The figure, recorded Sept. 8, broke a previous record for the minimum cover set Sept. 16, 2007, at 10,400 square miles, a release by the University of Bremen's Institute of Physical Analysis reported Monday.
The researchers analyzed data from a Japanese sensor on NASA's Aqua satellite, launched in 2002.
Satellite records of arctic sea ice go back to 1972, but the Bremen researchers led by Georg Heygster said they believe the new observation is "most probably" the lowest arctic sea ice coverage "since the last climate optimum about 8,000 years ago."
The summer extent of the sea ice has retreated 50 per cent since 1972, the researchers said.
"Moreover, the sea ice retreat can no more be explained with the natural variability from one year to the next," the researchers said in the release. "Climate models show rather, that the reduction is related to the man-made global warming."