PSU study: Wildfires affect snowmelt in Western US


PORTLAND, Ore. (KOIN) — Here’s the cycle: A forest fire causes snow to melt earlier in the season, which may affect water supplies and cause more fires.

That’s the finding of a new Portland State University study and published in Nature Communications.

The study done in conjunction with the Desert Research Institute and the University of Nevada Reno shows that fire-snow melt cycle will increase as forest fires become more frequent, last longer and cause more destruction in a warmer, drier climate.

More than 11% of all forests in the Western US are seeing snowmelt earlier because of the fires, the study found.

Read: Forest fires accelerate snowmelt in Nature Communications

Using state-of-the-art lab measurements, researchers found the snow melted about 5 days earlier after a fire — and is sped up the timing of the snowmelt for as long as 15 years after the fire.

Kelly Gleason, the lead author of the study and an assistant professor at PSU’s College of Liberal Arts and Sciences, said there are 2 reasons for the earlier snowmelt.

Fire often consumes the trees that provide shade. Less shade means more sunlight, which leads to more and faster snowmelt. 

“Forest fires accelerate snowmelt, they cause earlier and faster snowmelt all across the western US,” Gleason said. 

The other reason is more important, researchers said. The charred wood, bark and debris left behind, known as black carbon, makes the snow darker and lowers its reflectivity. 

“So like wearing a black shirt on a sunny day, the snowpack gets hot,” Gleason said. “It absorbs a lot more sunlight and then melts faster and earlier in the year.”

The fire outlook for May 2019. (NICC)

“Fires have been reported to us just in the last few days and it looks like it’s only going to get worse from here,” said John Saltenberger with the NW Interagency Coordination Center’s fire program. 

He said small fires early in the season are signs that point to potential bigger fires down the road.

“While I’m not anticipating a high number of large costly type fires for those areas, even one or two large fires in June is unusual for those areas and i do think that they are at risk this year,” he said. 

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