'Snow deluge' years on the decline across the US West, thanks to climate change: Study

While climate change is in general increasing the ferocity and frequency of severe weather events, the same effects may not apply to the massive snow dumps that occasionally pummel the U.S. West.

The quantity of snow that falls during so-called “snow deluge” years — such as the big 2023 snow season in California — is on the decline, according to a new study, published on Monday in the Proceedings for the National Academy of Sciences. 

“There’s a common narrative with climate change that extreme weather events are getting more extreme,” lead author Adrienne Marshall, an assistant professor of geology and geological engineering at Colorado School of Mines, said in a statement.

“But with snow deluge, we’re not seeing that’s the case,” Marshall continued. “Instead, what we’re seeing across the western U.S. is that snow deluges decline, too.”

To draw their conclusions, the scientists modeled snowpack data from California’s Sierra Nevada, while also accessing snow survey results and automated snow telemetry observations: unattended, automated snow measurement sites that transmit information to a central database.

The researchers found that the amount of snow during deluge years would drop up to 58 percent by late century under a moderate warming scenario. They observed that total snowfall in an average year would decline even more — by about 73 percent during the same period, per the study.

“Should we expect our big snow years to stop happening? The answer we get here is, ‘Kind of,’” Marshall said.

The snow-water-equivalent — the amount of water contained in snowpack — in peak April 1, 2023, readings showed that California’s deluge was about a one in 54 year event, according to the study.

Snow droughts, meanwhile, are becoming more common. These snow-free periods can materialize from either warmth or dryness alone, while deluges require both cool and wet conditions, the authors noted.

While warmth doesn’t necessarily mean less precipitation, it does increase the chance that such precipitation will appear as rain — which doesn’t accumulate on mountains and melt in the spring in the way that snowpack does.

Ultimately, the authors found that their results were not only applied to California, but also to areas across the U.S. West — and could potentially have far-reaching impacts on humans and wildlife.

Recent experiences have shown that snow deluges can either enhance the winter ski season by extending it or curtail activities due to infrastructural damage, the researchers explained. Summer recreation and hydropower operations are also affected by how much and when the snow accumulates as well as when it melts.

For all their capacity to boost a region’s water supply, snow deluges can also “breed complacency,” as they can generate deceptively high runoff during a given year, the authors warned. With that suddenly copious supply, managers might feel less pressed to develop adaptation plans, the researchers added.

“Snowpack acts as a massive reservoir that stores water for the summer when we need it most,” Marshall said. “When we lose that, we get runoff at a time of year when we don’t need it as much.”