above water part of ice can differ sharply from the density of its under-water part. Therefore, 

 making formula (2) more exact, we obtain 



(4) 



where 5 , is the density of the above water part, 

 6 is the density of the underwater part. 



From formula (4) we obtain 



h 8,.,-S, 



(5) 



Just how considerably the density can fluctuate is shown by Malmgren's measurements of the 

 density of ice in the same ice field. During the winter, when the brine and air cells in the cold ice 

 were isolated from each other and from the surrounding media, the density of the ice fluctuated 

 within the limits of 0. 914 to 0. 924, in May within the limits of 0.885 to 0.899. 



It has already been noted that according to Savelev's observations of 1939 the porosity of fast 

 ice increased from February to May and minimum porosity was noted in the middle levels of the 

 ice. Correspondingly, the density of the ice decreased from February to May and attained its max- 

 imum values in the middle parts of the ice. Thus in May 1939 at the 5 cm level, the density was 

 0.870, at 80 cm - 0.910, and at 172 cm - 0.875. The lowest density of sea ice, according to 

 Makarov's determination (13 August 1899) was 0.846, and the greatest was 0.929 with a 2. 8 o/oo 

 salinity of ice. 



Makarov calls the following ratio the buoyancy of sea ice 



h + Z 



h_ 

 i 



(6) 



TABLE 51. THE RATIO OF THE UNDERWATER TO THE 

 ABOVE -WATER PARTS OF HOMOGENEOUS 

 ICE FLOES HAVING HORIZONTAL UPPER 

 AND LOWER SURFACES AND VERTICAL 

 SIDE WALLS 



According to his measurements conducted in sea water having a temperature of -1.5° and a 

 salinity of 32. 4 o/oo (density, 1.0258), the buoyancy of 27 investigated samples fluctuated within 

 the limits of 1:6 to 1:15. 



171 



