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Today, you can buy a pair of sneakers partially made from carbon dioxide pulled out of the atmosphere. But measuring the carbon-reduction benefits of making that pair of sneakers with CO2 is complex. There’s the fossil fuel that stayed in the ground, a definite carbon savings. But what about the energy cost of cooling the CO2 into liquid form and transporting it to a production facility? And what about when your kid outgrows the shoes in six months and they can’t be recycled into a new product because those systems aren’t in place yet?

As companies try to reduce their carbon footprint, many are doing life cycle assessments to quantify the full carbon cost of products, from procurement of materials to energy use in manufacturing to product transport to user behavior and end-of-life disposal. It’s a mind-bogglingly difficult metric, but such bean-counting is needed to hold the planet to a livable temperature, says low-carbon systems expert Andrea Ramirez Ramirez of the Delft University of Technology in the Netherlands.

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Carbon accounting is easy to get wrong, she says. Differences in starting points for determining a product’s “lifetime” or assumptions about the energy sources can all affect the math.

Carbon use can be reduced at many points along the production chain—by using renewable energy in the manufacturing process, for instance, or by adding atmospheric CO2 to the product. But if other points along the chain are energy-intensive or emit CO2, she notes, the final tally may show a positive rather than a negative number.

A product is carbon negative only when its production actually removes carbon from the environment, temporarily or permanently. The Global CO2 Initiative, with European and American universities, has created a set of LCA guidelines to standardize measurement so that carbon accounting is consistent and terms such as “carbon neutral” or “carbon negative” have a verifiable meaning.

In the rush to create products that can be touted as fighting climate change, however, some firms have been accused of “greenwashing” – making products or companies appear more environmentally friendly than they really are. Examples of greenwashing, according to a March 2022 analysis by mechanical engineers Grant Faber and Volker Sick of the University of Michigan in Ann Arbor include labeling plastic garbage bags as recyclable when their whole purpose is to be thrown away; using labels such as “eco-friendly” or “100% Natural” without official certification; and claiming a better carbon footprint without acknowledging the existence of even better choices. An example would be “fuel-efficient” sport utility vehicles, which are only fuel efficient when compared with other SUVs rather than with smaller cars, public transit or bicycles.

Good LCA analysis, Sick says, can distinguish companies that are carbon-friendly in name only, from those that are truly helping the world clear the air.  More

It’s morning and you wake on a comfortable foam mattress made partly from greenhouse gas. You pull on a T-shirt and sneakers containing carbon dioxide pulled from factory emissions. After a good run, you stop for a cup of joe and guiltlessly toss the plastic cup in the trash, confident it will fully biodegrade into harmless organic materials. At home, you squeeze shampoo from a bottle that has lived many lifetimes, then slip into a dress fashioned from smokestack emissions. You head to work with a smile, knowing your morning routine has made Earth’s atmosphere a teeny bit carbon cleaner.

Sound like a dream? Hardly. These products are already sold around the world. And others are being developed. They’re part of a growing effort by academia and industry to reduce the damage caused by centuries of human activity that has sent CO2 and other heat-trapping gases into the atmosphere (SN: 3/12/22, p. 16).

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The need for action is urgent. In its 2022 report, the United Nations Intergovernmental Panel on Climate Change, or IPCC, stated that rising temperatures have already caused irreversible damage to the planet and increased human death and disease (SN: 5/7/22 & 5/21/22, p. 8). Meanwhile, the amount of CO2 emitted continues to rise. The U.S. Energy Information Administration predicted last year that if current policy and growth trends continue, annual global CO2 emissions could rise from about 34 billion metric tons in 2020 to almost 43 billion by 2050.

Carbon capture and storage, or CCS, is one strategy for mitigating climate change long noted by the IPCC as having “considerable” potential. A technology that has existed since the 1970s, CCS traps CO2 from smokestacks or ambient air and pumps it underground for permanent sequestration. Today, 27 CCS facilities operate around the world — 12 in the United States — storing an estimated 36 million tons of carbon per year, according to the Global CCS Institute. The 2021 Infrastructure Investment and Jobs Act includes $3.5 billion in funding for four additional U.S. direct capture facilities.

But rather than just storing it, the captured carbon could be used to make things. This year for the first time, the IPCC added carbon capture and utilization, or CCU, to its list of options for drawing down atmospheric carbon. CCU captures CO2 and incorporates it into carbon-containing products like cement, jet fuel and the raw materials for making plastics. Still in early stages of development and commercialization, CCU could reduce annual greenhouse gas emissions by 20 billion tons in 2050 — more than half of the world’s global emissions today, the IPCC estimates.

