Comparing sea ice extent of 2007 and 2012 melt records in NSIDC Arctic Ocean map.

As the days shorten and the summer sun is slowly setting under the horizon, the frost is returning to the Arctic and American scientists make up the balance of what has turned out to be an unprecedented melting season.

The new melting record was probably reached on September 16, at a minimum sea ice extent of 3.41 square kilometers. That is the lowest ever recorded since satellite measurements began in 1979, and 49 percent under the average extent of the period between 1979-2000. The 2007 record was broken by a margin of 18 percent, or 0.76 million square kilometers of ice.

Although wintery conditions seem to have returned to the Arctic over the last couple of days, the NSIDC warns the September 16 measurement could still be broken due to weather variability before the end of the month. In October the Arctic watchdog will present a full analysis of 2012’s melting season and record-low ice minimum.

Comparing Arctic records of 2005, 2007 and 2012 in NSIDC sea ice area graph. The greyband shows the two standard deviations margin from the 1979-2000 sea ice average, meaning values below it (including the sea ice minima of all the years between 2007 and 2012) should be confined to just 2.5 percent of years, if the recent melting events were to be down to natural climate variability, instead of a declining trend.

© Rolf Schuttenhelm | www.bitsofscience.org