Annualmeeting:2017 CSDMS meeting-093

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Evolving patterns of glaciers and summer streamflow in the Pacific Northwest US: 1960-2100

Erkan Istanbulluoglu, University of Washington Seattle Washington, United States. erkani@uw.edu

Chris Frans, University of Washington Washington, United States. cfrans@gmail.com

Dennis Lettenmaier, UCLA Los Angeles California, United States. dlettenm@ucla.edu

Andrew Fountain, Portland State University Portland Oregon, United States. andrew@pdx.edu

Jon Riedel, National Park Service Sedro Woolley Washington, United States. Jon_Riedel@nps.gov

[[Image:|300px|right|link=File:]]The Pacific Northwest is the only region in the conterminous United States with a sizable number of glaciers (328 glaciers totaling ~380 km ). The glaciers of this region have displayed ubiquitous patterns of retreat since the 1980’s mostly in response to warming air temperature. Glacier melt in partially glacierized river basins in the region provides water for downstream anthropogenic systems (e.g., agricultural water supply and hydroelectric power generation) and sensitive ecological systems (e.g., fisheries, upland riparian habitat). While changes in glacier area have been observed and characterized across the region over an extended period of time, the hydrologic consequences of these changes are not fully understood. We applied a state of the art high resolution glacio-hydrological simulation model along with regional gridded historical and projected future meteorological data, distributed observations of glacier mass and area, and observations of river discharge to predict evolving glacio-hydrological processes for the period 1960-2100. We applied this approach to six river basins across the region to characterize the regional response. Using these results, we generalized past and future glacier change across the entire PNW US using a k-means cluster analysis. Our analysis shows that while the rate of glacier recession across the region will increase, the amount of glacier melt and its relative contribution to streamflow displays both positive and negative trends. Among the characteristics that control the direction and magnitude of future trends, elevation dominates and climatic factors play a secondary role. In high elevation river basins enhanced glacier melt will buffer strong declines in seasonal snowmelt contribution to late summer streamflow for some time, before eventually declining. Conversely, in lower elevation basins, reductions in glacier melt will exacerbate negative trends in summer runoff in the near term.