Aboard a small pontoon, Elliott lowered herself to guide a rigid plastic tube vertically underwater while her colleague Josh Bregy lifted a metal pile driver up and down over her hard-hat-clad head – ding! ding! ding! — to push the tube deep into the bottom of the lake.
After hours on the water, they raised a 1½-foot cylinder from the lake bed. Sandwiched between sections of mud was what Elliott was looking for: a layer of sand, the potential remnants of a deadly storm that had hit the Florida Panhandle.
“It’s a beautiful example of a hurricane layer,” she said., running his finger through the transparent tube.
This soggy, dirty work is part of a field of research called paleotempestology, the study of ancient hurricanes. This growing and relatively new science seeks to understand the storms that hit this and other coasts before humans began recording the weather with modern instruments.
Researchers have so far discovered a warning in this ancient mud. By examining the sediments, paleotempestologists have spotted periods when intense storms hit the coasts more frequently than current records show. Their work suggests that the oceans are capable of producing hurricane seasons far more merciless than anything modern society has experienced to date.
Now, by burning fossil fuels and spewing heat-trapping gases into the air, the world is at risk of recreating those stormier conditions. Forecasters have already predicted that this year’s hurricane season, which began June 1, could be one of the worst in decades. Hurricane Beryl, which strengthened into a dangerous Category 4 hurricane on Sunday, is expected to swell across the Caribbean this week.
If the past is “any indication of what we’ll see,” Elliott said, “our coastal areas are really vulnerable.”
Hunting ancient hurricanes
In 1989, Kam-biu Liu, a professor at the University of Louisiana, was giving a lecture on the layers of ash left on the bottom of lakes by volcanic eruptions. A student, Miriam Fearn, asked him if scientists could also see the traces left by hurricanes.
“That got me thinking. I thought, ‘Sure, this should be doable,’” Liu said. That summer, he and Fearn found a layer of sand deep beneath an Alabama lake left behind by a 1979 storm.
Paleotempestology gained renewed interest after Category 5 Hurricane Andrew struck the Bahamas, Florida and Louisiana in 1992, killing dozens of people and causing billions of dollars in damage. The reinsurance industry, which financially backs home insurers and other insurance companies, has poured money into prehistoric hurricane research to better understand the risk of major storms.
“They really walked the talk and really kicked off the field,” said Jeff Donnelly, another researcher on early ancient hurricanes at the Woods Hole Oceanographic Institution.
To predict how hurricane trends will change in response to rising temperatures, climate scientists don’t have much: about 170 years of instrumental data, a blink of an eye in Earth’s history. Paleotempestology promises to extend the number of recorded storms by thousands of years and paint a more complete picture of the severity of hurricanes.
When a strong hurricane makes landfall, water crashes onto beaches and carries waves of sand inland. If a lake is located right along the coast, this material accumulates there and settles to the bottom. By measuring radioactive carbon in these layers, paleotempestologists can determine when a storm hit.
Over time, coarse beach sand deposited by storms becomes encased in mud or trapped between layers of finer sand. Generally, the more intense the storm, the coarser the sand, because more power is needed to sweep the heavier grains into the lakes.
Spotting a layer of hurricane sand among a pile of other sand can be difficult — like “looking for hay in a haystack,” Elliott said.
Elliott knows what perseverance is. She grew up in Michigan, helping her father build houses during summer breaks while she studied geology in college. She says she used to have tense conversations with her more conservative father about climate change.
But more recently, she took the time to present the data to him and answer his questions. “We sat down and talked about it,” she said. “And now we’ve gotten to a point where he’s at least more willing to have the conversation and recognizes that something is changing. »
Here in Campbell Lake, Topsail Hill Preserve State Park in Florida, only a thin ridge of blinding white sand separates the body of fresh water of the Gulf of Mexico. It is one of the few places in the world with coastal dune lakes. Elliott, a promising researcher of ancient hurricanes, thought it was the perfect place to look for signs of ancient storms.
“Coastal lakes are by far our favorite place to core,” she said.
After embedding the tube in the lake bed, Elliott and Bregy, a scientist at Clemson University, took turns operating a winch and pulling the cylinder by hand to bring up a chunk of the lake’s precious sediment.
