Midwinter Dry Periods Cause Severe Losses of Winter Snowpack in California’s Burnt Regions

Early pandemic years coincided with some of California's greatest wildfires on record, resulting in the frightening orange-tinted sky and vast swaths of charred terrain.

Some of the consequences of these fires are well documented, such as significant decreases in air quality, and a new study illustrated how these wildfires interacted with midwinter dry conditions to expedite snowmelt.

Wildfires are increasingly burning California's snowy landscapes

(Photo : Mario Tama/Getty Images)

A DRI-led research team explored what happens to mountain snowpacks when bright, midwinter dry periods occur in forests damaged by catastrophic wildfire in a report published on Jan. 20 in Geophysical Research Letters.

The researchers discovered a significant rise in flames burning in California's snowy landscapes in 2020 and 2021, when huge blazes such as the Dixie, Caldor, and Creek fires centered in snow zones.

Using a midwinter dry spell from 2013, they discovered that comparable weather in the winter of 2021-2022 resulted in 50% less snow cover.

The effects of wildfire on snow melt are compounded by an increase in solar exposure owing to the loss of forest canopy and a decrease in the snow's capacity to reflect sunlight.

According to Arielle Koshkin, M.S., a Ph.D. student present at the Colorado School of Mines who co-led the study as part of her master's research at DRI and the University of Nevada, Reno.

Satellite data revealed that, compared to the 2001 to 2019 average, wildfires burning in California's seasonal snow zones increased about tenfold in 2020 and 2021.

What it means is that there is an increased overlap between fire and snow, with all of these cascading and compounding effects on the system, particularly the hydrology, according to Ben Hatchett, Ph.D., a climatologist at DRI who co-led the study with Koshkin.

This massive spike in fire activity in California's icy regions is exactly what we anticipate seeing in the future.

A severe winter drought followed in 2021-2022 when Tahoe City endured a 46-day midwinter dry spell , which was the second-longest since reliable records began in 1917; the long-term median is 22 days without precipitation.

A comparable midwinter drought occurred in 2013, allowing the researchers to compare and contrast the consequences under more usual conditions with those that happened in a badly burned area.

Forests with extensive wildfires that have burned down the tree canopy have more exposed snowpacks, which increases melting caused by bright days and mild nights (another recent DRI study examined the snowmelt impacts of spring heatwaves).

Snowmelt is compounded further by the decrease of the snowpack's albedo, or the natural ability of white snow to reflect rather than absorb sunlight.

Snow is powdered with the black carbon of burnt plants, which can increase melting rates by up to 57% in the winters immediately after a wildfire.

The researchers discovered a total of 50 fewer days with snow cover in the winter of 2021 to 2022, the lowest number of snow cover days on record, inside the perimeter of the Caldor fire.

The increased midwinter snowfall complicates estimating water availability from the natural snowpack reservoir.

Water management must allow room in reservoirs throughout the winter months to prevent flooding, which means that early snowmelt may not be retained for later use in the dry season.

Such research gives water managers the tools they need to make more precise predictions about the time and quantity of snowmelt.

Koshkin intends to build on this study for her Ph.D. studies by looking at regional variations in fire effects on snow.

She pointed out that the effects of wildfires on snowmelt in the Sierra Nevada may differ in Colorado and Idaho owing to differences in weather and snowpack conditions.

The researchers stress that the wildfire consequences observed in this study are the result of high-severity wildfires rather than lower-severity burns such as managed fires.

"This study really emphasizes the need of reintroducing fire to our environment in the sense that we need fire - good fire is the solution to our wildfire problem," Hatchett added, as per ScienceDaily.

Reintroducing a more natural fire regime to our environment through the planned and cultural fire can help lessen the chance of future major fires.

Also Read: Study Shows How Wildfire Triggers Major Forest Changes

What are Exacerbating and Prolonging California Wildfires?

As a result of climate change, California has been experiencing higher temperatures and drier seasons, resulting in longer and more extreme drought seasons, as per Earth.org.

The conditions required to ignite a wildfire are more easily satisfied, enhancing the intensity of the fire once it begins.

This is evidenced by the fact that more than half of California's 20 biggest fires have occurred in the previous four years.

According to scientists, a 1°C increase in temperature each year may increase the median burnt area by up to 600% in some types of woods, while another model predicts that acreage burned by wildfire might increase by 30% by 2060 compared to 2011 values.

About 10-15% of wildfires occur spontaneously, and while they cannot be stopped, the severity and spread of these flames can be reduced.

The California Wildfire and Forest Management Task Force was formed with a comprehensive strategy to speed measures to minimize wildfire risk for vulnerable areas, enhance the health of forests and wildlands, and accelerate action to battle climate change.

This would entail prescribing controlled fire to decrease forest overgrowth, which serves as fuel for wildlife, as well as expanding sustainable timber harvesting programs.