Such recognition was a big victory for a movement that has struggled to emerge from the shadow of its more established cousin, CCS, says chemist and global CCU expert Peter Styring of the University of Sheffield in England. Many CCU-related companies are springing up and collaborating with each other and with governments around the world, he adds.

The potential of CCU is “enormous,” both in terms of its volume and monetary potential, said mechanical engineer Volker Sick at a CCU conference in Brussels in April. Sick, of the University of Michigan in Ann Arbor, directs the Global CO2 Initiative, which promotes CCU as a mainstream climate solution. “We’re not talking about something that’s nice to do but doesn’t move the needle,” he added. “It moves the needle in many, many aspects.”

The plastics paradox

The use of carbon dioxide in products is not new. CO2 is used to make soda fizzy, keep foods frozen (as dry ice) and convert ammonia to urea for fertilizer. What’s new is the focus on making products with CO2 as a strategy to slow climate change. Today’s CCU market, estimated at $2 billion, could mushroom to $550 billion by 2040, according to Lux Research, a Boston-based market research firm. Much of this market is driven by adding CO2 to cement — which can improve its properties as well as reduce atmospheric carbon — and to jet fuel, which can lower the industry’s large carbon footprint. CO2-to-plastics is a niche market today, but the field aims to battle two crises at once: climate change and plastic pollution.

Plastics are made from fossil fuels, a mix of hydrocarbons formed by the remains of ancient organisms. Most plastics are produced by refining crude oil, which is then broken down into smaller molecules through a process called cracking. These smaller molecules, known as monomers, are the building blocks of polymers. Monomers such as ethylene, propylene, styrene and others are linked together to form plastics such as polyethylene (detergent bottles, toys, rigid pipes), polypropylene (water bottles, luggage, car parts) and polystyrene (plastic cutlery, CD cases, Styrofoam).

But making plastics from fossil fuels is a carbon catastrophe. Each step in the plastics life cycle — extraction, transport, manufacture and disposal — emits massive amounts of greenhouse gases, mostly CO2, according to the Center for International Environmental Law, a nonprofit law firm based in Geneva and Washington, D.C. These emissions alone — more than 850 million tons of greenhouse gases in 2019 — are enough to threaten global climate targets.

And the numbers are about to get much worse. A 2018 report by the Paris-based intergovernmental International Energy Agency projected that global demand for plastics will increase from about 400 million tons in 2020 to nearly 600 million by 2050. Future demand is expected to be concentrated in developing countries and will vastly outstrip global recycling efforts.

Plastics are a serious crisis for the environment, from fossil fuel use to their buildup in landfills and oceans (SN: 1/16/21, p. 4). But we’re a society addicted to plastic and all it gives us — cell phones, computers, comfy Crocs. Is there a way to have our (plastic-wrapped) cake and eat it too?

Yes, says Sick. First, he argues, cap the oil wells. Next, make plastics from aboveground carbon. Today, there are products made of 20 to over 40 percent CO2. Finally, he says, build a circular economy, one that reduces resource use, reuses products, then recycles them into other new products.

“Not only can we eliminate the fossil carbon as a source so that we don’t add to the aboveground carbon budget, but in the process we can also rethink how we make plastics,” Sick says. He suggests they be specifically designed “to live very, very long so that they don’t have to be replaced … or that they decompose in a benign manner.”

 But creating plastics from thin air is not easy. CO2 needs to be extracted, from the atmosphere or smokestacks, for example, using specialized equipment. It often needs to be compressed into liquid form and transported, generally through pipelines. Finally, to meet the overall goal of reducing the amount of carbon in the air, the chemical reaction that turns CO2 into the building blocks of plastics must be run with as little extra energy as possible. Keeping energy use low is a special challenge when dealing with the carbon dioxide molecule.

A bond that’s hard to break

There’s a reason that carbon dioxide is such a potent greenhouse gas. It is incredibly stable and can linger in the atmosphere for 300 to 1,000 years. That stability makes CO2 hard to break apart and add to other chemicals. Lots of energy is typically needed for the reaction.

“This is the fundamental energy problem of CO2,” says chemist Ian Tonks of the University of Minnesota in Minneapolis. “Energy is necessary to fix CO2 to plastics. We’re trying to find that energy in creative ways.”

