SCIENTIFIC KESULTS 



175 



recent years. The fact that the vohiine of radio traffic handled by 

 the patrol in the last five years alone has increased '3(K) per cent, is 

 eloquent testimony of the use of this ice service by North Atlantic 

 sliipping. 



LANE Routes and the Critical iceberg area 



Figure 112. — The location of the principal traus-Atlantic 

 lane routes which are explained in tlie text, pajie 171. The 

 shaded portion of 20,000 square miles represents the ice- 

 berg area which receives the international ice patrol's 

 most vigilant attention. Bergs in this area are potential 

 menaces, liable at any time to drift southward across the 

 paths of the trans-Atlantic traffic. The ice patrol during 

 the past few years has attempted to keep on board an 

 up-to-date current chart of this area. A satisfactory 

 map. according to Bjerknes's method, can be constructed 

 from a total of 18 points of observation, as shown above. 



One of the most interesting scientific aids which the patrol is 

 using with considerable success is that of current mapping according 

 to the Bjerknes theory of dynamic oceanography. The patrol by 

 keeping an up-to-date current map of a 20,000 square mile area south 

 of the Grand Bank, at the junction of the Labrador current and the 



