system, and we are still working diligently to figure out its mysteries," she said.
The annual report card was released by the National Oceanic and Atmospheric Administration, with contributions from Woods Hole Oceanographic Institute, the Geophysical Institute, the University of Alaska-Fairbanks, the Byrd Polar Research Center and Environment Canada.