Climate Dynamics

, Volume 38, Issue 9–10, pp 1885–1899 | Cite as

Causes of recent changes in western North American snowpack

  • Sarah KapnickEmail author
  • Alex Hall


Monthly snow water equivalent (SWE) station observations and gridded temperature data are used to identify mechanisms by which warming affects the temporal and geographical structure of changes in western North American mountain snowpack. We first exploit interannual variability to demonstrate the sensitivity of snowpack to temperature during the various phases of the snow season. We show that mechanisms whereby temperature affects snowpack emerge in the mid to late portion of the snow season (March through May), but are nearly absent during the earliest phase (February), when temperatures are generally well below freezing. The mid to late snow season is precisely when significant loss of snowpack is seen at nearly all locations over the past few decades, both through decreases in snow accumulation and increases in snowmelt. At locations where April 1st SWE has been increasing over the past few decades, the increase is entirely due to a significant enhancement of accumulation during the earliest phase of the snow season, when the sensitivity analysis indicates that temperature is not expected to affect snowpack. Later in the snow season, these stations exhibit significant snowpack loss comparable to the other stations. Based on this analysis, it is difficult to escape the conclusion that recent snowpack changes in western North America are caused by regional-scale warming. Given predictions of future warming, a further reduction in late season snowpack and advancement in the onset of snowmelt should be expected in the coming decades throughout the region.


Snow water equivalent Climate change Climate sensitivity Trends Surface observations 



The authors would like to thank Philip Mote and one anonymous reviewer for their comments that greatly improved this manuscript. We are grateful to Christopher Cham for his help in compiling SWE observations for all stations used in this analysis. Sarah Kapnick’s work was supported by NASA headquarters under the NASA Earth and Space Science Fellowship Program—Grant #07-Earth07F-0232 and a 2010 Switzer Environmental Fellowship. Alex Hall is supported by NSF grant AGS-0735056. The writers would also like to gratefully acknowledge funding provided by JPL (#1312546) under a project entitled: “Evaluating key uncertainties in IPCC Climate Change projection of California snowpack: Topography, snow, physics and aerosol deposition.”


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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  1. 1.Department of Atmospheric and Oceanic SciencesUniversity of California, Los AngelesLos AngelesUSA

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