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Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Journal of Geophysical Research: Solid Earth

The explosive submarine Hunga Tonga-Hunga Ha’apai volcanic eruption of January 2022 is famous for its large volcanic plume that lifted nearly 60 kilometers into the mesosphere and for its tsunami that caused fatalities as far away as Peru. The eruption’s boom was heard even as far as Alaska (10,000 kilometers away), and the barometric pressure disturbances of this boom were tracked globally as it continued to circle the earth.

Using records from a large number of barometric and water well monitoring stations across China (see figure above), He et al. [2025] demonstrate a strong correlation between the boom’s pressure pulse and ground water levels. High permeability reservoirs displayed an immediate response. The responses in low permeability aquifers were, however, more muted. This work is notable in that it highlights a clear coupling between strong atmospheric pressure events to pressures within confined aquifers.

Citation: He, A., Liu, Y., Zhang, F., Zhang, H., Singh, R. P., & Wang, Y. (2025). Large-scale groundwater system characterization using pressure responses to barometric perturbations caused by the 2022 Hunga Tonga-Hunga Ha’apai volcanic eruption. Journal of Geophysical Research: Solid Earth, 130, e2025JB031616. https://doi.org/10.1029/2025JB031616

—Douglas R. Schmitt, Editor, JGR: Solid Earth

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body {background-color: #D2D1D5;} Research & Developments is a blog for brief updates that provide context for the flurry of news regarding law and policy changes that impact science and scientists today.

Nearly 300 current and former NASA employees have signed an open letter expressing concern that budget cuts to the agency will jeopardize safety, basic research, national security, and the nation’s economic health. 

The 21 July letter, titled “The Voyager Declaration,” in honor of the Voyager space probes, was addressed to Interim NASA Administrator Sean Duffy, who joined the agency on 9 July. 

“We are compelled to speak up when our leadership prioritizes political momentum over human safety, scientific advancement, and efficient use of public resources,” the letter states. “The consequences for the agency and the country alike are dire.”

The agency faces pressure to reduce its staff and a budget request proposing funding at levels described as an “extinction-level event for NASA science” by Casey Dreier, chief of space policy for the Planetary Society. 

 
Related

•  The Voyager Declaration
•  Hundreds of NASA Employees, Past and Present, Sign Letter of Formal Dissent
•  Get Involved: AGU Science Policy Action Center
 

In the letter, signatories asked Duffy to protect NASA from proposed budget and staffing cuts and dissented to several planned or already-enacted changes including spacecraft decommissioning; abandonment of international space mission partnerships; and termination of diversity, equity, inclusion, and accessibility programming.

The letter’s authors also pointed out a “culture of organizational silence” promoted at the agency that, combined with suggested changes to NASA’s Technical Authority—a system of safety oversight—represents a “dangerous turn away from the lessons learned following the Columbia disaster.” The letter was dedicated to astronauts who lost their lives in spaceflight incidents and was signed by at least 4 astronauts.

“We’re scared of retaliation,” Monica Gorman, an operations research analyst at NASA’s Goddard Space Flight Center and a signatory of the letter, told the New York Times. She said staff “go to the bathroom to talk to each other, and look under the stalls to make sure that no one else is there before we talk.”

Staff at the National Institutes of Health and the EPA signed similar letters to their administrators in June. Some of the signatories of the EPA letter have since been placed on leave. Stand Up for Science, a nonprofit science advocacy organization, helped coordinate all three letters. 

—Grace van Deelen (@gvd.bsky.social), Staff Writer

These updates are made possible through information from the scientific community. Do you have a story about how changes in law or policy are affecting scientists or research? Send us a tip at eos@agu.org. Text © 2025. AGU. CC BY-NC-ND 3.0
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Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Journal of Geophysical Research: Solid Earth

Understanding how rocks break in the brittle upper crust is critical for predicting earthquakes, managing reservoirs, and modeling subsurface mechanics. In JGR: Solid Earth, two new studies by Jacob et al. [2025] and Hurley et al. [2025] use cutting-edge synchrotron-based X-ray diffraction techniques to reveal how stress evolves at the grain scale inside sandstone samples under load.

