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Paleoclimate reconstructions of western North American snow droughts during the last millennium

Mountain snowpacks provide essential water supply for human populations and ecosystems in the western United States. Warmer temperatures and changing precipitation patterns will continue to alter both the quantity and persistence of snow over coming decades, yet snowpack observations are limited and forecasts contain considerable uncertainty. Likewise, the utility of snowpack projections may be greatly limited by significant internal climate variability. Here we compare a new spatial reconstruction of Snow Water Equivalent for the mountains of western North America covering the period 1400 to 1980 with downscaled SWE estimates from last millennium general circulation models. Both models and data reveal the spatial fingerprint of large-scale ocean-atmosphere variability on the space-time patterns of snowpack anomalies. We characterize internal and forced variability in both models and our paleoclimate reconstruction, and use this novel 600 yr record to evaluate the extent to which simulations are able to capture temporal, spatial, and spectral properties of snowpack variability and change in western North America.

Kevin Anchukaitis is Professor of Earth Systems Geography at the University of Arizona and a researcher at the Laboratory of Tree-Ring Research.  He uses an array of techniques to develop and interpret evidence for past, present, and future climate dynamics across a range of temporal and spatial scales, from local to global and interannual to millennial. These include dendroclimatology, climate field reconstruction and spatiotemporal data analysis, stable isotope geochemistry, proxy system modeling, and the integration of paleoclimate data with climate model simulations.  His research program includes extensive fieldwork throughout Asia and the Americas.