Considering the following values the most probable , 

 therefore S.= 1.02, S. = 0.90, 



k = 0.11 Az. 



Thus, the increase in the thickness of ice by accretion from below to 100 cm causes a shift of 

 the level of the sea with regard to the ice, and the increase of the height of the above-water part of 

 the ice 11 cm in all, and the increase of the height of the under- water part 89 cm. 



During the summer the processes which change the position of the isostatic line with regard 

 to the level of the sea results in the following: 



1. Evaporation and depositions or precipitations. It is possible to neglect in the first ap- 

 proximation the influence of these processes. 



2. Accretions of ice from below due to the low temperature, which is already preserved 

 within the ice. As we have seen, the thickness of the ice due to the secretion by freezing can thick- 

 en more than 5 to 10 per cent, so that we may also disregard for our purposes this phenomenon. 



3. The decrease in the density of the above- water part of the ice in summer time can produce 

 decreases in the salinity and increase porosity due to the increase in temperature. 



The decrease in the density of ice (see Section 65) even with an increase of 20° in temperature 

 does not exceed . 03 per cent. For our purposes, it is possible to disregard this value. 



The decrease in the density of the above-water part of the ice due to its decrease in salinity, 

 due to the flow of brine from the salt capillaries and subsequent replacement of the formed vacuums 

 by air may also be insignificant. 



There is another matter, the increase in the dimensions of the salt capillaries which is due to 

 melting, after all the brine flows from them. On the strength of the circumstance, sea ice is 

 gradually transformed to a granular ice which approximates in form and density the neve ice. 



Returning to formula (9), we note that with the quick raising of ice, the density of the part of 

 the ice with a thickness k which had been raised over the level of the sea cannot be changed sig- 

 nificantly. Therefore, formula (9) takes on the appearance 



(ha-M)\+{Zo+Az)8.^-(z,-k+Az) K, (13) 



and formula (10) resulting from (9) takes on the appearance 



/c8„,-A/iS^+Az(S, — S;,) = 0, (14) 



where 



k8^ + Az_(8,—S^) 





Futhermore, let us remember that the growth of ice in summertime from below, due to the 

 low temperatures of ice, cannot exceed 20 cm, and the difference of the density of the water and the 



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