|
Kampf and her team set out to determine whether more wildfires are burning at high elevations. The answer is unequivocally yes. And the consequences are dramatic: Snow in wildfire-burned areas is melting 18 to 24 days earlier than average. Climate change is already fueling an increase in the length, frequency and severity of the wildfire season. And the snowpack is critical to the health of Western people and ecosystems: According to the Natural Resources Conservation Service (NRCS), it contributes 20% to 90% of surface water used for agriculture, energy production, aquatic species habitat and more.
The researchers homed in on places where snow doesn’t completely melt off until or after May, called late-melt snow zones. These areas tend to stay cold long into spring, and then melt relatively quickly — often creating big snowmelt pulses in stream flow. The ground cannot absorb all that snow when it melts simultaneously, and as a result, the water ends up in streams for uses downstream.
Snow in wildfire-burned areas is melting 18 to 24 days earlier than average.
The authors found that from 1984 to 2020, 70% of late-melt snow zones saw a significant increase in wildfire activity. “What this study shows nicely is that fires are moving into places that we would think of as being more resistant because they’re cooler and wetter,” said Paul Brooks, a professor who studies mountain hydrology at the University of Utah. Brooks was not involved in the study but reviewed the manuscript. In zones that hold snow the longest in the Southern Rockies, more area burned in 2020 than the last 36 years combined. “It’s a shocking difference,” Kampf said. “Seeing that in many different mountain ranges, the trend towards larger fires in snowy areas, is really the most important finding.”
Wildfires can affect snow in numerous ways. Trees usually intercept some snow, but when they lose foliage or die, more snow initially reaches the ground. Sometimes, this leads to deeper snow. But then other competing factors take hold. A more exposed snowpack absorbs more solar radiation. Soot and other burned materials fall on the snow, reducing its ability to reflect sunlight back and also encouraging a faster melt. Open areas are also more vulnerable to being scoured by wind. “It’s a balancing act, which one of those wins to create the snow conditions you see at the end of the season,” Kampf said.
Low-latitude, south-facing slopes and sunny regions are particularly vulnerable to wildfire’s effect on snowpack, as they receive more sunlight and solar energy. So are areas that see severe fires. Regional variability exists: For example, cloudy areas in the Pacific Northwest will likely see different effects on snowpack than areas that see more sun.
Snow blankets the burn scar from 2020’s East Troublesome Fire in the high country near Grand Lake, Colorado.Courtesy of Nick Hanson
|
