Water exchange of seas, just like other meteorological and oceanographical processes, experiences 

 seasonal and long-term fluctuations, while within any single year, in certain limits, it undergoes 

 phase displacements. These variations may be expressed both in volume and heat of the currents 

 and these together may be reflected on fluctuations in ice abundance. 



In analogous fashion to the water exchange, coastal drainage exerts a great influence on ice 

 abundance of shallow seas. For example, in the coastal regions of the Kara, Laptev and East 

 Siberian Seas the coastal drainage is a primary factor in the ice quantity, changing the latter as a 

 result of the force and time of onset of spring flooding. 



More complicated are the fluctuations in ice-abundance in seas and regions where a more or 

 less intensive ice exchange with neighboring seas occurs , 



In the Barents Sea, ice of local origin predominates . The movement of ice out of this sea 

 and the movement of ice into it from the Arctic Ocean and the Kara Sea are slight and nearly bal- 

 ance each other. Therefore the main factors determining the ice abundance of this sea are the heat 

 conditions of the Norwegian current and the meteorological conditions which are to a great extent 

 regulated by the heat conditions of Atlantic water. 



In the Kara Sea, besides the synoptic conditions, the Ob and Yenisei and other rivers are of 

 great importance for the southern part of the sea. The ice exchange with Barents Sea is slight, 

 and the coming and going of ice is almost balanced. The ice exchange of this sea with the Arctic 

 Ocean and the Laptev Sea, however, is quite another matter. Fluctuations in the loss of ice may 

 be considerable in certain years, and these very fluctuations, especially in the prenavigational 

 period, may perhaps play the most important role in the ice conditions of this sea. 



These fluctuations and the carrying away of ice are determined not only by fluctuations in the 

 state of the Kara Sea itself but are also connected with the circulation of air masses over the adja- 

 cent parts of the ocean, over the Barents and Laptev Seas, and in particular over the central part 

 of the Arctic Ocean. 



In the northwestern part of the Laptev Sea the most important factor is the entry of ice from 

 the Kara Sea and the Arctic Ocean, while in the southeastern part the most important factor is the 

 water condition of the Lena River. The entry of ice will vary to a considerably greater extent than 

 the conditions of the Lena water, and therefore the ice conditions in the southeastern part of this 

 sea are subject to considerably less fluctuation from year to year than those in the northwestern 

 part. 



The East Siberian Sea is protected from ice movement from the north by islands and shallows, 

 and therefore its ice abundance depends mainly on hydrometeorological conditions. It is quite a 

 different matter with respect to Long Strait and Chuckchee Sea. Wind conditions in the summer 

 season are the basic determining factor as to whether these waters will have a great deal of ice or 

 be completely ice free during the navigational period. 



Appropriate observations and studies show that the spring season processes have the greatest 

 effect on ice abundance in the aictic seas during navigation. Arctic navigation began unusually 

 early in 1943 and continued under extremely favorable conditions. In this connection the following 

 data are of interest. 



Figure 190 shows the anomalies in melting of the snow cover in Siberia in 1943. In certain 

 regions the snow cover melted 30 days earlier than normal. This is an extremely favorable 



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