At 4.64 million square kilometres, this year’s Arctic sea ice minimum extent is the eighth lowest in the consistent long-term satellite record, which began in 1978, NASA’s satellite data analysis shows. Arctic sea ice appeared to have reached its yearly lowest extent on September 13, the US space agency said.
Its minimum summertime extent, which typically occurs in September, has been decreasing, overall, at a rapid pace since the late 1970s due to warming temperatures.
This year, temperatures in the Arctic have been relatively mild for such high latitudes, even cooler than average in some regions. Still, the 2017 minimum sea ice extent is 1.58 million square kilometres below the 1981-2010 average minimum extent, NASA said.
“The weather conditions have not been particularly noteworthy this summer,” said Claire Parkinson, senior climate scientist at NASA’s Goddard Space Flight Center.
“The fact that we still ended up with low sea ice extents is because the baseline ice conditions today are worse than the baseline 38 years ago,” Parkinson said.
The three years with the lowest Arctic ice extents on record — 2012, 2016 and 2007 — experienced strong summer storms that hammered the ice cover and sped up its melt.
“In all of those cases, the weather conditions contributed to the reduced ice coverage.
“But if the exact same weather system had occurred three decades ago, it is very unlikely that it would have caused as much damage to the sea ice cover, because back then the ice was thicker and it more completely covered the region, hence making it more able to withstand storms,” Parkinson said.
On the other side of the planet, Antarctica is heading to its maximum yearly sea ice extent, which typically occurs in September or early October, according to NASA.
This year’s maximum extent is likely to be among the eight lowest in the satellite record — a dramatic turn of events considering that 2012, 2013 and 2014 all saw consecutive record high maximum extents, followed by a sudden large drop in 2015 and a further decrease in 2016.
So far, the September Antarctic ice extents this year are comparable to those of a year ago, NASA said.
“What had been most surprising about the changing sea ice coverage in the past three decades was the fact that the Antarctic sea ice was increasing instead of decreasing,” Parkinson said.
“The fact of Arctic sea ice decreases was not as shocking because this was expected with a warming climate, although the overall rate of the decreases was greater than most models had forecast,” said Parkinson.