Author(s):
Dr. Daniel B. Fagre - United States Geological Survey
Abstract:
A suite of studies with many collaborators over the past 14 years has provided an emerging picture of Northern Rocky Mountain ecosystem responses to past and current climatic changes and has developed model-based estimates of future responses. Tree-ring climate reconstructions identified significant drought episodes for the past 460 years and point to the 1917-1942 drought as the most severe. This is coincident with accelerated rates of glacier recession and alpine treeline changes. Reconstructing snowpack sizes suggest that the Little Ice Age added significantly to glacier mass balances only during the few decades before 1850. This implies that the neoglacial maxima was somewhat anomalous over the past 500 years and is not a benchmark for regional warming. For the past 50 years, snowpacks have disappeared earlier by two weeks despite a shift to maximum snowpack accumulation later in the spring. This has resulted in more abrupt, higher magnitude snowmelt and streamflows earlier in the spring and has depleted summer snowpacks. The ecological significance is in wildfire potential and reduced summer baseflows for streams and rivers. Looking to the future, recent modeling incorporates both multidecadal climate patterns (e.g. Pacific Decadal Oscillation) and different scenarios from General Circulation Models. These describe greatest changes at mid-slope elevations in the Northern Rocky Mountains and significantly reduced water supplies for downslope ecosystems and human communities.