In both studies, researchers applied increasing axial compression to small cores of sandstone rocks, while scanning them with high-energy X-rays at a synchrotron radiation facility. Jacob et al. [2025] employed a technique called scanning three-dimensional X-ray diffraction to obtain high-resolution maps of intra-granular stress in the sandstone. By combining stress mapping with stepwise compression, the team observed increasing stress heterogeneity accompanied by dynamic reorientation of local stresses. High-stress clusters emerged and formed spatially persistent structures. These patterns were found to correlate with zones of higher grain rotation and strain, forming potential precursors to failure.

Hurley et al. [2025] combined X-ray tomography with three-dimensional X-ray diffraction and near-field high-energy diffraction microscopy to image stress and texture evolution in 3D. The researchers observed that larger grains showed more internal misorientation, possibly due to the presence of surface cements. By combining stress mapping with stepwise compression, the team showed that grain stresses demonstrated compressive stress alignment parallel to the loading direction and tensile stresses alignment orthogonal to the loading direction. This evolution was consistent with porosity evolution revealed by X-ray tomography, which showed pores closing parallel to the loading direction and opening normal to the loading direction.

Together, these studies reveal that rocks under stress behave more like collections of interacting grains than uniform solid blocks, showing similarities with inter-particle force transmission in granular materials. They also underscore the power of modern synchrotron tools in capturing these processes while performing rock deformation experiments, providing deeper insights into how brittle failure initiates in the Earth’s crust.

Citations:

Jacob, J.-B., Cordonnier, B., Zhu, W., Vishnu, A. R., Wright, J., & Renard, F. (2025). Tracking intragranular stress evolution in deforming sandstone using X-rays. Journal of Geophysical Research: Solid Earth, 130, e2025JB031614. https://doi.org/10.1029/2025JB031614

Hurley, R. C., Tian, Y., Thakur, M. M., Park, J.-S., Kenesei, P., Sharma, H., et al. (2025). Crystallographic texture, structure, and stress transmission in Nugget sandstone examined with X-ray tomography and diffraction microscopy. Journal of Geophysical Research: Solid Earth, 130, e2025JB031690. https://doi.org/10.1029/2025JB031690

—Yves Bernabé, Editor, JGR: Solid Earth

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Editors’ Vox is a blog from AGU’s Publications Department.

Karst groundwaters are vital resources, providing drinking water to nearly 10% of the world’s population. However, human activities and global change have deteriorated the karst water quality and dependent ecosystems.

A new article in Reviews of Geophysics explores contaminant transport in karst groundwaters and recent efforts to model it. Here, we asked the authors to give an overview of karst aquifers, how scientists model contaminant transport, and future research directions.

What are karst aquifers and where do they form?

Karst aquifers are underground water reservoirs that develop in soluble rocks like limestone or dolomite. Over thousands of years, these rocks dissolve to form complex underground networks of channels, caves, and fractures (Figure 1). These unique systems are found all over the world—from Florida to the Dinaric Alps—and they supply drinking water for nearly one in ten people globally while supporting ecosystem functioning.

Figure 1: Conceptual representations of transport processes in karst aquifer at differing spatial scales. a) 3D block diagram of a karst aquifer scale, b) aquifer scale, c) borehole scale, d) single-fracture scale, e) pore-scale level (described at the Representative Elementary Volume, REV). Here, contaminant degradation is described by the chemical transformation influenced by physical, chemical, and (biogeo)chemical processes. The figure only describes anthropogenic contamination by indicating diffuse (areal) and point sources because both are key contamination sources in karst aquifers. Credit: Çallı et al. [2025], Figure 1

Why are karst aquifers important to understand?

Karst aquifers are both vital and vulnerable. They respond quickly to environmental changes, and pollutants can spread rapidly through their distinctive underground networks. Because water moves so fast and through unpredictable pathways, it’s hard to know how long contaminants will persist or where they’ll go. Understanding them is key to ensuring safe drinking water and protecting the ecosystems that depend on them.

