Paracetamol, ibuprofen, carbamazepine, diclofenac, and other pharmaceuticals are being found in the Baltic Sea. Researchers say changing how some medicines are prescribed, used, and disposed of could help reduce the flow.

More than 90 percent of the estimated oil pollution in the oceans occurs within national waters – including in protected areas.

While at Brown University in Providence, R.I., oceanographer Lily Dove studied the physics of Antarctica’s Southern Ocean with the help of some unusual, furry assistants: Antarctic seals. “They’re oceanographers,” she says. “They are regularly making dives in areas that we don’t often get to sample.”

Dove didn’t work with the seals directly. Instead, she interpreted data collected by the Marine Mammals Exploring the Oceans Pole to Pole program. This international group of scientists collects ocean data through sensors attached to the foreheads of southern elephant and Weddell seals. (Don’t worry. The animals don’t mind.) The seals dive more than 100 meters (330 feet) in search of food, allowing researchers to monitor temperature, salinity and pressure at depths inaccessible to human divers.

Dove used these data to study how climate change is impacting the Southern Ocean. That’s the vast ocean that circles Antarctica. In certain areas of the Southern Ocean, atmospheric heat moves from the surface to the deep ocean. This heat is typically trapped for hundreds of years once it reaches the depths, further increasing ocean temperatures.

Now at the Georgia Institute of Technology, Dove works with autonomous robots to study polar oceans. Some, such as floats, ride sea currents. Others, such as gliders, are pilotable underwater vehicles, meaning Dove can target specific locations. “And this is all remote,” she says. “I can sit here in Georgia and tell my glider in a whole different hemisphere where I want it to go.” 

This tech is also more predictable than her past assistants. “Seals are very independent,” she says. Unlike a glider, “seals very much tell me where they want to go,” she says. In this interview, Dove shares her experience and advice with Science News Explores. (This interview has been edited for content and readability.)

What inspired your career? 

Growing up in Florida, the ocean interested me as this powerful system that we take for granted. But I didn’t really consider it as a career back then. I knew I loved science, like physics and chemistry. In college, I knew I wanted to do one of those things or some combination. I changed majors like five times.

Then I realized that I liked those topics because they could help explain what I cared about: the Earth and the environment. I learned that you need all different kinds of science to understand the Earth system. Biology, physics, chemistry, geology — all of them. I ended up researching atmospheric chemistry.

How did you get to where you are today? 

In graduate school, I took those skills from studying atmospheric chemistry and started doing oceanography instead. The atmosphere and ocean have the same physics. That made it feel like it was the perfect transition for me. I landed in a group that was investigating polar oceans, which wasn’t something I’d even considered before. I went to the Southern Ocean for the first time in 2020. The polar oceans are pretty remote and far away from where most people live. But they have massive impacts on our climate system, especially the Southern Ocean. It wasn’t until I was there that I realized that. That’s when I knew that this is exactly what I wanted to be doing.

What was your biggest challenge, and how did you overcome it? 

I’ve experienced quite a bit of discrimination in this field as a woman. There are a lot of assumptions people have about who is welcome to do polar science. Historically, women have not been included on research cruises. Women used to stow away on ships to get data for their research theses. There’s a famous case at the Woods Hole Oceanographic Institution of a woman stowing away on a research vessel in the 1950s.

That stigma is still present to an extent, but it’s changing a lot. And it’s not just about women. People of color, queer people and disabled individuals are also experiencing this less-overt discrimination.

Throughout my time in the field and in academia, there have been times when people have assumed I can’t do something. That’s really frustrating, but it’s also given me the skill to really speak up and advocate for myself.

What advice would you give to your younger self? 

Say “yes” to as many opportunities as possible. That could be attending an event, talking with a scientist or taking a course. The worst-case scenario is that you learn something new that’s just not super interesting to you. The best-case scenario is that something grabs your attention, and you can’t let it go.

I am also glad that I didn’t hyperfixate on a particular area of study super early. I’m glad I got a strong basis in a lot of different scientific fields before I decided on a focus. It allowed me to be really flexible and open to new ideas.

If you already know that you’d want to do something specific, listen to your gut. But if you are not quite sure, lean into just learning a lot.

One of Earth’s most vital ocean currents is rapidly weakening. The cause: global warming. A collapse of this current could send devastating ripples through the planet’s climate.

The current is known as the Atlantic Meridional Overturning Circulation. Most scientists just call it AMOC. If it were to shut down, the consequences could be catastrophic and far-ranging. In the worst case: Earth’s warming climate could flip to a deep-freeze. Scientists refer to this scenario as a “snowball Earth.”

Why might that happen?

AMOC moves warm surface waters in the Atlantic Ocean from the tropics northward toward Europe. This water ferries with it a massive amount of heat. If that transport were to shut down, scientists say, the world might see a host of dramatic weather. Europe could experience more temperature extremes, of both chilling and heating. The Southern Hemisphere would warm even more than it is now. The North Atlantic would trigger stronger storms. The drought in Africa’s Sahel would worsen. And summer rains in Europe could sharply decrease, with devastating outcomes for farmers.

Researchers have rung warning bells about the AMOC for decades. Its possible shutdown even was the theme of The Day After Tomorrow, a 2004 snowball-Earth disaster movie. 

But predictions of how long AMOC will hold out have been all over the map. And it’s only in the last couple of years that scientists have been able to figure out which way the current is really trending.

Their consensus: It’s not good — AMOC is weakening.

The stakes are so alarming that some scientists have proposed engineering changes to AMOC. One is building a series of dams to seal off the Bering Strait between Russia and Alaska. By cutting off the northward flow of water from the Strait into the AMOC, the current’s strength might stabilize. At least that’s what researchers claim in a report April 24 in Science Advances.

Such proposed changes are controversial. No one can be sure what unknown impacts they might trigger. And the Science Advances paper “is very much a conceptual study,” says Jelle Soons of Utrecht University in the Netherlands. By that he means it’s a clever idea — but no one yet knows how it might be achieved. And Soons should know. He’s not only a physical oceanographer but also a coauthor of that new report.

What such suggestions can do is focus attention on how serious a threat an AMOC shutdown is — and how little time remains to address it.

The role of sea salt

A system of currents — including the AMOC — moves ocean waters around the planet. The water’s density is what drives them.

Saltier masses of water sink below less-salty ones. Colder waters also sink relative to warmer ones. The constant shifting between these masses keeps those currents on the move, almost as if they were riding a conveyor belt.

