Sunday, May 10, 2015

Sea ice thermal flux profiles , as demonstrated by the horizon.

~Part 1 ,  sea water to very thin sea ice
~ An attempt to explain what happens at the sea to air interface when sea ice forms

    I was going to demonstrate possible clashing between buoy data and refraction observations.  But it is now known that above sea ice Mass Buoys thermistors exaggerate
the snow or air layer temperatures a great deal.   Buoy 2015A had 20 cm of snow with temperatures in excess of +7 C,  while surface temperatures was +1.48 C (thanks to Jim Hunt for good detective work).   It is not impossible for snow surface to be warmer than the air when its sunny.  But it is impossible to have snow at +7 C.     This obvious flaw asserts questions and doubts  about for above ice string thermistors.  Moreover this data is lost to what should have been computer Model output verifications.  It is a loss which may be compensated by refraction observations.

Simple initial sea ice formation;
     Easy as it seems,  thermally speaking it is not, we let the horizon demonstrate,  but after several freeze-up seasons of observation,  the problem was to be sure if the sea ice has been totally covered all the way till the horizon.   Any open water affects the horizon line elevation.    Arctic sea water is magnificently stable in temperature,  so its horizon line varies almost exclusively with air temperature change:

   A much lowered horizon is due to "sinking",  the surface temperature is "about" 6.2 degrees warmer than air,  "about" because the horizon line changes position with the temperature differences between the entire light path which is never measured.    The few bits of ice are also miraged.  

     The most difficult analysis possible is to see what happens when sea ice forms over a wide expanse at once,  but what seems fairly certain,  there is no ice thickness limit by which the horizon always rises above true astronomical horizon.  This seems to be an astounding discovery:

   2014 October 3 (left) and the next day.  The horizon at left is about 17 km distant,  (at right) more than 25 Kilometers away.   Mostly water horizon turns to 100 % sea ice.  Similar freeze-ups were re- observed in 2013 and 2012.   It does not matter how thick the ice is,  it will set the horizon above astronomical line as long as the sea is completely covered with ice.  But the finer details,  from very low horizon of open water under a deep freezing air,  to above astronomical when sea ice covers everything,  need be carefully studied since it helps determine thermal flux  balance in one glimpse.  Usually the very low pre-freezing sea water horizon does not last long because the very cold air changes the state of sea surface.   Recent years freeze-ups happened because of colder Southern in provenance atmospheric advection , with the exception of 2013,  sea water was so warmed air temperatures needed to be below -11 C.

    High precision satellite pictures along with a careful analysis of a surface phase change would be quite revealing.   The reason for various horizon heights have everything to do with thermal fluxes.  As winter progresses,  the horizon changes until spring when the sun literally gives a similar horizon look,  but for entirely different  reasons than at freeze-up.   The very low sinking horizon exists because of a very steep near surface adiabatic profile,  the raised horizon on account of a completely ice covered sea,  is caused by looming  by profiles having stable inversions varying in strength based entirely on the current thermal balance.  This indirectly identifies ice thickness because
thicker sea ice has a cold or warm "core", significantly affecting thermodynamic action.   WD May 10,2015

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