U.S. officials say the Arctic region has changed dramatically for the worse in the past five years.
It is melting at a near record pace, and it is darkening and absorbing too much of the sun's heat.
A new report card from the U.S. National Oceanic and Atmospheric Administration rates the polar region with blazing red stop lights on three of five categories and yellow cautions for the other two.
Overall, these are not good grades, but it doesn't mean the Arctic is doomed and it still will freeze in the winter, said report co-editor Jackie Richter-Menge.
The Arctic acts as Earth's refrigerator, cooling the planet.
What's happening, scientists said, is like someone pushing the fridge's thermostat much too high.
"It's not cooling as well as it used to," Richter-Menge said.
The dramatic changes are from both man-made global warming and recent localized weather shifts, which were on top of the longer term warming trend, scientists said.
The report, written by 121 scientists from around the world, said statistics point to a shift in the Arctic health in 2006. That was right before 2007, when a mix of weather conditions and changing climate led to a record loss of sea ice, from which the region has never recovered. This summer's sea ice melt was the second worst on record, a tad behind 2007.
'A new normal'
"We've got a new normal," said co-author Don Perovich, a geophysicist at the Army Corps of Engineers Cold Research and Engineering Lab. "Whether it's a tipping point and we'll never recover, who's to say?"
The report highlighted statistics to show an Arctic undergoing change:
- A NASA satellite found that 430 billion metric tons of ice melted in Greenland from 2010 to 2011, and the melting is accelerating. Since 2000, Greenland's 39 widest glaciers shrunk by nearly 530 square miles (1,375 sq. kilometres), about the equivalent of 22 Manhattans.
- The past five years have had the five lowest summer sea ice levels on record. For two straight years, all three major passages through the Arctic have been open in the summer, which is unusual.
- Seven of 19 polar bear sub-populations are shrinking.
- This year's temperature is roughly 2.5 degrees Fahrenheit (1.4 C) higher than what had been normal since 1980.
What's even more troubling to scientists is that there's been a record darkening of the normally white Arctic land and sea.
White snow and ice reflects solar energy, but a melting darker Arctic in the summer absorbs that heat.
Marco Tedesco of the City College of New York, a co-author, said the darkening is like a speeding train going downhill, adding to the acceleration of warming.
Richter-Menge said the darkening of the Arctic from melting ice and snow "causes more heating, which causes more melting, and on the cycle goes."
But there are some winners in the warming. The phytoplankton in the Arctic Ocean, at the base of the marine food chain, has increased 20 per cent compared with the past decade, and some plants are doing better, scientists said.