Abstract
Snowpack observations in the Intermountain West are sparse and short, making them difficult for use in depicting past variability and extremes. This study presents a reconstruction of April 1 snow water equivalent (SWE) for the period of 1850–1989 using increment cores collected by the U.S. Forest Service, Interior West Forest Inventory and Analysis program (FIA). In the state of Utah, SWE was reconstructed for 38 snow course locations using a combination of standardized tree-ring indices derived from both FIA increment cores and publicly available tree-ring chronologies. These individual reconstructions were then interpolated to a 4-km grid using an objective analysis with elevation correction to create an SWE product. The results showed a significant correlation with observed SWE as well as good correspondence to regional tree-ring-based drought reconstructions. Diagnostic analysis showed statewide coherent climate variability on inter-annual and inter-decadal time-scales, with added geographical details that would not be possible using courser pre-instrumental proxy datasets. This SWE reconstruction provides water resource managers and forecasters with better spatial resolution to examine past variability in snowpack, which will be important as future hydroclimatic variability is amplified by climate change.
Highlights
Water supplies in the U.S Intermountain West will be affected by a decrease in snowpack compounded by an amplified fluctuation of snowpack variability [1,2,3,4,5]; this tendency may be pronounced in the topographically diverse state of Utah [6]
SWEValidation model skill (R2 ) varied across the 38 snow coreses used in the state from as low as 0.25 to as high as 0.71, but averaged
Limiting the tree-ring data to ITRDB and WADR data varied across the state, R2adj ranged from 0.23 to 0.67, and averaged 0.46, and R2cv ranged from reduced the range of skill to 0.18–0.62, and averaged 0.43, when compared to the full tree-ring data
Summary
Water supplies in the U.S Intermountain West will be affected by a decrease in snowpack compounded by an amplified fluctuation of snowpack variability [1,2,3,4,5]; this tendency may be pronounced in the topographically diverse state of Utah [6]. Precipitation amounts are typically highest in the spring and lowest in the summer, but winter storms bring copious amounts of snow to the mountains. This leads to the development of heavy snowpack that is a critical form of water storage for the state. During the winter months (October thru March), nearly 70% of mountain precipitation arrives as snow [8]. This accumulation of snowpack peaks near April 1 and melts gradually over the summer, and is an important source of runoff. While 1000 mm is typical, in northern Utah snowpack measurement stations sometimes exceed 1500 mm, while in the southern portion of the state 500 mm
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