From optical based hypothesis to reality

~Must consider present snow layer as an upward extension of sea ice

~~Hypothesis largely confirmed!!!

   A typical day of a buoy,  taking temperatures 10 cm intervals from top of snow downwards.   The optical refraction method confirms that this buoy is functional!!!

  Please read hypothesis:

http://eh2r.blogspot.ca/2014/05/finding-sea-ice-underside-melting-at.html

   Consider snow layer as ice.   Then read the buoy data (written colour are my comments):
Yellow:  surface temperature,  blue background:  peak minima temperature in snow or ice layer.  Grey background is ice thickness in meters……:

April 7,2014:

~Buoy 2014b  72.54N 149.52W

Date,Latitude (degrees),Longitude (degrees),Quality (+/- km),Air Temp (C),Air Pressure (mb),Snow Surface Position (m),Ice Thickness(m),Ice Surface Position (m),Ice Bottom Position(m),T1 (C),T2 (C),T3 (C),T4 (C),T5 (C),T6 (C),T7 (C),T8 (C),T9 (C),T10 (C),T11 (C),T12 (C),T13 (C),T14 (C),T15 (C),T16 (C),T17 (C),T18 (C),T19 (C),T20 (C),T21 (C),T22 (C),T23 (C),T24 (C),T25 (C),T26 (C),T27 (C),T28 

(C),T29 (C),T30 (C),T31 ©

Overnight lower atmospheric INVERSION,  horizon appears high:

"04/07/2014 12:00","     72.5376","   -149.5226","GPS","    -28.61","   1012.55","      0.03","      1.54","      0.00","     -1.54","    -29.14","    -29.07","    -28.84","    -26.98","    -19.70","    -15.81","    -14.15","    -13.06","    -11.88","    -10.75","     -9.74","     -8.71","     -7.85","     -6.93","     -5.84","     -4.96","     -4.02","     -2.88","     -1.69","     -1.63","     -1.57","     -1.67","     -1.69","     -1.57","     -1.57","     -1.59","     -1.65","     -1.57","     -1.57","     -1.57","     -1.63"

Gradual diurnal warming … It was likely sunny.  

"04/07/2014 13:00","","","","    -29.03","   1012.68","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/07/2014 14:00","","","","    -28.61","   1012.68","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/07/2014 15:00","","","","    -27.96","   1012.41","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

Horizon near true astronomical Horizon:

"04/07/2014 16:00","     72.5374","   -149.5243","GPS","    -26.19","   1012.41","      0.03","      1.54","      0.00","     -1.54","    -25.97","    -26.16","    -26.05","    -24.57","    -19.26","    -16.06","    -14.40","    -13.25","    -11.94","    -10.81","     -9.80","     -8.77","     -7.79","     -6.93","     -5.84","     -4.96","     -4.08","     -2.88","     -1.69","     -1.63","     -1.63","     -1.67","     -1.69","     -1.57","     -1.57","     -1.53","     -1.65","     -1.57","     -1.50","     -1.57","     -1.63"

Further gradual warming:

"04/07/2014 17:00","","","","    -24.40","   1012.21","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/07/2014 18:00","","","","    -23.01","   1012.07","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/07/2014 19:00","","","","    -23.06","   1011.94","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

Close to LAN,  snow/ice temperature minima lowers downwards towards ice bottom,  horizon dropped significantly as well:

"04/07/2014 20:00","     72.5372","   -149.5284","GPS","    -22.86","   1011.94","      0.03","      1.54","      0.00","     -1.54","    -15.09","    -15.98","    -17.01","    -18.69","    -17.49","    -15.81","    -14.46","    -13.31","    -12.07","    -10.87","     -9.80","     -8.71","     -7.85","     -6.86","     -5.84","     -4.96","     -4.02","     -2.82","     -1.69","     -1.63","     -1.63","     -1.61","     -1.69","     -1.57","     -1.50","     -1.59","     -1.59","     -1.57","     -1.57","     -1.57","     -1.63"

Surface temperature stall:

"04/07/2014 21:00","","","","    -22.02"," 

 1012.14","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/07/2014 22:00","","","","    -21.42","   1012.07","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/07/2014 23:00","","","","    -21.47","   1012.01","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

Post-local apparent noon horizon at lowest point, there was a significant lower atmosphere adiabatic lapse rate:

"04/08/2014 00:00","     72.5367","   -149.5333","GPS","    -21.06","   1011.73","      0.02","      1.54","      0.00","     -1.54","     -5.96","     -4.02","     -5.29","    -13.33","    -16.17","    -15.37","    -14.21","    -13.31","    -12.07","    -10.87","     -9.86","     -8.77","     -7.79","     -6.86","     -5.84","     -4.90","     -4.08","     -2.82","     -1.69","     -1.63","     -1.63","     -1.67","     -1.69","     -1.57","     -1.50","     -1.59","     -1.65","     -1.57","     -1.57","     -1.57","     -1.63"

"04/08/2014 01:00","","","","    -20.47","   1011.60","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/08/2014 02:00","","","","    -21.28","   1011.53","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/08/2014 03:00","","","","    -22.29","   1011.33","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

Horizon still low despite slight cooling, suspect latent heat of fusion event

(perhaps at 01:00) where bottom ice froze by 1 cm but released heat:

"04/08/2014 04:00","     72.5363","   -149.5390","GPS","    -22.95","   1011.33","      0.03","      1.55","      0.00","     -1.55","    -13.33","    -13.71","    -15.75","    -18.12","    -16.48","    -15.12","    -14.02","    -13.25","    -12.13","    -10.93","     -9.93","     -8.83","     -7.85","     -6.93","     -5.84","     -4.96","     -4.08","     -2.88","     -1.69","     -1.63","     -1.63","     -1.67","     -1.69","     -1.57","     -1.50","     -1.53","     -1.59","     -1.57","     -1.50","     -1.57","     -1.63"

Diurnal evening cooling:

"04/08/2014 05:00","","","","    -24.79","   1011.19","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/08/2014 06:00","","","","    -26.44","   1011.06","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/08/2014 07:00","","","","    -26.92","   1011.06","","","","","","","","",""

 Inversion started a few hours prior,  horizon rose and was rising further; Snow/ice layer cooled more than surface air:

"04/08/2014 08:00","     72.5366","   -149.5449","GPS","    -26.74","   1011.06","      0.03","      1.55","      0.00","     -1.55","    -27.36","    -27.49","    -27.00","    -24.45","    -18.25","    -15.37","    -14.08","    -13.18","    -12.13","    -11.00","     -9.99","     -8.90","     -7.91","     -6.99","     -5.90","     -5.02","     -4.08","     -2.88","     -1.76","     -1.63","     -1.63","     -1.67","     -1.69","     -1.57","     -1.57","     -1.59","     -1.59","     -1.57","     -1.50","     -1.57","     -1.63"

