A new research paper by scientists of the Polar Science Center of the Applied Physics Laboratory of the University of Washington, has been published this week in the online version of Geophysical Research Letters. It's called The impact of an intense summer cyclone on 2012 Arctic sea ice retreat and discusses the role the Great Arctic Cyclone of 2012 - or GAC-2012 - played in the incredible, unequivocal and unspinnable record streak
we witnessed towards the end of the melting season.
From the UW press release:
Cyclone did not cause 2012 record low for Arctic sea ice
It came out of Siberia, swirling winds over an area that covered almost the entire Arctic basin in the normally calm late summer. It came to be known as “The Great Arctic Cyclone of August 2012,” and for some observers it suggested that the historic sea ice minimum may have been caused by a freak summer storm, rather than warming temperatures.
But new results from the University of Washington show that the August cyclone was not responsible for last year’s record low for Arctic sea ice. The study was published online this week in Geophysical Research Letters.
“The effect is huge in the immediate aftermath of the cyclone, but after about two weeks the effect gets smaller,” said lead author Jinlun Zhang, an oceanographer in the UW’s Applied Physics Laboratory. “By September, most of the ice that melted would have melted with or without the cyclone.”
Recent research [covered on the ASI Blog here, N.] showed that the Arctic cyclone was the most powerful ever seen during the month of August, and the 13th most powerful of all Arctic storms in more than three decades of satellite records.
“The storm was enormous,” said co-author Axel Schweiger, a polar scientist in the Applied Physics Laboratory. “The impact on the ice was immediately obvious, but the question was whether the ice that went away during the storm would have melted anyway because it was thin to begin with.”
The UW team performed the climate scientist’s equivalent of a forensic exam: They ran a computer simulation of last summer’s weather and compared it against a second scenario that was identical except that there was no cyclone.
Results showed the storm caused the sea ice to pass the previous record 10 days earlier in August than it would have otherwise, but only reduced the final September ice extent by 150,000 square kilometers (almost 60,000 square miles), less than a 5 percent difference. By comparison, the actual minimum ice extent was 18 percent less than the previous record set in 2007.
The storm apparently caused 150K km2 of extra melted ice and so the record(s) would have been broken anyway, as the difference with the 2007 minimum was much larger. The main reason the storm had such an effect, was that the ice was exceptionally thin. Just 10 years ago a storm, even of this size, wouldn't have had such an impact.
Read for instance this Skeptical Science article from October, with the figure below showing September Arctic sea ice extent data from NSIDC (blue) and years with Arctic summer storms similar to the 2012 storm depicted in red.
Remember that we started noticing that the ice seemed to be exceptionally thin weeks before the storm hit. It was the only way to explain the steadily rapid drop in extent and area levels, even though the weather wasn't conducive to that rate of melt.