Wildfires are burning away the West’s snow

This article was originally published in News from the Highlands.

The ground beneath researcher Stephanie Kampf’s boots was black and burned to a sooty crunch in June 2021 as she walked over the burn scar left by the 2020 Cameron Peak Fire. One summer after the fire blazed over 200,000 acres, there was no snow to be found in its footprint — despite being nearly 10,000 feet above sea level, where snow often falls in Colorado. In a nearby stand of unburned trees, Kampf noted, however, some “nice snow” appeared. “It was really noticeable,” she said. “It was so overwhelming for me.”

According to research published Monday in the journal Proceedings of the National Academy of Sciences, wildfires are progressively altering snowpack in the western United States Fires to date — inspiring her research because it began so close to the continental divide. That surprised fight. “We started to wonder if that’s something that’s happening elsewhere in the West?” she said.

Kampf and her team set out to determine whether more wildfires burn at high altitudes. The answer is definitely yes. And the consequences are dramatic: the snow in the areas burned by forest fires is melting 18 to 24 days earlier than the average. Climate change is already increasing the length, frequency and severity of wildfire seasons. And snow cover 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, power generation, habitat for aquatic life, and more.

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The researchers looked for places where the snow does not completely melt by or after May, so-called late-melt snow zones. These areas usually remain cold well into spring and then melt relatively quickly – large snowmelt pulses often occur in the current flow. The ground cannot absorb all the snow when it melts at the same time, and as a result the water ends up in streams for use downstream.

The authors found that from 1984 to 2020, 70% of late snowmelt areas experienced a significant increase in wildfire activity. “What this study shows nicely is that fires are moving to places that we would think are more resilient 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 the areas with the longest snowfall in the southern Rocky Mountains, more area burned in 2020 than in the past 36 years. “It’s a shocking difference,” Kampf said. “To see that in many different mountain ranges, the trend towards larger fires in snow-covered areas is really the most important finding.”

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Wildfires can affect snow in many ways. Trees usually catch some snow, but when they lose leaves or die, more snow initially reaches the ground. Sometimes this leads to deeper snow. But then other competing factors prevail. A more exposed snowpack absorbs more solar radiation. Soot and other burnt materials fall on the snow, reducing its ability to reflect sunlight back and also promoting faster melting. Open areas are also more prone to wind chafing. “It’s a balancing act of who wins from it to create the snow conditions that you see at the end of the season,” Kampf said.

Low latitudes, south-facing slopes, and sunny regions are particularly vulnerable to wildfire’s effects on snowpack because they receive more sunlight and solar energy. This also applies to areas where serious fires can be seen. Regional variability exists: For example, cloudy areas of the Pacific Northwest will likely have different effects on snowpack than areas with more sun.

The study also found that snow in burnt areas contains less water. “The maximum snow water equivalent, where the snowpack arrives at the end of the season, is pretty important,” Kampf said. “In a lot of places it’s really going to correlate to the amount of current flow.”

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A shorter snow season, which essentially means a longer summer, can have a cascading effect. “It’s like shutting down a drip irrigation system a month early,” Brooks said. Plants may be able to start growing earlier, but may also run out of water as the summer progresses or be prone to early season frosts. This can make it difficult for the forest to recover after a fire.

The researchers’ findings could have implications for how water will be used in the future. In areas already affected by drought due to climate change, fires can further exacerbate water shortages. Unless snow falls in great gusts from the late melt, and when parched, thirsty soils soak up moisture, less water is likely to find its way into streams, rivers, and eventually reservoirs. Snow cover surveyors watch with concern. “Wildfires have a tremendous impact on snowmelt,” said Erin Whorton, hydrologist with the NRCS’s Idaho Snow Survey.

Downstream water managers may need to prepare for an earlier meltdown that will contribute to reservoirs much sooner than necessary. “Timing is a really, really big thing,” Brooks said. “The surprising nature of less snow…should make people think.”

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