Aboard a small pontoon, Elliott sat down to run a rigid plastic tube vertically underwater while her colleague Josh Bregy raised a metal pole up and down over her hard-hatted head – it sounds! it sounds! it sounds! – to insert the tube deep into the bottom of the lake.
After several hours in the water, they raised a 1½-foot cylinder of the lake bed. Nestled among the patches of mud was what Elliott was looking for: a layer of sand, possibly the remnants of a deadly storm that had hit the Florida Panhandle.
“It’s a beautiful example of a hurricane layer,” she said, running your finger down the clean tube.
This wet and dirty work is part of a field of research called paleotempestology, the study of ancient hurricanes. The growing and relatively new science seeks to understand the storms that hit this and other coasts before people began recording the weather with modern instruments.
What researchers have found so far in that ancient mud offers a warning. By analyzing the sediment, paleotempestologists have pinpointed periods in which intense storms hit the coast more often than current records indicate. Their work suggests that the oceans are capable of producing hurricane seasons far more relentless than anything modern society has yet seen.
Now, by burning fossil fuels and pumping heat-trapping gases into the air, the world risks recreating those stormier conditions. Forecasters have already predicted that this year’s hurricane season, which began on June 1, could be among the worst in decades. Hurricane Beryl, which exploded into a dangerous Category 4 hurricane on Sunday, is forecast to batter the entire Caribbean this week.
If the past is “any indication of what we’re going to see,” Elliott said, “our coastal areas are really vulnerable.”
The hunt for ancient hurricanes
In 1989, Louisiana State University professor Kam-biu Liu was giving a lecture about ash layers left at the bottom of lakes by volcanic eruptions. One student, Miriam Fearn, asked if scientists could also see the marks left by hurricanes.
“That got me thinking. I said, ‘Sure, that should be possible,'” Liu said. That summer, he and Fearn found a layer of sand deep under an Alabama lake left by a 1979 storm.
Paleotempestology grew after Category 5 Hurricane Andrew hit the Bahamas, Florida and Louisiana in 1992, killing dozens and causing billions of dollars in damage. The reinsurance industry, which financially supports home insurers and other insurance companies, pumped money into prehistoric hurricane research to better understand the risk of major storms.
“They really put their money where their mouth was and really started the field,” said Jeff Donnelly, another early ancient hurricane researcher at the Woods Hole Oceanographic Institution.
To predict how hurricane patterns will change in response to rising temperatures, climate scientists don’t have much to go on: roughly 170 years of instrumental data, a blink of an eye in Earth’s history. Paleotempestology holds the promise of extending the storm record by thousands of years and painting a more complete picture of how bad hurricanes can get.
When a strong hurricane makes landfall, the water crashes onto the beaches and carries waves of sand inland. If a lake is positioned right along the shore, that material flows into it and settles to the bottom. By measuring the radioactive carbon in those layers, paleotempestologists can figure out when a storm hit.
Over time, that coarse beach sand deposited by storms becomes encased in silt or sandwiched between layers of finer sand. In general, the more intense the storm, the coarser the sand, as it takes more power to sweep heavier grains into the lakes.
Recognizing a hurricane layer of sand among another sand dune can be difficult — like “finding grass in a haystack,” Elliott said.
Elliott knows persistence. She grew up in Michigan, helping her father build houses during summer vacations while in college studying geology. She said she engaged in tense conversations with her more conservative father about climate change.
But recently, she has found time to review the data and answer his questions. “We just sat down and talked about it,” she said. “And now we’ve moved to a place where he’s at least more willing to have the conversation and acknowledge that something is changing.”
Here at Campbell Lake, in the Topsail Hill Preserve State Park in Florida, only a thin ridge of dazzling white sand separates the body of fresh water from the Gulf of Mexico. This is one of the few places in the world with coastal dune lakes. Elliott, a young researcher of ancient hurricanes, thought it was a perfect place to look for signs of ancient storms.
