Near-term acceleration of hydroclimatic change in the western U.S.

Journal Article · Tue Jan 01 04:00:00 EST 2013 · Journal of Geophysical Research: Atmospheres (Online)

DOI:https://doi.org/10.1002/jgrd.50816· OSTI ID:1115372

Ashfaq, Moetasim ^[1]; Ghosh, Subimal ^[1]; Kao, Shih-Chieh ^[1]; Bowling, Laura C. ^[2]; Mote, Phil ^[3]; Touma, Danielle E ^[1]; Rauscher, Sara ^[4]; Diffenbaugh, Noah ^[5]

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1. ORNL
2. Purdue University
3. Oregon State University
4. Los Alamos National Laboratory (LANL)
5. Stanford University

Given its large population, vigorous and water-intensive agricultural industry, and important ecological resources, the western United States presents a valuable case study for examining potential near-term changes in regional hydroclimate. Using a high-resolution, hierarchical, five-member ensemble modeling experiment that includes a global climate model (CCSM), a regional climate model (RegCM), and a hydrological model (VIC), we find that increases in greenhouse forcing over the next three decades result in an acceleration of decreases in spring snowpack and a transition to a substantially more liquid-dominated water resources regime. These hydroclimatic changes are associated with increases in cold-season days above freezing and decreases in the cold-season snow-to-precipitation ratio. The changes in the temperature and precipitation regime in turn result in shifts toward earlier snowmelt, baseflow, and runoff dates throughout the region, as well as reduced annual and warm-season snowmelt and runoff. The simulated hydrologic response is dominated by changes in temperature, with the ensemble members exhibiting varying trends in cold-season precipitation over the next three decades, but consistent negative trends in cold-season freeze days, cold-season snow-to-precipitation ratio, and April 1st snow water equivalent. Given the observed impacts of recent trends in snowpack and snowmelt runoff, the projected acceleration of hydroclimatic change in the western U.S. has important implications for the availability of water for agriculture, hydropower and human consumption, as well as for the risk of wildfire, forest die-off, and loss of riparian habitat.

• Research Organization: Oak Ridge National Laboratory (ORNL)
• Sponsoring Organization: ORNL LDRD Director's R&D
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1115372
• Journal Information: Journal of Geophysical Research: Atmospheres (Online), Journal Name: Journal of Geophysical Research: Atmospheres (Online) Journal Issue: 19 Vol. 118; ISSN 2169-8996
• Publisher: American Geophysical Union
• Country of Publication: United States
• Language: English