As the AMOC releases heat to the atmosphere at its North Atlantic destination, the water chills and sinks. That colder, denser water then heads back southward along the seafloor. To replace it, warmer water gets pulled northward along the surface.

For decades, researchers have worried that Earth’s changing climate could weaken AMOC’s strength.

Computer models have suggested the AMOC might weaken as the planet warms. But those models found it hard to know when and by how much — at least without data measured from the current. And such data had been lacking.

But scientists now have about two decades of direct observations to work with. These seem enough to start identifying a trend.

An April 15 paper in Science Advances that reviewed those data now issues a bleak conclusion: AMOC will become about 50 percent weaker by 2100.

Turning to the models

Predicting how the AMOC will change over time is “not as easy as predicting global temperature,” says Stefan Rahmstorf. He’s a physical oceanographer at the Potsdam Institute for Climate Impact Research in Germany. “It’s notoriously difficult to get [AMOC predictions] right,” he says.

The uncertainty is not strongly linked to future predictions of greenhouse-gas releases, says Valentin Portmann. He’s a climate-data scientist at the University of Bordeaux in France. He’s also lead author of the April 15 paper. Instead, he says, the issue comes down to differences between the many climate models.

The U.N. Intergovernmental Panel on Climate Change (IPCC) regularly updates its prediction of how Earth’s climate may change over the next few decades. To do this, it uses about 50 different computer models of climate. They’ve been developed by different scientists across the globe. Each model uses data on the current climate differently as it seeks to predict the future.

“The IPCC takes the mean of these to estimate what will be the future climate,” Portmann says. But the estimates can vary a bit above and below the mean, or average. This is known as standard deviation. For projections of Earth’s future heat, climate models show little disagreement. But for AMOC, the “spread is very high.”

The biggest problem, scientists say, is correctly projecting how salty different parts of the Atlantic Ocean’s future water will be. Where saltier and less-salty parts will be also matters, since saltier waters are more likely to sink, helping to drive currents.

To make an accurate prediction, Rahmstorf says, “you have to get the salinity all over the Atlantic Ocean right.”

To do that, scientists must also predict how precipitation will vary as the climate changes. Why? Rains can dilute the ocean’s saltiness. To predict rains, he says, “you’re talking about clouds — the biggest uncertainty in [climate] models.”

That’s one reason past models have varied widely when predicting how much AMOC will weaken over the next 75 years. The average drop hovers around 32 percent — give or take another 37 percent!

Portmann’s team used a branch of math known as statistics to get a less fuzzy estimate. One approach helped simplify complex problems with a lot of variables, like this one. This approach is “not often used in climate science,” Portmann notes, “but is very well known in statistical science.” Called ridge-regularized linear regression, it offered the best match to the problem.

It showed the likelier outcomes were those seen in models whose predictions were more dire. They now suggest AMOC will weaken by about 51 percent (plus or minus 8 percent) by the end of the century.

“What they have shown very convincingly is that, unfortunately, the simulations with the strongest decline are the most realistic ones,” says Rahmstorf. He did not take part in that analysis.

The biggest factor in this correction came from how one factor was weighted: how salty the surface of the future South Atlantic Ocean will be. Researchers had long suspected that the saltier those surface waters would be, the weaker the AMOC would become.

The new analysis now supports that link.

And measurements of these waters show they have been getting saltier. One reason is increased evaporation as the oceans have been warming. Another reason: More salty water has been leaking into the South Atlantic from the Indian Ocean as wind patterns shift.

The AMOC’s ins and outs are a lot to grasp

Scientists have identified many things that impact the AMOC besides the salinity of the South Atlantic. Those include circulation in the Nordic Seas and the release of freshwater into the oceans. This is especially likely in places such as the Arctic’s Bering Strait or where meltwater from Greenland’s ice sheet is flowing into the sea.

In fact, any big glut of freshwater entering the ocean is going to have a huge impact on its density. That in turn will drive changes in ocean currents.

Consider one 2025 study in the Earth ArXiv. Hundreds of thousands of years ago, it showed, meltwater from a decaying Greenland ice sheet triggered a weakening of the AMOC. That weakening lasted about 1,000 years!

Rapid melting of that ice sheet today again appears to be flooding huge amounts of freshwater into the North Atlantic.

Still, AMOC is one complex beast. It has a northern branch known as the Nordic Seas Overturning Circulation, or the NOC. Even as AMOC has been weakening, NOC appears to be stable. Some computer models even project it could strengthen a bit in coming years.

That might seem like good news, says Sasha Roewer. She’s a physical oceanographer at the Max Planck Institute for Meteorology in Hamburg, Germany. However, she warns, NOC’s strengthening might actually be another warning sign.

She, Rahmstorf and other researchers modeled what would happen as the North Atlantic Ocean became less salty. On April 20 in Ocean Science, they reported this would — for a time — strengthen the NOC current.

But “eventually it reaches a tipping point where convection in the Nordic Seas breaks down,” Roewer says. And then, she says, “both currents collapse.”

A damming proposal

The idea of damming the Bering Strait “really was a very spontaneous one,” says Soons at Utrecht. “It just started with a thought experiment.”

A study last year in Geophysical Research Letters analyzed what had played a role in a strong AMOC some 3 million years ago. And the Arctic’s Bering Strait was one factor.

It is narrow, just 82 kilometers (51 miles) wide. It’s also shallow, on average just 30 to 50 meters (100 to 160 feet) deep. So changing sea levels will alter how much water flows through this strait.

During ice ages, sea levels drop. That allows the Bering Strait to become a land bridge  between Asia and North America. Three million or so years ago, reduced freshwater flow through the Strait helped keep AMOC stable.

And that finding was like a light bulb going on, says Soons. “It made me think: Could we close the Bering Strait again?”

His simulations with Utrecht colleague Henk Dijkstra now suggest that damming the Bering Strait might work. But it’s also time sensitive. If the closure occurs during a very weak AMOC, they found, this stabilizing effect could backfire.

The damming idea has triggered mixed opinions. Notes Soons, “There are debates of whether we should even [study] geoengineering.” Why? “It would distract from the real problem,” says Soons — “give people a way out” of focusing on reducing the pollution behind climate change. (Soons admits that he and Dijkstra didn’t consider ecological and other impacts of damming the Strait.)

Even if the AMOC is speeding toward its tipping point, it’s in no way clear that a dam is the solution, other researchers say.

“I’m not a great fan [of the dam proposal], to put it mildly,” says Rahmstorf. “The most important thing we can do is stick to the Paris Agreement,” he says. This United Nations treaty aims to reduce emissions of greenhouse gases and slow global warming.