What are the main sources of contamination in karst aquifers?

Contaminants come from both natural and human-made sources. Industrial chemicals, agricultural runoff, sewage, and land use changes are common threats. Even natural elements like arsenic or uranium can pose risks if they dissolve into groundwater. Due to the thin soils and fast-moving water in karst aquifers, there’s little time or space for these pollutants to be filtered or degraded before they spread (Figure 1).

How do scientists monitor for contamination in karst aquifers?

Scientists use tracer tests—adding a harmless dye or chemical to water and tracking where it goes—to map water flow. They also analyze natural “tracers” like isotopes or chemical signals already in the water. These techniques help us understand how fast water travels, how long it stays underground, and how different sources mix (Figure 2). This information is essential for predicting contamination risks, and support efforts to protect karst water resources.

Figure 2: Monitoring spatiotemporal distributions of contaminant plumes across the karst systems. Here, the acronyms Adv, Dis, and Diff refer to advection (or advective flow), dispersion, and diffusion processes, respectively. Sp (sorption) and Rc (chemical reaction) indicate the impact of retardation and reactive processes on the movement of solute plume. In the figure, C0 and C refer to the initial solute concentration and the concentration of solute at a given time, respectively. Here, ti indicates the first detection time of solute of interest (e.g., at the observation well) and tobs refers to the observed concentrations at the time of interest. In the figure, the two-way red arrows indicate the solute/mass exchange between the conduit and the matrix. Credit: Çallı et al. [2025], Figure 3

What kinds of models are being developed to track the movement of contaminants within karsts?

Researchers are developing computer models that simulate how water and contaminants move through the complex karst network. These models range from simplified, large-scale representations to detailed simulations of karst flow through conduits and fractures (Figure 3). They help us explore different scenarios—like how a pollutant might spread after a flood or how land use changes affect water quality. Therefore, they are essential for effectively managing karst water quality and planning pollution prevention strategies.

Figure 3: Generic classification of karst simulation models based on the model parametrization considering process complexity and data requirement. a) Conceptualization of the karst aquifer physical boundaries depicted by the grey-shaded area with a blue-indicated karst conduit and conduit network (the blank circles also describe the swallets/sinkholes along the conduit network), b) Spatially lumped karst simulation models depicted based on the solute concentration distribution over different karst compartments including epikarst, conduit, and matrix, c) Spatially distributed karst simulation models described considering the spatial distribution of the solute concentration. The classification is adapted from Hartmann et al. [2014]. Herein, a tracer test is described only to demonstrate the spatial distributions of contamination plume across two main karst simulation approaches. Credit: Çallı et al. [2025], Figure 9

What are some of the challenges of karst transport modeling?

The biggest challenge is heterogeneity—karst systems are incredibly variable at all scales. We often lack detailed data on the shape of the underground conduits, flow speeds, or chemical conditions. This makes it difficult to build reliable models. Even small changes in how water moves can greatly affect contaminant behavior, so improving model accuracy is a major research focus.

What additional research, data, or modeling efforts are needed to overcome these challenges?

We need better field data—from tracer tests, groundwater monitoring, and mapping—to calibrate and validate models. Advances in remote sensing and machine learning also offer new tools. Future research should focus on integrating hydrological, chemical, and biological processes and on translating model results into actionable decisions. Collaboration across disciplines is key to (better) understanding, managing, and protecting karst water resources in a changing world.

