And while the salt water’s incursion has slowed over the last two weeks, experts say it could still hit New Orleans by the end of November, leaving officials two months to decide how to protect the city’s drinking water.
Worsening droughts could increase the risk of saltwater wedges. But intensifying downpours could have the opposite effect. There’s the potential for a kind of climate tug of war between intense wet and dry periods on the Mississippi River, and scientists don’t have a clear answer about which effect will win out.
That’s because climate models tend to disagree in their projections for the Mississippi River’s climate future, Muñoz said.
“There’s really no consensus,” he said. “Some of the models say that river flow discharge will go up. Other models say it will go down.”
Muñoz and other researchers published a scientific paper earlier this year presenting the results of a single model suggesting that flow will generally increase in a warming climate, increasing the odds of floods.
But it’s “just one model,” he cautioned. “There are others, and they would probably tell a different story if we really dug into them.”
Another study, published last year by researchers from the Army Corps, explored simulations from a suite of 16 models. Most projections suggested stronger flow as the climate warms, although the study notes that some models predicted the opposite.
Scientists are working to solve the mystery. Muñoz is involved in a project, funded by the National Science Foundation, to investigate how climate change will affect large-scale weather patterns like heavy precipitation and drought on the Mississippi River Basin, along with several researchers from Rice University.
Still, he said, there are other factors that could affect saltwater intrusion in the future.
Dredging, the construction of dams and reservoirs, and other human activities on the river are one factor. Americans have dramatically engineered the Mississippi River to control floods and increase navigability. And the Army Corps regularly dredges the river so barges can travel the waterway.
But “deepening the channel obviously makes things much more vulnerable,” said Törnqvist of Tulane, who noted that it can increase saltwater intrusion.
Sea levels are also rapidly rising along the Gulf Coast, as much as three times faster than the global average.
At the same time, the land itself is slowly sinking into the sea. Known as subsidence, the process has a variety of causes, some natural and some driven by human activities, like groundwater withdrawal.
The combination of rising seas and subsidence likely raises the potential risk of saltwater intrusion, Törnqvist said. But it’s unclear by how much — another question that few studies have addressed.
“I’m not sure if anyone has ever studied this in any detail,” he said. “That will remain probably a matter of some speculation for now. But I think it’s safe to say it’s something we need to understand for sure.
“I would also expect, because of this situation we’re facing right now, that it’s gonna happen pretty soon,” he added.
Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2023. E&E News provides essential news for energy and environment professionals.
ABOUT THE AUTHOR(S)
Chelsea Harvey covers climate science for Climatewire. She tracks the big questions being asked by researchers and explains what’s known, and what needs to be, about global temperatures. Chelsea began writing about climate science in 2014. Her work has appeared in The Washington Post, Popular Science, Men’s Journal and others.
