As Arctic sea ice melted to the lowest level ever recorded, researchers said they were unprepared for the speed of this facet of climate change. As Arctic ice melts, scientists worry it will add heat and moisture to the globe's climate system.
Arctic sea ice, a key indicator of climate change, melted to its lowest level on record this year before beginning its autumnal freeze, researchers at the U.S. National Snow and Ice Data Center said on Wednesday.
The extent of ice probably hit its low point on Sept. 16, when it covered 1.32 million square miles (3.42 million square km) of the Arctic Ocean, the smallest amount since satellite records began 33 years ago.
Changing weather conditions could further shrink the extent, the center said. A final analysis is expected next month.
The record was broken on Aug. 26, when the ice shrank below the record set in 2007. After that, it kept melting for three more weeks, bringing the ice extent - defined by NSIDC as the area covered by at least 15 percent ice - to nearly half of the 1979-2000 average.
"We are now in uncharted territory," Mark Serreze, the center's director, said in a statement. "While we've long known that as the planet warms up, changes would be seen first and be most pronounced in the Arctic, few of us were prepared for how rapidly the changes would actually occur."
The summer ice isn't just dwindling. It is also thin, relatively fragile seasonal ice instead of the hardier multi-year ice that can better withstand bright sunlight.
"The strong late-season decline is indicative of how thin the ice cover is," said NSIDC's Walt Meier. "Ice has to be quite thin to continue melting away as the sun goes down and fall approaches."
The Arctic is a potent weather-maker for the temperate zone, and is sometimes dubbed Earth's air conditioner for its cooling effects. However, as ice wanes and temperatures rise in the far north, the Arctic could add more heat and moisture to the climate system.