Section 152. Variation in Ice Circulation From Year to Year 



The distribution of atmospheric pressure over the earth and in particular over the Arctic 

 Basin varies not only from season to season, but also from year to year. In connection with this, 

 the ice circulation, which is determined by the pressure pattern likewise varies from year to year, 

 and within fairly large limits. 



At my request, Somov traced the drift of arctic ice for 1937 and 1938, basing his work on the 

 rules which I have derived, that is, that ice moves along the isobars and with a speed inversely pro- 

 portional to the distance between isobars. The results of these calculations are shown in figures 

 170 and 171. 



200 o 200 400 600 900 lOOO Ktl 



I I— I I I I I 



Figure 170. Computed drift of arctic ice in 1937. 



The small circles on these charts show the positions (for both years) on 1 January of individual 

 floes whose movements were subsequently traced. Their drifts were then computed from the 

 monthly pressure maps by consecutive vectors. 



It goes without saying that the maps which are shown must be considered as extremely rough 

 approximations. In compiling them no account was taken of permanent currents nor of the effect of 

 land and islands on the wind-caused drift of ice. Nevertheless these maps at least give some idea of 

 the fact that the transfer of ice into Greenland Sea was greater in 1937 than in 1938. 



435 



