Friday, July 24, 2015

2015 major melt contributor: lack of snowfall during preceding winter.

~Snowfall accelerates sea ice refreezing process
~Lack of snow increases accretion on existing sea ice  while reducing extent at yearly maxima

   One of the biggest factors of 2015 melt was the lack of snow driven by a pan-continental Russia to North america flow of middle Russia dry air.   In one hand , accretion is greater when sea ice is bare and exposed to Arctic long night sky.  On the other,  falling snow,  colder than sea water ,  floats and does not melt  below 0 C,  which is the definition of Arctic Ocean surface temperature in September.  In Arctic autumn, snow just floats or appears a bit submerged just under the surface, this stabilizes the sea surface and likely affects water column convection flow,   and creates just right conditions for refreezing.  I have documented Cryosphere Today mis-interpreting a snow laden sea as ice.   But very shortly after,  in a matter of days,  sea ice set.    Little precipitation during the long night also causes, and more importantly so,  less drifting snow,  which helps ice set much earlier in autumn,  or at any other time during the long dark winter.

  Looking at this CT Archive retrieval,  one would guess 2012 had a moderately greater melt than 2013.
Note the 2012 snow surface cover over lands of NW North-America and North-East Russia.  Logic would dictate more snow presence in tandem with more open water over these naturally colder regions,  it was so.  2012 Ice surface extent recovered remarkably quickly in no small part because it snowed more.

  But look again,  2012 at minima had a great deal less ice than 2013,  and not surprisingly more snow on said colder lands in 2012 rather than 2013,  despite the inferred warmer weather because of the Arctic Ocean massively open in 2012.

          But in 2012,  more than any other recent year,  this was filmed:

   No,  this is not ice,  not even grey ice,  but fresh snow covering sea water.   The winds were just right to create this result.
    Winds mixed the surface up,  and "snow cakes" still lingered on shore and not much further away covering most of the Strait, until the ice set in about 48 hours later.  There was no doubt that snow helped accelerating freeze-up.

     The lesson for 2015,  a dry Arctic winter decreases over all extent,  even though the ice, where it set became thicker, because of no insulation above it.  From the Great Lakes to Southwards towards Russia through the North Pole lied a greater winter imprint,  its lasting legacy is seen here today:
    Hudson Bay and Baffin Bay sea ice survives late in the melt season.  The imprint of a lesser snow cover has important significance.  WD July 24,2015


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