Section 86. Ice Accretion in the Region of Ice Removal 



As we have seen, the thickness of ice accretion as a function of freezing degree-days, can 

 be expressed by 



(1) 



where i is the ice thickness in centimeters and R is the number of freezing degree-days . 



This formula gives an idea of the accretion of a single floe, either stationary or drifting. 

 Let us use this formula to solve one of the frequent questions which arise in connection with the 

 study of the ice concentration of seas from which ice is constantly removed by winds and currents . 

 Let us attempt to determine the ice thickness at some geographic point of the sea where the rate 

 of ice drift is known. 



Let us assume that we have a rectangular channel, open at one end, and that there is con- 

 stant and uniform removal of ice through this open end. Let us also assume that the air tempera- 

 ture is uniform throughout the channel . 



Under such assumptions, it is obvious that the ice thickness will remain near zero and that 

 it will increase with distance. The question arises: under these conditions, what will the ice 

 profile be like along the axis of the channel after complete removal of all the ice which had formed 

 at the moment freezing started throughout the channel ? 



For the sake of simplicity, let us assume that the temperature differential between the air 

 and water is constant, and is 25 ° . Let point in figure 78 correspond to the origin of the co- 

 ordinates . Let the X-axis represent the distance traversed by the ice in 40 days . It is clear that 

 the ice, whose initial thickness at point was 0, will be subjected to 25 x 40 = 1000 freezing 

 degree-days in these 40 days . This same ice will be subjected to 2000 freezing degree-days at 

 the end of 80 days, etc. 



FREEZING DEGREE-DAYS 



SiJO WOO 1500 Zm 2500 3000 3S00 4000 H500 5000 



40 80 uo m 



DISTANCE ALONG THE AXIS OF REMOVAL, 

 COUNTING FROM SHORE, IN KNOTS 



Figure 78. 



Ice profile along the 

 channel axis. 



223 



