Tree Rings Reveal Multi-century Snowpack Dynamics of the Cascade Range, USA

Abstract:

Since the 1950s, the western United States has experienced ‘snow drought’ events of increasing duration and severity over time. Across this region 50-80% of surface water is derived from mountain snowpack and this is projected to decrease to 44% by the year 2100 in the Cascade Range alone. However, it is not known whether recent ‘warm’ snow droughts (winter precipitation as rain rather than snow) are unusual relative to past ‘dry’ snow droughts (lack of winter precipitation). Tree-ring chronologies provide precise, annually-resolved, multi-century paleoclimate information which can enhance our knowledge of the natural long-term variability in the climate system beyond the instrumental record. Here, we pair new and existing annual tree-ring chronologies with instrumental snow course data to develop multi-century snowpack reconstructions of warm and dry snow droughts for the Cascade Range, USA, and determine the unusualness of recent warm snow droughts relative to prior centuries. These Cascade Range snowpack reconstructions may serve policy makers and water managers in this region, as they incorporate a wider range of climate variability and future climate scenarios into future adaptation strategies.