Figure 110 shows the destruction of a separately floating ice block (nesiak) by waves 

 according to Burke. When the cornice (shown on the figure by a dotted line) fell off, the original 

 water line (also shown by dotted line) became inclined and a ram was formed on the ice block. 



In regard to the break-up of fast ice, it is obvious that in spring and summer, when the fast 

 ice has been weakened by the action of solar radiation and heat from the atmosphere, the breaking 

 requires the application of less force than in the winter. 



The break-up of fast ice in narrow straits, for example the straits of Matochkin Shar and 

 Yugorski Shar, is extremely characteristic. The formation of ice here, like everywhere else, 

 begins from the shores and gradually extends to the middle of the straits. The center part of the 

 straits with its rapid current usually does not freeze for a long time, even with low air tempera- 

 tures, since the ice particles which form on the surface of the open part of the straits are carried 

 down under the ice already formed near the shores by the action of the turbulent currents, and they 

 then adhere to the lower surface of this ice. As a result, in the spring the ice is thinnest and 

 breaks up earliest in the central part of the straits. On the other hand, we have seen that melting 

 also goes on comparatively rapidly by the shores. Thus, after the break-up, the ice cover of the 

 straits naturally falls apart into two strips parallel to the straits' axis. 



TABLE 87. CHANGE IN ICE THICKNESS AT KHABAROV (YUGORSKI SHAR) IN 1935 



Table 87 shows the change in thickness of fast ice in the period of melting in Yugorski Shar at 

 Khabarovo according to observations of Daniko in 1935. 



From this table there is evident, firstly, the springtime accretion of ice at comparatively 

 high air temperatures but low water temperatures, and secondly, the rapid decrease in ice thick- 

 ness under the cumulate effect of water and air temperatures. Thus, in the space of 10 days, from 

 18 to 28 June, the thickness of Ice in both holes decreased by 60 cm. In the entire 20 day period 

 the thickness of the 140 cm ice decreased by 40 cm; the 100 cm by 80 cm. 



LITERATURE: 23, 62, 77. 



310 