"04/08/2014 09:00","","","","    -25.90","  

-----------------------------------------------------------------------------

 On April 7, the measurement times were not in line with specific thermal events on that day, but on April 4  it was a different story:

April 4,  2014:

Pre-LAN horizon was already at low true astronomical horizon (a favourably warm or cloudy day combination),  at this point bottom ice melts earlier:

04/04/2014 12:00","     72.5080","   -149.2189","GPS","    -22.76","   1014.31","      0.03","      1.53","      0.00","     -1.53","    -22.74","    -22.04","    -21.56","    -20.65","    -17.30","    -15.18","    -13.90","    -13.06","    -11.94","    -10.87","     -9.80","     -8.65","     -7.66","     -6.68","     -5.59","     -4.64","     -3.70","     -2.70","     -1.69","     -1.63","     -1.63","     -1.67","     -1.69","     -1.57","     -1.57","     -1.59","     -1.59","     -1.57","     -1.57","     -1.57","     -1.63"

Surface temperature stall:
"04/04/2014 13:00","","","","    -23.22","   1014.24","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/04/2014 14:00","","","","    -23.17","   1014.18","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/04/2014 15:00","","","","    -23.60","   1013.77","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

Horizon was low, surface of snow/ice warms, bottom ice lost 1 cm (needs sonar confirmation):

"04/04/2014 16:00","     72.5125","   -149.2523","GPS","    -23.47","   1013.23","      0.04","      1.52","      0.00","     -1.52","    -23.05","    -22.17","    -21.81","    -21.28","    -17.81","    -15.43","    -14.08","    -13.12","    -11.94","    -10.81","     -9.80","     -8.71","     -7.72","     -6.74","     -5.59","     -4.64","     -3.77","     -2.70","     -1.69","     -1.63","     -1.63","     -1.67","     -1.69","     -1.57","     -1.57","     -1.59","     -1.65","     -1.57","     -1.57","     -1.57","     -1.63"

Very Slow or stalled diurnal warming:

"04/04/2014 17:00","","","","    -23.05","   1013.23","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/04/2014 18:00","","","","    -22.86","   1012.89","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/04/2014 19:00","","","","    -22.50","   1012.68","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

1 hour prior local apparent noon , lowest horizon:

"04/04/2014 20:00","     72.5179","   -149.2950","GPS","    -21.87","   1012.28","      0.03","      1.53","      0.00","     -1.53","    -19.58","    -19.58","    -19.28","    -19.32","    -17.30","    -15.37","    -14.08","    -13.12","    -11.88","    -10.81","     -9.74","     -8.65","     -7.66","     -6.74","     -5.59","     -4.71","     -3.77","     -2.57","     -1.69","     -1.63","     -1.63","     -1.67","     -1.69","     -1.57","     -1.57","     -1.53","     -1.65","     -1.57","     -1.57","     -1.57","     -1.63"

Slow surface temperature stall:

"04/04/2014 21:00","","","","    -20.94","   1011.94","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/04/2014 22:00","","","","    -20.39"," 

 "04/04/2014 23:00","","","","    -19.75","   1011.60","","","","","","","","","","","","","","","","","","","","","","","","",

"","","","","","","","","","",""

After LAN peak warming period consists of surface to air interface Adiabatic profile, horizon was low, ice minima at lowest point nearer middle of ice column.

"04/05/2014 00:00","     72.5258","   -149.3425","GPS","    -18.82","   1010.92","      0.03","      1.53","      0.00","     -1.53","    -13.77","    -14.53","    -13.66","    -15.47","    -16.04","    -14.99","    -13.90","    -13.06","    -11.88","    -10.75","     -9.74","     -8.65","     -7.66","     -6.68","     -5.59","     -4.64","     -3.77","     -2.63","     -1.69","     -1.63","     -1.63","     -1.67","     -1.69","     -1.57","     -1.57","     -1.53","     -1.59","     -1.57","     -1.57","     -1.57","     -1.63"

Surface Temperature stall:

"04/05/2014 01:00","","","","    -18.68","   1010.72","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/05/2014 02:00","","","","    -18.61","   1010.58","","","","","","","","","","","","","","","","","","","","","","","","",

 Snow/ice coldest layer rose towards surface: 

"","","","","","","","","","",""

"04/05/2014 03:00","","","","    -19.10","   1010.24","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/05/2014 04:00","     72.5327","   -149.3823","GPS","    -19.16","   1009.97","      0.03","      1.53","      0.00","     -1.53","    -17.55","    -17.87","    -17.96","    -17.56","    -15.92","    -14.74","    -13.77","    -12.99","    -11.94","    -10.87","     -9.80","     -8.71","     -7.72","     -6.74","     -5.65","     -4.77","     -3.83","     -2.76","     -1.69","     -1.63","     -1.63","     -1.67","     -1.69","     -1.51","     -1.57","     -1.59","     -1.59","     -1.57","     -1.57","     -1.57","     -1.63"

"04/05/2014 05:00","","","","    -18.86","   1009.56","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/05/2014 06:00","","","","    -18.89","   1009.43","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/05/2014 07:00","","","","    -18.99","   1009.29","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

 Inversion, beginning of "ice wall",   horizon risen (possible maximum bottom melt, needs calibration):

"04/05/2014 08:00","     72.5359","   -149.4102","GPS","    -19.21","   1009.16","      0.03","      1.52","      0.00","     -1.52","    -19.39","    -18.88","    -18.71","    -18.12","    -16.10","    -14.74","    -13.71","    -12.93","    -11.94","    -10.87","     -9.86","     -8.77","     -7.79","     -6.80","     -5.71","     -4.77","     -3.83","     -2.76","     -1.69","     -1.63","     -1.57","     -1.67","     -1.69","     -1.57","     -1.57","     -1.53","     -1.65","     -1.57","     -1.50","     -1.57","     -1.63"

"04/05/2014 09:00","","","","    -19.19","   1008.89","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"04/05/2014 10:00","","",""," -19.27"," 1008.89","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","" "04/05/2014 11:00","","",""," -19.28"," 1008.55","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

    Sometimes prior, bottom refroze, released latent heat of fusion warming throughout entire ice (ice thickness should be re-confirmed):

 04/05/2014 12:00","     72.5374","   -149.4334","GPS","    -19.28","   1008.48","      0.03","      1.53","      0.00","     -1.53","    -19.13","    -18.76","    -18.52","    -18.00","    -16.17","

---- ----------------------------------------------

   Hypothesis presented here confirmed by buoy.  But buoy data are really good for specific physical details.  Optical data is immediate and comprises all of this same information in general,  but in physical precise terms, all obtained in one swift glimpse….

