Assessing Historical Trends in Snowpack Variability Across the Northern Rocky Mountains Using Remote Sensing and Dendrochronology Approaches

Abstract

Mountain snowpack across the western United States is declining because of warming spring temperatures during the modern period. Earlier snowmelt has been documented for numerous localities throughout the American West using ground-based snow-water-equivalent measurements and gauged streamflow. This research uses historical satellite imagery, tree-ring records, and instrumental climate observations from the northern Rocky Mountain (NRM) region to evaluate the climatic controls on mountain snowpack spatiotemporal variability, assess historical spring snowmelt trends, and contextualize modern climatic change with pre-instrumental climate variability. A suite of methodological approaches is employed to develop and calibrate satellite, tree-ring, and instrumental climate records using time-series analysis techniques. Together, these NRM region climate records suggest that precipitation in the form of mountain snowpack extent varies on interannual to decadal timescales. Of more importance, spring mountain snowpack appears to be decreasing in areal extent during the 20th and early 21st centuries driven largely by modern spring warming.