Warming will push California’s snowline higher, study finds

This winter’s major storms have deposited one of the heaviest snowpacks on record in California’s Sierra Nevada, as well as an unusual amount of snow at lower elevations.

But such prolific snowfalls at low altitudes are expected to become increasingly rare in coming years as climate change drives temperatures higher, new research suggests.

In a study published this week, scientists found that mountain snowlines in California have already increased and could increase significantly more if nothing is done to slow the rate of global warming. Researchers projected that from the 2050s to 2100s, rising temperatures could push average snow lines 1,300 feet to 1,600 feet higher in the Sierra Nevada and southern Cascade mountain ranges compared to the previous century. .

As more precipitation falls as rain instead of snow at lower elevations, changing runoff patterns will pose significant challenges for water management in California and for the operation of dams designed to capture and store water. melt of ice.

“The snow lines are increasing,” said Alexander Gershunov, a research meteorologist who co-authored the study with other scientists at UC San Diego’s Scripps Institution of Oceanography.

“If we look towards the end of the century, the snow will be confined to much higher elevations most years,” Gershunov said. “Low-altitude mountains will be more and more likely to be snow-free.”

After reviewing more than 70 years of snow data, the researchers concluded that with unmitigated global warming, California’s mountains could lose more than half of their seasonal snow cover.

They said the average amount of snowfall from November to March in the northern Sierra could decrease by more than 70% by the second half of the century, while decreases of around 40% are likely in the high mountains. from the Central Sierra and the Southern Sierra.

Research similarly suggests that large increases in the amount of precipitation falling as rain will result in greater runoff during the winter.

This will mean larger flows from the mountains instead of gradually melting, a trend that is already apparent and will complicate the job of dam managers, Gershunov said.

“It becomes more difficult to balance the need for flood control provided by reservoirs as well as water retention,” Gershunov said. “We have to learn how to generate water resources from flood waters.”

On the one hand, he said, the trends show why it’s important for California to step up efforts to capture and use floodwaters to replenish groundwater — which officials say state water, is a priority to accommodate more intense fluctuations between drought conditions and rain events. time.

The study authors said that even though the average snow lines are receding, California will still have big snow years at times.

Scientists have found that as the planet warms with increasing levels of greenhouse gases, more of the snow that falls in the mountains will come into atmospheric rivers, which are warmer and have generally higher snow lines than other winter storms. And according to other research, these storms will become more powerful as temperatures rise, carrying more water vapor.

“At very high altitudes, ironically, we are increasingly susceptible to unprecedented snow accumulations as atmospheric-specific river storms become wetter,” Gershunov said.

Scientists also looked at how receding snow lines could affect the ski industry after 2050 under an unmitigated warming scenario. They estimated that lower-altitude ski areas, such as Northstar California Resort in Truckee and Palisades-Tahoe in Olympic Valley, could lose more than 60% of their average snow accumulation.

Higher ski runs, such as Mammoth Mountain in Mammoth Lakes, should have lower average snow loss.

The research, which was published in the journal Climate Dynamics, was funded by the US Bureau of Reclamation and the California Department of Water Resources.

The research brings new insights into the shift to more rain and less snow, including watershed-level projections that could help show where vulnerabilities in water management lie, said Michael Anderson, State climatologist for the Department of Water Resources. He said this study and other research is “helping to guide some of the choices we make in terms of defining these climate change adaptation strategies.”

The results add to other research showing that average snowfall amounts have declined in most parts of the continental United States and that large decreases in snowfall are likely by the end of this century. .

The latest research focuses on snow lines, said Philip Mote, a climatologist and graduate school dean at Oregon State University, who was not involved in the study.

“It is not surprising that, this year notwithstanding, a warming climate will generally lead to less snowfall. The questions are how much and how to deal with it,” Mote said.

He said the heavy snow cover of 2023 is “within normal variability, but major snow years will continue to be rarer”.

“I think 20 years from now we will still remember 2023,” Mote said.

Mote pointed out that the study used a high-emissions global warming scenario, but it seems unlikely that emissions will reach that trajectory, so he expects “things won’t be as bad as this picture describes.” article”.

Gershunov said the authors did not take into account efforts to mitigate climate change.

“There is still an opportunity to reduce some of the impacts that we have identified,” he said. “I would like to see both more aggressive climate mitigation on a global scale and more informed climate adaptation on a local and regional level, which this type of study should inform.”