Authors: Stockton Maxwell*, Radford University, Grant L. Harley, University of Idaho, Bryan A. Black, University of Arizona, Matthew F. Bekker, Brigham Young University
Topics: Paleoenvironmental Change, Biogeography, Climatology and Meteorology
Keywords: tree ring, dendrochronology, snowpack, climate change, paleoclimatology
Session Type: Virtual Paper
Presentation File: No File Uploaded
Cool-season precipitation is a critical component of western North American water supplies. In recent decades, snow water equivalent (snowpack) has declined dramatically, culminating in record lows along the northern Cascade Range, during the winters of 2014 and 2015. The extent to which these recent trends exceed historical ranges of variability remains poorly understood. Here, we use a network of 30 tree-ring chronologies to reconstruct April 1 snowpack in the northern Cascade Mountains (Washington, USA) over the past ca. 400 years that accounts for 62% of the instrumental period variability. The most conspicuous feature is a decline that began in the mid-1970s concurrent with a shift to above-average air temperature which has accelerated through to the most recent years of the record. The 2014–2016 snow drought across the northern Cascades is unprecedented within the context of the last 400 years. Not only is the twentieth–twenty-first century period characterized by the rapid decline in snowpack conditions, it is also highly volatile. Extreme flips in snowpack conditions (year-to-year changes between < 5th and > 95th percentiles) during the twentieth and twenty-first centuries were anomalous within the context of the record. These patterns described for the North Cascades are concurrent with anomalously low snowpack in the Sierra Nevada, and thus part of a broader trend toward reduced snowpack in western North America.