The ice cover in the Arctic may have reached its minimum extent of 4.14 million square kilometres this year – tying at second lowest in record with the 2007 minimum, scientists have found.
The record lowest extent in the 37-year satellite record occurred on September 17, 2012 when sea ice extent fell to 3.39 million square kilometres.
The 2007 minimum occurred on September 18 that year, when Arctic sea ice extent stood at 4.15 million square kilometres.
“It was a stormy, cloudy, and fairly cool summer,” said Mark Serreze, director of the US National Snow and Ice Data Centre (NSIDC).
“Historically, such weather conditions slow down the summer ice loss, but we still got down to essentially a tie for second lowest in the satellite record,” said Serreze.
“It really suggests that in the next few years, with more typical warmer conditions, we will see some very dramatic further losses,” said Ted Scambos, NSIDC lead scientist.
Arctic sea ice cover grows each autumn and winter, and shrinks each spring and summer. Each year, the Arctic sea ice reaches its minimum extent in September.
During the first ten days of September this year, the Arctic lost ice at a faster than average rate.
On average, the Arctic lost 34,100 square kilometres per day compared to the 1981 to 2010 long-term average of 21,000 square kilometres per day.
The early September rate of decline also greatly exceeded the rate observed for the same period during the record low year of 2012 (19,000 square kilometres per day).
By September, the air is cooling and there is little surface melt. This argues that that the fairly rapid early September ice loss was due to extra heat in the upper ocean.
Recent ice loss was most pronounced in the Chukchi Sea, northwest of Alaska. Scientists said ice may also relate to the impact of two strong storms that passed through the region during August.
“This has been an exciting year with several record low extents reached during winter and early summer but thanks to a colder than average summer, more ice remained than at the end of 2012,” said Julienne Stroeve, NSIDC senior scientist.
Researchers said there was a lot of thin ice at the beginning of the melt season, because thinner ice does not take as much energy to melt away, this may have also contributed to this year’s low minimum extent.
The Arctic sea ice extent number for 2016 is preliminary – changing winds could still push the ice extent lower, researchers said.