Rates of US coastal sea level rise break records

Sea levels along the US Southeast and Gulf coasts have been rapidly accelerating, reaching record-breaking rates over the past 12 years, according to a new study.

The researchers say they have detected rates of sea-level rise of about a half an inch per year since 2010. They attribute the acceleration to the compounding effects of man-made climate change and natural climate variability.

“These rapid rates are unprecedented over at least the 20th century and they have been three times higher than the global average over the same period,” says Sönke Dangendorf, assistant professor in the river-coastal science and engineering department at Tulane University and lead author of the study in Nature Communications.

The authors studied a combination of field and satellite measurements since 1900, pinpointing the individual contributors to the acceleration.

“We systematically investigated the different causes, such as vertical land motion, ice-mass loss, and air pressure, but none of them could sufficiently explain the recent rate,” says coauthor Noah Hendricks, an undergraduate student in Dangendorf’s team at his former institution, Old Dominion University.

“Instead, we found that the acceleration is a widespread signal that extends from the coasts of the Gulf of Mexico up to Cape Hatteras in North Carolina and into the North Atlantic Ocean and Caribbean seas, which is indicative for changes in the ocean’s density and circulation.”

Over the past 12 years this entire area, known as the Subtropical Gyre, has been expanding primarily due to changing wind patterns and continued warming. Warmer water masses need more space and thus lead to a rise in sea level.

The scientists suggest that the recent acceleration was an unfortunate superposition of man-made climate change signals and a peak in weather-related variability that lasted over several years. They conclude that the rates will likely return to the more moderate values as predicted by climate models in the coming decades.

“However, this is no reason to give the all clear,” says coauthor Torbjörn Törnqvist, a professor in the earth and environmental sciences at Tulane. “These high rates of sea-level rise have put even more stress on these vulnerable coastlines, particularly in Louisiana and Texas where the land is also sinking rapidly.”

The “results, once again, demonstrate the urgency of the climate crisis for the Gulf region. We need interdisciplinary and collaborative efforts to sustainably face these challenges,” says Dangendorf.

Additional coauthors are from Old Dominion University; the Jet Propulsion Laboratory; the National Oceanography Centre in Liverpool, UK; and the University of Central Florida.