Neoglaciation in the Southern Kenai Mountains, Alaska

Abstract

A preliminary late-Holocene glacial chronology from the west flank of the southern Kenai Mountains, Alaska, is characterized by two major episodes of advance. Outlet glaciers of both the Harding Icefield and the Grewingk-Yalik ice complex were expanding across their present positions at 545 A.D. and again during the Little Ice Age, about 1500 A.D. The earliest of these Neoglacial advances is dated by radiocarbon ages from the outer rings of tree trunks rooted near the margins of Grewingk and Dinglestadt glaciers. Subsequently, ice margins retreated some distance behind their present positions allowing marked soil development before the last readvance through mature forest. Wood preserved in lateral moraines at Grewingk Glacier and from an uprooted stump at Tustemena Glacier date this later ice advance. Tree-ring ages, correlated with lichen diameters, suggest that this last advance was widespread and culminated in its Neoglacial maximum about 1800 A.D.. Since this time, glacier retreat has dominated in the area, punctuated by at least two pauses. Historical accounts and photographs document a mean rate of retreat of 27 m a−1 for the past century with partial control exerted by calving of ice margins into proglacial lakes.