Even after a summer BOE, ice will still form in the Arctic during the dark, polar winter for many decades
So, this being merely 2018, it surely follows that Svalbard-FJL-SZ corridor froze over this winter?
Except it
never came close. And this year was only a continuation of a long-term regional trend, not a variational swing attributable to unusual weather, cycle, oscillation, phase or teleconnection event.
The interface to the Pacific Ocean and the once-icy Bering Sea is similar: the Chukchi had open water right up to January 20th (in the sense of persistent non lift-off UH AMSR2 0-10% sea ice concentration). It was fully frozen over only on
13 days over the entire winter (measured as 95% of Chukchi pixels at 80-100% concentration).
So the Chukchi is now partly open 242/365 or
93% of the year and again this is just 2018, not many decades out in a warmer future. The same can be said for basin margins affected by earlier melting major rivers.
Once again, a more nuanced assessment (area, time series) works better than binary binning (will/won't freeze over in winter). That is, the mean sea ice concentration over the winter has
already departed significantly from freeze-over in many peripheral areas.
Despite continuing -- and possibly accelerating -- Arctic Amplification that predominantly affects fall and winter, no doubt large central areas will indeed continue to freeze over for some time, but both extent and duration of coverage can be expected to diminish over time from the periphery inward, unless new Hail Mary feedbacks emerge. The Arctic Ocean with a thin but extensive ice cover over fall and winter in conjunction with a severely diminished summer coverage is actually the
worst case scenario for global warming.
Often termed the planet's refrigerator because the Antarctic can't do the job, the Arctic's loss of summer ice reduces reflection of sunlight energy back into space, which coupled with retention of the extra ocean heat by a thin ice cover during winter, will notably worsen the overall yearly heat budget. New feedbacks will surely emerge but both their qualitative and quantitative specifics are for now very much up in the air.
The first animation shows the retreating ice front on the Svalbard-FJL-SZ corridor. The second animation runs from 15 Nov 17 to 01 May 18. Zero concentration regions have been picked and replaced with blue-green rimmed with yellow; solid ice is shown as gray. Both are 'grown' by one pixel to reduce clutter.
The third 4-day animation to 02 Aug 18 shows the shocking deterioration of the ice pack in the Beaufort-Chukchi region. This time of year especially, sea ice concentration in products like AMSR2 have to show a consistent blue for three or more consecutive days, allowing for ice motion, for artifacts to be distinguished.
Jaxa is working fine with no data gaps: take the 36:36:18 to its rgb components and delete all but the blue channel (18V ghz) to get rid of seasonal weather artifacts. The lesser-resolution, different wavelength result is fully supportive of AMSR2, 4th animation.
RoxGeo had a thoughtful post a ways back on melt season topology, roughly being the time reversal of freeze season (LIFO in CS) but with a topological twist: the ice pack freezes and melts along its boundary, no holes or free blocks (connected with vanishing first homotopy). It appears that August 2nd saw some catch-up, with the seemingly solid loose block off the ESS and Wrangel perhaps flashing (and maybe the Alaskan shoreline block as well). But let's see what tomorrow brings.
