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The Curious Case of Projected Twenty-First-Century Drying but Greening in the American West

Justin S. Mankin; Jason E. Smerdon; Benjamin I. Cook; A. Park Williams; Richard Seager

Title:
The Curious Case of Projected Twenty-First-Century Drying but Greening in the American West
Author(s):
Mankin, Justin S.
Smerdon, Jason E.
Cook, Benjamin I.
Williams, A. Park
Seager, Richard
Date:
Type:
Articles
Department(s):
Lamont-Doherty Earth Observatory
Volume:
30
Persistent URL:
Book/Journal Title:
Journal of Climate
Geographic Area:
United States, West
Abstract:
Climate models project significant twenty-first-century declines in water availability over the American West from anthropogenic warming. However, the physical mechanisms underpinning this response are poorly characterized, as are the uncertainties from vegetation’s modulation of evaporative losses. To understand the drivers and uncertainties of future hydroclimate in the American West, a 35-member single model ensemble is used to examine the response of summer soil moisture and runoff to anthropogenic forcing. Widespread dry season soil moisture declines occur across the region despite increases in total water-year precipitation and ubiquitous increases in plant water-use efficiency. These modeled soil moisture declines are initially forced by significant snowpack losses that directly diminish summer soil water, even in regions where water-year precipitation increases. When snowpack priming is coupled with a warming- and CO2-induced shift in phenology and increased primary production, widespread increases in leaf area further reduces summer soil moisture and runoff by outpacing decreased stomatal conductance from high CO2. The net effects lead to the co-occurrence of both a “greener” and “drier” future across the western United States. Because simulated vegetation exerts a large influence on predicted changes in water availability in the American West, these findings highlight the importance of reducing the substantial uncertainties in the ecological processes increasingly incorporated into numerical Earth system models.
Subject(s):
Hydrology
Vegetation and climate
Climatic changes
Soil moisture
Evapotranspiration
Publisher DOI:
https://doi.org/10.1175/JCLI-D-17-0213.1
Item views
28
Metadata:
text | xml
Suggested Citation:
Justin S. Mankin, Jason E. Smerdon, Benjamin I. Cook, A. Park Williams, Richard Seager, , The Curious Case of Projected Twenty-First-Century Drying but Greening in the American West, Columbia University Academic Commons, .

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