This winter brought record snowfall to California, but a new study suggests the state should expect gradually diminishing snow accumulations, even if punctuated by occasional epic snowfalls, in the future.
An analysis by Tamara Shulgina, Alexander Gershunov and other climatologists at the Scripps Institution of Oceanography at the University of California, San Diego suggests that in the face of relentless global warming, the snow lines that mark where rain turns to snow have increased significantly in the last 70 years. The researchers’ projections suggest that the trend will continue with snow levels rising hundreds of meters in the second half of this century.
In the southern Sierra Nevada range, for example, snow lines are projected to rise more than 1,600 feet (500 meters) and even higher when the mountains receive precipitation from atmospheric rivers, jets of water vapor that are becoming into an increasingly powerful source of the state’s water supply.
“In an average year, snow cover will be increasingly confined to the winter peak and to higher elevations,” the study says.
The decline in snowfall is a consequence of a changing climate in which places like California will get an increasing portion of their winter precipitation as rain rather than snow. The authors said this study and related research suggest that water resource managers will need to adjust to a feast-or-famine future. California’s water supply will come less through the gradual melting of mountain snowpacks that sees the state through hot summers and more through bursts of rain and runoff delivered by atmospheric rivers, which are driven by warming and are associated with higher snow levels than other storms.
Such events will further complicate the balancing act between protecting people and infrastructure from winter flooding and ensuring sufficient water supplies during the hottest summers.
“This work adds information to the climate change narrative of more rain and less snow,” said Mike Anderson, a climatologist with the California Department of Water Resources (DWR). “DWR appreciates our partnership with Scripps to help water managers develop, refine and implement adaptation efforts as the world continues to warm and the impacts of climate change are realized.”
The study, funded by the US Office of Recovery and the DWR, appears in the journal Climate Dynamics May 25.
“This is the longest and most detailed account of snowpack in California,” Gershunov said, “resolving individual storms over 70 years of observed time combined with projections to 2100.”
The authors take note of what this could mean for ski resorts across the state if climate change continues unabated. For example, Mammoth Mountain, at elevations between 2,400 and 3,300 meters (7,900 and 11,000 feet), is projected to receive 28 percent less snowfall in the second half of the century. Lower elevation ski resorts, such as Palisades and Northstar, both near Lake Tahoe, span elevation ranges around 1,900 and 2,700 meters (6,200 to 8,900 ft). They are projected to lose more than 70 percent of their snowpack in an average winter.
“Future climate observations and projections show that snow levels that are already increasing will continue to rise,” Gershunov said. “However, epic winters will still be possible, and record snowfall will ironically be more likely due to wetter atmospheric rivers, but will be increasingly confined to the winter peak and higher elevations of the southern Sierra Nevada. ”.
Study co-authors include Kristen Guirguis, Daniel Cayan, David Pierce, Michael Dettinger and F. Martin Ralph of Scripps Oceanography, Benjamin Hatchett of the Desert Research Institute in Reno, Nev., Aneesh Subramanian of the University of Colorado at Boulder, Steven Margulis and Yiwen Fang of UCLA, and Michael L. Anderson of the California Department of Water Resources.