Arctic sea ice shrank to its smallest area on record this summer before beginning to refreeze, ­according to the National Snow and Ice Data Center.

The sea ice extent bottomed out Sept. 16 at 1.32 million square miles, about 293,000 square miles below the 2007 record. Arctic sea ice extent has been monitored by satellite since 1979.

This year’s record low extent follows a long-term decline. The six lowest extents on record have all occurred in the past six years.

“We are now in uncharted territory,” said Mark Serreze, NSIDC director. “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 National Oceanic and ­Atmospheric Administration reported that the ice loss during August occurred at the fastest clip on record for the month, the ice shrinking at the rate of 35,400 square miles per day.

“Climate models have predicted a retreat of the Arctic sea ice; but the actual retreat has proven to be much more rapid than the predictions,” said Claire Parkinson, a climate scientist at NASA.

NASA said a large Arctic storm in early August played a role in the record low extent.

“The storm cut off a large section of sea ice north of the Chukchi Sea and pushed it south to warmer waters that made it melt entirely,” NASA reported. “It also broke vast extensions of ice into smaller ­pieces more likely to melt.”

Arctic sea ice is viewed as a critical player in the Northern Hemisphere’s climate. The long-term decline in this cold air source is probably affecting weather patterns, according to researchers.

A 2012 study by Jennifer Francis of Rutgers University and Stephen Vavrus of the University of Wisconsin suggests Arctic sea ice loss is adding sufficient heat to the atmosphere to change the course of the jet stream, the river of air at high altitudes along which storms track toward the polesand the equator. It suggests the jet stream is slowing down and becoming more wavy, meaning extreme weather patterns may be becoming more persistent.

But this year’s record low sea ice extent doesn’t necessarily mean extreme winter looms.

“[Vavrus] cautioned that people should view their study as a launching point for more research, and not interpret it as having any predictive value for the upcoming winter,” wrote Climate Central’s Andrew Freedman.