Figure 58. The draft of an ice cake (density 0. 90) in water 

 (density 1. 01) according to Burke. 



It is clear that if the upper and lower surfaces of the ice floe are horizontal and its side walls 

 are vertical, formula (1) is simplified, namely; 



where h is the above water elevation, s is the underwater draft of the ice floe. 



From formula (2) we obtain 



2 Si 



(2) 



i ~ 8... ' 



(3) 



where i is the general thickness of the ice. 



Table 51 gives the relation between the draft of the underwater part of the ice floe to the 

 height of the above water part at different densities of water and ice for homogeneous ice floes. 



When examining table 51, we see that even a slight change in the density of the ice or water 

 causes a great change in the relation of the above water ice to the draft of the underwater part of 

 the ice fields. 



But we have seen that sea ice is a porous body in which part of the pores in the surface part 

 of the ice communicate with the air and the underwater part communicates with the sea water. It is 

 clear that such pores should be excluded from the volume of ice introduced into formula (1). Re- 

 membering these reservations, let us note that the porosity of sea ice increases considerably 

 during the simimer when air replaces the brine in the cells, and at this time, the density of the 



170 