“It better be mud,” Bregy said. “Keep going, keep going, keep going,” Elliott urged. “It has to come out. » This first 1½-foot core contained a layer of sand from a relatively recent storm, probably Hurricane Opal in 1995.
To find older storms, the team had to dig deeper into the lake bed – and into the past. Without a motor for the pontoon, Elliott and Bregy relied on their students in kayaks and canoes to tow it across the nearly 100-acre lake.
Far from the shade of the pines that bordered the lake, the small armada pulled the pontoon towards the middle of the lake. the lake. Another group of students sat on the shore, looking for alligators.
“Watch your heads,” Bregy said before he began to ding, ding, ding another hollow plastic tube into the bottom of the lake. Exhausted, he began to imagine what he would eat that night. “I’m going to have ice cream tonight,” he said. “I’m going to have strawberries.”
The next two cores were larger: about 3 feet and 13 feet long. The longest is probably more than 10,000 years old, Bregy said. Their chalky odor suggests they contain marine microfossils rich in calcium carbonate that can tell researchers which layers were washed away by the ocean.
Once back on dry land, Elliott and Bregy congratulated each other.
Other sediment cores from the Gulf Coast reveal a period of intense cyclone activity in the region – worse than what we see today. This lasted for centuries before abruptly ending around 600 to 800 years ago.
What made the storms rage and then subside? One theory is that a change in the position of a high pressure system over the Atlantic called the Bermuda High could have pushed storms away from the Gulf Coast and closer to the East Coast. This would explain why New England lakes are seeing an increase in storms just after hurricane activity declines along the Gulf Coast.
Another factor is the warm water current called the Loop Current, which flows through the Gulf of Mexico. It once flowed close to shore before sliding south into the Gulf, a shift that lowered water temperatures and robbed storms of wind power.
The fact that the Gulf’s surface temperature is warming today due to climate change worries those who study past hurricanes.
“What these records clearly show is that the climate system, apart from human interference, is already capable of adjusting itself in ways that are giving us activity like we haven’t seen in the last century,” Donnelly said. “The big question is: Now that we’re manipulating the climate knobs ourselves, what’s the likely outcome?”
To find the answer, paleotempestologists look beyond the layers of sand for further evidence of hurricanes: they explore caves for deposits of raindrops from cyclones, search lakes for blocks of coral washed up by storms, scour libraries for newspaper excerpts, logs and journal entries for accounts of hurricanes.
“When you have different techniques and they work together,” Liu said, “then that may be the best approach.”
Much of Elliott and Bregy’s work focuses on tree rings. Hurricanes leave subtle marks on coastal trees—at least when they aren’t felled—because their rings record extreme rainfall and saltwater flooding in the past.
Bregy goes to great lengths to find old wood, harvesting it from leftover stumps and even excavated coffins. He recently received a tetanus injection after being pricked by a rusty nail while sampling wood in an old attic.
“The problem here in the eastern United States is there’s so much logging,” Bregy said. “It’s hard to find old, living trees.”
Back on shore, Elliott knelt down and used a power tool to cut one of the sediment cores in half. A thin strip of plastic coiled as it guided the device along the tube. Always ready to teach a lesson, she helped one of her students complete the work.
“Beautiful,” she said, complimenting his work. He paused, but she urged him to continue. “You’re good, you’re good.”
A series of dark bands in the bisected sedimentary core could be hurricane layers, but only careful laboratory analysis will reveal the truth. Elliot and Bregy’s labs will search for marine fossils, measure sand grain sizes and analyze isotope levels to assess the intensity of ancient storms and determine when they struck.
“This is the beginning of our work,” Elliott said.
At his hotel after a day of work in Campbell Lake, Elliott called his father. “‘What did you see? What did you learn?'” she remembers him asking.
Later, in a telephone interview, Elliott’s father, Tony Timmons, acknowledged that the climate was changing, although he “can’t believe this is all man-made.” Having more scientists like her daughter looking at climate change might make people more accepting of it.
“Em explains things to me and it makes it interesting, and I understand,” he said.
He added: “What she does is important.”