Upper Feather River Watershed

Observed changes in the Sierra Nevada snowpack: Potential causes and concerns

A study of the California Sierra snowpack has been conducted using snow station observations and reanalysis surface temperature data. Monthly snow water equivalent measurements were combined from two data sets to provide sufficient data from 1930 to 2008. The monthly snapshots are used to calculate peak snow mass timing for each snow season. Since 1930, there has been a trend toward earlier snow mass peak timing by 0.6 days per decade. The trend towards earlier timing also occurs at most individual stations. The majority of stations have experienced simultaneous reductions in April 1 snow water equivalent. Reductions in April 1 snow water equivalent may therefore be due to earlier snowmelt rather than reductions in total snowfall. Analysis of individual years and stations reveals that warm early spring temperatures are associated with earlier snow mass peak timing for all spatial and temporal scales included in the data set. The influence is particularly pronounced for low accumulation years indicating the importance of albedo feedback for the melting of shallow snow. Regional mean averaged March and April temperatures have increased at a rate of 0.1°C or 0.2°F per decade since 1948, and the robustness of the average early spring temperature influence on peak timing suggests the trend towards earlier peak timing is attributable to the temperature trend. Given scenarios of warming in California, we can expect to see acceleration in the peak timing trend; this will reduce the warm season storage capacity of the California snowpack.

Kapnick, S. and A. Hall. 2009. California climate change center, California Energy Commission, Sacramento, CA.

Global or not applicable

Climate Change, Sierra Nevada, Snowmelt, Snowpack, Warming, Water

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