93 93 12 58 SO 42 37 33 30 28 25 23 25 28 30 33 37 42 50 53 72 33 



G-CAL/CM2 DAY 



Figure 77 . Ascent of isotherms beneath snow drifts. 



3. The flexure of ice under a drift, with a simultaneous temperature increase in the lower 

 layers of the ice, results in the washing away of the convexity by sea currents, especially tidal 

 currents . 



4. The amount of heat released to the atmosphere through the snow and ice can be computed 

 easily by formulas (1) and (2). Through ice 20 cm thick with a snow-free surface, 467 g-cal/cm2 

 day are released to the atmosphere which increases the ice thickness 16 cm, while only 233 g-cal/ 

 cm2 day are released through ice 10 cm thick and covered by a layer of snow also 10 cm thick, 

 which increases the ice thickness only 3 cm. 



Figure 77 shows the amount of heat (in g-cal/cm2 day) released by ice 100 cm thick with 

 snow covers of different depths . 



The decrease of heat release beneath snow, and the resulting decrease of ice accretion also 

 gradually destroy the convexity which had formed under the weight of the drift. 



Burke presents very interesting observations conducted during the winter of 1937-1938 on 

 Franz Joseph Land, of the effect of a snow cover on the rate of ice accretion. These observations 

 also prove the destructive action of sea currents . Burke writes: " Here, at the eastern cape of 

 Scott-Kelty Island, extremely strong tidal phenomena are observed. In November 1937, newly- 

 formed ice, located between hummocky fields over a quite extensive area, reached a thickness of 

 20 cm. Ice thickness measurements conducted every ten days showed that the ice thickness began 

 to decrease as snow accumulated on the ice, and by 10 February, the ice had disappeared com- 

 pletely . It became dangerous to walk on the snow and people fell through . By this time , the snow 

 layer had become 57 cm deep. Later, the wet snow began to freeze and new ice formed but now 

 it was snow ice, which was gray and not the usual green color. " 



LITERATURE: 23, 76, 77. 



222 



