Oct 31, 2016

West Coast record low snowpack in 2015 influenced by high temperatures | News and Research Communications | Oregon State University

by
Mark Floyd
,
Oregon State Univerisity

...

The western-most region of the continental United States set records for low snowpack levels in 2015 and scientists, through a new study, point the finger at high temperatures, not the low precipitation characteristic of past “snow drought” years.

The study suggests greenhouse gases were a major contributor to the high temperatures, which doesn’t bode well for the future, according to authors of a new study published today in the journal Geophysical Research Letters. 

In 2015, more than 80 percent of the snow measurement sites in the region – comprised of California, Oregon, Washington, western Nevada and western Idaho – experienced record low snowpack levels that were a result of much warmer-than-average temperatures. Most of the previous records were set in 1977, when there just wasn’t enough moisture to generate snow, according to Philip Mote, director of the Oregon Climate Change Research Institute at Oregon State University and lead author on the study.

The 2015 year was an eye-opener for the scope of the snow drought:

A total of 454 sites in the western United States (or 81 percent of the total sites) recorded record-low snowpack levels that year;

For 111 of the sites, the April 1 value was zero for the first time ever, essentially indicating that there was no snow left;

The overall snowpack level on April 1 in California and Oregon was 90 percent below average.

California has been in a drought since 2011 and this multi-year period of low precipitation, by some measures, is the state’s most severe in 500 years. In 2015, higher temperatures combined with low precipitation, leading to one of its lowest snowpack levels on record.

“The story of 2015 was really the exceptional warmth,” said Dennis Lettenmaier, distinguished professor of geography at University of California Los Angeles and co-author of the study. “Historically, droughts in the West have mostly been associated with dry winters, and only secondarily with warmth. But 2015 was different. The primary driver of the record low snowpacks was the warm winter, especially in California, but in Oregon and Washington as well.”