Atmospheric rivers will become more intense as temperatures rise

Those massive storms that drench the West Coast aren’t going to stay the same. Recent research shows that climate change will reshape atmospheric rivers – but not in the way you might expect.

While these storms will pack more punch everywhere, their evolution will look quite different in Seattle compared to San Diego.

The findings come from a team at the U.S. National Science Foundation National Center for Atmospheric Research (NSF NCAR), led by scientists Christine Shields and Hui Li.

Their work reveals how these sky-high rivers of moisture will respond differently to warming, depending on where they make landfall.

Contrasting impacts of atmospheric rivers

The changes split the West Coast into two distinct stories.

In Southern California, increasing ocean evaporation will drive the transformation of atmospheric rivers. Head north to Seattle and Portland, and it’s a different ball game – there, warmer temperatures in both the ocean and air will call the shots.

These differences matter. By 2100, storms hitting the Pacific Northwest could push ocean waters three times higher than today’s storms do. Southern California will see higher storm surges too, but not nearly as dramatic as their northern neighbors.

“On the ground, people will see a different response between the Southern California coast and the Pacific Northwest,” said Shields. “It’s not a one-size-fits-all situation. You have these regional responses that can be quite different.”

Science behind the split

The research team relied on advanced computing to understand how climate change will reshape atmospheric rivers.

Using the powerful Derecho supercomputer at the NSF NCAR-Wyoming Supercomputing Center, they ran detailed climate simulations.

The simulations captured atmospheric changes every 25 kilometers (15.5 miles) and ocean changes every 10 kilometers (6.2 miles), offering high-resolution insights into the behavior of these storms.

The results were surprising. In Southern California, the well-known “Pineapple Express” storms, which transport moisture from Hawaii, are expected to intensify due to increased evaporation from the ocean in a warmer climate. This added evaporation provides more fuel for the storms, making them more powerful.

In the Pacific Northwest, however, the dynamics are different. The storms there will strengthen due to a combination of rising air and ocean temperatures. These warming effects will amplify the storms’ intensity and lead to more dramatic impacts, such as higher sea levels and increased flooding.

This regional variation highlights how atmospheric rivers respond differently to climate change, depending on their location.

Why the difference matters

These aren’t just academic distinctions. Communities along the entire West Coast need to prepare for stronger storms, but their specific challenges will vary by location. The stakes are high – atmospheric rivers already pack a serious punch.

“Atmospheric rivers are like tropical cyclones in that they pack powerful winds and carry enormous amounts of water that can devastate local infrastructure,” noted Shields.

“Communities need to understand how they will change in the future so they can adapt and plan.”

Additional impacts of atmospheric rivers

The impacts don’t stop when the rain does. These atmospheric rivers leave their mark on the ocean too, stirring up waters and potentially affecting marine ecosystems long after the storms pass.

“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,” said Li.

Preparing for the future

This research gives coastal communities crucial information for planning their future. While all regions need to prepare for more intense storms, their specific challenges will depend on location.

Southern California needs to ready itself for storms supercharged by ocean evaporation, while the Pacific Northwest must prepare for even more dramatic changes driven by warming air and seas.

The study was conducted by researchers from NSF NCAR, Texas A&M University, and Pennsylvania State University, with funding from the U.S. Department of Energy and NSF.

For West Coast residents, the message is clear: the atmospheric rivers they know today won’t be the same ones their children will face. But now, at least, they have a better idea of what’s coming their way.

The study is published in the journal Nature Communications.

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