Tag: climate-change

Four billion particles of microplastics discovered in major body of water

Source:University of South Florida (USF Innovation)

Summary:While collecting water samples and plankton, researchers discovered a high concentration of microplastics, which are known to disrupt the marine food chain.Share:

    

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A new study from the University of South Florida St. Petersburg and Eckerd College estimates the waters of Tampa Bay contain four billion particles of microplastics, raising new questions about the impact of pollution on marine life in this vital ecosystem.

This is the first measurement of microplastic abundance and distribution in the region. Researchers hope the findings will provide necessary data to inform the debate around policies to reduce plastic in the marine environment.

Microplastics are tiny plastic particles less than 1/8 of an inch, barely or not at all visible to the eye. They come from the breakdown of larger plastics, such as water bottles, fishing gear and plastic bags, or from synthetic clothing and other items that contain elements of plastic. Previous studies have found these particles in every ocean on the planet and even in the Arctic.

“Very little is known about how much microplastics are out there and the full consequences of these particles on marine life,” said Kinsley McEachern, the first author of the study and a recent Environmental Science and Policy graduate student at USF St. Petersburg. “But emerging research indicates a wide range of impacts on marine ecosystems from the large accumulation of microplastics.”

Since particles are similar size as plankton, filter feeders such as oysters, clams, many fish and some birds ingest microplastics, allowing them to enter the food chain. Persistent organic pollutants, including toxic pesticides, and metals can stick to their surfaces, making ingestion potentially that much more damaging. Effects include cellular damage, reproductive disruption and even death.

The study revealed that the predominant type of these tiny particles in Tampa Bay — in both water and sediment — are thread-like fibers that are generated by fishing lines, nets and washing clothes. Synthetic fibers are released from clothes while they are being laundered, discharged to wastewater treatment plants and eventually released into the bay.

The next largest source are fragments that come from the breakdown of larger plastics.

“These plastics will remain in the bay, the gulf and ocean for more than a lifetime, while we use most plastic bags and bottles for less than an hour,” said David Hastings, Principal Investigator of the study, Courtesy Professor at USF College of Marine Science and a recently retired Professor of Marine Science and Chemistry at Eckerd College. “Although it is tempting to clean up the mess, it is not feasible to remove these particles from the water column or separate them out from sediments.”

“Only by removing the sources of plastics and microplastic particles can we successfully decrease the potential risks of plastics in the marine environment,” added McEachern.

Researchers found the largest concentrations of microplastics in water occurred after intense and long rainfall events, while in sediments the greatest amount of microplastics were located close to industrial sources.

For more than a decade, Hastings led annual research cruises in Tampa Bay with Eckerd College students to collect water samples and plankton. During these trips, he and his students were also seeing small pieces of plastic.

“We were looking at plankton, which form the base of the marine food web. But when we put the samples underneath the microscope, we were astonished to find many brightly colored pieces of microplastic. We wanted to learn more,” said Hastings.

Teaming up with McEachern, who was interested in focusing her graduate research on this issue, USFSP Associate Professor of Chemistry Henry Alegria and the Environmental Protection Commission of Hillsborough County, they set about counting microplastics in the region at 24 stations over a 14-month period. Collecting stations were located at the mouths of major rivers, near industrial facilities and in relatively pristine coastal mangroves. Particles believed to be plastic were probed with a hot dissecting needle. If the material quickly melted or disfigured, the sample was classified as a microplastic.

On average, the study found four pieces of microplastic per gallon of water at all sites, and more than 600 pieces of microplastic per pound of dry sediment. Extrapolating those findings to the entire Tampa Bay estuary, the researchers estimated there are approximately four billion particles in the water and more than 3 trillion pieces in surface sediments.

Researchers say the findings, though substantial, might also be conservative, since collection in the bay occurred several feet below the water surface, likely missing any buoyant microplastics at the surface.

“We collected only a few pieces of Styrofoam, most likely because we sampled below the surface and foam floats at the surface,” explained Hastings.

Plastic pollution in the marine environment has been a concern for decades. However, only recently have scientists started to uncover thwidespread abundance of microplastics in the environment. With mounting physical evidence of plastic pollution, there have been greater calls for action in coastal communities around the world. Recently bans on plastic bags and single-use plastics have been enacted by some local governments in Tampa Bay to reduce marine pollution and protect Florida’s largest open-water estuary.

The findings of billions of particles of microplastics in Tampa Bay waters could bring even greater calls for action and influence future decisions in the region and beyond. Researchers at USF St. Petersburg and Eckerd College are conducting further research to more fully understand microplastic pollution in the marine environment.

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https://www.sciencedaily.com/releases/2019/09/190912111819.htm

Satellites confirm 1990s sea-level predictions were shockingly accurate

Source:Tulane University

Summary:Satellite data reveals sea-level rise has unfolded almost exactly as predicted by 1990s climate models, with one key underestimation: melting ice sheets. Researchers stress the importance of refining local projections as seas continue to rise faster than before.Share:

    

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1990s Sea-Level Predictions Shockingly Accurate
1990s climate projections nailed sea-level rise, but underestimated ice-sheet melt. Now, with accelerating seas, scientists warn of regional risks and the slim chance of catastrophic collapse. Credit: Shutterstock

Global sea-level change has now been measured by satellites for more than 30 years, and a comparison with climate projections from the mid-1990s shows that they were remarkably accurate, according to two Tulane University researchers whose findings were published in Earth’s Future, an open-access journal published by the American Geophysical Union.

“The ultimate test of climate projections is to compare them with what has played out since they were made, but this requires patience – it takes decades of observations,” said lead author Torbjörn Törnqvist, Vokes Geology Professor in the Department of Earth and Environmental Sciences.

“We were quite amazed how good those early projections were, especially when you think about how crude the models were back then, compared to what is available now,” Törnqvist said. “For anyone who questions the role of humans in changing our climate, here is some of the best proof that we have understood for decades what is really happening, and that we can make credible projections.”