Catalysts offer a possible answer. These substances can increase the rate of a chemical reaction, and thus reduce the need for energy. Scientists in the CO2-to-plastics field have spent more than a decade searching for catalysts that can work at close to room temperature and pressure, and coax CO2 to form a new chemical identity. These efforts fall into two broad categories: chemical and biological conversion.

First attempts

Early experiments focused on adding CO2 to highly reactive monomers like epoxides to facilitate the reaction. Epoxides are three-membered rings composed of one oxygen atom and two carbon atoms. Like a spring under tension, they can easily pop open. In the early 2000s, industrial chemist Christoph Gürtler and chemist Walter Leitner of Aachen University in Germany found a zinc catalyst that allowed them to break open the epoxide ring of polypropylene oxide and combine it with CO2. Following the reaction, the CO2 was joined permanently to the polypropylene molecule and was no longer in gas form — something that is true of all CO2-to-plastic reactions. Their work resulted in one of the first commercial CO2 products — a polyurethane foam containing 20 percent captured CO2. Today, the German company Covestro, where Gürtler now works, sells 5,000 tons of the product annually in mattresses, car interiors, building insulation and sports flooring.

More recent research has focused on other monomers to expand the variety of CO2-based plastics. Butadiene is a hydrocarbon monomer that can be used to make polyester for clothing, carpets, adhesives and other products.

In 2020, chemist James Eagan at the University of Akron in Ohio mixed butadiene and CO2 with a series of catalysts developed at Stanford University. Eagan hoped to create a polyester that is carbon negative, meaning it has a net effect of removing CO2 from the atmosphere, rather than adding it. When he analyzed the contents of one vial, he discovered he had created something even better: a polyester made with 29 percent CO2 that degrades in high pH water into organic materials.

Chemist James Eagan and colleagues created a degradable polyester made partially with waste CO2.THE UNIV. OF AKRON

“Chemistry is like cooking,” Eagan says. “We took chocolate chips, flour, eggs, butter, mixed them up, and instead of getting cookies we opened the oven and found a chicken potpie.”

Eagan’s invention has immediate applications in the recycling industry, where machines can often get gummed up from the nondegradable adhesives used in packaging, soda bottle labels and other products. An adhesive that easily breaks down may improve the efficiency of recycling facilities.

Tonks, described by Eagan as a friendly competitor, took Eagan’s patented process a step further. By putting Eagan’s product through one more reaction, Tonks made the polymer fully degradable back to reusable CO2 — a circular carbon economy goal. Tonks created a start-up this year called LoopCO2 to produce a variety of biodegradable plastics.

Microbial help

Researchers have also harnessed microbes to help turn carbon dioxide into useful materials including dress fabric. Some of the planet’s oldest-living microbes emerged at a time when Earth’s atmosphere was rich in carbon dioxide. Known as acetogens and methanogens, the microbes developed simple metabolic pathways that use enzyme catalysts to convert CO2 and carbon monoxide into organic molecules. In the atmosphere, CO will react with oxygen to form CO2. In the last decade, researchers have studied the microbes’ potential to remove these gases from the atmosphere and turn them into useful products.

LanzaTech, based in Skokie, Ill., uses the acetogenic bacterium Clostridium autoethanogenum to metabolize CO2and CO emissions into a variety of industrial chemicals, including ethanol. Last year, the clothing company Zara began using LanzaTech’s polyester fabric for a line of dresses.

The ethanol used to create these products comes from LanzaTech’s two commercial facilities in China, the first to transform waste CO, a main emission from steel plants, into ethanol. The ethanol goes through two more steps to become polyester. LanzaTech partnered with steel mills near Beijing and in north-central China, feeding carbon monoxide into LanzaTech’s microbe-filled bioreactor.

Steel production emits almost two tons of CO2 for every ton of steel made. By contrast, a life cycle assessment study found that LanzaTech’s ethanol production process lowered greenhouse gas emissions by approximately 80 percent compared with ethanol made from fossil fuels.

In February, researchers from LanzaTech, Northwestern University in Evanston, Ill., and others reported in Nature Biotechnology that they had genetically modified the Clostridium bacterium to produce acetone and isopropanol, two other fossil fuel–based industrial chemicals. Company CEO Jennifer Holmgren says the only waste product is dead bacteria, which can be used as compost or animal feed.

