THE GLACIERS OF ALASKA 



THE rapidity with which the 

 Alaskan glaciers are changing, 

 some retreating and others ap- 

 parently advancing, gives special value 

 to the careful record of their present 

 character contained in "Alaska; Gla- 

 ciers and Glaciation,"* by Dr G. K. 

 Gilbert. Ur Gilbert states that Nuna- 

 tak Glacier between Professor Russell's 

 visit in 1891 and his own visit in 1899 

 retreated fully a mile and possibly twice 

 as much ; Muir Glacier between 1880- 

 1899 retreated i^? miles, and since the 

 earthquake of 1899 has retreated about 

 three miles. On the other hand, other 

 glaciers, like the Columbia and La Pe- 

 rouse, are now probably at their maxi- 

 mum, having been much smaller during 

 the past 100 years. 



While it is impossible to say absolutely 

 why certain glaciers are diminishing 

 while others a short distance away are 

 increasing, Dr Gilbert suggests that the 

 cause may be a change in the meteoro- 

 logic conditions. The glaciers are dif- 

 ferent, some being fed by open neve 

 fields and others by cirques. A rise in 

 ocean temperature probably increases 

 the wastage of the former class, but, on 

 the contrary, enlarges the latter class 

 by an increased fall of snow and rain, 

 which more than counterbalances the 

 wastage. 



' ' Nearly all the glaciers of Alaska 

 are comprised within a belt of moderate 

 width which follows the southern coast 

 from the Aleutian Islands to Portland 

 canal. Curving about the great bight 

 of the Pacific Ocean known as the Gulf 

 of Alaska, this belt has a length of 1 ,600 

 miles, and its extreme width, near the 

 middle, is about 250 miles. Within it 

 the arrangement of glaciers is irregular, 

 but their more important groups occupy 

 the middle region, while near the ends 

 they are comparatively sparse and small. 



' ' The explanation of this massing of 

 glaciers along the southern coast is not 

 far to seek. The general circulation of 

 the Pacific Ocean brings to the Gulf of 

 Alaska a current of water which has 

 been warmed in the tropics and still re- 

 tains so much heat that its mean tem- 

 perature is considerably above the nor- 

 mal for the latitude. The ocean is 

 therefore, at some seasons, warmer than 

 the contiguous land, and though air 

 currents passing from ocean to land 

 convey heat to the land they are them- 

 selves cooled. While traversing the 

 ocean the air becomes loaded with moist- 

 ure, the cooling over the land dimin- 

 ishes its water- carrying capacity, and 

 part of its load falls to the ground as 

 rain or snow. Moreover, all this coast 

 is mountainous, so that landward flow- 

 ing air is compelled to rise, and its 

 capacity is still further reduced by rare- 

 faction. At the greater altitudes the 

 ratio of snow to rain is comparatively 

 large, and the mountains thus become 

 gathering grounds for the snows that 

 feed glaciers. Farther inland the air 

 currents descend somewhat, and the pre- 

 cipitation is diminished until the con- 

 ditions for glacier formation cease. 

 Hayes states that while the neve line 

 of glaciers on the southward face of the 

 St Elias Alps lies at about 2,000 feet 

 above sea-level, its altitude on the north- 

 ern face is over 6,000 feet. 



"Along the western coast of Alaska 

 the conditions are different. Bering Sea 

 lies practically outside the influence of 

 the Pacific circulation, and the temper- 

 ature of its water is approximately 

 normal. Its power to change air cur- 

 rents with moisture is small, especially 

 in winter, and though the winter tem- 

 perature over the adjacent land is low 

 the snowfall is heavy. There are no 

 great mountain ranges to concentrate 



* "Alaska ; Glaciers and Glaciation," byGrove Karl Gilbert. Vol. Ill of the Harriman Alaska 

 Expedition Series. Edited by Dr C. Hart Merriam. With 18 maps and plates and 108 illus- 

 rations in text. Pp. 230. 5 by 10^ inches. New York : Doubleday, Page & Co. 1904. 



