Study shows broad decline in Rockies snowpack

By Pete Spotts, Staff writer
10 June 2011 A blend of natural climate swings and global warming appears to be driving a long-term decline in snowpack along the Rocky Mountains rarely seen in the past 800 years. In the process, and perhaps more important for the future, the dominant driver behind available snowpack along the continental spine appears to be shifting from precipitation to temperature, according to a study published Friday in the journal Science. If this shift holds, the study’s team adds, it could represent a change that would accelerate the loss of the West’s natural freshwater reservoirs – if long-term average temperatures continue to rise with increasing levels of industrial greenhouse gases, as most climate scientists are convinced they will. “I was shocked” when this result emerged, says Gregory Pederson, a hydrologist at the US Geological Survey’s Northern Rocky Mountain Science Center in Bozeman, Mont., who led the effort. Similar shifts show up in the 1300s and 1400s, when the Rockies experienced warming periods, he says, but temperatures then weren’t nearly as warm as today. Nor was the shift as strong. Many studies have documented the West’s declining snowpack. And at least as early as 2005, some researchers began to notice the potential regime shift that Dr. Pederson and his colleagues see, notes Klaus Wolter, a researcher at the National Oceanic and Atmospheric Administration’s Earth System Research Laboratory in Boulder, Colo. Still, this is the first time scientists have attempted to reconstruct the history of snowpack throughout the length of the Rockies in a systematic way and “for a very nice, long period,” he says. …

The new water wars? Study shows broad decline in Rockies snowpack.