Late Glacial and Holocene Glacier and Vegetation Fluctuations at Little Swift Lake, Southwestern Alaska, U.S.A

Abstract

Multiproxy data from Little Swift Lake, an alpine lake in southwestern Alaska, provide evidence for pronounced late glacial and Holocene environmental change. An alpine glacier upvalley of Little Swift Lake retreated following the Younger Dryas chronozone, as evidenced by sedimentological changes in the lake record. Glacier retreat was accompanied by local and regional vegetation changes, including the expansion of Betula and contraction of Cyperaceae, in response to climatic amelioration. Warm, moist conditions between ∼9800 and 8000 cal yr B.P. supported abundant Betula shrubs and high lake and watershed productivity. Alnus rapidly expanded near Little Swift Lake while the region cooled between 8000 and 7500 cal yr B.P. Environmental changes at Little Swift Lake appear to have been roughly synchronous with similar changes elsewhere in southwestern Alaska, but late glacial and Holocene changes in other parts of Alaska were different in nature and timing. The complex spatial and temporal patterns of late glacial and Holocene environmental change throughout Alaska point to the importance of local- and regional-scale factors, especially controls on moisture availability, as modulators of site-specific responses to hemispheric- and global-scale climate forcing.