___________________________________
NASA EOSDIS confirmed clear day :

     April 9 2014,  buoy 2014B:

    Evening prior diurnal cooling:

"04/09/2014 05:00","","","","    -21.08","   1010.85","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"04/09/2014 06:00","","","","    -22.22","   1010.99","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"04/09/2014 07:00","","","","    -24.69","   1011.12","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/09/2014 08:00","     72.5308","   -149.5788","GPS","    -26.22","   1011.67","      0.05","      1.54","      0.00","     -1.54","    -26.22","    -26.35","    -26.30","    -26.09","    -21.54","    -15.43","    -13.90","    -13.12","    -12.13","    -11.06","    -10.11","     -9.02","     -8.04","     -7.12","     -6.03","     -5.08","     -4.14","     -2.95","     -1.76","     -1.63","     -1.63","     -1.67","     -1.69","     -1.51","     -1.57","     -1.53","     -1.59","     -1.57","     -1.57","     -1.57","     -1.63"

  Next Day Morning cooling continues:

 
"04/09/2014 09:00","","","","    -27.07","   1012.14","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"04/09/2014 10:00","","","","    -26.98","   1012.75","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"04/09/2014 11:00","","","","    -28.08","   1013.23","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

   Bottom refreeze at about 10:00 UTC.  Note the surface warming. At 12:00 UTC, there was likely a 10 C/100 meter inversion.   This is significant enough to make special optical"effects"
"04/09/2014 12:00","     72.5309","   -149.5794","GPS","    -28.63","   1013.70","      0.04","      1.55","      0.00","     -1.55","    -28.82","    -28.82","    -28.71","    -28.57","    -23.25","    -16.00","    -14.02","    -13.12","    -12.07","    -11.00","    -10.05","     -9.02","     -8.04","     -7.12","     -6.03","     -5.08","     -4.14","     -2.95","     -1.76","     -1.63","     -1.57","     -1.67","     -1.69","     -1.57","     -1.57","     -1.53","     -1.59","     -1.57","     -1.57","     -1.63","     -1.63"

   Sun -4.7 degrees below the horizon,  sunrise may be visible due to surface to air inversion:
"04/09/2014 13:00","","","","    -29.04","   1014.18","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"04/09/2014 14:00","","","","    -29.44","   1014.58","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"04/09/2014 15:00","","","","    -29.94","   1014.99","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

    Sun 7.4 degrees above the horizon, enough to warm the snow/ice surface warmer than surface air,  the apparent horizon dropped  a lot, coldest ice layer sinks.  
"04/09/2014 16:00","     72.5309","   -149.5785","GPS","    -29.65","   1015.40","      0.05","      1.54","      0.00","     -1.54","    -29.07","    -29.26","    -29.22","    -29.07","    -24.07","    -16.50","    -14.21","    -13.18","    -12.07","    -11.00","    -10.05","     -9.02","     -8.10","     -7.12","     -6.03","     -5.15","     -4.21","     -3.01","     -1.76","     -1.63","     -1.57","     -1.67","     -1.69","     -1.57","     -1.57","     -1.53","     -1.59","     -1.57","     -1.57","     -1.57","     -1.57"

    Diurnal warming from sunshine, 

"04/09/2014 17:00","","","","    -29.56","   

1016.21","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"04/09/2014 18:00","","","","    -28.92","   1016.48","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"04/09/2014 19:00","","","","    -27.78","   1016.89","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

 Sun 22.75 degrees above the horizon, coldest ice layer got deeper below surface,

the horizon was low:

"04/09/2014 20:00","     72.5308","   -149.5734","GPS","    -26.88","   1017.57","      0.04","      1.54","      0.00","     -1.54","    -23.88","    -24.89","    -24.78","    -25.08","    -21.35","    -16.19","    -14.34","    -13.25","    -12.07","    -11.00","    -10.05","     -8.96","     -8.04","     -7.12","     -6.03","     -5.08","     -4.21","     -3.01","     -1.76","     -1.63","     -1.63","     -1.67","     -1.69","     -1.57","     -1.57","     -1.53","     -1.59","     -1.51","     -1.50","     -1.57","     -1.63"
"04/09/2014 21:00","","","","    -25.81","   1017.98","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"04/09/2014 22:00","","","","    -25.17","   1018.59","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"04/09/2014 23:00","","","","    -24.20","   1018.93","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
  The more than 22 degree in altitude sun significantly warmed the top of snow

by almost 6 degrees, the top ice layers even more, because of twin thermal heating from sun and sea.  

"04/10/2014 00:00","     72.5304","   -149.5623","GPS","    -23.71","   1018.86","      0.04","      1.54","      0.00","     -1.54","    -15.85","    -17.05","    -16.57","    -16.86","    -17.62","    -15.62","    -14.27","    -13.31","    -12.07","    -11.00","    -10.05","     -8.96","     -8.04","     -7.12","     -6.03","     -5.08","     -4.21","     -3.01","     -1.82","     -1.63","     -1.63","     -1.67","     -1.69","     -1.51","     -1.57","     -1.59","     -1.65","     -1.57","     -1.57","     -1.57","     -1.63"

Lowest horizon,  surface temperature stall,  bottom melting:

"04/10/2014 01:00","","","","    -23.43","   1018.99","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"04/10/2014 02:00","","","","    -23.47","   1018.99","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"04/10/2014 03:00","","","","    -24.04","   1019.20","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

 Lower sun. Diurnal cooling well in play, coldest layer rises:
"04/10/2014 04:00","     72.5299","   -149.5554","GPS","    -25.33","   1019.20","      0.04","      1.54","      0.00","     -1.54","    -14.53","    -16.23","    -18.78","    -19.45","    -17.05","    -15.24","    -14.08","    -13.25","    -12.13","    -11.06","    -10.05","     -9.02","     -8.04","     -7.12","     -6.03","     -5.15","     -4.21","     -3.07","     -1.82","     -1.63","     -1.63","     -1.67","     -1.69","     -1.57","     -1.50","     -1.53","     -1.65","     -1.57","     -1.50","     -1.57","     -1.63"
"04/10/2014 05:00","","","","    -26.97","   1019.20","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"04/10/2014 06:00","","","","    -28.61","   1019.20","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"04/10/2014 07:00","","","","    -28.91","   1019.33","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"04/10/2014 08:00","     72.5301","   -149.5535","GPS","    -29.70","   1019.47","      0.05","      1.54","      0.00","     -1.54","    -30.09","    -30.15","    -29.79","    -27.17","    -18.95","    -15.43","    -14.08","    -13.25","    -12.13","    -11.06","    -10.05","     -9.02","     -8.10","     -7.12","     -6.09","     -5.15","     -4.27","     -3.07","     -1.88","     -1.63","     -1.63","     -1.67","     -1.69","     -1.57","     -1.50","     -1.59","     -1.65","     -1.57","     -1.57","     -1.57","     -1.63"

