June 21, 2024

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Sea level rise along the southern United States is happening faster than previously thought

Scientists have documented an abnormal and dramatic rise in sea levels along the US Gulf and Southeast coasts since about 2010, raising new questions about whether New OrleansAnd Miami, Houston, and other coastal communities may be more at risk from rising sea levels than previously expected.

Although this acceleration is relatively short-lived so far, it could have far-reaching consequences in a region of the United States that has undergone explosive development as the wetlands, mangroves and beaches that once protected them shrink. An already fragile landscape that is home to millions of people is getting weaker and faster, which could put a large swath of America at greater risk from severe storms and flooding.

The increase was really big effects, the researchers found. One Stady He points out that recent devastating hurricanes, including Michael in 2018 and Ian last year, have been greatly exacerbated by a faster ocean rise. Federal tide gauge data from the National Oceanic and Atmospheric Administration reports that sea level, as measured by a tide gauge at Lake Pontchartrain in New Orleans, is eight inches higher than it was in 2006, immediately after Hurricane Katrina.

said Jianjun Yin, a climatologist at the University of Arizona and author of the book One to two Academic studies published in recent weeks describing the changes.

Yin’s study, published in the journal Climate, calculates the rate of sea level rise since 2010 in more than 10 millimeters – or one centimeter – per year in the area, or nearly 5 inches through 2022. This is more than double the global average of 4.5 mm per year since 2010, based on Satellite observations of sea level From experts at the University of Colorado at Boulder.

While annual totals may seem small, even small changes in sea levels over time can have devastating consequences. Yin’s study noted that Hurricanes Michael and Ian, two of the most powerful storms to ever hit the United States, were made largely worse by the additional rise in sea level.

“It turns out that the water level associated with Hurricane Ian was the highest ever due to the combined effect of sea level rise and storm surge,” Yin said.

a Second study A long list of sea level experts, led by Tulane University’s Sönke Dangendorf and published in Nature Communications, found the same trend since 2010 across the US Gulf Coast and Southeast coasts, calling the rise “unprecedented in at least 120 years.”

“It’s a window into the future,” said Dangendorf, who has collaborated with experts at several US institutions and the British National Oceanographic Centre. The rates are so high in recent years, Dangendorf said, that they resemble what would be expected at the end of the century in a very high greenhouse gas emissions scenario.

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In addition two studies About the rapid rise in sea level and how it affects the region has been released by scientists in preprint form but has not yet passed peer review, indicating a swell of scientific interest in the topic.

The new findings are surprising in part because the rapid rise appears to be caused by deep changes in the ocean. In parts of Texas and Louisiana, sinking land has long been a contributing factor to relatively high sea levels over time. But in the latest studies, scientists show a rapid rise in sea levels in places like Pensacola and Cedar Key, Florida, where land is located. Don’t sink so quickly As in places like Grand Isle, La. , or Galveston, Texas.

In general, high seas in the Gulf of Mexico and around Florida mean hurricane risks in some countries most vulnerable to storms Parts of the United States are growing more steeply.

In addition, as seas rise and people continue to move into high-risk areas along the coasts, scientists say millions of acres of American land and hundreds of thousands of homes and offices could slip under swollen tidal lines. Experts from the nonprofit First Street recently predicted that real estate in many coastal areas could lose value as floods intensify, a shift that could hurt homeowners and undermine local tax rules.

Scientists don’t quite agree with what drives this phenomenon, or whether the recent acceleration in sea level rise will continue at such a rapid clip. Researchers usually prefer to rely on decades of data to be more certain about trends in the climate system and their causes. In this context, the recent rise in sea level occurred over a relatively short period of time. This makes the trend as mysterious as it is disturbing.

However, this seems pretty obvious: The rapid rise in sea level appears to begin in the Gulf of Mexico, that was getting hot Much faster than the World Ocean. Warm waters naturally expand, causing sea levels to rise. These warm waters are also carried by currents from the Gulf and along the East Coast, affecting places like Georgia and the Carolinas.

Will this trend continue? Scientists say this is still less clear.

The waters that helped raise sea levels in the Gulf of Mexico are very warm even at deep levels, based on a Preprint study By Jacob Steinberg and colleagues at the Woods Hole Oceanographic Institution, NASA’s Jet Propulsion Laboratory, University of Hawaii at Manoa, and the National Center for Atmospheric Research.

