THE BACKGROUND 



11 



the arctic coast east of the Mackenzie (Flint, 1947). So in western 

 arctic America the glacial regime appears to have left large areas in the 

 Yukon-Porcupine Valleys and on the arctic slope of Alaska free from 

 ice fields during the late Wisconsin age. The conditions northwest 

 of the American ice cap were quite different from those on the massive 

 ice sheets which continuously covered the rest of Alaska, Canada, 

 and some northern States. 



The records of glacial geology lead Flint (1947) to propose that 

 Bering and Arctic seas were frozen during the last great Wisconsin 

 glaciation, and that the precipitation forming the arctic ice caps 

 came from the tracks of storms like those of the present. This moisture 

 would then have originated in the temperate oceans. However, re- 

 cently acquired oceanographic evidence of the history of temperatures 

 in the Atlantic Ocean has led Ewing and Donn (1956) to a novel 



SEA-LEVEL ISOTHERMS : MAY (»C) 



A. J. Connor, and others, "Climatic Maps of North America," Cambridge, Harvard 

 maps 1 and 3.) 