Sun elevation -8.9 degrees

"04/10/2014 09:00","","","","    -30.14","   1019.47","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"04/10/2014 10:00","","","","    -30.53","   1019.67","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

Bottom refroze latent heat of fusion released
"04/10/2014 11:00","","","","    -29.99","   1019.47","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

 Sun Elevation -7.2 degrees, entering dawn light, ice bottom froze 2 cm,  the heat produced has changed the diurnal cooling rate, coldest layer back at top of snow, sun and more light will be seen much earlier:
"04/10/2014 12:00","     72.5304","   -149.5509","GPS","    -30.35","   1019.20","      0.05","      1.56","      0.00","     -1.56","    -31.04","    -31.04","    -30.68","    -28.00","    -19.51","    -15.75","    -14.27","    -13.31","    -12.13","    -11.06","    -10.11","     -9.09","     -8.10","     -7.18","     -6.09","     -5.21","     -4.27","     -3.07","     -1.88","     -1.63","     -1.63","     -1.67","     -1.69","     -1.57","     -1.57","     -1.59","     -1.65","     -1.57","     -1.57","     -1.57","     -1.63"

--------------------------------------------------

It seems plausible that a diurnal cooling refreeze may induce further thickness increase than just the earlier melted layer. 

----------------------------------------------------

It is not always that simple,  when the weather is cloudy with some occasional clearing, accretion is chaotic,  here is one example:

VERY SLOW accretion (complicated autumnal action)

Buoy 2013l An October day of data acquisition over Arctic Basin Near Alaska:

"10/12/2013 08:00","","","","     -9.55","   1012.25","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/12/2013 09:00","","","","     -9.09","   1012.25","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/12/2013 10:00","","","","     -8.37","   1012.25","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

The ice is thick enough to stop "super accretion" but still most of the time warmer than the air, an adiabatic surface to air interface should increase thickness though:

"10/12/2013 11:00","     75.2560","   -154.5052","GPS","     -8.38","   1012.18","      0.09","      1.00","      0.00","     -1.00","     -6.59","     -5.46","     -4.52","     -3.95","     -3.51","     -3.14","     -2.70","     -2.13","     -1.57","     -1.50","     -1.44","     -1.50","     -1.57","     -1.50","     -1.50","     -1.57","     -1.57","     -1.63","     -1.57","     -1.44","     -1.57","     -1.44","     -1.57","     -1.38","     -1.38","     -1.50","     -1.44","     -1.44","     -1.44","     -1.50","     -1.50"

Detached diurnal warming all the action is in the air,  there is no sense of temperature direction:
"10/12/2013 12:00","","","","     -8.66","   1012.24","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/12/2013 13:00","","","","     -9.17","   1012.04","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/12/2013 14:00","","","","     -9.56","   1012.18","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/12/2013 15:00","     75.2704","   -154.5744","GPS","    -10.87","   1012.38","      0.10","      1.00","      0.00","     -1.00","     -6.97","     -5.40","     -4.46","     -3.95","     -3.58","     -3.14","     -2.70","     -2.13","     -1.57","     -1.50","     -1.44","     -1.50","     -1.57","     -1.50","     -1.50","     -1.57","     -1.57","     -1.63","     -1.57","     -1.44","     -1.57","     -1.44","     -1.50","     -1.38","     -1.38","     -1.44","     -1.38","     -1.44","     -1.44","     -1.57","     -1.50"

Probable diurnal cooling (cloud clears):
"10/12/2013 16:00","","","","    -11.59","   1012.45","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/12/2013 17:00","","","","    -12.38","   1012.39","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/12/2013 18:00","","","","    -13.77","   1012.38","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/12/2013 19:00","     75.2808","   -154.6458","GPS","    -13.36","   1012.25","      0.09","      1.00","      0.00","     -1.00","     -8.79","     -5.90","     -4.52","     -4.02","     -3.58","     -3.14","     -2.70","     -2.20","     -1.57","     -1.50","     -1.44","     -1.50","     -1.57","     -1.50","     -1.50","     -1.57","     -1.57","     -1.63","     -1.57","     -1.44","     -1.57","     -1.44","     -1.50","     -1.38","     -1.38","     -1.44","     -1.44","     -1.44","     -1.44","     -1.50","     -1.50"
"10/12/2013 20:00","","","","    -13.12","   1012.25","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/12/2013 21:00","","","","    -13.47","   1012.39","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/12/2013 22:00","","","","    -13.36","   1012.25","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/12/2013 23:00","     75.2940","   -154.7277","GPS","    -12.99","   1011.98","      0.09","      1.00","      0.00","     -1.00","     -9.48","     -6.28","     -4.71","     -4.08","     -3.64","     -3.20","     -2.70","     -2.13","     -1.57","     -1.50","     -1.44","     -1.50","     -1.50","     -1.50","     -1.50","     -1.57","     -1.57","     -1.63","     -1.57","     -1.44","     -1.57","     -1.44","     -1.57","     -1.38","     -1.38","     -1.50","     -1.44","     -1.44","     -1.44","     -1.50","     -1.50"
"10/12/2013 23:59","","","","    -12.50","   1011.70","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/13/2013 01:00","","","","    -11.66","   1011.43","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/13/2013 02:00","","","","    -10.92","   1011.16","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/13/2013 03:00","     75.3098","   -154.8211","GPS","    -10.40","   1011.02","      0.10","      1.01","      0.00","     -1.01","     -7.79","     -6.09","     -4.83","     -4.20","     -3.70","     -3.20","     -2.70","     -2.20","     -1.57","     -1.50","     -1.44","     -1.50","     -1.57","     -1.50","     -1.50","     -1.57","     -1.57","     -1.63","     -1.57","     -1.44","     -1.57","     -1.44","     -1.50","     -1.38","     -1.38","     -1.50","     -1.44","     -1.44","     -1.44","     -1.50","     -1.50"
"10/13/2013 04:00","","","","     -9.98","   1010.68","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/13/2013 05:00","","","","     -9.54","   1010.34","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/13/2013 06:00","","","","     -8.93","   1010.28","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/13/2013 07:00","     75.3285","   -154.9179","GPS","     -8.02","   1010.07","      0.09","      1.00","      0.00","     -1.00","     -6.78","     -5.71","     -4.83","     -4.27","     -3.76","     -3.26","     -2.76","     -2.20","     -1.57","     -1.44","     -1.44","     -1.50","     -1.50","     -1.50","     -1.50","     -1.57","     -1.57","     -1.63","     -1.50","     -1.44","     -1.50","     -1.44","     -1.50","     -1.38","     -1.38","     -1.44","     -1.44","     -1.44","     -1.44","     -1.50","     -1.50"
"10/13/2013 08:00","","","","     -7.09","   1010.07","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

