Abstract
Increasing wildfire and declining snowpacks in mountain regions threaten
water availability. We combine satellite-based fire detection with snow
seasonality classifications to examine fire activity in California’s
seasonal and ephemeral snow areas. We find a nearly tenfold increase in
fire activity during 2020 and 2021 compared to 2001-2019 as measured by
satellite data. Accumulation season snow albedo declined 17-77% in two
burned sites as measured by in-situ data relative to un-burned
conditions, with greater declines associated with increased soil burn
severity. By enhancing snowpack susceptibility to melt, decreased snow
albedo drove mid-winter melt during a multi-week midwinter dry spell in
2022. Despite similar meteorological conditions in 2013 and 2022, which
we link to persistent high pressure weather regimes, minimal melt
occurred in 2013. Post-fire differences are confirmed with satellite
measurements. Our findings suggest larger areas of California’s snowpack
will be increasingly impacted by the compounding effects of dry spells
and wildfire.