In fact, average temps this year are likely to blow through that treaty’s target: a warming of 1.5 degrees Celsius (2.7 degrees Fahrenheit) above what was typical in the 1700s. (That’s when heavy use of fossil fuels began.)

The world has likely not passed the point of triggering AMOC to stall, Rahmstorf says. When exactly that will be, he adds, is hard to know. But based on the most recent studies, that time might come as soon as the 2040s. That suggests, he says, “We have no time to lose.”

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Seasonal changes redistribute enough water around Earth to shift the planet’s center of mass back and forth by fractions of an inch relative to its geometric center. NASA scientists are on the case, tracking the oscillations because Earth’s center of mass is a crucial reference point for satellite navigation and elevation measurements.

A team, led by NASA’s Jet Propulsion Laboratory in Southern California, has proposed a way to calculate the seasonal swings with extreme precision. The technique and findings are detailed in a new study published in Geophysical Journal International. The authors paint a vivid picture of springtime thaws, churning oceans, and dense winter air shifting massive surface loads from season to season.

The study isn’t the first attempt to pin down Earth’s center of mass. Scientists over the decades have pioneered several space-based techniques to define and locate it. But it’s a moving goalpost. If Earth were a hard blue marble, its center of mass would simply overlap its geometric center. In reality, the planet is sloshing and sagging under the weight of water, ice, and air. Because of this, Earth’s center of mass continually swivels around its geometric center by as much as several millimeters.

How accurate are existing methods to measure the size of the swivel? The last two international estimates, made in 2017 and 2023, differ by 0.27 inches (7 millimeters), about the height of three stacked nickels. The difference is almost as large as the motion itself.

To reduce uncertainty, JPL geoscientist Donald Argus led the development of a new technique based on ultraprecise satellite tracking.

Driven by gravity, satellites naturally orbit Earth’s center of mass, as if bound by invisible tethers. Tiny changes in the distance between satellites and ground stations reflect Earth’s shifting center of mass.

Using satellites to locate Earth’s center of mass is not a new idea. In fact, dense metal satellites, launched in 1976 and 1992, are dedicated exclusively to this purpose. Resembling 900-pound (408-kilogram) disco balls, both Laser Geodynamics Satellites (LAGEOS 1 and 2) are studded with reflective prisms and tracked with laser precision via ground stations globally distributed across more than 20 countries.

However, one limitation of satellite laser ranging is the uneven distribution of ground stations around Earth. The new technique improves accuracy in two ways: It adds GPS tracking into the mix along with orbital data from several satellites in low Earth orbit to provide a diverse array of targets. And it considers how the weight of water and ice deforms Earth’s crust, taking ground stations along for the ride.

The technique was developed by Argus along with researchers from JPL’s satellite orbit determination team, the University of Nevada, University of Montana, and the Helmholtz Centre for Geosciences in Germany.

“We’re now estimating the size of the movement of Earth’s mass center back and forth each year to be about half of what we believed it to be eight years ago,” said Argus. “Our findings suggest that the mass of Earth’s water and air moving between the hemisphere is smaller than previously thought.”

Felix Landerer, one of the study’s coauthors at JPL, noted that “while these movements might appear tiny, our modern world relies on extremely accurate positioning measurements. By unraveling and understanding the mechanisms that change reference systems, we can build better reference systems that ultimately benefit mapping and navigation — from global shipping logistics to precision agriculture.”

What they found

The study authors tracked Earth’s center of mass oscillating seasonally and attributed the cause to three categories: oceans, atmosphere, and continental water (made up of land ice, snow, lake and river water, soil moisture, and groundwater).

They found that snow accumulation in North America and Eurasia reaches a maximum in March and shifts Earth’s center of mass about 3 millimeters toward the North Pole. A month later, in April, rainwater in the Amazon River basin peaks at 2,400 gigatons, swinging Earth’s center of mass 2.2 millimeters toward South America. Monsoon water in southeast Asia attains a maximum of 600 gigatons six months later in November, adding slightly to the annual oscillation.

Between August and October, the oceans swell with meltwater and rain, and Earth’s center of mass shifts toward the South Pacific Ocean. The Pacific Ocean is so large that mass changes there overshadow the loss or gain in other oceans, though seasonal dynamics in the Mediterranean, Red, North, Baltic, and Barents seas all help shift Earth’s center of mass in their own small way.

The researchers used a model developed by the European Centre for Medium-Range Weather Forecasts to estimate how atmospheric changes affect Earth’s center of mass throughout the seasons. They found that cold, dense, winter air helps tip the scales over Arabia, Asia, and northern Africa around Dec. 21 each year, and over South America and South Africa around June 21.

The mass calculations in the study are consistent with observations made by the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission. Launched in 2018, the mission is made up of twin satellites that map monthly fluctuations in Earth’s gravitational pull due primarily to the mass movement of water above and below ground. The two satellites fly in precise formation, and when the lead satellite passes over a dense body, like a swollen river basin, the extra gravitational tug changes the distance between its twin by a small but measurable amount.

The GRACE-FO mission is a joint partnership between NASA and the German Research Centre for Geosciences (GFZ). The next-generation GRACE-Continuity (GRACE-C) mission is targeting a launch in late 2028 to extend the nearly 25-year GRACE-series data record.

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Written by Sally Younger

2026-061

A major report has found that 12.5 trillion tons of ice from Greenland and Antarctica have melted since 1979.

Stretching from West Africa to the Gulf of Mexico, a massive bloom of sargassum seaweed is swamping beaches and killing coastal wildlife. But scientists have discovered the floating algae also shelters a vast array of ocean creatures, and some are now calling for its protection. 

The ocean has quietly absorbed billions of tons of humanity’s carbon emissions over the past two centuries, but scientists and companies racing to supercharge that natural service have long been hampered by a stubborn and costly engineering problem. Now researchers at Stony Brook University, working with the Research Foundation for the State University of New York, have unveiled a method for electrochemical ocean alkalinity enhancement that they say can dramatically lower the cost of ocean-based carbon dioxide removal by eliminating one of the most expensive steps in the entire process: the pretreatment of seawater before it enters an electrochemical reactor. The innovation, now available for licensing through SUNY TechConnect, promises high-quality carbon offsets at a substantially reduced cost while simultaneously helping to counteract the acidification that threatens marine ecosystems worldwide.