Other researchers are skipping the living microbes and just using their catalysts. More than a decade ago, chemist Charles Dismukes of Rutgers University in Piscataway, N.J., began looking at acetogens and methanogens as a way to use atmospheric carbon. He was intrigued by their ability to release energy when making carbon building blocks from CO2, a reaction that usually requires energy. He and his team focused on the bacteria’s nickel phosphide catalysts, which are responsible for the energy-releasing carbon reaction.

Dismukes and colleagues developed six electrocatalysts that are able to make monomers at room temperature and pressure using only CO2, water and electricity. The energy­-releasing pathway of the nickel phosphide catalysts “lowers the required voltage to run the reaction, which lowers the energy consumption of the process and improves the carbon footprint,” says Karin Calvinho, a former student of Dismukes who is now chief technical officer at RenewCO2, the start-up Dismukes’ team formed in 2018.

RenewCO2 plans to sell its monomers, including monoethylene glycol, to companies that want to reduce their carbon footprint. The group proved its concept works using CO2 brought into the lab. In the future, the company intends to obtain CO2 from biomass, industrial emissions or direct air capture.

Barriers to change

Yet researchers and companies face challenges in scaling up carbon capture and reuse. Some barriers lurk in the language of regulations written before CCU existed. An example is the U.S. Environmental Protection Agency’s program to provide tax credits to companies that make biofuels. The program is geared toward plant-based fuels like corn and sugar­cane. LanzaTech’s approach for making jet fuel doesn’t qualify for credits because bacteria are not plants.

Other barriers are more fundamental. Styring points to the long-standing practice of fossil fuel subsidies, which in 2021 topped $440 billion worldwide. Global government subsidies to the oil and gas industry keep fossil fuel prices artificially low, making it hard for renewables to compete, according to the International Energy Agency. Styring advocates shifting those subsidies toward renewables.

“We try to work on the principle that we recycle carbon and create a circular economy,” he says. “But current legislation is set up to perpetuate a linear economy.”

The happy morning routine that makes the world carbon cleaner is theoretically possible. It’s just not the way the world works yet. Getting to that circular economy, where the amount of carbon above ground is finite and controlled in a never-ending loop of use and reuse will require change on multiple fronts. Government policy and investment, corporate practices, technological development and human behavior would need to align perfectly and quickly in the interests of the planet.

In the meantime, researchers continue their work on the carbon dioxide molecule.

“I try to plan for the worst-case scenario,” says Eagan, the chemist in Akron. “If legislation is never in place to curb emissions, how do we operate within our capitalist system to generate value in a renewable and responsible way? At the end of the day, we will need new chemistry.” More

Hurricane Maria struck the island of Puerto Rico early on September 20, 2017, with 250-kilometer-per-hour winds, torrential rains and a storm surge up to three meters high. In its wake: nearly 3,000 people dead, an almost yearlong power outage and over $90 billion in damages to homes, businesses and essential infrastructure, including roads and bridges.

Geologist and diver Milton Carlo took shelter at his house in Cabo Rojo on the southwest corner of the island with his wife, daughter and infant grandson. He watched the raging winds of the Category 4 hurricane lift his neighbor’s SUV into the air, and remembers those hours as some of the worst of his life.

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For weeks, the rest of the world was in the dark about the full extent of the devastation, because Maria had destroyed the island’s main weather radar and almost all cell phone towers.

Far away on the U.S. West Coast, in Santa Cruz, Calif., oceanographer Olivia Cheriton watched satellite radar images of Maria passing over the instruments she and her U.S. Geological Survey team had anchored a few kilometers southwest of Puerto Rico. The instruments, placed offshore from the seaside town of La Parguera, were there to track pollution circulating around some of the island’s endangered corals.

More than half a year went by before she learned the improbable fate of those instruments: They had survived and had captured data revealing hurricane-related ocean dynamics that no scientist had ever recorded.

The wind-driven coastal currents interacted with the seafloor in a way that prevented Maria from drawing cold water from the depths of the sea up to the surface. The sea surface stayed as warm as bathwater. Heat is a hurricane’s fuel source, so a warmer sea surface leads to a more intense storm. As Cheriton figured out later, the phenomenon she stumbled upon likely played a role in maintaining Maria’s Category 4 status as it raked Puerto Rico for eight hours.

“There was absolutely no plan to capture the impact of a storm like Maria,” Cheriton says. “In fact, if we somehow could’ve known that a storm like that was going to occur, we wouldn’t have put hundreds of thousands of dollars’ worth of scientific instrumentation in the water.”