"10/13/2013 09:00","","","","     -6.23","   1009.80","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/13/2013 10:00","","","","     -5.57","   1009.66","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/13/2013 11:00","     75.3509","   -155.0021","GPS","     -4.94","   1009.53","      0.09","      1.00","      0.00","     -1.00","     -5.33","     -5.21","     -4.71","     -4.27","     -3.76","     -3.26","     -2.76","     -2.20","     -1.57","     -1.50","     -1.44","     -1.50","     -1.57","     -1.50","     -1.50","     -1.57","     -1.57","     -1.63","     -1.57","     -1.44","     -1.57","     -1.44","     -1.50","     -1.38","     -1.38","     -1.50","     -1.44","     -1.44","     -1.44","     -1.50","     -1.50"
"10/13/2013 12:00","","","","     -4.55","   1009.32","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/13/2013 13:00","","","","     -4.06","   1009.19","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/13/2013 14:00","","","","     -3.81","   1009.11","","","","","

  And so it went on until finally a gain, note the presence of an inversion the horizon rose:

"10/13/2013 15:00","     75.3721","   -155.0279","GPS","     -3.23","   1009.53","      0.09","      1.00","      0.00","     -1.00","     -3.95","     -4.58","     -4.52","     -4.14","     -3.76","     -3.32","     -2.76","     -2.20","     -1.57","     -1.50","     -1.44","     -1.50","     -1.50","     -1.50","     -1.50","     -1.50","     -1.57","     -1.63","     -1.57","     -1.44","     -1.57","     -1.44","     -1.57","     -1.38","     -1.44","     -1.44","     -1.38","     -1.44","     -1.44","     -1.50","     -1.50"

   Diurnal cooling, sign of cold air advection or clearing sky:
"10/13/2013 16:00","","","","     -4.21","   1009.80","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/13/2013 17:00","","","","     -5.48","   1010.34","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/13/2013 18:00","","","","     -6.28","   1010.55","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

    Note the increase in thickness was somehow tied with the overnight inversion:
"10/13/2013 19:00","     75.3816","   -154.9967","GPS","     -7.24","   1011.16","      0.09","      1.01","      0.00","     -1.01","     -5.90","     -4.71","     -4.33","     -4.02","     -3.76","     -3.32","     -2.82","     -2.26","     -1.57","     -1.50","     -1.44","     -1.50","     -1.57","     -1.50","     -1.50","     -1.57","     -1.57","     -1.63","     -1.57","     -1.44","     -1.57","     -1.44","     -1.50","     -1.38","     -1.38","     -1.44","     -1.38","     -1.44","     -1.44","     -1.50","     -1.50"
"10/13/2013 20:00","","","","     -8.54","   1011.29","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""
"10/13/2013 21:00","","","","    -12.53","   

-------------------------------------------------------------

 Thinner ice mixed with clouds makes the analysis difficult,  if observed visually ,  simultaneously at buoy location,  physical processes understanding would be much more comprehensive.  

  WD June 19-20 2014

HRPT skin temperature muddle

~  Satellite temperature data impossible unless great portions of sea ice are covered with water.
~  Even in coexistence with much colder surface air.
~ An ice sandwich not!
~Buoy data correlates well with some NOAA/NCEP  (June 23 corrections), but doubts still persist.

    The corrections in red were written after I read some quite intriguing higher resolution buoy data...  

    Average "skin" temperature data for recent June days:

 NOAA/ESRL skin temperatures are above 0 C for a great portion of the Arctic ocean.  Very well!
It must be water ponds or wide open water …  (the 0 C average may due to really interesting water under the top of snow,  or something likewise exotic (June 23,2014 )Not so:

   NASA Modis on the 14th of June,  peering through the clouds there are a lot of leads, broken ice.  But no great water coverage (Hence the interesting possible presence of water under top of snow).

     OK here is the problem, NOAA also had much cooler surface temperatures (a look inspired by Neven):

    Same time period surface air,  2 meters high above the ice,  a good deal of it under -2 C.
The adiabatic lapse rate potentially caused could be as large as 1 C/meter or 1000 C per Kilometers.   A geophysical impossibility.  If achievable by artificial means (here the sun may have forced a warming at about  the skin surface) without , it would cause some extraordinary inferior mirages, making the ice look like water though (the optical irony here is sweet).    The constraint for adiabatic lapse rates are governed by gravity and the specific heat capacity of air at constant pressure 10 C  per km.  Unless there is sun on a black surface  (The black surface may be in fact green sea ice),  like a road mirage,  the idea of accepting this data is preposterous  questionable.   The possibility of sea ice existing above surface air temperatures has not been observed optically but for thin newly formed sea ice (the apparent horizon not lowering further than true astronomical horizon turns out the be more complex than I thought, more study is needed).  It is possible by sudden advection of colder air, but this would create rapid cooling of ice surface by adiabatic and convection processes.   But just how  shallow ice pond water above 0 C can subsist with surface air -2 C right above suggests an impossible scenario (Correct,  buoy data suggests diurnal solar forcing followed by rapid cooling on top of ice surface,  its possible by external forcing).  

I rather believe the data was muddled by open water (possible, but solar forcing was more plausible),  which can be +1 C or more,  mixed ice and water surface temperatures are taken as one "skin" perhaps.  Surface temperatures can be equally warmed by the open water.

     My observations have shown that thick ice should be colder than air (correct,  but top of sea ice is greatly affected by sun rays),  especially at this time of year.
However melt ponds would change the surface temperatures.  But since we don't have extensive melt ponds now.  We must consider a lot of open sea water.

  Considering this reasoning, looking back at 2012 the Arctic Ocean was awash with melt ponds or open water:

    Was it an ocean covered with melt Ponds in 2012?

   

   Modis June 14 2012.  …… No,  may be more open water?  Or was the surface temperature giving the same illusion?

         No, but a clue is given by the surface temperatures in the Western sector of 80 N to North Pole, especially the swat in the Alaskan sector of the Pole,  where surface temperatures were +3 C above the ice surface (Here there was   likely bad data because of the solar forcing lesson just learned,  average temperature of top of ice/snow layer should be warmer than surface air,  although there were few buoys in the sector, 2011j did not show such contrasting temperature).  That is more acceptable. However an inversion of 150 C/ 100 meters has never been officially (with great precision) observed naturally,  as far as I know,  another impossibility has been recorded as data.  Since no melt ponds were observed, the 0 + "skin" temperature was equally impossible (not so, very possible), unless there was a great deal of open sea water , not apparently present  (There was the sun capable of warming top of ice/snow layer by 6 C or more, an incredible warming).