—Kübra Özdemir Çallı (kuebra.oezdemir_calli@tu-dresden.de, 0000-0003-0649-6687), Institute of Groundwater Management, TU Dresden, Germany; and Andreas Hartmann (andreas.hartmann@tu-dresden.de, 0000-0003-0407-742X), Institute of Groundwater Management, TU Dresden, Germany

Citation: Çallı, K. Ö., and A. Hartmann (2025), Groundwater pollution in karst regions: toward better models, Eos, 106, https://doi.org/10.1029/2025EO255022. Published on 22 July 2025. This article does not represent the opinion of AGU, Eos, or any of its affiliates. It is solely the opinion of the author(s). Text © 2025. The authors. CC BY-NC-ND 3.0
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Source: AGU Advances

As temperatures, biodiversity losses, and sea levels rise globally, scientists are concerned about the likelihood of abrupt climatic shifts occurring, particularly within sensitive subsystems of the climate system such as the Amazon rainforest, Antarctic sea ice, and the Tibetan Plateau. Abrupt shifts can manifest as, for example, large and sudden changes in the rate of precipitation in a monsoon system, ice melt in Antarctica, or permafrost thaw in the Northern Hemisphere.

Terpstra et al. sought to identify abrupt shifts that might occur in the future, focusing on climate subsystems discussed in the 2023 Global Tipping Points Report. The team examined outputs from 57 models from the Coupled Model Intercomparison Project Phase 6 (CMIP6). All the models simulated a climate change scenario over 150 years, with carbon dioxide concentration increasing by 1% annually until it reached 4 times preindustrial levels.

They then applied a method called Canny edge detection, which was originally created to identify edges in computer images, to the modeled climate data. In this case, they used it to detect edges, or points in time and space, where abrupt changes occurred within a decade across 82 variables, such as sea surface salinity, soil moisture content, and carbon mass in vegetation and soil. Prior research used a similar method to scan for edges in climate data, but not at the subsystem scale.

Although the researchers observed large variations among the model scenarios, 48 of the 57 showed an abrupt shift in at least one subsystem over the modeled period. Monsoon systems were outliers: Only one model indicated an abrupt shift in the Indian summer monsoon, and none indicated abrupt shifts in the South American and West African monsoons.

They also found that the more global warming a model simulated, the higher the likelihood was of abrupt shifts happening. At 1.5°C above average preindustrial temperatures, the target limit set by the Paris climate agreement, the researchers found that 6 out of 10 studied climate subsystems showed large-scale abrupt shifts across multiple models. (AGU Advances, https://doi.org/10.1029/2025AV001698, 2025)

—Sarah Derouin (@sarahderouin.com), Science Writer

Citation: Derouin, S. (2025), Abrupt climate shifts likely as global temperatures keep rising, Eos, 106, https://doi.org/10.1029/2025EO250270. Published on 22 July 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
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This article originally appeared on Inside Climate News, a nonprofit, non-partisan news organization that covers climate, energy, and the environment. Sign up for its newsletter here.

A pair of new climate studies suggest an intensification of strong storms called nor’easters and other disruptive extremes affecting the East Coast of North America on an overheated planet.

Nor’easters generally form within about 100 miles of the East Coast between North Carolina and Massachusetts, often when cooler air from Canada meets warm, moist air over Gulf Stream waters. Those contrasting air masses can start to spin with a nudge from the jet stream, fueling storms that can produce damaging winds, coastal flooding and intense, disruptive snowfall in the winter.

The strongest nor’easters are already significantly windier and rainer than they were in the middle of the 20th century, said University of Pennsylvania climate scientist Michael Mann, a coauthor of a study published on 14 July in the Proceedings of the National Academy of Sciences.

A 2022 study showed a similar trend of intensification for storms forming over the Atlantic and hitting Europe, and that the track of those storms is moving northward, potentially putting unsuspecting areas more at risk.

Mann said the increases in the intensity and precipitation rates of the strongest nor’easters have likely been fueled by increases in ocean temperatures and the increased moisture capacity of a warming atmosphere.

“There are two reasons to look at the most intense nor’easters,” Mann said via email. “First, from an impact standpoint, they do the most damage, including coastal erosion, destruction and paralyzing snowfalls. The 1962 Ash Wednesday storm, with 84 mile per hour gusts, is a great example. In today’s dollars, it did $21 billion worth of damage.”

And just last February, a classic nor’easter described at the time as a “bomb cyclone” dropped several feet of snow over parts of Virginia and North Carolina and caused damaging flooding along parts of the Massachusetts coast, Eastern Long Island, and the Jersey Shore.

