CAUSE OF VARIATIONS III 



There is, therefore, a temperature of ocean water which 

 is more favorable for the development of glaciers in the 

 coastal mountains than a higher or lower temperature. 

 But this temperature is not the same for all parts of the 

 coastal belt; it must vary with local topographic charac- 

 ters. The glaciers of a low range may be more sensitive 

 to variations of the snow-line than those of a high 

 range. Glaciers facing the sea may be more sensitive 

 to the variations of wastage dependent on the tempera- 

 ture of the incoming winds than are glaciers facing the in- 

 terior. Glaciers fed from cirques, where snow is concen- 

 trated by wind and avalanche, may respond to variations 

 of precipitation in a very different way from glaciers fed 

 by open neve fields, where much of the annual snowfall is 

 dissipated by dry evaporation. The laws of variation for 

 high-grade glaciers may be quite different from those for 

 glaciers of gentle slope. And so, when the ocean tem- 

 perature approximates the value most favorable for the 

 development of glaciers in the district as a whole, it will 

 be too warm for the highest development of certain gla- 

 ciers and glacier systems and too cool for others. And 

 whenever such a condition obtains, a change in ocean 

 temperature will cause some glaciers to enlarge and 

 others to contract. 



It is of course impossible that one of the meteorologic 

 conditions determining Alaskan glaciation should vary by 

 itself while all other conditions remain constant, and the 

 case assumed for the sake of illustration is therefore 

 purely ideal. It has served its purpose if it has given 

 plausibility to the suggestion that a change in some 

 meteorologic factor or factors may result in simultaneous 

 modifications of glaciers which differ not only in amount 

 but in algebraic sign. 



Whatever may be the causes of the variations of gla- 

 ciers, Alaska affords an inviting field for their investiga- 