     Conclusion:

        Arctic "Skin"  temperatures and surface temperatures by NCEP are to be taken with a lot of extrapolation in mind, especially at spring time when temperatures between ice top and air become close to 0. Unless somehow re-calibrated,  or with open water areas in mind.  I suggest field observations from buoys,  or optical refraction horizon measurements to correct the apparent mis-calibration.    For those avid sea ice followers,  use buoy data,  whenever if ever available.   2012 surface temperatures should be compared with 2014 strictly with buoy data for greater precision.  WD June 16, 2014

     Conclusion correction June 23, 2014

     I  still some doubt about about NCEP skin data vs air temperature during the period when snow and ice melts amongst open leads.  Considering Buoy data comparisons,  2014 data looks more reasonable with NCEP rather than 2012.  Buoy data should be prime and NCEP always useful but with the seasonal faults cited kept in mind.  

Arctic Ocean lake models

~Smaller,  much easier to understand Arctic lakes are great examples of sea ice melting processes

   June 1 Northern Quebec Picture.  Note the lakes which are mostly frozen are the biggest ones, the land lost its snow carpet.  All seems to be normal.  Except here in this single picture we can see all sea ice melting processing in one swift glance.    First the land,  which like Siberia or Northern Canada,
sea ice does not melt first, but rather the snow over land.  But here is the kicker, it is a common misconception to believe that land heat capacity is greatest,  not so,  it is lesser compared to water and ice.   Heat capacity of land is twice as less than ice,  yet the snow is mostly all gone.    For every 2 joules of heat gained by land gives  about 2 C of temperature increase.  While the same 2 joules raises ice temperature by 1 C.  The heat capacity differences of each physical feature explain this picture. But there is more,  the smaller lakes lost their ice first,  as opposed to the bigger ones.  Again land dominates the smaller bodies of water, either by shedding comparatively more snow melt water or their land spread dominance creates greater surface temperatures than at the middle of a big lake;

    A large lake  coincidentally looking like the Arctic Ocean,  has exactly the same melt features as during later summer over the Arctic Ocean.  There are melt ponds.  But these go along with the shorelines broken from their bonds of ice.  The ice appears also shattered and in new packs,  the smaller bits will last not long enough to look like sea ice pancakes.  But the shores melt first not the lake centre,  which has its own micro climate spreading outwards.

    Further to the South, an even bigger lake shows watershed on its surface,  causing different albedo properties.  Even sturdy and massive this ice end is nigh, for now,  the shores are not open, it is massive, its micro climate is so much bigger than the lake looking like the Arctic Ocean,  that its influencing neighbouring region making adjoining smaller lakes  still frozen .  We have here a good example of climates to come,  a much wider open Arctic ocean influences a huge Hemispherical chunk of planet Earth.  If it is all frozen up during summer the planet remains cooler,  but if vast segments of its extent are open water,  the lands next to it warm, and the lands next to the warmed lands warm further.  But ice,  consolidated, thick and white is like a single sunlight reflector.  If lake ice nowhere as thick as sea ice has a local significant impact, sea ice influences weather worldwide.  Ice is like an entity,    part of our climate system.  Once gone so goes cooling.   We know ice does not melt completely unless surrounded by heat,  from bottom, then from sides and finally top.    The weighted temperature of the ice column  must be colder than its surroundings for it to exist.  wd June 2,2014

Finding sea ice underside melting at any time

~ A refraction discovery is dwarfed by its much larger data application.  
~ Observing underside melting will help understand sea ice dynamics.  


 From the fascinating revelation of actually observing whether the underside of sea ice is melting or not.  We can can take it to a  much larger scale,  to the space platforms.   Where the thawing action is visible whenever they display their daily average temperature results. At first glance, it may surprise some,  the underside overall melts in a wide section  one day,  then to another area much further away the next,  leaving the impression of chaos which if you go underwater at the North Pole,  you would see just that,  underside art of mix geometry and light,  art only nature can achieve.

Refraction Discovery …

THIN SEA ICE  horizon

     Going back to several articles on EH2r,  sketches are needed to explain how we can see what is going on under more than hundred of centimeters of ice.   First we must observe what happens during Arctic Ocean late fall,  nascent sea ice sheet grows quite rapidly:

Super accretion
Tw : temperature of top of sea water;   Ti: top of sea ice temperature;   Ta :   air surface temperature.

 In Arctic autumn,  with  new sea ice just formed, thermal fluxes are aligned upwards to space.  Sea ice thickens quickly in direct relation to Ta,  surface Air Temperature,  the colder surface air is, the faster ice accretes .   In late fall , Ta is coldest of the mediums.  Conduction from either sea water and ice  go upwards just alike.   Adiabatic convection affects the cooling process accelerating it much further.  This gives super accretion optically seen by the lowering of the horizon:

Super accretion mirages of the freshly formed sea ice,  the horizon is dramatically low,  because new sea ice is quite warmer than the air just above.   The horizon line should be on top of the grey cloud like layer, right under is the refracted sky by an inferior mirage.

LONG NIGHT ice

     After the start of the long Arctic night,  where sea ice thickness exceeds 50 cm,  thermal flux to space is not as strong when cloud free,  as the ice thickens, absent sun makes top of sea ice largely always colder than surface air,   surface to air adiabatic lapse rates with thin ice turns to stable isothermal layers.  A near permanent thermal inversion  exists.  Up to hundreds of meters above ice in darkness,  the air subsists almost always warmer,  but does nothing but cooling.   The horizon at that time is almost always much higher than fall [unless fall time has a rare huge influx of warm air temperatures].   Surface air temperature colder than top of ice is a super accretion event of late fall, theoretical possible with winter thick ice (by cold air advection).   However,  I have very few observations of the lower horizon during darkness (most are caused by low clouds).   Therefore super accretion with thick sea ice is a very rare or unlikely event.    No atmospheric adiabatic convection along with less long wave radiation escaping to space slows sea ice accretion.  With numerous cumulative days in darkness,  top of sea ice becomes coldest  making a progressively thicker coldest strata from top towards bottom.   Much warmer air can only be found higher above,  from its peak in warmest temperature a stable near continuous inversion is made which has a profound impact in slowing further extreme cooling of sea ice. The equivalent to thick sea ice insolation exists invisibly but not near the horizon:

Near permanent inversion leaves the horizon risen throughout the dark season,  only lowered by low clouds.   Sea ice has a totally different look,  its white instead of dark,  snow also covers most of its surface.   The height of the horizon varies according to the lapse rate ,  a calculation:

    Horizon Height is directly proportional to the difference in temperature between Ta and Ti.   The colder Ti the higher the horizon,  like the example above. 