Mann said the increases in the intensity and precipitation rates of the strongest nor’easters have likely been fueled by increases in ocean temperatures and the increased moisture capacity of a warming atmosphere.

The researchers tracked 900 nor’easters back to 1940 in combination with a careful reanalysis of historical climate conditions surrounding the storms, including notable events like the Perfect Storm in 1991, Storm of the Century in 1993, and Snowmaggedon in 2010.

In the very strongest storms, the wind speeds have increased about 5.4%, from 69 to 71 mph, “but since destructive potential goes as the wind speed cubed, that’s a roughly 17% increase in destructive potential,” Mann said.

Overall, he added, a lot of research suggests that extra warming in the Arctic, which reduces the temperature contrast between high latitudes and midlatitudes, will lead to less storminess overall, but the destructive potential of intensifying nor’easters warrants attention.

Compared to other types of storms, nor’easters feed more off the heat of the ocean, which remains considerable in winter, “So those storms that can make it past the obstacles to development have the potential to grow stronger than they otherwise would have,” he said. “While we don’t see any evidence of increased intensity for the ‘average’ nor’easter, the strongest ones are clearly getting stronger.”

“My interest in these storms, and how they’re being impacted by climate change has been inspired by two personal experiences,” he said, first noting the March 1993 “storm of the century,” which caused 270 deaths and $12.2 billion worth of damage across 26 states, according to the National Ocean and Atmospheric Administration.

Mann said the storm disrupted a spring break road trip in Florida, where the temperature in St. Augustine dropped from the 70s to 40s in a few hours.

“We drove past Okefenokee Swamp later that day and it was snowing,” Mann said. “Then we stopped off in Southern Georgia for the night and temperatures dropped to the mid 20s. We froze. I will never forget that.”

“The strongest nor’easters can have impacts comparable to category 1 and 2 hurricanes, with effects encompassing a larger area.”

He said he remembers another infamous nor’easter, Snowmaggedon, from February 2010 because a U.S. senator who rejects science that proves human-caused warming used the occasion to build what he called an igloo in an attempt to cast doubt on climate science. At the same time, Mann said he ended up stuck in a hotel room for three days with several feet of snow blocking most roads in Pennsylvania.

As such storms grow stronger in a warming world, said Anthony Broccoli, an atmospheric scientist at Rutgers University who was not involved in the new study but who also researches nor’easters, “it will be important to remember that the strongest nor’easters can have impacts comparable to category 1 and 2 hurricanes, with effects encompassing a larger area.”

With sea level rise accelerating along the East Coast, Broccoli added that nor’easters “will lead to greater coastal flooding even without any changes in storm intensity.”

The increased thermal energy from warming oceans is likely driving the trend toward stronger nor’easters, and there could be other large-scale changes to ocean currents and winds that could shift the tracks of nor’easters, potentially raising unexpected risks in new areas, he said.

The new research doesn’t mean that temperatures are getting colder, but that the frigid air that still does form over the Arctic in winter will still make its way south, showing up perhaps more frequently in unexpected regions, or with increased unusual seasonal extremes that can damage crops.

The Arctic Connection

Large-scale changes affecting nor’easters and cold weather extremes in the United States likely include accelerated warming of the Arctic region, climatologist Judah Cohen said in an email interview. Cohen, a visiting scientist at MIT and director of seasonal research with Atmospheric and Environmental Research, published an 11 July study in Science Advances that bolsters evidence for a climate connection.

Cohen said that, as far as he’s concerned, the new paper is “preaching to the choir,” because its conclusions are consistent with his own research showing that “Arctic change can lead to episodic increases in severe winter weather in the U.S. east of the Rockies including extreme cold and disruptive snowfalls.”

The temperature contrast between the Arctic and the midlatitudes is one of the main forces that creates key winds at different altitudes, like the jet stream and polar vortex, and moves weather systems around the Northern Hemisphere.

Cohen’s work over recent years suggests that accelerated warming of the Arctic “stretches” the polar vortex—like elongating a round rubber band—into positions that let cold polar air spill southward more frequently.

