Hurricane Francine struck southern Louisiana on Wednesday as a Category 2 storm, packing winds of 100 mph and bringing a storm surge to coastal areas. Much of southern Louisiana is at or below sea level, meaning the storm surge could flow inland unimpeded. The last hurricane to strike the state was Ida in 2021. Devastating storm surge And caused $75 billion in damages, 55 deaths.
“Storms are a real problem,” says University of Miami hurricane researcher Brian McNoldy, “because hurricane winds bulldoze the ocean onto land. There’s no other way to escape.”
Scientists warn that the Gulf Coast’s storm surge problem will only get worse in the future because of competing phenomena: Climate change is not only causing sea levels to rise but also making hurricanes more powerful, and parts of the Louisiana and Texas coastlines are sinking, a phenomenon known as subsidence.
Any loss of elevation would make sea level rise and storm surges more severe, but for a long time projections didn’t take subsidence into account because researchers didn’t have the data. That meant parts of the Gulf Coast were submerged. Underestimating the potential damageThe coastal parishes of Louisiana have already 2,000 square miles of land Sea levels rose and subsidence occurred between 1932 and 2016. The state’s wetlands act as natural buffers against storm surges, but their ecosystems Close to collapse.
Warming waters in the Gulf of Mexico helped transform Francine into a deadly cyclone. A hurricane is like an atmospheric engine: its fuel is warm ocean water, which evaporates and sends energy skyward. When the wind conditions are right, the storm spins and moves out to sea. And if the waters in its path are especially warm, that fuel gets even more powerful, and the hurricane intensifies into a monster. “When ocean surface temperatures get really high, a hurricane can start to grow very quickly,” says Daniel Gilford, who studies hurricanes at the nonprofit research institute Climate Central. “It’s like stepping on the gas and fuel going into the engine and igniting it.”
The Gulf Coast is naturally warmer due to rising temperatures over the summer. analysis When Francine formed, it was feeding on ocean temperatures that had risen by at least 200 times due to climate change, according to Climate Central.
“The conditions we’re seeing right now in the Atlantic and Gulf of Mexico certainly make it more conducive to more powerful storms that are rotating faster and carrying more moisture, which could lead to more rainfall,” Guilford said. In general, warmer air holds more moisture, which means more water can be squeezed out of the sky for any given storm.
While water flows down from above, storm surges push water in from the side. The stronger the winds, the bigger the storm surges. This is happening on top of a bedrock of sea-level rise caused by climate change. “So if sea levels are, on average, higher than the built environment can handle, then we could see greater flooding from these storms,” Guilford said.
At the same time, communities are dealing with subsidence as parts of the Gulf Coast steadily lose elevation. Subsidence occurs when people overextract groundwater, oil, and gas, causing the earth to collapse like an empty water bottle. It also occurs naturally as sediments settle over time. (Beyond sea-level rise considerations, subsidence is also a problem.) Destabilizing roads, levees, and other critical infrastructure.
in paper In a paper published last week in the geophysical research journal Earth’s Surface, scientists used satellite radar measurements to quantify land subsidence along the Gulf Coast from Corpus Christi to New Orleans, finding that some areas are sinking by more than half an inch per year. That may not seem like much, but it’s happening every year, the same as sea levels steadily rising. Thus, the researchers concluded, land subsidence will significantly increase the risk of future hurricane flooding.
But the rate of subsidence is not uniform. Some parts of the Gulf Coast, such as Galveston County, Texas, and New Orleans, Louisiana, are sinking rapidly, while other parts have stopped sinking. Subsidence is a tricky issue to account for because state agencies need accurate data to determine the risks that specific sections of coastline face. Without taking into account simultaneous subsidence, we can’t get the full picture of how much land will be lost to sea level rise and how severe storm surges will be.
“When the land surface is lost, buildings, trees and structures are also lost, which could remove some of the protective barrier and allow the storm surge to push further inland,” said An Jingyi Chen, a geophysicist at the University of Texas at Austin and co-author of the paper.
Chen’s analysis shows that subsidence has largely stopped in cities that stopped overpumping groundwater. More radar data will allow scientists to incorporate subsidence rates into storm surge models, helping them find problem areas and take steps to mitigate subsidence. Avoiding even a small amount of subsidence would reduce the damage from a storm surge like Francine. “For planning purposes, it’s good to know so we don’t wait until it’s too late,” Chen said.