Moderate accretion happens by the shear thickness of the ice, now a large insulator,  thermal flows upwards towards space are similar to the fall scenario except less heat escapes,  more often than not,  it is the top of the ice which is the coldest medium, the difference in temperature between very near ice air may be small with gradual warming further aloft.  Cooling of air near the ice adds a downward thermal flux, but since air has significantly less heat capacity,  the ice absorbs a fraction of this long wave heat but does not warm up much from the gain and re-emits thermal rays towards space.   Unlike during Autumn,  the thicker colder ice layer causes accretion.

      These sketches are done without the presence of clouds in mind.   Thermal flows dramatically change when low overcast cloud conditions exist, when so,  sea ice horizon height lowers similar to effects by the noon sun.  In addition to a cold on top and warm ice strata below, a thinner top of ice temperature variance zone always susceptible to weather must be common.   But the net effect of the long Arctic night creates a large coldest ice layer which becomes steep in proportion to the severity of winter degree days, accordingly,  spring  season onwards sea ice requires significant warming before the structure of the lower Arctic Ocean atmosphere changes more permanently. 

Return of the sun

       In Early Spring, Ice Thickness depends on how long night climate conditions were.    But more than 100 cm First year ice , as usually measured throughout the Arctic at winter sunrise, has specific thermal properties in relation to depth which changes diurnally.  A coldest temperature layer lurks near top of ice,  but when sunny,  is found deeper above sea ice centre column.  When evening occurs, top of ice cools by short lived adiabatic convection,  the coldest layer just below ice surface accelerates the re-cooling strangely faster than the lower specific heat capacity of air.  Top of ice and subsequently the air right above cools,   this gives the sea ice rising horizon diurnal effect in a cloud free atmosphere:

     Left picture horizon was lowered from solar ray battering,  layers of the near and gradually more distant horizon appear to grow on top of each other until they form an ice wall (center and right).  Ice is warmest after Local Apparent Noon,  coldest in the morning prior to sunrise and for a few hours after.  This rising horizon simply indicated that the top of sea ice was only partially warmed, as the sun lowered,  cooled fast by convection  and contact conduction by the larger much colder ice layer immediately under.  Surface air  cooled less as rapidly,  but only very near top of the ice first,  then upwards in altitude. 

    In the evening after a sun ray bath,  top of ice appears to cool fastest.   From a starting point of surface air and top of sea ice having the same temperature,  the lowest air stratum in direct contact cools along with sea ice,  causing readily visible thermal layering which becomes the famous Norse "ice wall".   This "wall" becomes higher as the inversion becomes steeper at the ice surface to air interface.  The inversion peak also rises in altitude,  this makes "ducting",  a refraction phenomenon similar to fibre optics, possible at higher above the horizon.  Accretion continues in such  a time of day,  but much weaker,  because the ice is thick and was warmed by earlier solar heating,  a bottom refreeze can make this accretion unnoticeable. 

After Local Apparent Noon Melting of sea ice  

Here is where an horizontal observation is linked to satellite data,  after a few hours exposure to sun rays,  the ice horizon lowers until bottoming at the true astronomical horizon:

    About 2 hours after Local Apparent Noon , April 10 2014,  the horizon is at its lowest point.  Top of ice warmed no more,  the horizon stayed fixed,   underside of ice melting has occurred for about an hour.  

   As seen from the refraction largely nullified,  the ice horizon is at the same height as with open sea water in autumn when the temperatures between sea and surface air are the same.   Ti = Ta  means there is very little or no more loss of thermal heat from sea to space,  especially since short wave heat is added to the ice by the sun warming  its top layer.  The coldest ice layer shrinks,  more thermal heat from sea water is focused on the bottom of the ice.  The  underside melts until  very top of sea ice becomes coldest again. The reason for the temperature stalemate is found with the latent heat of melting at bottom.  Excess heat can't increase temperature because excess heat goes to melting ice. 

Applied formulas

   Since sea ice can have 2 distinct surface to air attributes;   very warm air above the freezing point of sea ice does not need much consideration whether the surface to air profile is adiabatic or stable.  Any underside melting formula should be adjusted accordingly .   The summer formula:  

    Ta >= Ti  hypothetical formula for determining where thick sea ice underside melts. Applies when Ta is equal or greater than -1.8 C .

         If the average surface temperature is greater or equal to the average temperature of top of sea ice,  its underside melts because thermal rays no longer escape from sea towards space.  3 meter sea ice bottom also melts for the same reason.  Even melting thicker sea ice just as much.    According to many buoy data,  the bottom of the ice column temperature  is nearly the same to adjoining sea water.   The process of accretion,   which exists when top of sea water thermal rays escape to space,  adds more ice onto the underside,   but when there is no longer any heat escaping,  ice bottom melting should start.   

          When the daily average temperature  of surface air exceeds or equals top of  ice average temperature,  there is an overall net melting of sea ice. Thickness loss is not seen above on the surface aside from the snow which appears to sublimate and becoming more porous.   At any given day with good satellite data,  we can observe where the melting occurs. Apparently it varies with the weather towards the centre of the Arctic Ocean.  Applying the formula to satellite data charts,  we can clearly delineate Arctic Ocean pack adjoining open water where  temperatures  of air and sea ice match,  obviously there is melting along sea ice shores: 

University of Maine excellent daily temperature averages of both sea ice top and surface air can be joined or superimposed to reveal where Ta is greater or equal to Ti:

A confirmation of sorts can be seen,  I traced by hand where Ta is >= Ti in black.  Of Course, Arctic Ocean sea ice shorelines must have underside melting especially at this time of the year.   What is most interesting are the long segments of apparent melting deep towards the North Pole.  These are weather related, as with weather, they are not consistent until  overwhelming heat takes charge of the Arctic:

A few days later and Hudson Bay underside sea ice appeared  completely melting.  But note Central Arctic Ocean melt zones with a totally different look.  This is not surprising.  But a long time chart of underside melting averages may be interesting.  

During early Polar spring days (Ta < -1.8 C), the melting period lasts as long as Ta = Ti. After the long night sunrise, the melting period gradually increases day by longer day by solar rays increasing in power with the sun rising in altitude.  Despite sea ice albedo and or reflection of rays back upwards, there is a significant enough absorption of solar rays to warm up top of sea ice to change thermal flux pattern diurnally. 

At lower surface temperatures than -1.8 C, the formula Ta = Ti maintains an isothermal interface, in such instances top of ice has a net positive or downward thermal flux towards the coldest layer, sea ice underside can melt even during the presence of very cold surface temperatures. (Ti > Ta has not been optically observed with thick ice with clear air ).

