Comparative Glacier Photographs from Northern Alaska

Abstract

Early photographs of a cirque glacier complex in the Arrigetch Peaks of the south-central Brooks Range date from 1911, and are the second oldest known set of glacier photographs from northern Alaska. Matching photographs and supplementary observations made in 1962 indicate that changes over the past 51 yr. in this area include general glacial recession and thinning, the emergence of pronounced trimlines and partial melting of ice cores beneath recent moraines. Renewed post-hypsithermal glacial activity in the Arrigetch Peaks area attained two maxima in the recent past. The younger moraines lie close to glacier positions shown in the 1911 photographs, contain ice cores which extend practically to their surfaces and were probably formed in the latter part of the nineteenth century. More weathered deposits, underlain by ice cores at relatively greater depths, were formed at some unknown earlier date. The moraines are correlated with the two-substage recent Fan Mountain advance of northern Alaska and may correspond to dated mid-eighteenth century and middle to late nineteenth century advances of alpine glaciers in the north Pacific coastal mountains of North America.