A team of climate specialists from the NSF National Center for Atmospheric Research, Climate and Global Dynamics Lab, Texas A&M University, and Pennsylvania State University has found evidence for a rise in ocean levels during future atmospheric rivers (ARs) that form in the Pacific Ocean and make their way to the North American coast.

In their paper published in the journal Communications Earth & Environment, the group describes their study of previous ARs and how they applied what they learned to ARs of the future, when taking into account global warming.

Over the next century, dramatic changes to the world's climate are expected, from warming temperatures to more rain in some places and less in others. Another aspect of climate change that has not received as much press is the ongoing changes to the world's oceans. In addition to warmer air over the oceans, the water temperature is also growing warmer.

The same carbon dioxide that is helping to warm the planet is also making the oceans more acidic—and ocean levels around the world have been rising as ice from the polar regions has been melting. Together such changes are expected to have a major impact on ARs. Most models suggest they will not only happen more often but they will bring much more rain and higher winds.

In this new study, the research team notes that there is another impact from ARs that has not been very well studied—ocean level rise along the part of the shoreline where ARs come ashore, which is similar in some respects to storm surges from hurricanes.

To find out what sort of ocean level rise North America might expect, they created models using data from past ARs that have formed and surged into parts of California, Oregon, and Washington, state to attempt to predict the amount of rise in ocean levels during future ARs, while taking climate change into account.

By adding data from recent ARs to their model and using it to run simulations that allow for adjusting factors such as predicted air and water temperature, the researchers could see that future ARs could lead to a rise in sea levels by as much as 200% compared to those in the past—levels that could be catastrophic for some communities along California's coast, especially considering the massive amounts of rain associated with ARs.

The simulations also showed that different parts of California will likely see different amounts of ocean level rise—parts in the south, for example, such as the Los Angeles area, are likely to see more ARs, each bringing more rain and wind than has been seen in the past, thus they will likely see higher ocean levels than areas in northern parts of the state as well.

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