may occur in the case of wind-driven changes of level. As a result, the stamukha will attain a 

 stable position only at the highest water level of the given region, whether tidal or wind-driven. 



Along a shallow shore where, in addition, the tidal and wind-driven variations of level are 

 sharply defined, the stamukha may travel considerable distances before it finally stops. It is 

 natural also that as a result of this travelling, the ratio of sub- surface depth to height above water, 

 which for ice blocks is about 5 , may for the stamukha become equal to 2 or even 1 . The tidal move- 

 ments of stamukhi are particularly noticeable in Mezenski Gulf where the flood tides are great and 

 where the spring tide amplitudes are several times greater than those of the neap tides. 



In high latitudes the stamukhi are massive formations and many of them survive the short 

 polar summer. While the tides assist in increasing the size and solidity of the stamukhi in winter, 

 in the summer they assist in destroying them. First of all they strongly alter their shape. Actually, 

 in the course of time the fluctuations of level and accompanying tidal currents wash away a hollow 

 at the height of the variations of level. This hollow girdles the stamukha on all sides at a height 

 somewhat greater than the amplitude of the tide and is bordered from above by a sharply traced 

 cornice and from below by a rounded base washed by the water. The hollow which encircles the 

 stamukha gradually penetrates deeper and deeper into the ice and the stamukha acquires its 

 characteristic mushroom shape with fanciful outlines. 



If the stamukha sits near a shore which is open to wave movement the action of the tidal 

 fluctuations in level is considerably strengthened but the cornice is quickly destroyed by the shock 

 of the waves and the cap of the mushroom becomes considerably smaller than its base. In places 

 shut off from wave movement the cap of the mushroom keeps its dimensions for a long time and the 

 cornice crumbles away only due to its own weight. 



Stamukhi, as we have seen, consist of extremely heterogenous ice floes cemented together 

 by freezing of thaw water mixed with snow. Therefore, their individual parts represent formations 

 of diverse durability and present different resistance to the washing action of the water. In this 

 connection, the stamukhi are washed by the water in many different ways. The upper cap may rest 

 on one or several pillars so that transverse grottoes and bridges are formed in the stamukha. These 

 shapes are especially diverse when the stamukhi are located in places closed off from wave move- 

 ment where the upper cap can be retained longest. 



LITERATURE: 62, 77. . 



Section 124. Tidal Movements of Sea Ice 



Due to the influence of the tide, floating ice is in constant movement and it traces ingenious 

 patterns. Individual fields and ice floes sometimes collide, press together and hummock up, some- 

 times drift apart and become sparse . The greater the tidal amplitude in the given region the more 

 sharply are these movements defined. With spring tides they are greater than with neap tides, and 

 in calm or weak wind conditions they are clearer than in strong winds. 



During the drift of the icebreaker i era in in the southwestern part of the Laptev Sea in the 

 winter of 1937-38 some interesting observations of tidal movements of ice were made. The shal- 

 low depth of the drift region (about 45 m) permitted the use of an extremely simple, but at the same 

 time accurate, method of determination of elements of drift, namely, by the length of a paid-out 

 line. 



336 



