No sea ice horizon upwards rebound observed close to Midnight sun

~Optical Thermal observation method further explained,   proving Ti<=Ta
~Likely  24 hour bottom melt  earliest captured....

   Preceding article questioning NCAR  calculations can be seen here.  The sea ice Horizon would
drop below Astronomical Horizon (AH) if top of sea ice was warmer than surface air.  In many years of observations it was never observed doing that,  the much lower sea water horizon observations with colder than sst air were never repeated with ice.  Instead spring sea ice horizons maintain AH until evening or until under sea ice melting is 24 hours a day.   This likely happened yesterday,  South Cornwallis Island looking at westward MW Passage.

May 19 2014-2015-2016 Horizon comparisons (left center right).   2016 was taken 40 minutes later same date,  but with horizon at AH.  While 2014 and 15 rose above and kept on rising,  despite cloudy conditions, whiter streaks are breaks in clouds sun ray reflections.  The rising horizon 2014-15 was created by cooling of air accelerated by minima top of sea ice core temperature.
2016  core appears warmer,  if not significantly out of cooling potential.   

     On a given Arctic spring day, the horizon drops to AH when the air temperature Ta is equal to top of sea ice temperature Ti.  When reaching AH,  it is highly likely that the bottom of sea ice melts,
but during spring the AH horizon lasts a few minutes when it first shows, in March or early April,  so accretion keeps on making net gains.  AH horizons gradually become longer, but when AH is maintained more than 12 hours,  the bottom of sea ice melts more than forms,  net bottom melting occurs.   This has happened yesterday,  when AH was observed 1 hour before the midnight sun.  For the first time I have observed this in May,  this makes Spring 2016 fast ice the weakest heat resisting sea ice observed since 2010 when spring observations have started.

While taken at same evening time,  the same 19 May Ice horizon appeared at different altitudes.   2015 (left) kept rebounding upwards,  while 2016 remained steady so 1 hour prior the midnight sun.   Sea ice bottom accretion has stopped in 2016,  and now bottom daily melting has started.  

      These key observations capture the very thermal structures instantaneously.  Its all about sea ice temperatures affecting the air right above,  with of course radiation forcing,  when the sun gets through.  wd May 20,2016