Co-author Sönke Dangendorf, David and Jane Flowerree Associate Professor in the Department of River-Coastal Science and Engineering, said that while it is encouraging to see the quality of early projections, today’s challenge is to translate global information into projections tailored to the specific needs of stakeholders in places like south Louisiana.

“Sea level doesn’t rise uniformly – it varies widely. Our recent study of this regional variability and the processes behind it relies heavily on data from NASA’s satellite missions and NOAA’s ocean monitoring programs,” he said. “Continuing these efforts is more important than ever, and essential for informed decision-making to benefit the people living along the coast.”

A new era of monitoring global sea-level change took off when satellites were launched in the early 1990s to measure the height of the ocean surface. This showed that the rate of global sea-level rise since that time has averaged about one eighth of an inch per year. Only more recently, it became possible to detect that the rate of global sea-level rise is accelerating.

When NASA researchers demonstrated in October 2024 that the rate has doubled during this 30-year period, the time was right to compare this finding with projections that were made during the mid-1990s, independent of the satellite measurements.

In 1996, the Intergovernmental Panel on Climate Change published an assessment report soon after the satellite-based sea-level measurements had started. It projected that the most likely amount of global sea-level rise over the next 30 years would be almost 8 cm (three inches), remarkably close to the 9 cm that has occurred. But it also underestimated the role of melting ice sheets by more than 2 cm (about one inch).

At the time, little was known about the role of warming ocean waters and how that could destabilize marine sectors of the Antarctic Ice Sheet from below. Ice flow from the Greenland Ice Sheet into the ocean has also been faster than foreseen.

The past difficulties of predicting the behavior of ice sheets also contain a message for the future. Current projections of future sea-level rise consider the possibility, albeit uncertain and of low likelihood, of catastrophic ice-sheet collapse before the end of this century. Low-lying coastal regions in the United States would be particularly affected if such a collapse occurs in Antarctica.

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https://www.sciencedaily.com/releases/2025/09/250906013453.htm

Central Asia’s last stable glaciers just started to collapse

When the Soviet Union’s collapse means no glacier data for decades in Tajikistan.

Source:Institute of Science and Technology Austria

Summary:Snowfall shortages are now destabilizing some of the world’s last resilient glaciers, as shown by a new study in Tajikistan’s Pamir Mountains. Using a monitoring station on Kyzylsu Glacier, researchers discovered that stability ended around 2018, when snowfall declined sharply and melt accelerated. The work sheds light on the Pamir-Karakoram Anomaly, where glaciers had resisted climate change longer than expected.Share:

    

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Central Asia’s Resilient Glaciers Just Collapsed
Toward the glacier, September 2023: The field team walks toward the Kyzylsu Glacier on its true left side moraine. Northwestern Pamir mountains, central Tajikistan. Credit: © Jason Klimatsas/ISTA

Too little snowfall is now also shaking the foundations of some of the world’s most resilient ‘water towers’, a new study led by the Pellicciotti group at the Institute of Science and Technology Austria (ISTA) shows. After establishing a monitoring network on a new benchmark glacier in central Tajikistan, the international team of researchers was able to model the entire catchment’s behavior from 1999 to 2023. The results, showing decreasing glacier health, were published in Communications Earth & Environment.

High-mountain Asia has been nicknamed the Third Pole due to its massive meltwater reserves, which are second only to the Arctic and Antarctic polar caps. In Central Asia, the northwestern Pamir Mountains in Tajikistan have been home to some of the last stable or growing glaciers outside the polar regions. However, between the collapse of the Soviet Union and the return of new monitoring networks, this region has also suffered from a dire lack of observational data for decades.

Researchers from Professor Francesca Pellicciotti’s group at the Institute of Science and Technology Austria (ISTA) are contributing to an international effort to address this issue. They teamed up with local researchers in Tajikistan and collaborators in Switzerland, Austria, and France to establish their own climate station on a benchmark catchment and model the glacier’s changes over more than two decades. Now, their first joint publication shows evidence that the glacier likely reached its tipping point in 2018.

“Due to the general lack of data and robust future projections in the region, we can’t tell yet whether this was truly the ‘point of no return’ for Pamir glaciers,” says the study’s first author, Achille Jouberton, a PhD student in the Pellicciotti group at ISTA. “We must keep in mind that this study only considers one specific catchment and extends from 1999 to 2023. However, it is the first study of its kind. Similar efforts will need to address these issues on a larger geographical scale.”

Understanding an anomalous state

Climate change has had a substantial impact on glaciers worldwide. While those in the Alps, Andes, and elsewhere in the world have been melting at a disconcerting rate, some glaciers in the Central Asian Pamir and Karakoram mountains were found to be surprisingly stable, possibly even growing. This unexpected and counterintuitive behavior of the glaciers has been termed the Pamir-Karakoram Anomaly. “Central Asia is a semiarid region that is highly dependent on snow and ice melt for downstream water supply,” says ISTA Professor Pellicciotti. “But we still do not fully understand the causes of this anomalous glacier state.” Are these the last resilient glaciers in the face of climate change?

The team chose to establish their monitoring site on Kyzylsu Glacier in the northwestern Pamir, in central Tajikistan. This climate station is situated at an elevation of just below 3400 meters above sea level in a country where half of the territory rises above 3000 meters. “Kyzylsu is becoming a benchmark monitoring site due to the various observational sites recently established on and around the glacier,” explains Jouberton. There, the researchers aim to start to shed light on the glaciers’ anomalous behavior in the region.

“The challenge is that there is almost no data at all.”

Since setting up their monitoring network at the Kyzylsu catchment in 2021, the team has collected extensive data about snowfall and water resources in the area. Using these observations and climate reanalysis data as inputs to their computational models, they were able to simulate the glacier’s behavior from 1999 to 2023. “We modeled the catchment’s climate, its snowpack, the glacier mass balances, and the water movements,” says Jouberton. “But whichever way we analyzed the model, we saw an important tipping point in 2018 at the latest. Since then, the decreased snowfall has changed the glacier’s behavior and affected its health.”

