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The unusual nature of recent snowpack declines in the North American Cordillera

Tree Ring and Snow Course Sites
Tree Ring and Snow Course Sites
The unusual nature of recent snowpack declines in the North American Cordillera

Vol. 333, no. 6040, pp. 332-335, 15 July 2011.
DOI: 10.1126/science.1201570
Published Online June 9 2011

Gregory T. Pederson1,2,3, Stephen T. Gray3,4, Connie A. Woodhouse3,5, Julio L. Betancourt6, Daniel B. Fagre1, Jeremy S. Littell7, Emma Watson8, Brian H. Luckman9, and Lisa J. Graumlich10
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 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 USA.
Download data from the WDC Paleo archive:
Data Description, Snow Water Equivalent (SWE) Reconstructions, Excel format, Northern Cordillera and Southern Cordillera drainage basins, plus Supplementary Tables containing locations, formulas, and statistics.
The 66 tree ring width data sets are available in the International Tree Ring Data Bank,
and also in a ZIP archive file for this study.

To read or view the full study, please visit the Science website.
Published online 9 June 2011, Sciencexpress
DOI: 10.1126/science.1201570

For additional information on the reconstructions, please visit the USGS Northern Rockies (NOROCK) Snowpack Variability project website.
1 U.S. Geological Survey, Northern Rocky Mountain Science Center, 2727 University Way (Suite 2), Bozeman, MT 59715, USA
2 School of Natural Resources, University of Arizona, 325 Biosciences East, Tucson, AZ 85721, USA
3 Laboratory of Tree-Ring Research, University of Arizona, 105 W. Stadium, Tucson, AZ 85721, USA
4 Department of Civil and Architectural Engineering, University of Wyoming, Laramie, WY 82071, USA
5 School of Geography and Development, 412 Harvill Building, University of Arizona, Tucson, Arizona 85721-0076, USA
6 U.S. Geological Survey, National Research Program, Water Resources Division, Tucson, AZ 85719, USA
7 Climate Impacts Group, University of Washington, Post Office Box 355672, Seattle, WA 98195-5672, USA
8 Aurora, Ontario, Canada
9 Department of Geography, University of Western Ontario, London, Ontario N6A 5C2, Canada
10 College of the Environment, University of Washington, Post Office Box 355679, Seattle, WA 98195-5679, USA
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