A storm’s path is guided by readily observable, large-scale atmospheric features such as trade winds and high-pressure zones. Its intensity, on the other hand, is driven by weather events inside the hurricane and wave action deep below the ocean’s surface. The findings by Cheriton and colleagues, published May 2021 in Science Advances, help explain why hurricanes often get stronger before making landfall and can therefore help forecasters make more accurate predictions.

Reef pollution

Cheriton’s original research objective was to figure out how sea currents transport polluted sediments from Guánica Bay — where the Lajas Valley drains into the Caribbean Sea — to the pristine marine ecosystems 10 kilometers west in La Parguera Natural Reserve, famous for its bioluminescent waters.

Endangered elkhorn and mountainous star corals, called “the poster children of Caribbean reef decline” by marine geologist Clark Sherman, live near shore in some of the world’s highest recorded concentrations of now-banned industrial chemicals. Those polychlorinated biphenyls, or PCBs, hinder coral reproduction, growth, feeding and defensive responses, says Sherman, of the University of Puerto Rico–Mayagüez.

Elkhorn coral (left) and mountainous star coral (right) were once ubiquitous in the Caribbean. Their numbers have dropped greatly due to bleaching and disease. Pollution is partly to blame.  FROM LEFT: NICK HOBGOOD/WIKIMEDIA COMMONS (CC BY-SA 3.0); NOAA FISHERIES

Half of corals in the Caribbean have died since monitoring began in the 1970s, and pollution is a major cause, according to an April 2020 study in Science Advances. Of particular interest to Cheriton, Sherman and their colleagues was whether the pollution had reached deepwater, or mesophotic, reefs farther offshore, which could be a refuge for coral species that were known to be dying in shallower areas.

The main artery for this pollution is the Rio Loco — which translates to “Crazy River.” It spews a toxic runoff of eroded sediments from the Lajas Valley’s dirt roads and coffee plantations into Guánica Bay, which supports a vibrant fishing community. Other possible contributors to the pollution — oil spills, a fertilizer plant, sewage and now-defunct sugar mills — are the subject of investigations by public health researchers and the U.S. Environmental Protection Agency.

In June 2017, the team convened in La Parguera to install underwater sensors to measure and track the currents in this threatened marine environment. From Sherman’s lab on a tiny islet overrun with iguanas the size of house cats, he and Cheriton, along with team leader and USGS research geologist Curt Storlazzi and USGS physical scientist Joshua Logan, launched a boat into choppy seas.

Marine geologist Clark Sherman dives amid colonies of healthy great star corals, black corals, a large sea fan and a variety of sponges along the steep island shelf of southwest Puerto Rico. Sherman helped investigate whether pollution was reaching these deepwater reefs.E. TUOHY/UNIV. OF PUERTO RICO–MAYAGÜEZ

At six sites near shore, Storlazzi, Sherman and Logan dove to the seafloor and used epoxy to anchor pressure gauges and batonlike current meters. Together the instruments measured hourly temperature, wave height and current speed. The team then moved farther offshore where the steep island shelf drops off at a 45-degree angle to a depth of 60 meters, but the heavy ocean chop scuttled their efforts to install instruments there.

In June 2017, research geologist Curt Storlazzi (left) and physical scientist Joshua Logan (right) prepare to dive near Puerto Rico’s Guánica Bay to install instruments for monitoring currents suspected of delivering pollution to coral reefs.USGS

For help working in the difficult conditions, Sherman enlisted two expert divers for a second attempt: Carlo, the geologist and diving safety officer, and marine scientist Evan Tuohy, both of the University of Puerto Rico–­Mayagüez. The two were able to install the most important and largest piece, a hydroacoustic instrument comprising several drums fastened to a metal grid, which tracked the direction and speed of currents every minute using pulsating sound waves. A canister containing temperature and salinity sensors took readings every two minutes. Above this equipment, an electric thermometer extended to within 12 meters of the surface, registering temperature every five meters vertically every few seconds.

The instruments installed by Storlazzi, Logan and others collected unexpected underwater ocean observations during Hurricane Maria. An acoustic Doppler current profiler (left) used pulsating sound waves to measure the direction and speed of currents at the shelf break and slope site about 12 kilometers offshore of La Parguera. A Marotte current meter (right) measured wave height, current speed and temperature at six spots close to shore.USGS

Working in concert, the instruments gave a high-resolution, seafloor-to-surface snapshot of the ocean’s hydrodynamics on a near-continuous basis. The equipment had to sit level on the sloping seafloor so as not to skew the measurements and remain firmly in place. Little did the researchers know that the instruments would soon be battered by one of the most destructive storms in history.