In fact, the glacier ice melt has increased, compensating for around a third of the lost water resources from reduced precipitation. Therefore, it seems the anomalous phase of the glacier’s relative stability in the face of climate change has reached its end.

The researchers used computational models driven by their critically important, new local observations. However, observational data alone would not have answered all questions, even if dense coverage was provided. “We need models and simulations anyway in our work, from the bottom of the valley to the top of the glacier. Even in Europe and Canada, where the monitoring networks are much more extensive, climate stations remain small, localized points on the map,” says Jouberton. “But the challenge in the Pamir region is that there is almost no data at all.” Therefore, the researchers have to densify the observational mesh. “In light of all these challenges, we are not sure how accurate the input to the model is. But since it performed well against independent observations, we are quite confident about the output. Our work is a first step in the right direction.”

Backpacks loaded with precious equipment

Since establishing the collaboration in 2021, while the Pellicciotti group was located at the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), the researchers have visited Tajikistan seven times. “We’ve planned field trips every summer with the local research institutes in Dushanbe and hiked with our backpacks loaded with precious equipment to set camp in remote mountains, cut off from the world. Having local scientists as part of the field trip not only favors close collaboration and scientific exchange but also helps us overcome the language barrier while interacting with the local inhabitants who depend on the glaciers,” says Jouberton.

2025 marks a milestone as this summer’s field trip was the last one within the project’s current funding period. Among this year’s goals were updating and automating the monitoring networks to ensure they remain functional for decades to come. By also sharing essential knowledge about the equipment’s maintenance with local inhabitants, they hope to make their work more sustainable and reduce the need for frequent field trips. Up to now, they had to travel to exchange the equipment’s internal batteries, maintain the stations’ functionality, and collect their data using USB sticks.

Considerable local impact

The team’s work relies on close cooperation with the locals. “The shepherds know us. They see us every year and often invite us for lunch. They know where we set up our stations and do their best to ensure that nothing disturbs the measurements,” says Jouberton. The team discusses the data with the locals, shares information, and works in the wilderness amid the local inhabitants, their children, and livestock. Frequently, the locals report events that have happened in the mountains. “It is impressive to hear the locals tell us about things we only saw in satellite data. This gives a real and personal impact to our work.”

The Kyzylsu catchment contributes to the drainage basin of the Amu Darya, one of the major rivers in Central Asia, whose water originates almost entirely from glaciers. The Amu Darya is also a former inflow of the now mostly dried-up Aral Sea. This inland sea has suffered from the ongoing decades-long diversion of its two main inflow rivers, the Amu Darya to the south and the Syr Darya to the northeast, to irrigate cotton fields created in the desert during Soviet times. “But the effects of the glaciers are the strongest in their immediate ecosystems,” says Jouberton. “Even though the Kyzylsu Glacier and likely other Pamir glaciers seem to be melting faster and pumping more water into the system, it is unlikely that they will refill what’s left of the Aral Sea.”

The present study was conducted by researchers from the Pellicciotti group at the Institute of Science and Technology Austria (ISTA), previously at the Swiss Federal Research Institute WSL, Switzerland, in collaboration with scientists from the Institute of Environmental Engineering, ETH Zurich, Switzerland, the University of Zurich, Department of Geography, Glaciology and Geomorphodynamics Group, Switzerland, the Department of Geosciences, University of Fribourg, Switzerland, the Institut des Géosciences de l’Environnement, Université Grenoble-Alpes, CNRS, IRD, France, the Department of Atmospheric and Cryospheric Sciences, University of Innsbruck, Austria, the Geophysical Institute, University of Alaska Fairbanks, USA, the Center for the Research of Glaciers of the Tajik Academy of Tajikistan, Dushanbe, Tajikistan, and the Mountain Societies Research Institute, University of Central Asia, Dushanbe, Tajikistan.

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https://www.sciencedaily.com/releases/2025/09/250902085147.htm

Oceans could reach a dangerous tipping point by 2050

Source:University of California – Santa Barbara

Summary:UC Santa Barbara researchers project that human impacts on oceans will double by 2050, with warming seas and fisheries collapse leading the charge. The tropics and poles face the fastest changes, and coastal regions will be hardest hit, threatening food and livelihoods worldwide.Share:

    

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Oceans Near Breaking Point by 2050
By 2050, ocean impacts from climate change and overuse could double—unless urgent action is taken. Credit: Shutterstock

The seas have long sustained human life, but a new UC Santa Barbara study shows that rising climate and human pressures are pushing the oceans toward a dangerous threshold.

Vast and powerful, the oceans can seem limitless in their abundance and impervious to disturbances. For millennia, humans have supported their lives, livelihoods and lifestyles with the ocean, relying on its diverse ecosystems for food and material, but also for recreation, business, wellness and tourism.

Yet the future of our oceans is worrying, according to researchers at UCSB’s National Center for Ecological Analysis and Synthesis (NCEAS).

“Our cumulative impact on the oceans, which is already substantial, is going to double by 2050 — in just 25 years,” said marine ecologist and NCEAS director Ben Halpern, who led the effort to forecast the future state of marine environments as they bow under the combined pressures of human activities, which include ocean warming, fisheries biomass loss, sea level rise, acidification and nutrient pollution, among other impacts. “It’s sobering. And it’s unexpected, not because impacts will be increasing — that is not surprising — but because they will be increasing so much, so fast.”

The research team, which includes collaborators from Nelson Mandela University in South Africa, also finds that the tropics and the poles will experience the fastest changes in impacts, and that coastal areas will feel the brunt of the increased impacts.

Their research, supported in large part by the National Science Foundation, is published in the journal Science.

A comprehensive global model of human impacts

As human activity on the ocean and along the coast has intensified, so have impacts on the marine environment. Halpern and a group of scientists first tackled the challenge of understanding how these pieces fit together to affect the ocean nearly 20 years ago, laying the groundwork for the current study.

