Recent decreases in snow water storage in western North America

Katherine E Hale; Keith S Jennings; Keith N Musselman; Ben Livneh; Noah P Molotch

doi:10.1038/s43247-023-00751-3

Recent decreases in snow water storage in western North America

Commun Earth Environ. 2023;4(1):170. doi: 10.1038/s43247-023-00751-3. Epub 2023 May 22.

Authors

Katherine E Hale^{1

2

3}, Keith S Jennings⁴, Keith N Musselman^{1

2}, Ben Livneh^{5

6}, Noah P Molotch^{1

2

7}

Affiliations

¹ Department of Geography, University of Colorado at Boulder, Boulder, CO USA.
² Institute of Arctic and Alpine Research, University of Colorado at Boulder, Boulder, CO USA.
³ Department of Civil and Environmental Engineering, University of Vermont, Burlington, VT USA.
⁴ Lynker, Boulder, CO USA.
⁵ Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, CO USA.
⁶ Department of Civil, Environmental, and Architectural Engineering, University of Colorado at Boulder, Boulder, CO USA.
⁷ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA USA.

Abstract

Mountain snowpacks act as natural water towers, storing winter precipitation until summer months when downstream water demand is greatest. We introduce a Snow Storage Index (SSI), representing the temporal phase difference between daily precipitation and surface water inputs-sum of rainfall and snowmelt into terrestrial systems-weighted by relative magnitudes. Different from snow water equivalent or snow fraction, the SSI represents the degree to which the snowpack delays the timing and magnitude of surface water inputs relative to precipitation, a fundamental component of how snow water storage influences the hydrologic cycle. In western North America, annual SSI has decreased (p < 0.05) from 1950-2013 in over 25% of mountainous areas, as a result of substantially earlier snowmelt and rainfall in spring months, with additional declines in winter precipitation. The SSI and associated trends offer a new perspective on hydrologic sensitivity to climate change which have broad implications for water resources and ecosystems.

Keywords: Cryospheric science; Hydrology.