He noted that two of the most recent nor’easters specifically named in the new paper by Mann and his coauthors, in March 1993 and January 2018, occurred during stretched polar vortex events. The new paper, he said, “provides a medley of possible causes but doesn’t settle on any one cause.”

His own recent paper, he said, shows “for the first time that stretched polar vortex events are overwhelmingly associated with extreme cold and heavy snowfall in the Eastern U.S.,” compared to other polar vortex configurations.

Often the polar vortex flows in a tight coil around the North Pole, containing the Arctic air, but Cohen’s study, and other research, suggest a trend to more frequent stretched polar vortexes and the associated cold-air outbreaks and storm impacts. Taken altogether, he said the new research helps explain regional “winter cooling trends and an increased number of heavy snowfalls in the Eastern U.S. over the past two and a half decades.”

—Bob Berwyn (@bberwyn), Inside Climate News

Artificial light and higher temperatures in cities may lengthen the growing season by up to 24 days, according to a new study in Nature Cities.

Previous studies have observed that plant growth starts earlier and ends later in cities than in rural areas. But these studies haven’t concluded whether this difference depends more on heat or light, both of which regulate the growing season and are amplified in urban centers.

The new study’s authors used satellite data to estimate nighttime light pollution in cities and pinpoint the start and end of the growing season. They found that the amount of artificial light at night plays a bigger role in growing season length than temperature does, especially by delaying the end of the season.

“This study highlights artificial light at night as a powerful and independent force on plant phenology,” said Shuqing Zhao, an urban ecologist at Hainan University in China who was not involved in the research. “It marks a major step forward in our understanding of how nonclimatic urban factors influence plant life cycles.”

City Lights Trick Plants

“Plants rely on both temperature and light as environmental cues to regulate their growth,” explained Lin Meng, an environmental scientist at Vanderbilt University and a coauthor of the study. In the spring, warmer temperatures and lengthening days signal to plants that it’s time to bud and produce new leaves. In the fall, colder, shorter days prompt plants to drop their leaves and prepare for winter.

“Plants evolved with predictable cycles of light and darkness—now, cities are flipping that on its head.”

But in cities, these essential cues can be disrupted. Cities are typically hotter than surrounding rural areas—the so-called urban heat island effect—and much brighter because of the abundance of artificial light. These disrupted cues “can trick plants into thinking the growing season is longer than it actually is,” Meng said. “Plants evolved with predictable cycles of light and darkness—now, cities are flipping that on its head.”

To assess how heat and light are affecting urban plants, Meng and her coauthors used satellite data from 428 cities in the Northern Hemisphere, collected from 2014 to 2020. For each city, the researchers analyzed correlations between the amount of artificial light at night (ALAN), air temperature, and the length of the growing season.

The scientists found that on average, the growing season started 12.6 days earlier and ended 11.2 days later in city centers compared with rural areas. ALAN apparently played an important role in extending the growing season, especially in the autumn, when ALAN’s influence exceeded that of temperature.

Anna Kołton, a plant scientist at the University of Agriculture in Krakow who was not part of the research, highlighted the significance of this result. “The impact of climate change, including increased temperatures on plant functioning, is widely discussed, but light pollution is hardly considered by anyone as a significant factor affecting plant life.” The new study is among the first to bring ALAN’s effects into the spotlight.

“Every Day Needs a Night”

“The extension of urban vegetation may at first glance appear positive,” said Kołton. But this positive impression is deceiving. In reality, an extended growing season “poses a threat to the functioning of urban greenery.”

Delaying the end of the growing season may be especially disruptive. In the fall, shortening days prompt plants to reduce their metabolic activity, drop their leaves, and toughen up their cell walls to withstand the coming winter. But if they are constantly stimulated by artificial light, Kołton pointed out, urban plants may miss their cue and be unprepared when the cold hits.

“Every day needs a night, and so do our trees, pollinators, and the rhythms of nature we all depend on.”