“People tracked one issue at a time, but not everything together,” Halpern said. “More importantly, there was a pervasive sense that the ocean is so huge the human impacts couldn’t possibly be that bad.”

Their quest to build a comprehensive model of human impacts on the ocean led to a 2008 paper in the journal Science, a landmark study that synthesized 17 global data sets to map the intensity and extent of human activity on the world’s oceans. That initial view revealed startling results: No place was untouched, and 41% of the world’s marine environments were heavily impacted.

“The previous paper tells us where we are; the current paper tells us where we are headed,” Halpern said.

Ocean warming and biomass loss due to fisheries are expected to be the largest overall contributors to future cumulative impacts. Meanwhile, the tropics face rapidly increasing rates of impact, while the poles, which already experience a high level of impact, are expected to experience even more. According to the paper, the high level of future impacts “may exceed the capacity of ecosystems to cope with environmental change,” in turn posing challenges for human societies and institutions in a variety of ways.”

The world’s coasts are expected to bear the brunt of these increasing cumulative impacts — an unsurprising reality, the researchers say, given most human uses of the ocean are near coasts. Yet it’s also a “worrisome result nonetheless,” according to the paper, because the coasts “are where people derive most value from the ocean.” Additionally, many countries are dependent on the ocean for food, livelihood and other benefits. “Many of these countries will face substantial increases,” Halpern said.

The authors contend that enacting policies to reduce climate change and to strengthen fisheries management could be effective ways to manage and reduce human impacts, given the outsize roles that ocean warming and biomass loss play in the estimate of future human impacts on the ocean. Likewise, prioritizing management of habitats that are expected to be heavily impacted — such as salt marshes and mangroves — could help reduce the pressures on them.

In presenting these forecasts and analyses, the researchers hope that effective action can be taken sooner rather than later to minimize or mitigate the effects of increased pressures from human activity.

“Being able to look into the future is a super powerful planning tool,” Halpern said. “We can still alter that future; this paper is a warning, not a prescription.”

Research in this paper was also conducted by Melanie Frazier and Casey C. O’Hara at UCSB, and Alejandra Vargas-Fonseca and Amanda T. Lombard at Nelson Mandela University in South Africa.

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https://www.sciencedaily.com/releases/2025/09/250905180728.htm

Even the toughest corals are shrinking in warming seas

Resilient coral growth predicted to decrease over next 3 decades, study finds.

Source:Ohio State University

Summary:Scientists found that Red Sea corals can endure warming seas but grow much smaller and weaken under long-term heat stress. Though recovery is possible in cooler months, rising global temperatures may outpace their resilience, endangering reefs and the people who depend on them.Share:

    

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Even the Toughest Corals Are Shrinking
Resilient Red Sea corals survive extreme heat but shrink and weaken, raising alarms about the future of marine life and reef-dependent communities. Credit: Shutterstock

As coral reefs decline at unprecedented rates, new research has revealed that some coral species may be more resilient to warming temperatures than others.

By studying how six months of elevated ocean temperatures would affect a species of coral from the northern Red Sea called Stylophora pistillata, scientists found that although these organisms can certainly survive in conditions that mimic future warming trends, they don’t thrive.

Stylophora pistillata tend to be tolerant of high ocean temperatures, but when continuously exposed to temperatures of 27.5 and 30 degrees Celsius (81.5 and 86 degrees Fahrenheit) — baseline warming expected in tropical oceans by 2050 and 2100 — scientists saw various changes in coral growth, metabolic rates, and even energy reserves. For instance, coral in 27.5 degrees Celsius waters survived, but were 30% smaller than their control group; those placed in 30 degrees Celsius waters wound up being 70% smaller.

“In theory, if corals in the wild at these temperatures are smaller, reefs might not be as diverse and may not be able to support as much marine life,” said Ann Marie Hulver, lead author of the study and a former graduate student and postdoctoral scholar in earth sciences at The Ohio State University. “This could have adverse effects on people that depend on the reef for tourism, fishing or food.”

Overall, the team’s results suggest that even the most thermally tolerant coral species may suffer in their inability to overcome the consequences of warming seas.

The study was published on September 3 in the journal Science of the Total Environment.

While current predictions for coral reefs are dire, there is some good news. During the first 11 weeks of the experiment, researchers saw that corals were only minimally affected by elevated baseline temperatures. Instead, it was the cumulative impact of chronic high temperatures that compromised coral growth and caused them to experience a higher metabolic demand.

The coral later recovered after being exposed for a month to 25 degree Celsius waters, but had a dark pigmentation compared to corals that were never heated. This discovery implies that despite facing ever longer periods of threat from high ocean temperatures in the summer months, resilient coral like S. pistillata can bounce back when waters cool in the winter, researchers say.

Still, as ocean temperatures are expected to increase by 3 degrees Celsius by 2100, expecting coral reefs to predictably bend to projected climate models can be difficult, according to the researchers.

This team’s research does paint a more detailed picture of how coral reefs may look and function in the next 50 years, said Andrea Grottoli, co-author of the study and a professor in earth sciences at Ohio State.

“Survival is certainly the No. 1 important thing for coral, but when they’re physiologically compromised, they can’t do that forever,” said Grottoli. “So there’s a limit to how long these resilient corals can cope with an ever increasing warming ocean.”

Gaining a more complex understanding of how warming waters can alter coral growth and feeding patterns may also better inform long-term conservation efforts, said Grottoli.

“Conservation efforts could focus on areas where resilient coral are present and create protected sanctuaries so that there are some ecosystems that grow as high-probability-success reefs for the future,” she said.

For now, all coral reefs are still in desperate need of protection, researchers note. To that end, Hulver imagines future work could be aimed at investigating the resilience of similar species of coral, including replicating this experiment to determine if sustained warming might cause trade-offs in other biological processes, such as reproduction.

“For coral, six months is still a very small snapshot of their lives,” said Hulver. “We’ll have to keep on studying them.”