At the heart of the challenge is a delicate chemical balancing act. As atmospheric carbon dioxide dissolves into seawater, it forms carbonic acid, which lowers the ocean’s pH and erodes the carbonate chemistry that corals, shellfish and other calcifying organisms depend upon. Ocean carbon dioxide capture exploits a simple principle: if the ocean becomes more alkaline, it can absorb more CO2 from the air and lock it away safely as bicarbonate, one of the most stable and abundant forms of inorganic carbon on Earth. This process, known as ocean alkalinity enhancement, effectively turns the surface ocean into a vast, distributed carbon sink. But adding alkalinity to seawater is not trivial, and doing it in a way that is energy-efficient, scalable and safe has become one of the central engineering puzzles of the emerging carbon removal industry.

One of the most promising approaches relies on electrochemistry, specifically a technique called bipolar membrane electrodialysis. In this system, ion-selective membranes are stacked between two end electrodes, and the arrangement allows operators to split ordinary saltwater into its constituent acid and base. When brine containing sodium chloride flows through the stack, the process generates hydrochloric acid on one side and sodium hydroxide, a strong base, on the other. The elegance of the scheme lies in its product handling: if the hydrochloric acid is kept on land, where it can be stored, neutralized or put to industrial use, and only the sodium hydroxide along with the treated seawater is returned to the ocean, the receiving waters gain a net infusion of alkalinity. That added alkalinity shifts the carbonate equilibrium, allowing the ocean to draw down carbon dioxide from the atmosphere and convert it into dissolved bicarbonate that remains stable for millennia.

This electrochemical pathway has attracted serious commercial interest precisely because it produces what carbon markets call negative emissions, meaning carbon dioxide is durably removed from the atmosphere rather than merely avoided. Companies pursuing net-zero targets increasingly rely on such carbon removal credits to offset their residual emissions, and ocean alkalinity enhancement is widely regarded as one of the largest-capacity avenues available, given the sheer scale of the world’s oceans. Yet the technology has been held back by a deceptively mundane problem: what flows into the reactor matters just as much as what flows out.

Seawater, and many other brine streams that might feed these systems, contains divalent cations, most notably calcium and magnesium ions, alongside the sodium and chloride that the process is designed to split. When these divalent ions encounter the high-pH conditions created at the base-producing side of a bipolar membrane stack, they precipitate as solid calcium and magnesium compounds that coat the membranes in a crust known as scale. The consequences are cascading. Scaled membranes lose their ion-selective efficiency, forcing the system to push harder and consume more electricity to achieve the same output. Over time, the deposits shorten membrane lifetime, increasing maintenance frequency and replacement costs. The conventional answer has been water softening pretreatment, in which the incoming seawater is stripped of calcium and magnesium before it ever reaches the electrodialysis unit. While effective, such pretreatment adds significant capital and operating expense, undermining the economic case for the entire carbon removal operation and eroding the value proposition of the resulting carbon credits.

The Stony Brook researchers behind the new method have essentially designed around this bottleneck. Their technology enables electrochemical enhancement of ocean alkalinity without any pretreatment of the incoming seawater at all. By rethinking how the electrochemical system handles brine streams laden with divalent cations, the researchers have created a process that tolerates raw seawater directly, sidestepping the water softening infrastructure that previous designs demanded. According to the announcement from the Research Foundation for SUNY, the result is a system that produces negative emission carbon offsets of very high quality at a substantially reduced cost, simply because the most expensive upstream step has been engineered out of existence. The advantages claimed for the approach are straightforward and commercially significant: it is cheaper, more energy efficient, and requires no expensive water softening pretreatment.

The implications ripple across both the carbon markets and the broader climate technology landscape. Carbon offset buyers, including corporations striving to meet net-zero commitments, place a premium on removal credits that are durable, verifiable and cost-competitive. Ocean alkalinity enhancement already offers exceptional permanence, since bicarbonate dissolved in seawater represents one of the most long-lived forms of carbon storage known. By cutting costs at the front end, the Stony Brook method could help push the price of these high-quality ocean-based offsets toward levels that make them viable at gigatonne scale, a threshold that analysts consider essential if carbon removal is to play a meaningful role in stabilizing the global climate. Cheaper alkalinity generation also strengthens the second major application of the technology: mitigating ocean acidification directly, without necessarily framing it as a carbon market product at all.

Ocean acidification itself is a mounting crisis. Since the industrial revolution, the average surface ocean pH has dropped measurably as the sea has absorbed roughly a quarter to a third of anthropogenic CO2 emissions. The consequences have been documented across coral reefs, oyster hatcheries, pteropods and other calcifying organisms whose shells and skeletons become harder to build in increasingly acidic waters. A technology that adds alkalinity to coastal waters and open ocean regions simultaneously addresses this chemical stress and harvests the carbon removal benefit, a dual function that distinguishes ocean alkalinity enhancement from many other carbon removal approaches. In regions where fisheries, aquaculture and reef ecosystems are economically vital, localized deployment of alkalinity-enhancing electrochemical systems could offer both environmental resilience and revenue through carbon credit sales.

The scientific pedigree of the work reflects the growing maturity of the carbon removal field. Stony Brook University, a flagship research institution within the SUNY system, has become an active hub for climate and energy innovation, and the new method is protected under intellectual property identified in the licensing announcement. The Research Foundation for the State University of New York, the nation’s largest research foundation supporting the nation’s largest public university system, is actively seeking development partners, commercial partners and licensees to translate the laboratory advance into deployed systems. The foundation describes a broad portfolio of SUNY-led research spanning artificial intelligence for the public good, quantum technologies, next-generation semiconductors, biotechnology and medicine, and energy and climate solutions, with system-wide research expenditures approaching 1.5 billion dollars in fiscal year 2025.

For the carbon removal industry, the timing of the announcement is notable. As voluntary and compliance carbon markets mature, buyers are demanding higher fidelity in the offsets they purchase, favoring durable removal over avoidance-based credits. Electrochemical ocean alkalinity enhancement, with its well-understood chemistry and measurable inputs and outputs, is well positioned to meet rigorous monitoring, reporting and verification standards. The obstacle has always been cost, and the pretreatment bottleneck has been a substantial contributor. If the Stony Brook design performs as described at industrial scale, it could remove one of the largest cost wedges standing between laboratory demonstration and commercial deployment, accelerating a technology class that many climate analysts view as indispensable to achieving deep decarbonization.

