Declining snow cover in the Rocky MountainsOver 70 million people in the United States rely on the w

Declining snow cover in the Rocky MountainsOver 70 million people in the United States rely on the winter snows in the Rocky Mountains. The water trapped in that snowpack travels down the rivers in the Western U.S. every year, filling reservoirs, irrigation channels, and the pipes leading to homes.This image shows a portion of the Rocky Mountain snowpack towards the end of the winter. Thick piles of snow, starting to turn darker colors from dust and the beginning of melting.It’s been known for a while that the snowpack in the Rockies has become less consistent over the last few decades. Here at TES, we recently covered the emptying of Lake Powell, one of the main man-made reservoirs on the Colorado River (http://tinyurl.com/p3a3bdv). Thanks to new research, some of the causes of the declining water supply and declining snowpack can be better understood.A recent study led by researchers from the US Geological Survey and published in the journal Geophysical Research Letters looked at measurements of the Rocky Mountain snowpack going back over a century. They looked at precipitation variations and temperature fluctuations, and found a few noteworthy trends.First, the 1930’s “Dust Bowl” era stood out as having particularly low precipitation compared to any of the other periods they looked at.Second, in the other decades, they found there was an oscillating pattern; in some years the northern part of the snowpack would melt early, in other years the southern part would, with the timing driven by local weather variations.But finally, everything changed starting in 1980. After 1980, both the sections of the snowpack they looked at started melting earlier and earlier in the year. At this point, the early melting has accounted for a 20% decrease in the total snowpack cover in an average year, and this warming trend has begun completely dominating the variation observed in previous years.This snowpack decrease is really bad for the people who rely on it as a water source. Melting earlier in the season means that there is longer for evaporation to take place and longer for plants to grow, using up that water before the manmade systems can harvest it. It also leads to more intense fire seasons, because plants grow earlier in the year and have longer to dry out.Tens of millions of people and billions of dollars of industry and agriculture rely on the supply of water from these snowpacks. But, as the climate warms, the water supply that supports the Western U.S. is becoming increasingly tenuous.-JBBFull study:http://onlinelibrary.wiley.com/doi/10.1002/grl.50424/abstractUSGS Press release:http://www.usgs.gov/newsroom/article.asp?ID=3587&from=rss_home#.UZY9f8pHPDVImage credit: T. H. Painter, Snow Optics Laboratory, JPL/Caltechhttp://www.nasa.gov/topics/earth/features/snow-patrol.htmlRutgers University Global Snow Lab:http://climate.rutgers.edu/snowcover/ -- source link

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