Other Ohio state co-authors include Shannon Dixon and Agustí Muñoz-Garcia as well as Éric Béraud and Christine Ferrier-Pagès from the Centre Scientifique de Monaco, and Aurélie Moya, Rachel Alderdice and Christian R Voolstra from the University of Konstanz. The study was supported by the National Science Foundation and the German Research Foundation.

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https://www.sciencedaily.com/releases/2025/09/250905112308.htm

Scientists fear the Atlantic’s great ocean conveyor could shut down

Source:Potsdam Institute for Climate Impact Research (PIK)

Summary:A new study projects that the Atlantic Meridional Overturning Circulation (AMOC)—the system of currents that includes the Gulf Stream—could shut down after 2100 under high-emission scenarios. This shutdown would drastically reduce heat transport northward, leaving Europe vulnerable to extreme winters, summers of drying, and shifts in tropical rainfall. Climate models show the tipping point is linked to collapsing winter convection in the North Atlantic, which weakens vertical mixing and creates a feedback loop that accelerates decline.Share:

    

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Atlantic’s Great Ocean Conveyor Could Shut Down
Scientists warn the AMOC could collapse after 2100, unleashing extreme winters, shifting rainfall, and climate upheaval. Early signals show the system weakening, making emission cuts vital to slow the risk. Credit: Shutterstock

Under high-emission scenarios, the Atlantic Meridional Overturning Circulation (AMOC), a key system of ocean currents that also includes the Gulf Stream, could shut down after the year 2100. This is the conclusion of a new study, with contributions by the Potsdam Institute for Climate Impact Research (PIK). The shutdown would cut the ocean’s northward heat supply, causing summer drying and severe winter extremes in northwestern Europe and shifts in tropical rainfall belts.

“Most climate projections stop at 2100. But some of the standard models of the IPCC – the Intergovernmental Panel on Climate Change – have now run centuries into the future and show very worrying results,” says Sybren Drijfhout from the Royal Netherlands Meteorological Institute, the lead author of the study published in Environmental Research Letters. “The deep overturning in the northern Atlantic slows drastically by 2100 and completely shuts off thereafter in all high-emission scenarios, and even in some intermediate and low-emission scenarios. That shows the shutdown risk is more serious than many people realize.”

Collapse of deep convection in winter as the tipping point 

The AMOC carries sun-warmed tropical water northward near the surface and sends colder, denser water back south at depth. This ocean “conveyor belt” helps keep Europe relatively mild and influences weather patterns worldwide. In the simulations, the tipping point that triggers the AMOC shutdown is a collapse of deep convection in winter in the Labrador, Irminger and Nordic Seas. Global heating reduces winter heat loss from the ocean, because the atmosphere is not cool enough. This starts to weaken the vertical mixing of ocean waters: The sea surface stays warmer and lighter, making it less prone to sinking and mixing with deeper waters. This weakens the AMOC, resulting in less warm, salty water flowing northward.

In northern regions, then, surface waters become cooler and less saline, and this reduced salinity makes the surface water even lighter and less likely to sink. This creates a self-reinforcing feedback loop, triggered by atmospheric warming but perpetuated by weakened currents and water desalination.

“In the simulations, the tipping point in key North Atlantic seas typically occurs in the next few decades, which is very concerning,” says Stefan Rahmstorf, Head of PIK’s Earth System Analysis research department and co-author of the study. After the tipping point the shutdown of the AMOC becomes inevitable due to a self-amplifying feedback. The heat released by the far North Atlantic then drops to less than 20 percent of the present amount, in some models almost to zero, according to the study.

Lead author Drijfhout adds that “recent observations in these deep convection regions already show a downward trend over the past five to ten years. It could be variability, but it is consistent with the models’ projections.”

It is crucial to cut emissions fast

To arrive at these results, the research team analyzed CMIP6 (Coupled Model Intercomparison Project) simulations, which were used in the latest IPCC Assessment Report, with extended time horizons to years from 2300 to 2500. In all nine high-emission simulations, the models evolve into a weak, shallow circulation state with the deep overturning shutting down; this result is produced in some intermediate and low-emission simulations as well. In every case, this change follows a mid-century collapse of the deep convection in North Atlantic seas.

“A drastic weakening and shutdown of this ocean current system would have severe consequences worldwide,” PIK researcher Rahmstorf points out. “In the models, the currents fully wind down 50 to 100 years after the tipping point is breached. But this may well underestimate the risk: these standard models do not include the extra fresh water from ice loss in Greenland, which would likely push the system even further. This is why it is crucial to cut emissions fast. It would greatly reduce the risk of an AMOC shutdown, even though it is too late to eliminate it completely.”

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https://www.sciencedaily.com/releases/2025/08/250830001201.htm

A monster seaweed bloom is taking over the Atlantic

Source:Florida Atlantic University

Summary:Sargassum has escaped the Sargasso Sea and exploded across the Atlantic, forming the massive Great Atlantic Sargassum Belt. Fueled by nutrient runoff, Amazon outflows, and climate events, these blooms now reshape ecosystems, economies, and coastlines on a staggering scale.Share:

    

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Monster Seaweed Bloom Taking Over the Atlantic
Sargassum on a beach in Palm Beach County in 2021. Credit: Brian Lapointe, FAU Harbor Branch

Researchers at Florida Atlantic University’s Harbor Branch Oceanographic Institute have released a landmark review tracing four decades of changes in pelagic sargassum – free-floating brown seaweed that plays a vital role in the Atlantic Ocean ecosystem.

Once thought to be primarily confined to the nutrient-poor waters of the Sargasso Sea, sargassum is now recognized as a rapidly growing and widely distributed marine organism, whose expansion across the Atlantic is closely linked to both natural processes and human-induced nutrient enrichment.

The review, published in the journal Harmful Algae, sheds new light on the origins and development of the Great Atlantic Sargassum Belt, a massive recurring bloom of sargassum that stretches across the Atlantic Ocean from the coast of West Africa to the Gulf of America.

