In a sadly familiar refrain, the Arctic has set another record for losing sea ice. Last month, the extent of sea ice in the Arctic hit the lowest mark for any June since satellite records started in 1979, according to a press release from the National Snow and Ice Data Center (NSIDC) at the University of Colorado at Boulder. Climate researchers are watching carefully to see if the record rate of loss continues throughout the rest of summer.

The icy skin over the Arctic Ocean grows during each winter and shrinks during summers, reaching its yearly low point in September. The monthly average for June 2010 was 10.87 million square kilometres, which was just below the previous record June low of 11.06 million square kilometres, established in 2006. The NSIDC says that the ice loss may slow over the next few weeks as melting reaches patches of thicker ice in the central Arctic Ocean.

In 2007, melting accelerated during late June and early July, when it declined by an average 210,000 square kilometres a day for a period of two weeks. By September of 2007, there was less ice in the Arctic than at any other time in the instrumental record.

The September ice minimums in 2008 and 2009 came in second and third for least amount of sea ice. Since 1979, the extent of September sea ice in the Arctic has dropped at a rate of more than 11 percent per decade. Rapid warming of the Arctic has caused the overall long-term ice decline, with atmospheric pressure patterns making some years, such as 2007, particularly bad. That summer, winds helped push ice out of the Arctic into the North Atlantic Ocean. A similar pressure pattern developed this summer, but meteorologists are not sure whether it will continue throughout the rest of the summer.

Image: NSIDC