Arctic sea ice surpassed all previous records for the lowest absolute minimum summer extent in September 2007. The "stunning record low" of 4.13 million square kilometers was recorded by satellite images on September 16, according to the National Snow and Ice Data Center. The previous record, 5.32 million square kilometers, was measured on September 20-21, 2005.
The minimum for 2007 is smaller by 1.19 million square kilometers (460,000 square miles) than the previous low. 2007 also saw the extended opening of the Northwest Passage through islands north of Canada for the first time. See http://nsidc.org