Arctic sea ice has reached its second-lowest level since satellite observations began over 30 years ago, scierntists at the University of Colorado Boulder's National Snow and Ice Data Center say.
The extent of the coverage fell to 1.67 million square miles last week - more than a million square miles less than the 1979-2000 average for September.
This is well below the long-term average, and well outside the range of natural climate variability, says the team.
There's even a chance the sea ice extent could fall even further because of changing winds or late season melt.
"Every summer that we see a very low ice extent in September sets us up for a similar situation the following year," says NSIDC director Mark Serreze.
"The Arctic sea ice cover is so thin now compared to 30 years ago that it just can't take a hit anymore. This overall pattern of thinning ice in the Arctic in recent decades is really starting to catch up with us."
In 2007, the year of record low Arctic sea ice, there was a 'nearly perfect' set-up of specific weather conditions, says Serreze. Winds pushed in more warm air over the Arctic than usual, helping to melt sea ice, and winds also pushed the floating ice chunks together into a smaller area.
"It is interesting that this year, the second lowest sea ice extent ever recorded, that we didn't see that kind of weather pattern at all," he says.
The last five years have been the five lowest Arctic sea ice extents ever recorded since satellite measurements began in 1979, says NSIDC scientist Walt Meier.
"The primary driver of these low sea ice conditions is rising temperatures in the Arctic, and we definitely are heading in the direction of ice-free summers," he says. "Our best estimates now indicate that may occur by about 2030 or 2040."