Perspectives on the causes of exceptionally low 2015 snowpack in the western United States

Journal article

Augmenting previous papers about the exceptional 2011-15 California drought, we offer new perspectives on the ‘snow drought’ that extended into Oregon in 2014 and Washington in 2015. Over 80% of measurement sites west of 115°W experienced record low snowpack in 2015, and we estimate a return period of 400-1000 years for California’s snowpack under the questionable assumption of stationarity. Hydrologic modeling supports the conclusion that 2015 was the most severe on record by a wide margin. Using a crowd-sourced superensemble of regional climate model simulations, we show that both human influence and sea surface temperature anomalies contributed strongly to the risk of snow drought in Oregon and Washington: the contribution of SST anomalies was about twice that of human influence. By contrast, SSTs and humans appear to have played a smaller role in creating California’s snow drought. In all three states, the anthropogenic effect on temperature exacerbated the snow drought.

Authors: Mote, P; Rupp, D; Li, S; Sharp, D; Otto, F

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Wiley
• Journal: Geophysical Research Letters
• Publication date: 2016-10-01
• Acceptance date: 2016-10-10
• DOI: 10.1002/2016GL069965
• ISSN: 1944-8007
• Keywords: supersensemble; regional climate model; attribution; weather@home; snow-drought