Arctic sea ice extent last week dropped to a new record minimum. At 4.24 million square kilometres, sea ice cover on 8 September was 27,000 sq km below the previous record low, observed in 2007.
Maps produced by scientists at the University of Bremen in Germany — on the basis of high-resolution microwave data from a sensor on board NASA’s Aqua satellite — first showed on 5 September that ice extent was lower than on the same date in 2007.
Satellite observations of Arctic sea ice have been available only since 1972. However, this year’s sea ice minimum may well be the lowest in 8,000 years.
Last year’s seasonal minimum — around 4.76 sq km on 10 September 2010 — was the third-smallest on record.
Increased sea ice melt is an unerring indicator of climate change. With ice cover now also thinner than in previous decades, there is “a greater potential for late season ice-loss, caused by warm water melting ice from below or winds that push the ice together”, say scientists with the National Snow and Ice Data Center in Boulder, Colorado.
Map and graph: University of Bremen