The broader lesson of the advance may be as important as the technology itself. In the race to scale carbon removal, progress often comes not from exotic new chemistry but from eliminating the hidden costs and fragilities that make promising concepts uneconomic in practice. Water softening pretreatment is exactly the kind of unglamorous engineering detail that determines whether a climate technology remains a paper exercise or becomes infrastructure. By designing a bipolar membrane electrodialysis system that thrives on untreated seawater, the Stony Brook researchers have addressed one of those decisive details. The ocean, meanwhile, stands ready. Every unit of alkalinity added is an invitation for the sea to take up more carbon dioxide and, in doing so, to heal a little of the acidification that a warming world has inflicted upon it. What remains now is the work of scaling, partnering and commercializing, and the SUNY licensing announcement signals that the researchers and their institution intend to see this chemistry leave the laboratory and reach the sea.

Kristi West, a lead researcher from the University of Hawaiʻi at Mānoa's Health and Stranding Lab, found that 23% of the pilot whales she examined over a 13-year period had plastic in their stomachs.

Since China banned the import of plastic waste in 2018, plastic pollution has had a growing impact on the people and ecosystems of Latin America.

Imaginez un monde dans lequel nous pourrions émettre autant de CO2 que nous le voulons, sans crainte des conséquences, puisque tous ces gaz à effet de serre seront ensuite stockés dans un endroit sûr. Cela paraît trop beau pour être vrai, et pourtant, c'est ce qu’essaye de faire l’entreprise...

The morning of October 29, 2020, was cool and clear in Nazaré. This coastal town in Portugal is famous for its beaches and vibrant nightlife. It’s also known for its waves. They’re among the largest surfable ones anywhere. Every year, surfers flock here to ride down the monsters that rise out of the sea, especially off the north end of the beach. On this day, conditions were perfect for record-breaking waves.

In the early morning, a jet ski towed German surfer Sebastian Steudtner away from shore to where he met a towering wall of water. The jet ski zipped away to safety in one direction as Steudtner coasted right up to the breaking point.

Then gravity took over.

For 25 seconds, he tore down the wave. As the water broke above him, he raced to the side. Tears streamed out of his eyes because of the wind. “My face was melting,” he later told a Spanish newspaper. He had never felt faster on a surfboard.

Even for Nazaré, this wave had been a colossus. After Steudtner’s ride, scientists and surfing officials studied footage. They determined this wave had roared in at 26.21 meters (85.99 feet) tall. He had set a new record for the tallest wave ever surfed.

The previous record — 24.38 meters — was also set at Nazaré, in 2017. Steudtner may have since broken his own record. In February 2024, he surfed a wave estimated to be 28.57 meters (93.73 feet) tall. Drone-mounted cameras gauged that height (which hasn’t been formally confirmed) using tech designed in part by Porsche, the German sports car company.

Extreme waves rise from waters around the world. In some places, like the coast of Portugal, they’re the norm. On average, Nazaré’s waves measure 15 to 20 meters (50 to 65 feet) tall.

But those aren’t even the biggest or most dangerous waves known. Enormous waves called tsunamis can cause widespread destruction when they reach shore. Then there are rogue waves: unusual, solitary waves that rise higher than all the waves around them. These can be particularly dangerous for ships that don’t see them coming.

Scientists have found other unusual, risky waves. So-called “sneaker waves,” for instance, can sweep into a beach much farther than expected. People die every year off the U.S. Pacific coast and elsewhere as such sneakers pull them out to sea.

Big waves aren’t limited to oceans, either. Earthquakes or storms can cause seiches (saysh-əs) in an enclosed body of water, such as a lake. These waves roll back and forth like water splashing in a bathtub. Some waves we can’t even see. Internal waves can move below the surface of a waterway, for example.

Some scientists study waves because they’re simply fascinating.

But waves are important in many areas of science. Climate researchers are curious about waves that form where air and water meet. Oceanographers study them to understand how energy moves through water and to find ways to better protect coastlines. Knowing more about waves can help navigators find safer shipping routes. Physicists study waves to understand how moving fluids behave. And watery waves can provide insight into the movement of light and sound.

Tori Tomiczek is an ocean engineer at the U.S. Naval Academy in Annapolis, Md. By learning what types of waves cause the most destruction after hurricanes and other big storms, she hopes to design buildings that will better survive them. But, she adds, there’s another reason to study waves. They’re inherently captivating, she says. “I have always just loved the ocean.”

How to build a giant

A wave represents pure energy moving through a fluid. Sometimes it’s a lot of energy. The largest wave ever recorded slammed into the protected Lituya Bay in southeast Alaska in 1958. This wave reached a towering 524 meters (1,720 feet).

Scientists determined its height by observing that all trees and loose soil lower than that height had vanished. It created a new treeline. The bay itself was only about 220 meters (720 feet) deep, which means the wave was more than twice as tall. Imagine standing on the shore and seeing an approaching wall of water that was far taller than the Empire State Building.

Three fishing boats had anchored in that bay on the night of July 9. Just after 10:15 p.m., a wave about 30 meters (98 feet) high began moving into the bay. One boat lifted its anchor and tried to escape. Its two occupants were never seen again. A second boat, crewed by a man and his seven-year-old son, made it over the crest of the wave and skated down the other side. The captain of the third boat later reported that when his boat was lifted by the wave, he found himself looking down at the trees on the rugged hillsides. His boat was destroyed. He and his wife survived by holding on to debris.

How does a wave get to be so mammoth? The 1958 monster began with a powerful magnitude 7.8 earthquake. It shook the area for a few minutes. Some 90 million tons of rock plunged into the ocean. This released a tremendous amount of energy, causing big waves to rise and race away.

Earthquakes often give rise to big waves. On December 26, 2004, a magnitude 9.1 earthquake rocked Southeast Asia. The tsunami it unleashed reached 30 meters (98 feet) tall by the time it hit Indonesia. More than 200,000 people across the Indian Ocean died, making this one of the deadliest natural disasters in history.

On March 11, 2011, another magnitude 9.1 quake triggered a tsunami off the coast of Japan. It swept ashore killing about 18,000 people there — and caused the meltdown of three nuclear reactors.

From seasonal to surprising

Storms, too, whip up big waves. So can the shape of the seafloor. Geologists have traced the big surfing waves off Nazaré, for instance, to a deep undersea canyon — one of the largest in Europe.

That narrow canyon runs east to west. It stretches from near the coast to about 210 kilometers (130 miles) offshore. Waves streaming in over the canyon pile up higher and higher. When they merge with waves coming from other directions, they can produce true monsters. The October 2020 Nazaré wave had yet another contributor: energy from the remnants of a hurricane that had recently passed through. By the time Steudtner took to the water, the waves had become ginormous.

