Researchers uncover clearer patterns in extreme storm surge trends amid rising sea levels

Storm surges—sudden, abnormal rises in sea levels during storms—pose a major threat to low-lying coastal communities. Some of the most extreme sea levels occur during major tropical cyclones, when harsh winds and low atmospheric pressure drive ocean waters higher.  

Currently, there is a strong scientific consensus on the long-term changes of mean sea-level rise that is supported by tide gauge observations and data-informed modeling.  However, estimates of extreme storm surge trends in these events have been inconsistent and largely constrained to studies analyzing tide gauge data from a limited number of locations.  These limitations hinder scientists’ ability to evaluate how extreme storm surge events may respond to climate variability and change, thereby complicating the development of cost-effective strategies for coastal flood adaptation.  In a recent study conducted by the University of Central Florida, Princeton, Rutgers, and four other research centers, researchers analyzed tide gauge data from across the U.S. to better identify trends in extreme storm surges.  

The Data

The United States maintains a network of tide gauges that offers a rich archive of storm surge data, but there are some limitations.  These gauges are spaced far apart and often have short or incomplete records.  Because of this, it’s hard to accurately estimate how often extreme storm surges happen or detect long-term changes. While spatial models can improve estimates by combining data from multiple locations, they often still rely on a small number of long-term records and outdated assumptions.

In their study, Dr. Joao Morim and his research team fill this gap.  Analyzing sea level records from 208 tide gauges across the U.S., Dr. Morim and his co-authors used a Bayesian hierarchical model to combine 70 years of data spanning 1950 to 2020. This approach allowed them to more clearly and reliably identify trends in storm activity over time.

"Traditional methods analyze tide gauges one by one, which can miss the bigger picture,” says Joao Morim, a postdoctoral researcher at the University of Central Florida’s Coastal Risk & Engineering Research Lab. “Our approach is different—we link all stations together in a layered model. This lets each site share insights with its neighbors, so even stations with limited data benefit from the broader regional patterns. Nearby stations often experience the same storm systems, so by working as a network, they paint a clearer picture of storm surge trends."

The Results: Looking at the Trends

According to the results, numerous regions along the U.S. coastline have exhibited increasing trends in storminess since 1950.  In particular, the authors saw increasing likelihoods of extreme storm surges along the entire U.S. Atlantic coastline, the eastern part of the Gulf Coast, and southwest Alaska.  

In some regions, these trends have accelerated, with storm surge increases from 1975–2020 matching or exceeding the growth rate of other key phenomena that have contributed to regional sea-level rise.  Two distinct hotspots were identified: one from southeast Florida to Georgia, and another from Mississippi to northeast Florida, where long-term increases in peak annual water levels are very likely to have occurred (>90% probability) and are currently between 0.5 and 1 mm per year.

In contrast, negligible trends are found along the western Gulf Coast, Puerto Rico, and the U.S. Virgin Islands.  Negative trends were found along the U.S. Pacific Coast and around Hawaii, but did not exceed mean sea-level changes of -0.2 mm/year.  Southeast Alaska also showed a negative mean sea-level trend (-0.6mm/year).  

The researchers note that while the detected storm surge trends are small, they should not be dismissed. It’s possible that natural climate variability and human-driven warming may have had opposing effects, partially masking a larger underlying signal. They note that more research is needed to separate these influences.

Additionally, the researchers found that traditional estimates from tide gauge data underestimate storm surge extremes at 80% of locations nationwide, including key coastal cities. This finding is critical, as even modest underestimations can have significant repercussions—particularly for rare, high-impact events that inform the design standards of coastal infrastructure in the U.S.

“The days of assuming a stable climate in coastal engineering design are over,” says D.J. Rasmussen, a former CPREE postdoc who assisted with the study. “Although sea-level rise is a primary focus of long-term planning, our findings show that increasing storm intensity can rival its impact in some U.S. regions.”

The Implications

Although the study does not directly attribute storm surge trends to human-induced climate change, the researchers hypothesize that observed shifts in storm surge trends likely reflect long-term changes in ocean and atmospheric conditions that amplify storm intensity and impact —such as warmer sea surface temperatures and the compounding effects of rising sea levels. These drivers are expected to increase over time, presenting potentially catastrophic consequences if coastal flood defenses are not properly designed to withstand the increasing severity of future storms.  

“Regardless of the cause, long-term planners and engineers should account for both sea-level rise and potential increases in storm intensity,” says Michael Oppenheimer, a Professor at Princeton’s School of Public and International Affairs, the Department of Geosciences, and the High Meadows Environmental Institute.  “Incorporating higher safety margins in infrastructure design—such as those outlined in the now-revoked Federal Flood Risk Management Standard (FFRMS)—remains a practical approach for addressing long-term shifts in coastal flood drivers.”

The article, “Observations reveal changing coastal storms around the United States,” was published in Nature Climate Change on April 17th, 2025.  The authors include Joao Morim (Department of Civil, Environmental and Construction Engineering and the National Center for Integrated Coastal Research, University of Central Florida), Thomas Wahl (Department of Civil, Environmental and Construction Engineering and the National Center for Integrated Coastal Research, University of Central Florida), DJ Rasmussen (Princeton School of Public and International Affairs, Princeton University), Francisco M. Calafat (Marine Physics and Ocean Climate, National Oceanography Centre, Liverpool, UK; Department of Physics, University of the Balearic Islands), Sean Vitousek (U.S. Geological Survey (USGS), Pacific Coastal and Marine Science Center), Soenke Dangendorf (School of Science & Engineering, Department of River-Coastal Science and Engineering, Tulane University), Robert E. Kopp (Department of Earth and Planetary Sciences and Rutgers Climate and Energy Institute, Rutgers University, New Brunswick), and Michael Oppenheimer (Princeton School of Public and International Affairs, the High Meadows Institute, and the Department of Geosciences, Princeton University).  This research was supported by the National Science Foundation as part of the Megalopolitan Coastal Transformation Hub.  This research was also supported by the National Aeronautics and Space Administration (NASA) - Sea Level Change Team.  The authors also acknowledge support from David and Jane Flowerree.