Wildfires burn snow in the American West

This article originally appeared in High Country News.

The ground under researcher Stephanie Kampf’s shoes was black and burnt to a brittle in June 2021 as she walked through the burn scar left by the Cameron Peak fire in 2020. After a summer after more than 200,000 acres were blazing, there was no snow to be found in her footprint. Despite its elevation of nearly 10,000 feet above sea level, snowfall often continues in Colorado. However, Kampf noted that somewhere near the unburned trees some “gentle snow” appeared. “It was really amazing,” she said. “It was so amazing to me.”

According to research published Monday in the Proceedings of the National Academy of Sciences, wildfires are increasingly altering snow mass in the western United States, and the lead author and professor of watershed sciences at Colorado State University said wildfires are the largest in the state. Colorado. Fire so far – inspired her search, because it started near the continental divide. This surprised Kampf. “We’re starting to wonder, is this something that’s happening elsewhere in the West?” She said.

Kampf and her team set out to determine if more wildfires were burning at higher altitudes. The answer is undoubtedly yes. The results are tragic: Snow in areas burned by wildfires melts 18 to 24 days earlier than average. Climate change is already causing the season, frequency and intensity of wildfires to increase. Snow mass is essential 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 settled in places where snow doesn’t melt completely until May or after, called regions of late melting. These areas tend to stay cool for a long time in the spring, and then melt relatively quickly – often creating large pulses of melting ice in the stream’s flow. The Earth can’t absorb all of that snow when it melts all at once, and as a result, the water ends up in streams for uses downstream.

The authors found that from 1984 to 2020, 70% of areas of melted snow experienced a significant increase in wildfire activity. “What this study shows very well is that fires are moving to places that we think are more resilient because they are 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 the areas with the longest snow in the southern Rockies, more area was burned in 2020 than in the past 36 years combined. “It’s an appalling difference,” Kampf said. “Seeing that in so many different mountain ranges, the trend towards larger fires in the snowy regions, is really the most significant finding.”

Wildfires can affect snow in many ways. Trees usually catch some snow, but when they lose foliage or die, more snow reaches the ground at first. Sometimes, this results in deeper snowfall. But then other competing factors take hold. The exposed mass of ice absorbs more solar radiation. Soot and other burning materials fall onto the snow, reducing its ability to reflect sunlight back and also encouraging faster melting. Open areas are also more susceptible to wind exposure. “It’s a balancing act, in which one of those wins to create the snow conditions you see at the end of the season,” Kampf said.

Slopes with low and southern latitudes and sunny areas are especially vulnerable to the impact of wildfires on ice masses, because they receive more sunlight and solar energy. As well as areas experiencing severe fires. There is regional variation: for example, overcast areas in the Pacific Northwest are likely to see different effects on snow mass than areas that see more sunlight.

The study also found that snow in burned areas contained less water. “The peak water-glacial equivalent, where the snow mass arrives at the end of the season, is very important,” Kampf said. “In a lot of places, it’s going to be really related to the amount of flow there is.”

A shorter snowy season, which essentially means a longer summer, can have a cascading effect. “It’s like turning the drip system off a month ago,” Brooks said. Plants may be able to start growing sooner, but they may also run out of water as summer progresses or be prone to early season frosts. This can hinder forest recovery after fires.

The researchers’ findings may influence how water is managed in the future. In areas already experiencing drought due to climate change, fires can exacerbate water shortages. If the snow did not come in the form of large pulses of late melting, and if the earth was dry and thirsty to absorb moisture, the waters would likely turn into streams, rivers, and eventually reservoirs. Snowpack surveyors are watching anxiously. “Bungalfires have a huge, massive impact on how the thaw occurs,” said Erin Wurton, a hydrologist with the Idaho Snow Survey at NRCS.

Downstream water managers may need to prepare for early melting that would contribute to reservoirs much earlier than required. “Timing is a really big deal,” Brooks said. “The amazing nature of less snow… should make people think.”

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