Weather and earthquakes can’t explain every type of wave. Consider rogues, which were once the stuff of legends.

More than 500 years ago, Christopher Columbus reported a giant wave nearly swamped his ship as it sailed through a strait off the coast of present-day Venezuela. And in 1826, French explorer Jules Dumont d’Urville described a huge, catastrophic wave in the Indian Ocean. At the time, almost no one believed him.

Today, oceanographers define rogue waves as those at least twice the average height of the waves around them. And they can emerge without warning.

The first rogue wave ever observed by scientists, known as the Draupner Wave, hit an oil platform in the North Sea on January 1, 1995. It damaged railings and equipment. Laser sensors mounted on the platform revealed the wave reached 25.6 meters (84 feet) tall.

This wave didn’t injure anyone. But that wasn’t true for three rogue waves in 2010, each less than half the Draupner’s height. After leaving Barcelona, Spain, the cruise ship Louis Majesty was headed for Genoa, Italy. But somewhere off the French coast, a giant rogue wave pummeled the ship, tossing it around and breaking windows. Two passengers died.

Physicists do not agree on how rogues form. Some have investigated the idea of “crossing waves.”

When lines of waves intersect, they can pile up on each other, boosting their height. Two waves with the same height can combine to form one far taller wave. This is called constructive interference. The energy from individual waves gets concentrated into a larger wave that stands taller, explains Francesco Fedele. He’s an engineer at the Georgia Institute of Technology in Atlanta.

“When you have an intensification of waves, they can grow up more and more,” he says.

But that’s not the whole story.

Waves are complicated. They are shaped both by the water and the air. When they collide, something called “second order” effects may develop. These are like side effects of side effects. You can get unexpected behaviors and unexpected heights not predicted by just adding individual waves together.

In recent work, Fedele showed how second-order effects can give rise to rogue waves. This work may not only help scientists better understand waves but also assist navigators who steer ships through rough waters. Energy companies and government agencies have used his models to help forecast where these waves will emerge and how to withstand them.

How to measure a big wave

Miguel Onorato is an oceanographer at the University of Torino in Italy. He’s studied the behaviors of rogues and other waves for more than two decades. In June 2018, he boarded the S. A. Agulhas II, a ship designed to support scientific research. It was headed from Cape Town, South Africa, to Antarctica.

This was winter in the Southern Hemisphere. Some scientists on board planned to study birds, including albatrosses and penguins. Others wanted to measure pollution in the water. An artist came along looking for inspiration. Onorato was part of a team that came to study waves.

Winds are relentless and strong in this part of the world. They whip through the Southern Ocean at the highest average speeds on the planet. Storms rage all the time. In 2022, scientists found two sources of tempests here. They’re so strong partly because of how energy travels through the ocean, and partly because there are fewer mountains in the Southern Hemisphere. Mountains can break up storm systems and winds.

Strong winds mean big waves. And waves here can be enormous. “The boat was rolling. I got so sick,” Onorato recalls. “It was incredible.” The artist was seasick almost the entire voyage. But once Onorato was back on his feet, his team set up its equipment on deck.

In the past, he says, scientists measured big waves with floating buoys. Their instruments can track how far up and down the water’s surface moves them. By tracking the rise and fall of these buoys, scientists had a pretty good idea of a wave’s shape.

But the buoys gave only one point of information. They didn’t show how the waves were changing as they moved. To overcome that problem, one of Onorato’s colleagues developed a new system. It uses stereoscopic vision.

The idea was inspired by human vision, Onorato says. Because the brain combines signals from two eyes, people can see in three dimensions. (It’s why someone with only one functional eye will struggle with depth perception.)

Training its two cameras on the same patch of sea gave their new system 3-D vision. A computer helped analyze the resulting video and determine wave heights, as well as other behaviors of the sea.

Rogue waves can form when strong winds cause steep waves to form and intersect, measurements by Onorato’s team showed. These rogues can rise higher than would be predicted just by adding two waves together. 

Protecting people

Knowing how and when big waves form offers benefits beyond satisfying scientific curiosity. For instance, Tomiczek at the U.S. Naval Academy wants to help make coastlines safer.

She’s run some of her experiments in an unusual laboratory at Oregon State University in Corvallis. Its long, narrow tank of water — a wave flume — produces big waves. Scientists study how those waves form and what slows them. Tomiczek was part of a group studying how the plume’s waves damaged a house that had been built at one-tenth scale. Learning which types of waves are the most destructive may help her design structures that will better withstand them.

That research calculated how much force a wave exerts on a structure horizontally. This can help engineers figure out the best way to build and which materials to use. These studies could also show how to improve other structures battered by waves, such as bridges and highways.

In other work, Tomiczek is studying how natural features — such as mangrove trees and coral reefs — can buffer waves. Nature may help us find ways to better protect coastlines, she says.

Such data may also help at-risk communities. If people better understand the local threat that big waves pose, they can prepare. Tomiczek says they can build stronger structures and plan how to help each other when a destructive one hits. This could build “kind of a community resilience,” she says.

Her wave research was launched by her love of the ocean. But Tomiczek also enjoys thinking about how the ocean connects people around the world. At one beach, she says, people can surf or bodysurf or enjoy the waves. Somewhere on the other side of the country or world, the waves might be too powerful for swimming.

“When I was living on the West Coast, we called [the ocean] the mighty Pacific because it’s this different, untamable, incredible thing,” she says. If you love the ocean, Tomiczek says, it’s hard not to wonder about what makes a big wave. “It’s just so cool to me to think about all of the incredible processes that are behind that.”

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The Caspian Sea, the world's largest inland body of water, is in major trouble. Since the mid-1990s, this saline lake, located between Europe and Asia, has lost an area nearly the size of Sicily. But until now, it wasn't clear why.

Researchers finally provided answers in a study published June 5 in the journal Earth's Future. Using ground- and satellite-based observations, they connected falling water levels to a drastic drop in river inputs from Iran, Turkmenistan, Azerbaijan, Kazakhstan and Russia, all of which border the Caspian Sea.

The team particularly highlighted losses from Russia's Volga River, the longest river in Europe, which supplies roughly 80% of the Caspian's inflow.

To find out why the Volga is discharging less water into the Caspian Sea now than it did 30 years ago, we spoke with Amir AghaKouchak, a co-author of the study and professor of civil and environmental engineering at the University of California, Irvine.

