P2C2: Spatiotemporal Variability in Western United States Snowpack During the Common Era

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Annual snowpack and snow meltwater supplies have deteriorated across the western United States since 1950. While climate projections indicate these trends will continue throughout the 21st century, short instrumental snow records prevent an assessment of whether these recent declines fall outside the natural range of long-term snowpack variability or if they are exceptional relative to prior centuries. A lack of long snow observations also makes it difficult to identify and characterize decadal-scale and longer-term climatic drivers of annual snow accumulation, changes in those drivers over time and space, and the magnitude of internal variability in the snow system. Yet information at these timescales are most important for effective climate change adaptation. To address these critical knowledge gaps, this project will develop gridded spatial field reconstructions of snow water equivalent spanning the western United States that explicitly capture the period of negative snow trend within model calibrations using tree rings. The researchers aim to test the ability of climate models to simulate the range of forced and internal snow hydroclimate variability in western United States over the last millennium.The potential Broader Impacts include the generation of long Snow Water Equivalent (SWE) tree ring chronologies to test different hypotheses of environmental forcing on the pre-industrial timescales and their comparison with last millennium climate model output; the testing of a possible anthropogenic fingerprint on changes in SWE over the last thirty years relative to pre-Industrial forcing and the possible implications for water resource management in the future; and support of an early-career scientist who has helped pioneer the tree-ring SWE discipline. The project also supports an undergraduate student, a post-doctoral research scientist, and outreach to water resource managers in Western North America.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.