waterfell wrote: This will be the 10th straight year since the all-time minimum of 2012 without setting a new low. I don’t know what it was about 2012, but every year since has had a higher minimum.
I think a primary cause of the extraordinary low of 2012 was a powerful storm that hit the Arctic that August, churning the ocean, bringing heat to the surface, and breaking up ice floes into smaller pieces that melted easier.
The Great Arctic Cyclone…was a powerful extratropical cyclone that was centered on the Arctic Ocean in early August 2012. Cyclones of this magnitude are rare in the Arctic summer, although common in the winter. The Great Arctic Cyclone was the strongest summer storm in the Arctic and the 13th strongest storm observed at any time in the Arctic, since satellite observations began in 1979.
Looking at https://nsidc.org/arcticseaicenews/charctic-interactive-sea-… , and selecting the years since 2012, it’s notable that every single year was below or at the bottom boundary of the interdecile range, i.e. bottom 10%. I think that’s the interdecile range of data 1981-2010, though it’s not 100% clear.
Bob wrote: The trend for the last 15 years (2007-2021) is -0.012 million sq km/yr, not significantly different from zero (p=0.70).
I’m sure you wouldn’t have to go back much further than that to see a strong downward trend. 2007 was the first year that the minimum dropped down into the range it currently inhabits, at or well below the bottom of the interdecile range, with 2007 well below. Before 2007 no year had dropped below the interdecile range, and there were numerous years 2000-2006 that were up in the current interquartile range and one year, 2001, was even above 1981-2010 average.
The trend for the last 15 years (2007-2021) is -0.012 million sq km/yr, not significantly different from zero (p=0.70).
I’m sure you wouldn’t have to go back much further than that to see a strong downward trend.
Indeed. Which raises the question: why the dramatic change in trend? I remember posts by Peter and Loren on the Climate Change board which were projecting “ice free” September conditions (less than a million square kilometers of ice extent) in only a few years.
“Thinner ice thickness and thinner snow cover favors earlier basal freeze onset. The ocean plays a cross-seasonal role in regulating the growth or decay of sea ice,” explains lead author Long Lin from the Polar Research Institute of China.
The researchers found that the overall average basal freeze onset of Arctic multiyear ice was almost 3 months later than the surface…
According to Lin, although thinner ice generally experiences a longer freezing season, the total ice growth still cannot offset the sea ice loss in summer. “From another point of view, the self-regulation of the Arctic sea ice-ocean system will delay the loss of Arctic sea ice.”