AghaKouchak, who directs UC Irvine's Center for Hydrometeorology and Remote Sensing, explained why river inputs have dropped and how decades of water withdrawals have put the Caspian Sea on a path to collapse. He also touched on a solution to this crisis — and revealed why Russia's hunger for ammunition to attack Ukraine is making it harder to save the Caspian Sea.

Sascha Pare: Falling water levels in the Caspian Sea have been attributed to natural variability, and more recently, there's been a focus on climate change and increased evaporation due to rising temperatures. But what did the results of your study show?

Amir AghaKouchak: People quickly jump to conclusions about climate change. Of course, that is important, but it cannot explain the change that we have observed. Over the last 30 years, water levels in the Caspian Sea have shrunk by around 2 meters [6.5 feet] or so. Just to put things in perspective, this translates to about 24,000 square kilometers [9,300 square miles] of sea area loss — about 5%. When we look at drivers, we notice that rainfall hasn't changed significantly over the lake and upstream, so the decline cannot be explained simply by changes in rain.

Evaporation has increased, so it explains maybe about one-third of the change. There is less water in the lake, and that indicates there's probably some water lost along the way. We don't have a lot of human-related data ‪—‬ for example, water withdrawal for irrigation or groundwater wells. That area is very difficult; the countries are not open to sharing data. A lot of our results are based on looking at proxies. Our interpretation is that temperature caused about 30% of the change and the rest is probably because of human activities.

SP: Which human activities does your research suggest are responsible for the Caspian Sea's decline?

AA: Several of the countries on the Caspian Sea have built large dams — Russia, for example. They are all desperate for hydropower. All of the countries around the lake [have also built infrastructure to supply agriculture], and one reason is that they want to create jobs and improve the local economy. Water demand is increasing in all those countries around the Caspian Sea. It's not surprising to see lakes drying or groundwater levels falling.

It's hard to find data about how much water countries are using; they keep data very private, especially places like Russia. We don't have detailed information, but the Volga-Don Canal in Russia is one of the projects that is contributing to this crisis. [Editor's note: The Volga-Don Canal is a ship canal that connects the Volga and Don rivers at their closest points.]

But we cannot blame this whole thing on that. We have to be careful with our language; we can't say one project is responsible. Most likely, this is the collective impact of many different small withdrawals from here and there, overall contributing to a significant decline in the Volga River outflow into the lake. In the paper, we have different rivers, but the Volga dominates because it's the largest river. The Volga has a higher impact than all the other rivers combined. There are lots of demands along that river basin.

SP: Did you expect human activities to play such a big role, or were you surprised?

AA: We did not have any expectations at the beginning. In fact, when we started this project, I reached out to a lot of colleagues from neighboring countries around the Caspian Sea. We didn't want to do it on our own, sitting in California, looking at another area of the world, without having local people involved. If you look at the co-authors, you see people from Azerbaijan, Iran, Kazakhstan — so, we have local experts. We thought this was really important to have those perspectives. I didn't want to reflect the opinions of only one research group. What we have here is the collective opinion of people who have not met in person; we only exchanged emails to look at the results, and then we came up with those conclusions.

We do have a Russian involved, but not from an official Russian institution. I thought this was really important, because there's more back-and-forth [with a large group of people]. If two people have to convince themselves of an idea, it's much easier than with 20. Also, we brought in people from other countries who had projects in the area; for example, there is one group from Finland and another group from Germany. We tried to come up with something that this large group of people could agree on. It was not easy, but it worked out.

SP: What is the worst-case future scenario for the Caspian Sea if shoreline countries fail to decrease their water demands?

AA: My concern is that, in the same general area, we have the Aral Sea, which is now about 5% to 10% of what it used to be, and Lake Urmia, in northwest Iran, that has also shrunk really fast and is now very small, with low levels of ecological activity. So we have two smaller lakes in a very similar climate that, from an ecological perspective, are dead. Because we have seen those degrade, we have to consider that this is the worst-case scenario for the Caspian Sea, too.

The Caspian Sea is much, much bigger. I hope it doesn't happen, but it's on the same path. Again, it's much larger, so it would probably take 100 years [to shrink as much as the Aral Sea and Lake Urmia], even with the current trend. But because we have seen those lakes shrink really fast, it deserves attention. Due to the size of this lake, the potential impacts will be huge. Even if 20% of the Caspian Sea dries out, the consequences will be very significant. It would be a disaster.

SP: You mentioned that drying lakes can become ecologically "dead." What other impacts could the Caspian Sea's falling water levels have on the surrounding landscape and people?

AA: The lake's retreat will expose the lake bed, and because it's saline, you have all kinds of minerals that will be exposed. With the next strong wind, they will go into the air. The health impacts include respiratory diseases, and even eye diseases, that are linked to salt minerals in the atmosphere. Those are the immediate consequences. Additionally, those minerals can travel long distances. In general, salt deposition on agricultural land reduces productivity. It takes a while, but if those lands are exposed for a long time, this will have an impact on the agricultural sector in those areas, which means potential food security issues. We don't exactly know what those materials are on the lake bed, so it's hard to know precisely what the consequences will be.

There is also serious shipping happening in this region. Right now, most of the shrinking is happening in the Caspian Sea's northern part, which is shallower [than the rest of the lake]. The drop in water levels is about 2 meters, and you can imagine that if you have a port and water levels drop more, you won't be able to operate. You'll need to extend your shipping routes southward; you'll need to invest and spend a lot of money to use other ports and docking sites. We have evidence of that around the Aral Sea and also Lake Urmia. There used to be these docking sites and ports, but those are now far away from the water.

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SP: What must bordering countries do to save the Caspian Sea and prevent these negative effects?

AA: Demand management is absolutely critical. Demand management doesn't get a lot of attention, because unlike big projects that make the news, management means you have to cut things and do things that people don't notice. Some people argue that politicians don't show a lot of interest in demand management, but it's something that we have control over. The technological opportunities are there.

But when you look at that area, there is a big war ‪—‬ so probably it's not the priority to invest in management. There are a lot of things that we don't talk about in the paper that are relevant. I recently learned through discussions with people from the region — this is something that came to us from co-authors and collaborators — that many countries in that area grow cotton, which uses a lot of water. It has a lot of applications, but apparently, one of them is military. Cotton is used to produce ammunition. Russia needs a lot of ammunition, so not only are they growing it themselves, but they also bought neighboring reserves from Uzbekistan and Kazakhstan. So now, even those countries have an incentive to grow more cotton. This is driving more irrigation, more groundwater extraction, more surface water depletion, and probably more impacts on the Caspian Sea.

