According to a recent National Oceanic and Atmospheric Administration report, U.S. coastlines are likely to face an additional foot of rising seas over the next three decades. The report’s projections are particularly high for the Gulf Coast. If sea level rise along the eastern part of the Gulf Coast continues apace, it will match the high-end sea level forecast for 2050. NASA, too, reports seas rising at a rate exceeding even high-end forecasts at sites like Pensacola, Fla., and Dauphin Island, Ala.
At Pensacola, seas rose 10 inches since 2010, 1/2 inch per year above the 1983-2001 average, according to NOAA. Since 2000, high tide flooding has more than doubled throughout the Gulf Coast and southeast coastal regions, interrupting daily life, corroding cars and infrastructure.
In low-lying areas, even modest sea level rise can make storms more destructive. Waves push closer to shore, wetlands erode, surges push further inland. With a higher water level, a hurricane today will be far more damaging than the same hurricane 150 years ago.
Other studies also highlight an abnormal rate of sea level rise since 2010 along the Gulf of Mexico and southeastern U.S. coast, raising new concerns about whether Miami, Houston, New Orleans, and many coastal communities might be even more at risk from rising seas than predicted.
The speed-up could have far-reaching consequences in an area of the U.S. under massive development. Wetlands, mangroves and dunes that once protected it are shrinking. An already vulnerable area with a population of millions is growing even more vulnerable, putting a large swath of the U.S. at greater risk from severe storms and flooding. Indeed, the sea level, as measured by tide gauge at Lake Pontchartrain in New Orleans, is already 8 inches higher than it was in 2006, just after Hurricane Katrina.
One study by Jianjun Yin & al. of the University of Arizona suggests that recent devastating hurricanes, like Michael in 2018 and Ian in 2022, were made considerably worse by a faster-rising ocean. Published in the Journal of Climate, Yin’s study calculates the regional rate of sea level rise since 2010 at over 10 millimeters per year, nearly 5 inches in total through 2022. That’s more than double the global average rate of about 4.5 millimeters per year since 2010, based on satellite observations at the University of Colorado, Boulder.
Another study, led by Sönke Dangendorf, of Tulane University, and published in Nature Communications, sees the same trend since 2010, calling the rise “unprecedented in at least 120 years.” Recent rates are similar to what would be expected at the end of the century in a very high greenhouse gas emissions scenario. Dangendorf collaborated with experts at multiple U.S. institutions and Britain’s National Oceanography Center.
A third study has been released by Jacob Steinberg and colleagues at the Woods Hole Oceanographic Institution, NASA’s Jet Propulsion Laboratory, the University of Hawaii at Manoa, and the National Center for Atmospheric Research. It implicates the warm Loop Current, which is part of a broader pattern of circulation in the Atlantic Ocean and enters the gulf from the Caribbean Sea. That current often extends hundreds of yards beneath the sea surface and spins off warm water “eddies” moving across the gulf.
A fourth study by researchers at the University of Miami and multiple U.S. and Australian institutions, found that the large southeastern sea level rise since 2010 accounts for “30 to 50% of flood days in 2015-2020.”
In low-lying coastal regions, an increase of even fractions of an inch in the sea level can lead to coastal inundation.
In general, higher seas in the Gulf of Mexico and around Florida mean that hurricane risks in some of the most storm-prone parts of the U.S. are becoming more acute. As seas rise and people continue to move to high-risk coastal areas, millions of acres of land, and hundreds of thousands of homes and offices slip below tide lines. The First Street Foundation projects coastal properties losing value, harming homeowners, and eroding tax bases.
Sea level rise is accelerating globally and will continue to do so even if humans cut greenhouse gas emissions. The Gulf of Mexico has been warming far faster than the global ocean. Warm water naturally expands, causing sea levels to rise. It gets carried by currents out of the Gulf and along the East Coast, already affecting Georgia and the Carolinas.
Yin’s study suggests that the Loop Current is an aftereffect of a major change in warming-caused ocean circulation. What if these changes spread northbound to coastal Maine — leading to over a foot of additional sea level rise along the east coast in coming decades? How long before we seriously cut our carbon emissions?
(Paul Kando is a co-founder of the Midcoast Green Collaborative, which promotes environmental protection and economic development via energy conservation. For more information, go to midcoastgreencollaborative.org.)