     A totally new perspective of analyzing sea ice optically has important features which become even grander when taken to a much larger scale. From all available data to date, the underside of sea ice melts when sea water thermal flux loss towards space becomes cut off by surface heat input either by the sun or by clouds. Low clouds resends lost Long Wave Radiation towards the surface, obviously this heat feedback is not as strong as high sun warming, studying the cloudy horizon has many pitfalls related to low contrast resolution. I suspect low clouds, a feature of warmer Arctic weather may contribute to much slighter bottom melting or certainly a stop of accretion, as long as surface temperatures are equal or higher than top of sea ice, in this case warmer air matters more.  Arctic Ocean  summer season of 2013 had more underside thawing than from the sun, extent and area was muddled by the lack of sea ice compaction by the extensive presence of cloud laden cyclones,   nevertheless a significant minimum was achieved.  

      Hypothetical proof:

      Observation data can prove underside melt despite lack of actual high resolution measurements.    Phase change is key, it takes energy to melt ice,  but when it freezes there is a release of latent heat.  This latent heat of fusion should reverse the cooling of top of sea ice, hence it should be seen lowering the horizon again.  A clear  day on April 24 2014 with the right conditions showed exactly this:

                                               Time        horizon
                                                               elevation   

  LAN                             2.97      

+ 1 hr 1 min 3.37

+3 hr 09                   3.69

+ 4 hr 30 3.14

+5  hr 49 4.43

 +6 hr 25 4.25

+7 hr 31 4.58

    + 8 hr 3 min  4.89

   At local apparent noon the ice horizon was 2.97' above a fixed point.  1 hour later, 3.37 minutes of arc, and so it should rise without interruption given the clear day.  Not so,  the horizon rose in steps, as often does on clear days, so for hour 4.5  sun rays significantly less hot can't lower the horizon.   Same at hour 5 49 min.   Another possible candidate of heat is the air next to ice loosing heat to the colder ice layer.   But 1 joule of heat loss of air (about 1 C cooling) transposes to top of ice at about +.25 joules.  While 1 cm of sea water at 1 meter square weighs 10 Kg,  that is 3340 kiloJoules per meter square released upwards.   There has to be such diurnal steps. 

WD May 25, June 5-11 2014

Sea ice thermal balance appears to be extremely sensitive to net solar radiation flux

~A small example simply reveals a big mystery.
~ For horizon observations,  sea ice must warm or cool faster than surface air,  this is impossible with a standard physics interpretation.
~There must be an unknown thermal transfer factor which has huge implications with sea ice models.

   Basic refraction optics are easy to understand.  A road mirage exists because there is very hot air above the pavement,  a mere few centimeters above,  where the temperature interface has a very steep unstable adiabatic profile immediately on top of the road.  The much hotter air creates an inferior mirage.   Similar inferior mirages are possible mainly during Arctic fall. A lesser  optical effect with a not so steep but strong adiabatic lapse rate are horizon shifts  which are called dips.  It was observed repeatedly that refraction horizons vary greatly over sea ice,  but these variations are linked with the surface to air interface just as much.  Like the hot pavement,   sea ice is a thermal body,  however much unlike road materials,  sea ice reflects more incoming sunlight without absorbing it.  But the following sequence suggests that sunlight,  even a fraction of it, was very significant,  in fact heated top of sea ice enough to lower the horizon dip significantly before the horizon rose again as with:

     Left to right April 20 2014 evening sequence of sea ice horizon rising within less than 1 hour.  The winds were light (10 knots or less),  the recorded surface temperatures fluctuated less than 0.5 degrees Centigrade.  Yet the sea horizon rose while the sun astronomical elevation dropped from 5.5  to 2.3 degrees.  The only thermal variance is with the sun basically weaker,  injecting less net rays.

     By theory,  sea ice has greater thermal capacity than air, it should not change in temperature at the same time rate as air does.  But this sequence suggests surface of sea ice cooled faster than the air right above.  A colder than air sea ice surface causes thermal inversions,  with horizontal layers readily seen in the left  and center photos.  Atmospheric inversions raise any object in the sky,  including the horizon.

    A same sequence during wide open water Arctic fall time will not repeat the same phenomena,  unless there is ice present.  The relation between not so varying sea surface temperature and the height of the horizon was made clear (paper almost done). There is a direct relation between sea surface and surface air temperature.  The steadier sea surface temperatures revealed a robust repeatable temperature proportionality.

  Current spring sea ice horizon diurnal effect is likeliest due to sea ice deeper frozen core temperature cooling the top of ice more rapidly than the usual swifter double rate of air cooling caused by less sunlight.  Thermal conductivity of  ice is nearly the same as soil, and is several orders of magnitude greater than air.   There may be something else at play,  like an inversion nearer to the camera (disproved very lately),  or a diurnal temperature variation  of near bottom ice sea water column (very unlikely).   This may be why sea ice  models can't replicate great sea ice melts.  The sun and clouds are  linked much more intimately with sea ice thermal exchanges.  This is very well observed.   The famous 2007 Arctic ocean ice melt had a lot of very thick multiyear year ice vanishing under the warm higher in altitude summer sun,  the astounding speed by which very thick ice melted definitely had something to do with the sun and clear air.   It seems that sea ice may be more complicated than simple,  there are known biological interactions,  not so known thermal features associated with structural differences as well.   Here is an example, amongst hundreds, of something worth taking time to achieve a more profound study.  WD April 28, 2014

Theory vs Observations:

       Heat capacity of ice is twice as great as air,  air heat capacity is greater than dry soil.
On a normal mid latitude night,  the air cools slower than dry land,  soil cools faster,
this creates often observed morning inversions.  Eventually likely by direct contact conduction , soil cools surface air.   Not theoretically so for sea ice.   Air should cool faster than ice.  But air cools uniformly,  at any given  time,  given a starting point of sea ice temperature being the same as its surface air (the true astronomical horizon achieved),  the lowering sun should create a warmer sea ice under cooler surface air.  If so, the cooler surface air should be warmed  by the top of sea ice.   If so,  the horizon should drop.   But what is observed is the opposite,  the horizon rises.   The pictures above
strongly suggests colder sea ice than surface air.  Because multiple stacked inversions reveal near surface thermal layers,  of which the top layer is the most distant and last inversion.    If surface air cools faster than sea ice ,  the layer 1 meter above cools at the same rate as the higher ones.  Radiative cooling should be uniform.  It is highly unlikely that the layer of air immediately on top of sea ice cools faster than the immediate air layers above especially if sea ice is warmer.   WD May 4,2014.

Huge near North Pole leads

State of Arctic Sea Ice is answered,  at least near the North Pole,  in the wake of 2 significant Cyclones, multiple leads appeared so early in the season, it looks like a great melt in the making has started especially near the Russian  coast Laptev and East Siberian sea.  

   O degrees meridian North Pole leads look very similar to late May off Ellesmere when "Spring Break" occurs.  WD April21,2014