California’s 2023 snow deluge: Contextualizing an extreme snow year against future climate change

Journal Article · 28 April 2024 · Proceedings of the National Academy of Sciences of the United States of America

DOI: https://doi.org/10.1073/pnas.2320600121 · OSTI ID:2341702

Marshall, Adrienne M.  ^[1]; Abatzoglou, John T.  ^[2]; Rahimi, Stefan ^[3]; Lettenmaier, Dennis P.  ^[4]; Hall, Alex ^[5]

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1. Hydrologic Science and Engineering Program, Colorado School of Mines, Golden, CO 80401
2. Department of Management of Complex Systems, University of California, Merced, CA 95343
3. Department of Atmospheric Science, University of Wyoming, Laramie, WY 82071, Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095
4. Department of Geography, University of California, Los Angeles, CA 90095
5. Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095

The increasing prevalence of low snow conditions in a warming climate has attracted substantial attention in recent years, but a focus exclusively on low snow leaves high snow years relatively underexplored. However, these large snow years are hydrologically and economically important in regions where snow is critical for water resources. Here, we introduce the term “snow deluge” and use anomalously high snowpack in California’s Sierra Nevada during the 2023 water year as a case study. Snow monitoring sites across the state had a median 41 y return interval for April 1 snow water equivalent (SWE). Similarly, a process-based snow model showed a 54 y return interval for statewide April 1 SWE (90% CI: 38 to 109 y). While snow droughts can result from either warm or dry conditions, snow deluges require both cool and wet conditions. Relative to the last century, cool-season temperature and precipitation during California’s 2023 snow deluge were both moderately anomalous, while temperature was highly anomalous relative to recent climatology. Downscaled climate models in the Shared Socioeconomic Pathway-370 scenario indicate that California snow deluges—which we define as the 20 y April 1 SWE event—are projected to decline with climate change (58% decline by late century), although less so than median snow years (73% decline by late century). This pattern occurs across the western United States. Changes to snow deluge, and discrepancies between snow deluge and median snow year changes, could impact water resources and ecosystems. Understanding these changes is therefore critical to appropriate climate adaptation.

• Sponsoring Organization: USDOE
• OSTI ID: 2341702
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America, Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Issue: 20 Vol. 121; ISSN 0027-8424
• Publisher: Proceedings of the National Academy of SciencesCopyright Statement
• Country of Publication: United States
• Language: English