The surge is startling scientists, amplifying impacts such as hurricane storm surges.

Across the American South, tides are rising at accelerating rates that are among the most extreme on Earth, constituting a surge that has startled scientists such as Jeff Chanton, professor in the Department of Earth, Ocean and Atmospheric Science at Florida State University.

“It’s pretty shocking,” he said. “You would think it would increase gradually, it would be a gradual thing. But this is like a major shift.”

Worldwide sea levels have climbed since 1900 by some 1.5 millimeters a year, a pace that is unprecedented in at least 3,000 years and generally attributable to melting ice sheets and glaciers and also the expansion of the oceans as their temperatures warm. Since the middle of the 20th century the rate has gained speed, exceeding 3 millimeters a year since 1992.

In the South the pace has quickened further, jumping from about 1.7 millimeters a year at the turn of the 20th century to at least 8.4 millimeters by 2021, according to a 2023 study published in Nature Communications based on tidal gauge records from throughout the region. In Pensacola, a beachy community on the western side of the Florida Panhandle, the rate soared to roughly 11 millimeters a year by the end of 2021.