Steinberg and colleagues suggest that the trend indicates a warm current called the Loop Current, which enters the Gulf from the Caribbean Sea and In turn, it is part of a broader pattern of circulation in the Atlantic Ocean.

The ring’s warm current, Steinberg said, “brings in water, not just at the surface but from deep.” The current often extends hundreds of meters below the surface of the sea, Steinberg added, and will emit bubbles of warm water, which scientists call “eddies,” that move across the bay.

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Yin also relates the change to the loop current and takes his study further, describing it as an after-effect of a major slowdown in the Atlantic General Circulation event that occurred in 2009-2010. If correct, this suggests that these changes in sea level may be related to a broader pattern that reflects how climate change alters ocean circulation.

Dangendorf, lead author for Nature Communications study, not convinced. Noting the rapid rise in sea level in recent years like other works, his study determines that the cause is a combination of factors, some of which are natural.

“We have this forced acceleration, but on top of that we have this natural variance, and over the last couple of years we’ve been unlucky, that acceleration has been superimposed on the natural variance,” Dangendorf said.

However, Dangendorf said that the rapid changes in sea level are worrisome, It has immediate effects, and is more like what scientists once predicted only if the world continued to pump massive amounts of planet-heating gases into the atmosphere.

Data from NOAA appear This “high flood,” even on sunny days, has doubled throughout the Gulf Coast and Southeast coastal regions since 2000.

“It disrupts your daily life. It interrupts your daily life,” said Thomas Wahl, professor of coastal hazards and engineering at the University of Central Florida. and one of the authors of the paper in Nature Communications. “It spoils the infrastructure. It corrodes the cars that drive through salt water on a daily basis. You can’t open your business or go to work.”

Then there’s the fact that in low-altitude regions, even small amounts of sea level rise can make storm surges more dangerous. Waves approach the shore, exacerbating erosion. Impulses push inward more. Wetlands can erode quickly.

“You now have a higher level of essential water,” Wahl said. “If you have a hurricane now compared to the same hurricane 150 years ago, the effects will be different.”

a Fourth study In preprint form, by scientists from the University of Miami, NOAA, NASA and multiple institutions in the US and Australia, the significant rise in sea level in the Southeast since 2010 has been found to account for “30-50% of the flood days in a year.” 2015-2020″.

The study notes that “in low-lying coastal areas, even a few centimeters of background sea level rise can break regional flood thresholds and lead to coastal inundation.”

The critical question, of course, is whether the current rates of change documented by the researchers will continue—probably leading to an additional sea-level rise of more than a foot in the coming decades—or whether they will return to levels more in line with the global level. averages.

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Rapid rise in sea level

Pensacola, Florida


1/2 inch per year


1/12 inch per year

Rapid rise in sea level in Pensacola, Florida


1/2 inch per year


1/12 inch per year

Rapid rise in sea level in Pensacola, Florida


1/2 inch per year


1/12 inch per year

Based on sea level records from Pensacola and Galveston, dating back a century or more, the Gulf Coast also experienced a rapid sea level rise in the 1940s, a trend that reversed by the 1950s. But it is not yet clear whether this event will be similar.

In general, the pace of sea level rise Acceleration globallyand scientists unequivocal That seas will continue to rise in the future, even if humans succeed in drastically reducing greenhouse gas emissions.

In a report released last year, the National Oceanic and Atmospheric Administration (NOAA) and other federal agencies found average U.S. coastlines It is expected to experience an additional foot of sea level rise over the next three decades. The report presented particularly high forecasts for the Gulf Coast, due in large part to recent trends. Earlier this year, new research documented how the amount of excess heat buried in the planet’s oceans, a strong sign of climate change, is again at a record high in 2022.

In the same NOAA report is found that if sea level rise along the eastern part of the Gulf Coast continues on its recent trajectory, it will rival high-end sea level projections for the year 2050. NASA recently released a report sea ​​level instrument It includes similar results, showing sea levels rising at a rate that exceeds even advanced forecasts in locations such as Pensacola, Florida., And Dauphin Island, Ala.

Despite the ongoing scientific debate regarding the cause of the current rise in sea level in the Gulf of Mexico and the southeastern United States, the tangible effects it has on societies are likely to grow.

“It’s very difficult for me to say what will happen in the near term,” said Ben Hamlington, a NASA sea level expert and co-author of the Steinberg study. “It’s not like those rates are going to change right away.”