Since its first appearance in 2011, this belt has formed nearly every year – except in 2013 – and in May, reached a new record biomass of 37.5 million tons. This does not include the baseline biomass of 7.3 million tons historically estimated in the Sargasso Sea.

By combining historical oceanographic observations, modern satellite imagery, and advanced biogeochemical analyses, this review provides a comprehensive framework for understanding the dramatic changes in sargassum distribution, productivity and nutrient dynamics. It also highlights the broader implications of anthropogenic nutrient enrichment on ocean ecology and the need for coordinated international efforts to monitor and manage the impacts of these massive seaweed blooms.

“Our review takes a deep dive into the changing story of sargassum – how it’s growing, what’s fueling that growth, and why we’re seeing such a dramatic increase in biomass across the North Atlantic,” said Brian Lapointe, Ph.D., lead author and a research professor at FAU Harbor Branch. “By examining shifts in its nutrient composition – particularly nitrogen, phosphorus and carbon – and how those elements vary over time and space, we’re beginning to understand the larger environmental forces at play.”

Early in the review, Lapointe and co-authors Deanna F. Webber, research coordinator; and Rachel Brewton, Ph.D., an assistant research professor, both with FAU Harbor Branch, explain that early oceanographers charted the Sargasso Sea based on surface sightings of sargassum, believing the seaweed thrived in its warm, clear, but nutrient-poor waters. However, this notion created a paradox when mid-20th-century oceanographers described the region as a “biological desert.”

However, recent satellite observations, ocean circulation models, and field studies have resolved this paradox by tracing the seasonal transport of sargassum from nutrient-rich coastal areas, particularly the western Gulf of America, to the open ocean via the Loop Current and Gulf Stream. These findings support early theories by explorers who proposed that Gulf-originating sargassum could feed populations in the Sargasso Sea.

Remote sensing technology played a pivotal role in these discoveries. In 2004 and 2005, satellites captured extensive sargassum windrows – long, narrow lines or bands of floating sargassum – in the western Gulf of America, a region experiencing increased nutrient loads from river systems such as the Mississippi and Atchafalaya.

“These nutrient-rich waters fueled high biomass events along the Gulf Coast, resulting in mass strandings, costly beach cleanups and even the emergency shutdown of a Florida nuclear power plant in 1991,” Lapointe said. “A major focus of our review is the elemental composition of sargassum tissue and how it has changed over time.”

Laboratory experiments and field research dating back to the 1980s confirmed that sargassum grows more quickly and is more productive in nutrient-enriched neritic waters than in the oligotrophic waters of the open ocean. Controlled studies revealed that the two primary species, sargassum natans and sargassum fluitans, can double their biomass in just 11 days under optimal conditions. These studies also established that phosphorus is often the primary limiting nutrient for growth, although nitrogen also plays a critical role.

From the 1980s to the 2020s, the nitrogen content of sargassum increased by more than 50%, while phosphorus content decreased slightly, leading to a sharp rise in the nitrogen-to-phosphorus (N:P) ratio.

“These changes reflect a shift away from natural oceanic nutrient sources like upwelling and vertical mixing, and toward land-based inputs such as agricultural runoff, wastewater discharge and atmospheric deposition,” said Lapointe. “Carbon levels in sargassum also rose, contributing to changes in overall stoichiometry and further highlighting the impact of external nutrient loading on marine primary producers.”

The review also explores how nutrient recycling within sargassum windrows, including excretion by associated marine organisms and microbial breakdown of organic matter, can sustain growth in nutrient-poor environments. This micro-scale recycling is critical in maintaining sargassum populations in parts of the ocean that would otherwise not support high levels of productivity.

Data from sargassum collected near the Amazon River mouth support the hypothesis that nutrient outflows from this major river contribute significantly to the development of the GASB. Variations in sargassum biomass have been linked to flood and drought cycles in the Amazon basin, further connecting land-based nutrient inputs to the open ocean.

The formation of the GASB appears to have been seeded by an extreme atmospheric event – the negative phase of the North Atlantic Oscillation in 2009 to 2010, which may have helped shift surface waters and sargassum from the Sargasso Sea southward into the tropical Atlantic.

However, the researchers caution that there is no direct evidence of this movement. Moreover, genetic and morphological data suggest that some sargassum populations, particularly the dominant S. natans var. wingei, were already present in the tropical Atlantic prior to 2011, indicating that this region may have had an overlooked role in the early development of the GASB.

“The expansion of sargassum isn’t just an ecological curiosity – it has real impacts on coastal communities. The massive blooms can clog beaches, affect fisheries and tourism, and pose health risks,” said Lapointe. “Understanding why sargassum is growing so much is crucial for managing these impacts. Our review helps to connect the dots between land-based nutrient pollution, ocean circulation, and the unprecedented expansion of sargassum across an entire ocean basin.”

This work was funded by the Florida Department of Emergency Management, United States Environmental Protection Agency, South Florida Program Project, and the NOAA Monitoring and Event Response for Harmful Algal Blooms program. Historical studies included within the review were funded by the NASA Ocean Biology and Biogeochemistry Program and Ecological Forecast Program, NOAA RESTORE Science Program, National Science Foundation, “Save Our Seas” Specialty License Plate and discretionary funds, granted through the Harbor Branch Oceanographic Institute Foundation, and a Red Wright Fellowship from the Bermuda Biological Station.

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https://www.sciencedaily.com/releases/2025/08/250830001159.htm

Geologists got it wrong: Rivers didn’t need plants to meander

Source:Stanford University

Summary:Stanford researchers reveal meandering rivers existed long before plants, overturning textbook geology. Their findings suggest carbon-rich floodplains shaped climate for billions of years.Share:

    

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Geologists Were Wrong About Meandering Rivers
A view of seasonal flow in Shoshone Creek – an unvegetated meandering stream in Nevada. Credit: M. Hasson and M. Lapôtre

A new Stanford study challenges the decades-old view that the rise of land plants half a billion years ago dramatically changed the shapes of rivers.

