The Unusual Nature of Recent Snowpack Declines in the North American Cordillera

The snowpack covering the mountains of western North America has decreased dramatically during the past 50 years. In western North America, snowpack has declined in recent decades, and further losses are projected through the 21st century. Here, we evaluate the uniqueness of recent declines using snowpack reconstructions from 66 tree-ring chronologies in key runoff-generating areas of the Colorado, Columbia, and Missouri River drainages. Over the past millennium, late 20th century snowpack reductions are almost unprecedented in magnitude across the northern Rocky Mountains and in their north-south synchrony across the cordillera. Both the snowpack declines and their synchrony result from unparalleled springtime warming that is due to positive reinforcement of the anthropogenic warming by decadal variability. The increasing role of warming on large-scale snowpack variability and trends foreshadows fundamental impacts on streamflow and water supplies across the western United States.

[1]  K. Kipfmueller,et al.  Reconstructed Temperature And Precipitation On A Millennial Timescale From Tree-Rings In The Southern Colorado Plateau, U.S.A. , 2005 .

[2]  C. Torrence,et al.  A Practical Guide to Wavelet Analysis. , 1998 .

[3]  B. Luckman,et al.  Summer temperatures in the Canadian Rockies during the last millennium: a revised record , 2005 .

[4]  E. Cook,et al.  A 1,200-year perspective of 21st century drought in southwestern North America , 2010, Proceedings of the National Academy of Sciences.

[5]  Malcolm K. Hughes,et al.  Medieval drought in the upper Colorado River Basin , 2007 .

[6]  B. Santer,et al.  Human-Induced Changes in the Hydrology of the Western United States , 2008, Science.

[7]  E. Cook,et al.  Two Modes of North American Drought from Instrumental and Paleoclimatic Data , 2009 .

[8]  Andrew G. Bunn,et al.  A dendrochronology program library in R (dplR) , 2008 .

[9]  Michael D. Dettinger,et al.  North–South Precipitation Patterns in Western North America on Interannual-to-Decadal Timescales , 1998 .

[10]  David L. Peterson,et al.  MOUNTAIN HEMLOCK GROWTH RESPONDS TO CLIMATIC VARIABILITY AT ANNUAL AND DECADAL TIME SCALES , 2001 .

[11]  J. Abatzoglou.  Influence of the PNA on declining mountain snowpack in the Western United States , 2011 .

[12]  C. Zweck,et al.  Cycles and shifts: 1,300 years of multi-decadal temperature variability in the Gulf of Alaska , 2007 .

[13]  T. Swetnam,et al.  Contingent Pacific–Atlantic Ocean influence on multicentury wildfire synchrony over western North America , 2007, Proceedings of the National Academy of Sciences.

[14]  Connie A. Woodhouse,et al.  A 431-Yr Reconstruction of Western Colorado Snowpack from Tree Rings , 2003 .

[15]  M. D. Schwartz,et al.  Northern Hemisphere Modes of Variability and the Timing of Spring in Western North America , 2011 .

[16]  Vincent R. Gray.  Climate Change 2007: The Physical Science Basis Summary for Policymakers , 2007 .

[17]  A. Comrie,et al.  A winter precipitation ‘dipole’ in the western United States associated with multidecadal ENSO variability , 2004 .

[18]  Thomas H. Painter,et al.  Mountain hydrology of the western United States , 2006 .

[19]  B. Luckman.  The Little Ice Age in the Canadian Rockies , 2000 .

[20]  Philip W. Mote,et al.  Climate-Driven Variability and Trends in Mountain Snowpack in Western North America* , 2006 .

[21]  T. Swetnam,et al.  Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity , 2006, Science.

[22]  R. Stouffer,et al.  Stationarity Is Dead: Whither Water Management? , 2008, Science.

[23]  R. Ahas,et al.  Onset of spring starting earlier across the Northern Hemisphere , 2006 .

[24]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[25]  E. Cook,et al.  Tree-ring reconstructed megadroughts over North America since a.d. 1300 , 2007 .

[26]  C. Daly,et al.  A knowledge-based approach to the statistical mapping of climate , 2002 .

[27]  G. McCabe,et al.  Associations of multi-decadal sea-surface temperature variability with US drought , 2008 .

[28]  L. Graumlich.  Precipitation Variation in the Pacific Northwest (1675–1975) as Reconstructed from Tree Rings , 1987 .

[29]  G. McCabe,et al.  Recent Declines in Western U.S. Snowpack in the Context of Twentieth-Century Climate Variability , 2009 .

[30]  George H. Leavesley,et al.  Assessment of climate change and freshwater ecosystems of the Rocky Mountains, USA and Canada , 1997 .

[31]  T. Ault,et al.  Climatic Controls on the Snowmelt Hydrology of the Northern Rocky Mountains , 2011 .

[32]  Donald K. Perovich,et al.  Radiative forcing and albedo feedback from the Northern Hemisphere cryosphere between 1979 and 2008 , 2011 .

[33]  E. Cook,et al.  Long-Term Aridity Changes in the Western United States , 2004, Science.

[34]  Connie A. Woodhouse,et al.  Updated streamflow reconstructions for the Upper Colorado River Basin , 2006 .

[35]  E. Aguado,et al.  Use of April 1 SWE measurements as estimates of peak seasonal snowpack and total cold‐season precipitation , 2001 .

[36]  D. Peterson,et al.  Climate and wildfire area burned in western U.S. ecoprovinces, 1916-2003. , 2009, Ecological applications : a publication of the Ecological Society of America.

[37]  Corinne Le Quéré,et al.  Climate Change 2013: The Physical Science Basis , 2013 .

[38]  C. Daly,et al.  Physiographically sensitive mapping of climatological temperature and precipitation across the conterminous United States , 2008 .