“Coastal lakes are far from our favorite place to founder,” she said.
After embedding the tube in the lake bed, Elliott and Bregy, a scientist at Clemson University, took turns picking up a winch and pulling the cylinder by hand to retrieve a piece of the lake’s valuable sediment.
“This better be mud,” said Bregy. “Go on, go on, go on,” Elliott urged. “It has to come out.” The first 1½-foot core contained a layer of sand from a relatively recent storm, possibly Hurricane Opal in 1995.
To find the oldest 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 graduate students’ kayaks and a canoe to pull it across the nearly 100-acre lake.
Away from the shady pines along the edge of the lake, the little armada pulled the pontoon toward the middle of the The lake. Another group of students sat on the shore – in search of alligators.
“Watch your heads,” Bregy said before he began to clink, clink, toss another empty plastic tube down onto the lake bed. Exhausted, he began to imagine what he would eat that evening. “I’m going to get some ice cream tonight,” he said. “I’ll get some strawberries.”
The next two cores were larger: about 3 feet and 13 feet long. The longest probably dates back more than 10,000 years, Bregy said. Their chalky smell suggested they contain calcium carbonate-rich marine microfossils that could tell researchers which layers were washed down by the ocean.
Once back on dry land, Elliott and Bregy high-fived each other.
Other Gulf Coast sediment cores reveal a period of intense hurricane activity in the region—worse than we see today. It lasted for centuries before ending abruptly about 600 to 800 years ago.
What caused storms to 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 may have pushed the storms away from the Gulf Coast and toward the Eastern seaboard. This would explain why New England lakes see an increase in storms right after hurricane activity has dropped along the Gulf Coast.
Another factor is a warm water current called the Loop Current, which runs through the Gulf of Mexico. It once flowed close to the coast before sliding south into the Gulf, a change that lowered water temperatures and deprived storms of wind power.
The fact that the surface temperature of the Gulf is warming again today due to climate change is of concern to those who study ancient hurricanes.
“What these data clearly show is that the climate system, outside of human intervention, is already able to regulate itself in ways that give us activity that we haven’t seen in the last century or so,” Donnelly said. “The big question is, now that we’re actually turning the climate stamps ourselves, what’s the likely outcome?”
To find the answer, paleotempestologists are looking beyond the sand layers for other evidence of hurricanes: exploring caves for drop deposits formed by cyclonic rain, searching lakes for storm-washed coral rocks, scouring libraries for newspaper clippings, ship logs and journal entries for hurricane accounts.
“When you have different techniques and they work together,” Liu said, “then that might 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’re not downed — as their rings record extreme rainfall and saltwater flooding from the past.
Bregy goes to great lengths to find old wood, harvesting it from leftover logs and even excavated coffins. He recently received a tetanus shot after being hit by a rusty nail while sampling lumber in an old loft.
“The problem here in the eastern US is that there’s just been 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 flexed as she guided the device along the length of the tube. Always ready to offer a lesson, she helped one of her students complete the work.
“Nice,” she said, complimenting his work. He stopped, but she urged him on. “You’re fine, you’re fine.”
A series of dark bands in the halved sediment core may be hurricane layers, although only a thorough laboratory analysis will reveal the truth. Elliot and Bregy’s labs will search for marine fossils, measure the size of sand grains and analyze isotope levels in order to estimate the intensity of ancient storms and understand when they struck.
“This is the beginning of our work,” Elliott said.
At her hotel after a day of work in Campbell Lake, Elliott called her father. “‘What did you see? What did you learn?'” she recalled asking him.
Later, in a phone interview, Elliott’s father, Tony Timmons, acknowledged that the climate is changing, though he “can’t wrap his hands around it being all man-made.” Having more scientists like his daughter look into climate change might make people more willing to accept it.
“Em will explain things to me and it makes me interesting, and I get it,” he said.
He added: “What she is doing is important.”