Becoming Maria

The word hurricane derives from the Caribbean Taino people’s Huricán, god of evil. Some of the strongest of these Atlantic tropical cyclones begin where scorching winds from the Sahara clash with moist subtropical air over the island nation of Cape Verde off western Africa. The worst of these atmospheric disturbances create severe thunderstorms with giant cumulonimbus clouds that flatten out against the stratosphere. Propelled by the Earth’s rotation, they begin to circle counterclockwise around each other — a phenomenon known as the Coriolis effect.

Weather conditions that summer had already spawned two monster hurricanes: Harvey and Irma. By late September, the extremely warm sea surface — 29º Celsius or hotter in some places — gave up its heat energy by way of evaporation into Maria’s rushing winds. All hurricanes begin as an area of low pressure, which in turn sucks in more wind, accelerating the rise of hot air, or convection. Countervailing winds known as shear can sometimes topple the cone of moist air spiraling upward. But that didn’t happen, so Maria continued to grow in size and intensity.

Meteorologists hoped that Maria would lose force as it moved across the Caribbean, weakened by the wake of cooler water Irma had churned up two weeks earlier. Instead, Maria tracked south, steaming toward the eastern Caribbean island of Dominica. Within 15 hours of making landfall, its maximum sustained wind speed doubled, reaching a house-leveling 260 kilometers per hour. That doubling intensified the storm from a milder (still dangerous) Category 1 to a strong Category 5.

NOAA’s computer forecasting models did not anticipate such rapid intensification. Irma had also raged with unforeseen intensity.

After striking Dominica hard, Maria’s eyewall broke down, replaced by an outer band of whipping thunderstorms. This slightly weakened Maria to 250 kilometers per hour before it hit Puerto Rico, while expanding the diameter of the storm’s eyewall — the area of strong winds and heaviest precipitation — to 52 kilometers. That’s close to the width of the island.

Hurricane Maria made landfall on Puerto Rico early in the morning on September 20, 2017, and cut across the island diagonally toward the northwest. Its eyewall generated maximum sustained winds of  250 kilometers per hour and spanned almost the width of the island.CIRA/NOAA

It’s still not fully understood why Maria had suddenly gone berserk. Various theories point to the influence of hot towers — convective bursts of heat energy from thunderclouds that punch up into the stratosphere — or deep warm pools, buoyant freshwater eddies spilling out of the Amazon and Orinoco rivers into the Atlantic, where currents carry these pockets of hurricane-fueling heat to the Gulf of Mexico and the Caribbean Sea.

But even though these smaller-scale events may have a big impact on intensity, they aren’t fully accounted for in weather models, says Hua Leighton, a scientist at the National Oceanic and Atmospheric Administration’s hurricane research division and the University of Miami’s Cooperative Institute for Marine and Atmospheric Studies. Leighton develops forecasting models and investigates rapid intensification of hurricanes.

“We cannot measure everything in the atmosphere,” Leighton says.

Without accurate data on all the factors that drive hurricane intensity, computer models can’t easily predict when the catalyzing events will occur, she says. Nor can models account for everything that happens inside the ocean during a hurricane. They don’t have the data.

Positioning instruments just before a hurricane hits is a major challenge. But NOAA is making progress. It has launched a new generation of hurricane weather buoys in the western North Atlantic and remote control surface sensors called Saildrones that examine the air-sea interface between hurricanes and the ocean (SN: 6/8/19, p. 24).

Underwater, NOAA uses other drones, or gliders, to profile the vast areas regularly traversed by tropical storms. These gliders collected 13,200 temperature and salinity readings in 2020. By contrast, the instruments that the team set in Puerto Rico’s waters in 2017 collected over 250 million data points, including current velocity and direction — a rare and especially valuable glimpse of hurricane-induced ocean dynamics at a single location.

A different view

After the storm passed, Storlazzi was sure the hurricane had destroyed his instruments. They weren’t designed to take that kind of punishment. The devices generally work in much calmer conditions, not the massive swells generated by Maria, which could increase water pressure to a level that would almost certainly crush instrument sensors.

But remarkably, the instruments were battered but not lost. Sherman, Carlo and Touhy retrieved them after Maria passed and put them in crates awaiting the research group’s return.

