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In 2017, a team of USGS researchers and academic partners deployed oceanographic equipment off the coast of Puerto Rico to study how land-based pollution travels offshore to impact coral reefs. They weren’t intending to gain unique insight into the interaction between hurricanes, currents, and ocean islands, but that’s what transpired as Hurricane María, the most powerful storm to hit Puerto Rico since 1928, made landfall on September 20, 2017.

Oceanographer Olivia Cheriton, Research Geologist Curt Storlazzi, Oceanographer Kurt Rosenberger, Physical Scientist Josh Logan (all with the Pacific Coastal and Marine Science Center) and colleagues from the University of Puerto Rico-Mayagüez had originally planned to monitor pollutants flowing from shore to threatened coral reefs nearby.

Nearshore, they deployed instruments to measure water pressure, temperature, wave height, and current speed. Further offshore, a larger array of sensors was installed on the seafloor 60 meters down. These sensors took continuous measurements of currents and salinity, as well as water temperature readings along a vertical transect, every five meters from the seafloor to within 12 meters of the surface.

The instruments not only survived the passage of Hurricane María—they also collected a rare, high-resolution set of underwater ocean observations not detectable by more common surface observation platforms, such as buoys or satellites. These data revealed previously unknown interactions between storms and ocean islands, which can generate stratified underwater currents that trap warm water at the surface, amplifying storms.

The researchers’ findings were published in Science Advances in May 2021. As a USGS press release at the time noted, “Understanding how the underlying ocean temperature changes in response to hurricane forces is critical to accurately forecasting the tracks and intensities of extreme storms. Hurricane María caused thousands of deaths, more than $90 billion in damage and the largest electrical blackout in U.S. history.”

For an in-depth look at how this research was conducted, please see this recent Science News article highlighting the study.