This soiling is especially marked in coastal or shallow water ice where particles of shore 

 origin fall onto the ice by one means or another and also on open sea ice where the ice surface is 

 dirtied as a result of biological process. For example, Nansen noted that on 18 June 1895, when 

 the Frnm was at 81° 21' north in the midst of ice at least three years old, a dirty brownish ice was 

 predominant. 



Foreign particles embedded in the ice decrease its total reflecting capacity and become cen- 

 ters around which the melting is concentrated. However, even completely clean ice which is 

 covered with clean snow will finally yield to the action of radiant energy since a certain part of this 

 energy does penetrate and is absorbed. Obviously, the first to melt are the surface snow flakes, 

 which fuse Into a solid mass having great reflecting capacity (solar korka or ice-rind). The snow 

 surface acquires at this time a bluidtng white color which gives rise to a painful eye inflammation 

 in the early spring at polar stations - commonly known as "snow blindness. " The horizon becomes 

 indistinct and sometimes a strong refraction is observed. If the sky is covered with a thin cloud 

 layer, the whole atmosphere appears to be filled with a peculiar silvery light, similar to the light 

 reflected from a polished silver plate. 



But the solar radiation, which falls onto the snow surface and fuses the surface flakes, at the 

 same time penetrates into the snow and causes its settling or packing. Along with the packing the 

 heat conductivity of the snow is increased and thus the heat transfer from the snow to the ice is 

 hastened. 



Despite the fact that in the early spring in the southern parts of the Arctic Basin the air 

 temperature does not go above -10° during the day and often falls below -30° at night due to radia- 

 tion, the first icicles and liquid drops of ice brine appear on the jutting prominences of hummocks 

 which are turned toward the south and the sharp edges of the ice floes begin to melt and become 

 rounded. * 



With further raising of air temperature and increase in solar radiation the surface layer of 

 the snow is saturated with water and its absorption ability is increased. 



In case of a sudden cold spell, ice rind is always formed on the snow surface. This ice rind 

 is of great significance for further melting. Actually, as we have seen, even very thin layers com- 

 pletely block the passage of long wave radiation. From this it follows that after an initial or re- 

 peated formation of ice rind on the snow cover over the ice, the radiant energy entering the ice is 

 transformed into heat but cannot radiate back onto the atmosphere due to the "hot-house effect" of 

 the ice rind. 



Thus the heat is gradually stored up in the snow and ice, and makes itself felt in the tempera- 

 ture increase in that part of the ice which is lighted by the sun. In the deeper parts of the ice this 

 heat is absorbed primarily not by the ice crystals themselves but by the foreign matter. This ex- 

 plains the fact, as we have seen, that pond ice which has formed under quiet or calm conditions 

 acquires in thawing a typical honeycomb appearance and that all accretion ice, including sea 



*0n Sosnovets Island, 26 to 29 February 1928, a settling of snow due to influence of solar 

 radiation was registered with a temperature of -15°. During the wintering of the Russian Polar 

 Expedition in the Laptev Sea instances were observed of melting of sea snow in the sun with 

 temperatures of -15° to -20°. 



299 