Rivers generally come in two styles: braided, where multiple channels flow around sandy bars, and meandering, where a single channel cuts S-curves across a landscape. Geologists have long thought that before vegetation, rivers predominantly ran in braided patterns, only forming meandering shapes after plant life took root and stabilized riverbanks.

The new study, which was published online by the journal Science on Aug. 21, 2025, suggests the theory that braided rivers dominated the first 4 billion years of Earth’s history is based on a misinterpretation of the geological record. The research demonstrates that unvegetated meandering rivers can leave sedimentary deposits that look deceptively similar to those of braided rivers. This distinction is crucial for our understanding of Earth’s early ecology and climate, as a river’s type determines how long sediment, carbon, and nutrients are stored in floodplains.

“With our study, we’re pushing back on the widely accepted story of what landscapes looked like when plant life first evolved on land,” said lead author Michael Hasson, a PhD student in Mathieu Lapôtre’s lab at the Stanford Doerr School of Sustainability. “We’re rewriting the story of the intertwined relationship between plants and rivers, which is a significant revision to our understanding of the history of the Earth.”

The muddy floodplains of meandering rivers – dynamic ecosystems created over thousands of years by river overflow – are among the planet’s most abundant non-marine carbon reservoirs. Carbon levels in the atmosphere, in the form of carbon dioxide, act as Earth’s thermostat, regulating temperature over vast timescales. Accurately budgeting for the carbon caches created by meandering rivers could help scientists build more comprehensive models of Earth’s ancient and future climate.

“Floodplains play an important role in determining how, when, and whether carbon is buried or released back into the atmosphere,” Hasson said. “Based on this work, we argue carbon storage in floodplains would have been common for much longer than the classic paradigm that assumes meandering rivers only occurred over the last several hundred million years.”

Where the river flows

To gauge vegetation’s impact on river channel patterns, the researchers examined satellite imagery of about 4,500 bends in 49 current-day meandering rivers. About half of the rivers were unvegetated and half were densely or partly vegetated.

The researchers keyed in on point bars – the sandy landforms that develop on the inside bends of meandering rivers as water flow deposits sediments. Unlike the sandy bars that form in the middle of braided rivers, point bars tend to migrate laterally away from the centers of rivers. Over time, this migration contributes to meandering rivers’ characteristically sinuous channel shapes.

Recognizing that these sandy bars form in different places based on river style, geologists for decades have measured the trajectory of bars in the rock record to reveal ancient river paths. The rocks, typically of sandstones and mudstones, provide evidence for divergent river styles because each deposits different kinds of and amounts of rock-forming sediment, giving geologists clues for reconstructing long-ago river geometries. If sandstones showed little variation in the angle of bar migration, geologists interpreted the bars as moving downstream, and thus that a braided river created the deposits.

Using this technique, geologists had noticed that rivers changed the way they behaved around the time that plants first evolved on Earth. This observation led to the conclusion that land plants made river meandering possible, for instance by trapping sediment and stabilizing riverbanks.

“In our paper, we show that this conclusion – which is taught in all geology curricula to this day – is most likely incorrect,” said Lapôtre, the paper’s senior author and an assistant professor of earth and planetary sciences at the Doerr School of Sustainability.

By looking at modern rivers with a wide range of vegetation cover, the researchers showed that plants consistently change the direction of point bar migration. Specifically, in the absence of vegetation, point bars tend to migrate downstream – like mid-channel bars do in braided rivers.

“In other words, we show that, if one were to use the same criterion geologists use in ancient rocks on modern rivers, meandering rivers would be miscategorized as braided rivers,” Lapôtre said.

Rivers over time

The findings offer a provocative new window into Earth’s past eons, upending the conventional picture of how rivers have sculpted continents. If indeed carbon-loaded floodplains were laid down far more extensively over history, scientists may need to revise models of major natural climate swings over time, with implications for our understanding of ongoing climate change.

“Understanding how our planet is going to respond to human-induced climate change hinges on having an accurate baseline for how it has responded to past perturbations,” Hasson said. “The rock record provides that baseline, but it’s only useful if we interpret it accurately.”

“We’re suggesting that an important control on carbon cycling – where carbon is stored, and for how long, due to river type and floodplain creation – hasn’t been fully understood,” he said. “Our study now points the way to better assessments.”

Additional co-authors are from the University of Padova and the University of British Columbia.

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https://www.sciencedaily.com/releases/2025/08/250831010533.htm

Wildfires threaten water quality for up to eight years after they burn

A study of 100,000 water samples from 500 river basins found elevated levels of contaminants persist for years after a fire.

Source:University of Colorado at Boulder

Summary:Wildfires don’t just leave behind scorched earth—they leave a toxic legacy in Western rivers that can linger for nearly a decade. A sweeping new study analyzed over 100,000 water samples from more than 500 U.S. watersheds and revealed that contaminants like nitrogen, phosphorus, organic carbon, and sediment remain elevated for up to eight years after a blaze.Share:

    

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Wildfires Leave Rivers Polluted for 8 Years
Wildfires leave a hidden trail: rivers tainted by long-lasting pollution. New research shows water contamination can linger up to eight years, with storms often triggering delayed surges of toxic runoff. Credit: Shutterstock

Years after wildfires burn forests and watersheds, the contaminants left behind continue to poison rivers and streams across the Western U.S. — much longer than scientists estimated.

A new study, published on June 23 in Nature Communications Earth & Environment, analyzed water quality in more than 500 watersheds across the Western U.S., and is the first large-scale assessment of post-wildfire quality.

The research was led by scientists from the Cooperative Institute for Research in Environmental Science (CIRES) at the University of Colorado Boulder.

“We were attempting to look at notable trends in post-wildfire water quality across the entire U.S. West, to help inform water management strategies in preparing for wildfire effects,” said Carli Brucker, lead author and former CU Boulder and Western Water Assessment PhD student.

