Approximately 71% of the Earth’s expanse is enveloped by the immense oceans. When breezes sweep across the ocean’s surface, they convey energy to the water, generating waves. Some of these waves, influenced by robust winds, crash and release microscopic airborne droplets that transform into sea spray aerosols. This phenomenon occurs throughout all oceans and stands as one of the planet’s major sources of aerosols. Despite extensive research over the years, scientists still do not completely grasp the influence on the Earth’s climate, particularly regarding their role in forming particles that create clouds, known as cloud condensation nuclei.
In contrast to the vast oceans, the shallow waters adjacent to coastlines constitute only a minuscule portion of the oceanic surface. Nevertheless, numerous observation stations for marine aerosols are situated near coastlines, and their data frequently aids in the examination of aerosols over open oceans. This prompts a significant inquiry: Do nearshore sea spray aerosols genuinely represent what occurs in open oceans, concerning their formation, concentration levels, and their contribution to cloud condensation nuclei?
An international group of scientists discovered that vigorous wave breaking along the coastline, especially during periods of significant wave activity, can generate substantial quantities of sea spray aerosols, considerably heightening the number of cloud condensation nuclei and the concentration of airborne particles in coastal areas. Jian Wang, a professor of energy, environmental, and chemical engineering at the McKelvey School of Engineering at Washington University in St. Louis, spearheaded the team.
The aerosol generation mechanism at the shoreline fundamentally differs from that in the open oceans. Consequently, relying on coastal aerosol measurements to estimate sea spray aerosols in open waters can lead to significant overestimations. Findings from the research were published on August 27 in Science Advances.
Wang and his team, which included Shengqian Zhou, a postdoctoral researcher in Wang’s lab and the paper’s primary author, also uncovered that swell waves — long-traveling waves originating far from the shore and not directly associated with local winds — frequently dominate wave energy in coastal regions. Since wave energy, rather than local wind speed, governs sea spray production near the coast, the concentration of sea spray aerosols in these areas often shows minimal correlation with wind speed. This contradicts the common belief that wind speed can assist in predicting sea spray aerosol emissions.
“Storms over the open seas generate wind waves,” Zhou stated. “After the storm passes, these waves are transformed into swell waves and can continue to propagate for thousands of kilometers. When they arrive at the coastline, even on tranquil, windless days, they can break due to friction with the seafloor or by crashing directly onto shorelines, thereby releasing a portion of their energy into the atmosphere as sea spray.”
Their data indicated that the contribution of sea spray aerosols to cloud condensation nuclei and aerosol mass concentration can surge by more than three times, exceeding 10 micrograms per cubic meter. These effects are widespread, as a significant portion of coastlines worldwide regularly experience powerful waves. An analysis of wave statistics near 12 coastal atmospheric observatories, spanning from the North Atlantic to Australia, revealed that high-wave periods occur more than half the time during certain seasons at multiple stations, with swell waves playing dominant roles.
“We knew that this wave breaking at the shoreline generates sea spray aerosols, but many researchers concentrated on particles larger than 1 micrometer, which may dominate the mass concentration despite being few in number,” Wang remarked. “Our study demonstrates that this shoreline wave breaking produces an abundance of smaller particles that significantly contribute to the coastal cloud condensation nuclei. This implies that numerous earlier studies relying on coastal measurements to analyze sea spray aerosols over open oceans likely overestimated their input to cloud condensation nuclei and consequently their impacts on clouds and climate.”
Moreover, nearshore sea spray may also have considerable environmental consequences in coastal regions. During high wave events, the concentration of particulate matter (PM) increases — a crucial factor for air quality.
While sea salt itself may not pose a threat, Zhou explained, the contaminants in seawater, such as biogenic toxins, harmful algae, and other anthropogenic pollutants, are released into the atmosphere by the sea spray and subsequently inhaled by humans. This could have severe implications for public health, particularly in coastal areas with high waves, polluted seawater, and dense populations.
“Current regional models do not account for shoreline aerosol production, or they inaccurately calculate it by relying on local wind speed,” Zhou added. “This hampers models’ abilities to accurately represent the true abundance and variations of sea spray aerosols in coastal environments. A more profound understanding of this aerosol production process is essential to better evaluate and predict the potential environmental and health ramifications for communities along coastlines.”
Zhou S, Salter M, Bertram T, Brito Azevedo E, Reis F, Wang J. Shoreline wave breaking significantly enhances the coastal sea spray aerosol population: climate and air quality implications. Science Advances, Aug. 27, 2025. DOI: https://doi.org/10.1126/sciadv.adw0343.
Funding for this investigation was provided by the Office of Biological and Environmental Research of the U.S. Department of Energy Atmospheric System Research Program (DE-SC0021017, DE-SC0021985); the Swedish Research Council (Vetenskapsrådet) (2020-05025); a collaboration project between Los Alamos National Laboratory and the University of the Azores (548320 ENA/ARM); and the McDonnell Academy Global Incubator Seed Grant from Washington University in St. Louis.
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