104 POLAR PROBLEMS 



This life cycle of the ice cover is caused by processes of heating 

 and changes of water temperature during a period of time that does 

 not last longer than three months. 



Summary 



Thus, in summary, the main features of the annual cycle of the 

 ice cover of the Arctic Sea are as follows : 



a) Fast-ice, as one of the three classes of ice making up the ice 

 cover, disappears in summer, passing over into the pack ice. 



b) Pack ice continuously feeds the Arctic Pack, part of which 



c) drifts out of the Arctic Basin through its outlets all the 

 year round (the main outlet is the strait between Green- 

 land and Spitsbergen) 



In winter the main processes are: 



i) Formation, growth, and development in breadth of the fast- 

 ice. This brings with it 



2) a decrease of the area of the pack-ice region, which, as well 

 as the Arctic Pack, 



3) increases its strength and consolidated areas, thereby decreas- 

 ing the areas of open water among its parts. 



In summer the ice of all classes undergoes: 



i) a decrease in thickness through thawing (the most subject 

 to it are the inshore parts of the fast-ice) ; 



2) a breaking up into constituents of lesser size; 



3) a decrease in area, which takes place in two ways: 



a) by the piling up or telescoping of the ice, which in turn 

 produces an increased strength of the separate parts of ice ; 



b) by the destruction of pieces of ice through crushing and 

 attrition (the most subject to this is the fast-ice). 



Variability of the State of the Ice 

 IN Consecutive Years 



As all these processes are immediately connected with and de- 

 pendent upon the meteorological elements, which mostly differ from 

 year to year, the degree of development of these processes varies with 

 the years. For this reason, and because of the lack of sufficient 

 systematic observations and data, it is impossible to outline the exact 

 state of the ice over the greater part of the Arctic Sea — a state which 

 it would be very important to know for the purposes of navigation 

 in the pack-ice and fast-ice belts. '^ 



' For the Kara Sea, for instance, there is available, however, the excellent detailed investigation 

 of this question by E. Leshaft, who, on the basis of a study of the distribution and state of the ice for 



