What's New
Our changing climate is set to dramatically alter atmospheric rivers—powerful storms that carry vast amounts of water vapor and heavy rainfall—that batter the West Coast of the United States.
That's according to a new study from the U.S. National Science Foundation National Center for Atmospheric Research (NSF NCAR), published in the journal Nature Communications Earth & Environment.
As the planet warms, the storms will evolve differently in Southern California and the Pacific Northwest—regions hit regularly by atmospheric rivers, especially in winter months.
Southern California will see intensified storms driven by increased ocean evaporation, while atmospheric rivers in the Pacific Northwest will become more powerful, fueled by rising temperatures in the ocean and atmosphere.
Why It Matters
Atmospheric rivers are often described as "rivers in the sky," delivering crucial rainfall and replenishing snowpacks in a region reliant on them for water supplies.
They can carry water at flows up to 15 times greater than at the mouth of the Mississippi River, according to the National Oceanic and Atmospheric Administration (NOAA).
In the last few weeks alone, the region has been battered by such storms, with more on the way as we head into the holidays.
However, their growing intensity poses a significant threat to coastal communities.
By 2100, the study warns, storms in the Pacific Northwest could temporarily raise ocean heights up to three times more than current levels, dramatically increasing flood risks.
Southern California residents will also face rising waters, though to a lesser extent.
"Communities need to understand how they will change in the future so they can adapt and plan," Christine Shields, an NSF NCAR scientist and co-lead author of the study, said in a statement.
What To Know
Using advanced climate simulations, the research team explored how future atmospheric rivers will interact with oceanic conditions such as surface temperatures and water mixing.
Their high-resolution modeling, run on the NSF NCAR-Wyoming Supercomputing Center's Derecho supercomputer, provided unprecedented detail, revealing stark regional differences in how these storms will behave.
The modeling was so granular that the scientists were able to investigate atmospheric river processes at 16-mile increments and ocean processes at 6-mile increments. For context, atmospheric rivers often stretch for thousands of miles across the ocean.
Atmospheric rivers are typically driven forward by the evaporation of ocean waters, which temporarily cools the atmosphere providing the propulsion for the storm.
In Southern California, warming ocean temperatures will amplify the effects of the "Pineapple Express," a type of atmospheric river that brings moisture from Hawaii.
Meanwhile, storms hitting the Pacific Northwest will begin to be driven by a combination of atmospheric and oceanic warming, resulting in intensified precipitation, stronger winds and sea-level rises during landfall.
Atmospheric rivers in the Pacific Northwest already tend to be windier and more meandering than their southern counterparts.
"The strong winds and precipitation linked to atmospheric rivers can significantly impact the upper ocean, potentially impacting ocean dynamics and ecosystems over larger spatial scales and longer timescales than the present," Hui Li, another co-lead author, said in the statement.
What They Are Saying
Christine Shields, an NSF NCAR scientist and co-lead author of the study: "On the ground, people will see a different response between the Southern California coast and the Pacific Northwest. It's not a one-size-fits-all situation. You have these regional responses that can be quite different."
Hui Li, another co-lead author: "It is important to understand the influence of atmospheric rivers under the current climate and how they may change in the future."
What's Next
The findings highlight the critical need for tailored strategies to address regional challenges.
More research is needed to pin down the exact reasons for these different effects, but regardless, the impact will be felt by the millions who call the West Coast home, especially if greenhouse emissions are not sufficiently curbed in coming years.
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Reference
Shields, C. A., Li, H., Castruccio, F. S., Fu, D., Nardi, K., Liu, X., & Zarzycki, C. (2024). Response of the upper ocean to northeast Pacific atmospheric rivers under climate change. Communications Earth & Environment, 5(1), 1–12. https://doi.org/10.1038/s43247-024-01774-0
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