Milton Carlo (left) and Evan Tuohy (right), shown in an earlier deepwater dive, helped  place the current-monitoring instruments at the hard-to-reach sites where hurricane data were collected.MIKE ECHEVARRIA

When Storlazzi and USGS oceanographer Kurt Rosenberger pried open the instrument casings in January 2018, no water gushed out. Good sign. The electronics appeared intact. And the lithium batteries had powered the rapid-fire sampling enterprise for the entire six-month duration. The researchers quickly downloaded a flood of data, backed it up and started transmitting it to Cheriton, who began sending back plots and graphs of what the readings showed.

Floodwaters from the massive rains brought by Maria had pushed a whole lot of polluted sediment to the reefs outside Guánica Bay, spiking PCB concentrations and threatening coral health. As of a few months after the storm, the pollution hadn’t reached the deeper reefs.

Then the researchers realized that their data told another story: what happens underwater during a massive hurricane. They presumed that other researchers had previously captured a profile of the churning ocean depths beneath a hurricane at the edge of a tropical island.

Remarkably, that was not the case.

“Nobody’s even measured this, let alone reported it in any published literature,” Cheriton says. The team began to explore the hurricane data not knowing where it might lead.

“What am I looking at here?” Cheriton kept asking herself as she plotted and analyzed temperature, current velocity and salinity values using computer algorithms. The temperature gradient that showed the ocean’s internal or underwater waves was different than anything she’d seen before.

Oceanographer Olivia Cheriton realized that data on ocean currents told a new story about Hurricane Maria.O.M. CHERITON

During the hurricane, the top 20 meters of the Caribbean Sea had consistently remained at or above 26º C, a few degrees warmer than the layers beneath. But the surface waters should have been cooled if, as expected, Maria’s winds had acted like a big spoon, mixing the warm surface with cold water stirred up from the seafloor 50 to 80 meters below. Normally, the cooler surface temperature restricts the heat supply, weakening the hurricane. But the cold water wasn’t reaching the surface.

To try to make sense of what she was seeing, Cheriton imagined herself inside the data, in a protective bubble on the seafloor with the instruments as Maria swept over. Storlazzi worked alongside her analyzing the data, but focused on the sediments circulating around the coral reefs.

Cheriton was listening to “An Awesome Wave” by indie-pop band Alt-J and getting goosebumps while the data swirled before them. Drawing on instincts from her undergraduate astronomy training, she focused her mind’s eye on a constellation of data overhead and told Storlazzi to do the same.

“Look up Curt!” she said.

Up at the crest of the island shelf, where the seafloor drops off, the current velocity data revealed a broad stream of water gushing from the shore at almost 1 meter per second, as if from a fire hose. Several hours before Maria arrived, the wind-driven current had reversed direction and was now moving an order of magnitude faster. The rushing surface water thus became a barrier, trapping the cold water beneath it.

As a result, the surface stayed warm, increasing the force of the hurricane. The cooler layers below then started to pile up vertically into distinct layers, one on top of the other, beneath the gushing waters above.

Cheriton calculated that with the fire hose phenomenon the contribution from coastal waters in this area to Maria’s intensity was, on average, 65 percent greater, compared with what it would have been otherwise.

Oceanographer Travis Miles of Rutgers University in New Brunswick, N.J., who was not involved in the research, calls Cheriton and the team’s work a “frontier study” that draws researchers’ attention to near-shore processes. Miles can relate to Cheriton and her team’s accidental hurricane discovery from personal experience: When his water quality–sampling gliders wandered into Hurricane Irene’s path in 2011, they revealed that the ocean off the Jersey Shore had cooled in front of the storm. Irene’s onshore winds had induced seawater mixing across the broad continental shelf and lowered sea surface temperatures.

The Puerto Rico data show that offshore winds over a steep island shelf produced the opposite effect and should help researchers better understand storm-induced mixing of coastal areas, says NOAA senior scientist Hyun-Sook Kim, who was not involved in the research. It can help with identifying deficiencies in the computer models she relies on when providing guidance to storm-tracking meteorologists at the National Hurricane Center in Miami and the Joint Typhoon Warning Center in Hawaii.

And the unexpected findings also could help scientists get a better handle on coral reefs and the role they play in protecting coastlines. “The more we study the ocean, especially close to the coast,” Carlo says, “the more we can improve conditions for the coral and the people living on the island.” More