Longer growing seasons also affect animals and people. “Flowers might bloom before their pollinators are active, or leaf-out might not align with bird migration,” said Meng. “And for people, a longer growing season means earlier and prolonged pollen exposure, which can make allergy seasons worse.”

As cities become bigger and brighter, their growing seasons will likely continue to lengthen unless the impacts of ALAN are addressed. “The good news is that unlike temperature, artificial light is something we can manage relatively easily,” said Meng. She and Zhao both suggested that swapping blue-rich LED lamps for warmer LEDs (which are less stimulating to plants), introducing motion-activated or shielded lights, and reducing lighting in green spaces could limit light pollution in cities.

“Every day needs a night,” Meng said, “and so do our trees, pollinators, and the rhythms of nature we all depend on.”

—Caroline Hasler (@carbonbasedcary), Science Writer

Citation: Hasler, C. (2025), Artificial light lengthens the urban growing season, Eos, 106, https://doi.org/10.1029/2025EO250254. Published on 18 July 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

A computer model drawing on satellite and climate data could give scientists an early warning of coastal marsh decline.

Using the model, scientists detected a decline in underground plant biomass across much of Georgia’s coastal marshes between 2014 and 2023. Critically, this loss occurred even though the marsh grasses appeared green and thriving at the surface.

The findings, published last month in Proceedings of the National Academy of Sciences of the United States of America, could help land managers identify targets for restoration before more severe damage takes hold.

Roots of Concern

Marshes “are not only economically but culturally and recreationally important places for the people who both live along the coast and visit the coast.”

Marshes “are not only economically but culturally and recreationally important places for the people who both live along the coast and visit the coast,” said study coauthor Kyle Runion, a landscape ecologist at the University of Georgia. They help control flooding, sequester carbon, and provide space for hunting, fishing, and wildlife spotting.

But rapid sea level rise has threatened coastal marsh grasses, as higher waters and more frequent flooding inundate the soil and choke oxygen supply at the roots. In a healthy ecosystem, underground plant biomass staves off erosion and adds organic matter that eventually decomposes into more soil, boosting the marsh’s resilience to sea level rise, so declining root systems can be an early sign of trouble in marshlands.

Marshlands can appear healthy even as their roots are dying off, said Bernard Wood, a wetland ecologist at the Coastal Protection and Restoration Authority of Louisiana who was not involved in the study.

A trip into the marsh itself tells a different story, however. “You could just pick up this huge clump of grass with one hand, and it barely has anything holding it to the ground,” Wood said.

Sea level rise can threaten the roots of smooth cordgrass, even as the leafy part of the plant can appear healthy. The exposed roots of smooth cordgrass are seen here at a marsh edge along the Folly River in Georgia. Credit: Kyle Runion/Colorado State University BERM and Biomass

To understand how Georgia’s marshes are responding to changing conditions, researchers developed and tested the Belowground Ecosystem Resilience Model (BERM) in 2021. BERM draws from satellite and climate data to estimate the belowground biomass of Spartina alterniflora, or smooth cordgrass, in coastal areas.

In the 2021 study, the team collected information on environmental conditions in Georgia salt marshes from Landsat 8, Daymet climate summaries, and other publicly available datasets. They built a machine learning model that could predict belowground biomass and trained it on field data from four marsh sites. Researchers found that elevation, vapor pressure, and flooding frequency and depth were some of the most important variables in predicting root biomass.

How a salt marsh looks on the surface isn’t necessarily an indicator of how it’s truly faring.

In the new study, Runion and his colleagues applied the model to estimate changes in S. alterniflora root biomass over nearly 700 square kilometers of Georgia coast between 2014 and 2023.

During that time, belowground biomass decreased about 1% per year on average, the team found. About 72% of the salt marsh area saw declines in underground plant mass. At the same time, aboveground biomass—the visible part of the marsh grass—increased over most of the study area.

The disparity between biomass above and below could occur because aboveground biomass is less sensitive to flooding than root systems. Or the increase might be temporary, as flooding initially delivers nutrients but eventually drowns the plant. In either case, how a salt marsh looks on the surface isn’t necessarily an indicator of how it’s truly faring.

