2016 2017 2018 new class extreme low sea ice extent maxima along with 2019, despite different atmospheric circulations.

       At present,   February 8 2019  Arctic sea ice extent is #2 in lowest extent:
  
       2009----  2010-----  2011-----  2012-----  2013----  2014----  2015----  2016-----  2017----  2018----  2019

   
   January 31 to February 8 JAXA  sea ice measurements reveal only 2018 being lesser in extent by about 16 thousand kilometers square on the 8th.  This is an extraordinary feature of winter 2019 with a distinctively dissimilar general circulation than the preceding 6 seasons.......

2019's general circulation to date can be characterized in part by by a snow footprint:

                    Snow cover has very similar features to sea ice extent,  it can define the degree of winter,
mild , severe or extreme.  If sea ice is widely spread out and thick,  Northern Hemisphere winter may be more  severe as well.  These two Cryospheric features make the story of winter which shapes the Arctic Polar Vortex:

   NOAA daily composites 600 mb temperatures (close to the density weighted temperature of the entire troposphere),  Arctic Polar Vortex average location January

4 to February 4 2019.   Siberia dominates,  which is contrary to all winters going back to 2012.  There are some similarities from season to season, but very prominent differences were distinguishable by analyzing maps daily,  overall PV average extent calculations may appear somewhat similar,  but they are not:

The way to analyze any given Polar Vortex season,  is to break it down in smaller periods,  January 24 to February 4  sequences 2016 to 2019 demonstrate differing flow structures.  These are winters of interest having the least sea ice extent in history.  All 4 recent seasons including 2019  had different Arctic Polar Vortex configurations,; 2016 had a very mangled weaker  and smaller Polar Vortex,  with mainly 2 continental much weaker and smallish  vortices acting independently from each other. Arctic Ocean  sea ice  became badly broken up by minima 2016.   2017  had a Pole warming  flow pattern in particular with North of Greenland Atlantic in origin cyclones heading Northwards,  2018 had a massive extreme Polar vortice dwarfing all others above the Canadian Arctic Archipelago,  Russian side vortice appeared weaker on most occasions then.   2019 to date has the opposite of 2018,  but with a difference,  continental vortices within the Polar Vortex were more balanced with Siberia dominating on most days, so far  the Polar Vortex rarely split  in two and appears stretched out.  This gives open sea water inroads from the North Pacific,   a strong  Siberian vortice pushes massive cyclones Northeastwards more often,  To date, North Atlantic cyclones went towards Eurasia, and in effect help refreeze the North Pole area sea ice which keeps the Polar Vortex more or less together.

    Given that 4 recent seasons created differing circulation features,  it is amazing that sea extent at Maximum extent date remains near all time record lows.  This strongly suggests a greater warming of the Oceans and sea ice has the potential to collapse to extreme low summer extents only not doing so because of,  you guessed it, summer circulation features. WD February 9th 2019