This interview has been condensed and edited lightly for clarity.

Each year, tons of soil, silt and rocks flow into reservoirs in the U.S. and get stuck there, creating a "ticking time bomb" that threatens lives and livelihoods. According to a new study, around a fifth of the world's reservoirs are currently at high risk of filling with sediment, and by 2060, half could be inoperable as a result.

The sediment takes up space meant for water, putting additional pressure on structures that were not built to contain large quantities of sand and sludge. As the reservoir fills with the material instead of water, sediment-filled reservoirs pose a serious threat to water security and the safety of people living near or downstream of them — and as the climate changes, scientists expect the problem to worsen.

"We are losing storage space in our reservoirs faster from sediment accumulation than we gain space from new dam construction," Amy East, a geologist at the U.S. Geological Survey, told Live Science.

What is dam sedimentation?

Dam sedimentation is not a uniquely U.S. problem. Rain pulls sediment down slopes into waterways. Normally, this sediment would travel through the river system, shaping the water flow, creating habitats, and fortifying coastal wetlands and estuaries against erosion. In many parts of the world, this sediment is also a vital natural fertilizer for crops. But after a river is dammed, this sediment can collect in the reservoir.

A 2023 study published in the journal Science found that sediment buildup was the greatest threat to global water storage in existing reservoirs — even more than drought.

New research, which includes smaller reservoirs, has offered a more nuanced and concerning picture. In the study, published June 5 in the journal Nature Sustainability, researchers assessed the state of reservoir sedimentation globally. They looked at more than 550,000 reservoirs, most of which spanned less than 0.4 square miles (1 square kilometre). They found that almost 1 in 5 of reservoirs globally are at high risk of filling up with sediment.

The researchers found that sedimentation is eating into global reservoir storage capacity at about 7.3% every decade. There are 16 global hotspots that are at high risk of reservoir sedimentation, threatening water supplies to more than 2 billion people and impacting more than a quarter of global irrigated land. One of these hotspots includes the western U.S.

The authors found that sedimentation risk was especially pronounced in regions with dense small-reservoir networks supporting key crop systems.

"Without intervention, we project that, by 2060, more than half of all reservoirs could become functionally inoperable," the authors wrote. This includes more than half of all small reservoirs and more than a third of large reservoirs globally.

Where is it a problem in the U.S.?

North America has the second largest number of reservoirs, after Asia, according to the global survey. And at 7.8%, its sedimentation rate is higher than the global average, ranking it third after Oceania (9.9%) and South America (8.1%),

The U.S. is home to many small dams, said Matthias Kondolf, a geomorphologist at the University of California, Berkeley who wasn't involved in the study. "All the focus tends to be on the big dams, and these many, many small ones have been neglected," he told Live Science.

From the 1940s to 1970s, there was a big push by the U.S. government to build "farm ponds," he said. In western Oklahoma, for example, "all these dams are now filling up with sediment, and there's nothing in place to assess the safety of these features, which have now become threats."

Some of these dams have already failed, following large storms as the ageing dams were not able to cope with the volume of water. A 2018 study found that since 1980, there have been on average 24 dam failures a year in the U.S.

Reservoirs in some regions are more at risk than others. The western U.S. is a natural hotspot because it has a steeper topography, meaning more sediment naturally ends up in watersheds, East, who wasn't involved in the new research, said.

And in areas where human activities like farming or logging disrupt the landscape, rainfall is likely to drag even more sediment into reservoirs, East said. "Those types of land use can create sediment-producing hotspots almost anywhere."

In California, for example, more than half of small reservoirs in maize-growing areas are filling up with sediment at a rate of more than 10% a year, which threatens local maize production.

The threat to water security will be particularly acute in places struggling with wildfires, such as the western U.S. After fires, rain washes the debris and sediment into watersheds. A 2024 study in California found that most of this post-fire sediment erosion occurred upstream of reservoirs, rather than in places where sediment would move downstream directly to the ocean.

The dam-sedimentation situation is likely to get worse as the climate changes, researchers said. As the climate changes, there will be more extreme weather events, such as droughts and wildfires, adding more sediment to watersheds. Dams are designed to cope with the pressure of water, not sediment which exerts more force on dam walls. Moreover, in seismically active areas, the sediment vibrates at a different frequency than the concrete of the dam, which creates further impact against the structure. Additionally, the dams are just getting older.

"What do we do 50 or 100 years from now when we have all these reservoirs across the landscape filled with sediment, sitting there as ticking time bombs?" Kondolf said.

What can be done about it?

For a reservoir to be sustainable long-term, the amount of sediment entering it and leaving it should be the same.

"A big part of preventing reservoir sedimentation problems is upstream soil conservation in the watershed," East said. Interventions include ensuring that land use, such as agriculture or timber harvesting, follow best practice to reduce the amount of sediment washing off the landscapes.

If sediment is already in the dam, it can be difficult to manage and expensive to remediate, Kondolf said. Some dams, such as Fall Creek Dam in Oregon, have mechanisms that enable engineers to release sediment. But in the past, reservoirs were not designed to manage sediment and little thought was given to how to decommission them.

"This is one of those issues that falls in the cracks between different agencies and responsibilities," Kondolf said. Some larger facilities fall under the remit of the federal government. Other dams fall under state governments. California, for example, recently launched a state-sponsored program to future-proof the state's dams.

But smaller dams often get overlooked, Kondolf said.

One option is to remove the dams entirely. For example, sediment-related concerns contributed to the decision to remove the Elwha and Glines Canyon dams in Washington. The Elwha River later carried most of the sediment to its river mouth.

For smaller dams with a relatively small amount of sediment, "you just blow up the dam and let the sediment work its way downstream", Kondolf said.

There are other technological solutions, but they are expensive, such as retrofitting dams to enable them to pass sediment; creating a bypass to route sediment-heavy water around the dam; and mechanical dredging.

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Another option is to empty the reservoir of water and let the river cut a channel through the sediment, Kondolf said.

However, released dam sediment brings its own risks. If not managed carefully, sediment can flood the river system and disrupt downstream ecosystems.

"The economics of managing reservoir sediment long-term were not generally incorporated into dam design and planning in the last century when many western-U.S. water projects began," East said. This has "pushed the cost burden on future generations."

But the reality is that reservoirs around the country are filling with sediment. It is reducing their ability to store water and potentially endangering the communities living downstream of them — and unless addressed, the problem will only get worse.

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