The results showed contaminants like organic carbon, phosphorus, nitrogen, and sediment can degrade water quality for up to eight years after a fire. Water managers can use this data to help them plan for the future and respond appropriately when wildfires strike.

CIRES Fellow and Western Water Assessment Director Ben Livneh was the principal investigator and co-author of the study. Much of his research focuses on hydrology, or water supply, on a continental scale. When he realized he could use the same approach to understand large-scale trends in water quality, he was excited to test the method.

“There’s been a lot of work, for example, in the National Climate Assessment and the International Panel on Climate Change talking about changes in global water supply,” said Livneh, associate professor in the Department of Civil, Environmental and Architectural Engineering. “But those assessments point to this gap in water quality assessments in a continental scale context, whereas people like me in physical hydrology have been thinking about the continental scale challenges for a while.”

Researchers have long known that fire ash and soil destruction contribute to degraded water quality. Yet, past research has largely been limited to state and municipal studies — cities and towns test water quality in local streams and rivers following large fires.

For the new study, the team analyzed more than 100,000 water samples from 500 sites: half from burned river basins and half from unburned. They measured levels of organic carbon, nitrogen, phosphorus, and sediment as well as turbidity, or cloudiness, of each sample.

To understand wildfire-driven impacts, the team built data-driven models to measure how much contaminants changed in each basin before and after wildfires. In the final step, they compiled data to find the average across the burned basins for each pre- and post-wildfire year, and then compared those to the unburned basins.

The results showed watersheds take longer to recover after wildfires than previous studies found. Organic carbon, phosphorus, and turbidity are significantly elevated in the first one to five years post-fire. Nitrogen and sediment show significant increases up to eight years post-fire. Fire-driven impacts were worse in more forested areas.

“It can take two years, up to eight years, for the effect to be fully felt,” Livneh said. “Sometimes it can be a delayed effect, meaning, it’s not all happening right away, or sometimes you need a big enough storm that will mobilize enough of the leftover contaminants.”

Each watershed in the study felt the impacts differently. This is likely tied to where the fire struck — a fire closer to the river would be worse than an upstream fire. Different soils, vegetation, and weather also change the impact in each watershed, making it difficult to plan for the future.

“There’s a huge amount of variability in sedimentation rates,” said Brucker, who now works as a consultant. “Some streams are completely clear of sediment after wildfires, and some have 2000 times the amount of sediment.”

Despite variability across river basins, the study provides concrete numbers that give insight to water managers across the Western U.S. Researchers hope the results provide better direction on informing future planning efforts for increasing wildfire resilience.

“I’m hoping that providing concrete numbers is very impactful to water managers,” Brucker said. “You can’t fund resilience improvements on general concerns alone. Water managers need real numbers for planning, and that’s what we’re providing,” Brucker said.

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https://www.sciencedaily.com/releases/2025/06/250624044332.htm#google_vignette

Drought Depletes Turkey’s Tekirdag Reservoirs, Forcing Emergency Water Curbs

By Reuters

Reuters

Reuters

A drone view shows the receding waterline and exposed lakebed in the dried basin of Turkmenli Dam, as drought conditions continue to affect water levels, in Marmara Ereglisi, in the northwestern Tekirdag province, Turkey, August 11, 2025. REUTERS/Murad Sezer

By Ali Kucukgocmen

TEKIRDAG, Turkey (Reuters) -A drought in Turkey’s northwestern province of Tekirdag has left the area’s main dams without potable water, straining infrastructure and leaving some homes without water for weeks, due to a sharp drop in precipitation in the country this year.

Authorities say drought is a critical issue, with several provinces warning of limited fresh water supply this summer.

Various areas in Izmir, Turkey’s third-most populous province, have experienced frequent water cuts this month, while the municipality in the western province of Usak was told over the weekend it would have access to water just six hours a day, with the main water reservoir depleted.

Rainfall slumped 71% in July across the country from a year ago, according to Turkey’s Meteorological Service. In the Marmara region, which includes Tekirdag and Istanbul, it shrank 95% below the monthly norm in July.

In the ten months to August, precipitation sank 32% in Marmara compared to the norm, while it fell 26% across Turkey to the lowest in 52 years.

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The water level in Tekirdag’s Naip Dam, which has not seen any rainfall in June and July, fell to zero percent in August.

MORE: Places the U.S. Government Warns Not to Travel Right Now

That has forced authorities to find alternatives like delivering irrigation water for domestic use and building a pump system for delivery into urban areas.

The dam’s water level was 21% this time last year, according to the State Hydraulic Works.

Mehmet Ali Sismanlar, head of Tekirdag’s Water and Sewerage Administration (TESKI), said rainfall in Tekirdag has reduced dramatically over the past decade, and severe drought over the last two years has spurred frequent water cuts in some areas this summer.

“We are the area and the province that has been affected the most by the drought in Turkey,” he said, attributing it to climate change.

The water in Turkmenli dam, usually used for irrigation, was used to supply water to Tekirdag’s Marmaraereglisi district, where some neighbourhoods faced water cuts.

TESKI was working to open new wells to use ground water, not usually a preferred measure, Sismanlar said. He said ground water had sunk to twice its original depth over the years.

Mehmet, 70, a resident who lives in the Dereagzi neighbourhood with his family, said their home has had no water for two months, leaving them unable to shower or perform chores, and they were fetching water from nearby areas in large bottles.

“I have been living in filth for the past two months,” he said, standing among dirty piles of dishes in the kitchen, and adding that he last showered when he went to Istanbul, around 130 kilometres (81 miles) away.

His wife, Fatma, 65, said the family stayed up at night to fill up bottles in case water supply is resumed.

Remzi Karabas, 71, said he takes his laundry to Istanbul to be washed, but was done with living in Tekirdag. 

“We’ll leave some day soon. What can we do here? Water does not flow at all.”

(Editing by Tuvan Gumrukcu and Bernadette Baum)

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https://www.usnews.com/news/world/articles/2025-08-19/drought-depletes-turkeys-tekirdag-reservoirs-forcing-emergency-water-curbs