Tree-ring-based reconstructions of North American glacier mass balance through the Little Ice Age — Contemporary warming transition

Abstract

AbstractGlacier mass-balance reconstructions provide a means of placing relatively short observational records into a longer-term context. In western North America, mass-balance records span four to five decades and capture a relatively narrow window of glacial behavior over an interval that was dominated by warming and ablation. We use temperature- and moisture-sensitive tree-ring series to reconstruct annual mass balance for six glaciers in the Pacific Northwest and Alaska. Mass-balance models rely on the climatic sensitivity of tree-ring chronologies and teleconnection patterns in the North Pacific. The reconstructions extend through the mid to latter portions of the Little Ice Age (LIA) and explore the role of climate variability in forcing mass balance across multiple environmental gradients. Synchronous positive mass-balance intervals coincide with regional moraine building and solar minima, whereas differences in LIA glacier behavior are related to synoptic climate forcing. Secular warming in the late 19th century to present corresponds with the only multi-decadal intervals of negative mass balance in all glacier reconstructions. This suggests that contemporary retreat in western North America is unique with respect to the last several centuries and that regional patterns of glacier variability are now dominated by global climate forcing.