Similar tables may readily be compiled for any region, given the duration of the melting 

 period and the thickness of melting ice, characteristic of the given region. Thus, for example, 

 with T = 40 days and h = 50 cm, using equation (3) we obtain 



.. 2S,X50 



and by equation (2), 



T^ = 32 h. 



Observations show that in the seas of the Soviet Arctic the melting from above in August 

 varies on the average from 1 to 3 cm per day. Piotrovich notes that in the Chuckchee Sea, at 70° 

 north latitude and 182° east longitude, for the 24 hour period from 20 to 21 August 1935, approxi- 

 mately 3.5 cm of ice melted, the weather being completely clear and warm. Thus, the melting of 

 ice from above is a slow but fundamental process for close ice, occurring at all times for ice of the 

 central arctic and in the spring season for ice of the neighboring seas. 



In the case of many- year-old ice this process is connected with an extremely typical vertical 

 movement in the ice of all kinds of foreign matter. In many-year-old ice, which melts for the most 

 part from above and which grows by freezing from below, all foreign matter which freezes to the 

 lower surface of the ice in one way or another will finally appear on the upper surface. Many 

 observers, including myself, have noted that the brown deposit on the ice consists of quartz. Many 

 observers have been suprised to find comparatively large stones and even boulders on the surface 

 of the ice far away from the shores, which can be explained by the phenomena described above. 



LITERATURE: 68, 77, 115. 



Section 117. Melting of Ice Due to Thermal Action of Water 



While melting of close ice occurs for the most part from above (and from below if such ice is 

 carried by the winds into warm waters), for open ice, on the other hand, great importance is 

 attached to the melting due to heat accumulated from the water layers adjacent to the ice. This 

 factor is greater the more open or scattered the ice is. 



For simplicity of calculation in estimating the significance of this process I have made an 

 extreme assumption; e. g. : in the melting process a reduction occurs only in the horizontal dimen- 

 sions of individual ice floes equidistantly separated in the sea. This assumption is in part justified 

 by the fact that the reflection from the water is very small, while that from snow and ice, on the 

 other hand, is very great. 



Let us suppose that the heat absorbed by the water is immediately and completely used in 

 melting. This assumption more or less corresponds to reality with considerable percentages of 

 ice, and is proven by the low water temperature near the ice during melting. This phenomenon is 

 made possible by two processes: (a) the mixing or stirring of water caused by the wind and ebb and 

 flood tides, and (b) the natural circulation which always results from the conjunction of water and 

 ice of different temperature . 



Let the heat absorbed by the water be equal to 



mwdT, 



316 



