conditions are created characterized by the depth of the upper surface of the Atlantic waters . 

 During years when the influx of Atlantic waters is intensive and their temperature high, and when 

 the winters are warm, this surface rises somewhat; during years when the influx of Atlantic 

 waters is weak and when the winters are severe, it sinks somewhat. 



The warm Atlantic waters which penetrate into the Arctic Basin as a deep current, and the 

 changes in their regime, i.e. , temperature and thickness, are extremely important, but as yet 

 they have not been evaluated properly, mainly because these waters are, so to speak, "buried" 

 under the cold, desalinified surface layers. Nevertheless, this effect can be detected easily by 

 simple computations similar to the ones already given . This effect is particularly apparent where 

 Atlantic waters, moving from west to east and forced to the right toward the continental shelf by 

 the force of the earth's rotation, enter from the north into the Soviet Arctic Seas and here, as it 

 were, "creep up" to shallower depths. I shall return to this interesting question later. 



LITERATURE: 87. 



Section 85. Effect of a Snow Cover on 

 the Rate of Ice Accretion 



As we have seen, the heat conductivity of snow is considerably less than that of ice; conse- 

 quently, ice beneath a snow cover is considerably thinner than snow-free ice, and its temperature 

 is correspondingly higher. 



Figure 76 by Ponomarev shows ice accretion on the Severnaya Dvina during the winter of 

 1941-1942 from the moment that the ice cover was established. The middle curve shows the 

 average thickness of the natural ice beneath the snow. The upper curve shows the snow depth. 

 The lower curve represents the average ice thickness along a railroad ice crossing which was 

 always kept clear of snow. 



■100 



Figure 76. Ice accretion beneath snow and with no snow. 



220 



