Increasing wildfire impacts on snowpack in the western U.S

Area of Science:

• Ecology
• Hydrology
• Climate Science

Background:

• Wildfire area is increasing across western US ecoregions, affecting snowpack dynamics.
• Impacts of fires on snow accumulation, ablation, and duration vary significantly by region.

Purpose of the Study:

• To compare spatiotemporal patterns of western US wildfires across ecoregions and snow zones.
• To analyze the influence of wildfires on snow-free dates and water availability.

Main Methods:

• Analysis of wildfire area data from 1984 to 2020 across western US ecoregions and snow zones.
• Comparison of wildfire distribution shifts between early and late snowmelt zones.
• Snow measurements and modeling to assess fire impacts on snow-water equivalent and snow-free dates.

Main Results:

• Significant increases in wildfire area observed from 1984 to 2020 in western US ecoregions, including snow-dominated areas.
• 70% of ecoregions in late snow zones showed increased wildfire area since 1984.
• Wildfire distribution shifted towards later-melting snow zones, with notable acceleration in the Southern Rockies.
• Fires advanced snow-free dates by an estimated 18-24 days, reducing snow-water equivalent and peak timing.

Conclusions:

• Wildfires are increasingly impacting late snow zones in the western US, altering critical snowmelt processes.
• Fire-driven snow loss reduces ecosystem water availability and streamflow, particularly in regions dependent on mountain snowpack.
• Understanding these fire-snow-water dynamics is crucial for water resource management in snow-dominated western landscapes.