Tool for Conservation

Early-warning signs of marsh decline provided by the model could be crucial for conservation. “Once [marsh] loss occurs, that can be irreversible,” Runion said. “By getting a sign of deterioration before loss happens, that’s when we can intervene and much more easily do something about this.”

Mapping which areas of the marsh are most vulnerable could also combat the tendency to see marshes as either “doomed” or “not doomed” and target conservation efforts to the areas most in need, said Denise Reed, a coastal geomorphologist at the University of New Orleans who was not involved in the study. Though belowground biomass is declining on average, some areas of the coast are experiencing less change than others.

“There are some complex patterns going on—probably something that it would be great to understand a little bit better,” Reed said. But “this idea of being able to detect areas which are in worse condition versus areas that are in better condition from the soil’s perspective is really helpful.”

For now, BERM can predict belowground biomass only in Georgia marshes. Other regions have different plant species and flooding dynamics that could alter the relationships BERM relies on. But with additional calibration data from other salt marshes, the team could make the model more widely applicable, Runion said.

“We are looking to expand this sort of modeling framework to include different species along the Gulf and East Coast,” Runion said.

—Skyler Ware (@skylerdware), Science Writer

Citation: Ware, S. (2025), Machine learning model flags early, invisible signs of marsh decline, Eos, 106, https://doi.org/10.1029/2025EO250253. Published on 17 July 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Source: Geophysical Research Letters

Monitoring changes in water temperature and pressure at the seafloor can improve understanding of ocean circulation, climate, and natural hazards such as tsunamis. In recent years, scientists have begun gathering submarine measurements via an existing infrastructure network that spans millions of kilometers around the planet: the undersea fiber-optic telecommunications cables that provide us with amenities like Internet and phone service.

Without interfering with their original purpose, the cables can be used as sensors to measure small variations in the light signals that run through them so that scientists can learn more about the sea. Liu et al. recently developed a new instrument, consisting of a receiver and a microwave intensity modulator placed at a shore station, that facilitates the approach.

Transcontinental fiber-optic cables are divided into subsections by repeaters, instruments positioned every 50 to 100 kilometers that boost information-carrying light signals so that they remain strong on the journey to their destination. At each repeater, an instrument called a fiber Bragg grating reflects a small amount of light back to the previous repeater to monitor the integrity of the cable.

By observing and timing these reflections, the new instrument measures the changes in the time it takes for the light to travel between repeaters. These changes convey information about how the surrounding water changes the shape of the cable, and the researchers used that information to infer properties such as daily and weekly water temperature and tide patterns. Most previous work using telecommunications cables for sensing efforts treated the entire cable as a single sensor, and work that did use them for distributed sensing required ultrastable lasers. This instrument allowed the team to do distributed sensing using more cost-effective nonstabilized lasers.

The research team included geophysicists, electronics engineers, and cable engineers. They tested the instrument over 77 days in summer 2024 on EllaLink, an operation cable with 82 subsections running between Portugal and Brazil. As temperatures and tides rose and fell, the transatlantic cable stretched and contracted, providing measurable changes in the light traveling within it.

The study showed that the existing network of submarine cables could be a valuable resource for monitoring ocean properties, enabling everything from early tsunami warnings to long-term climate studies. (Geophysical Research Letters, https://doi.org/10.1029/2024GL114414, 2025)

—Saima May Sidik (@saimamay.bsky.social), Science Writer

Citation: Sidik, S. M. (2025), A transatlantic communications cable does double duty, Eos, 106, https://doi.org/10.1029/2025EO250252. Published on 16 July 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Industrial whaling was historically a grisly affair enacted with brutal efficiency. With an eye to harpooning as many whales as possible, whalers created detailed records intended to inform and improve future expeditions.

Those records, stretching back more than a century, provide rich datasets that scientists have used to answer questions about our planet’s past, including how sea ice surrounding Antarctica ebbed and flowed in the decades before satellites enabled continuous monitoring.

“I find it a paradox. We decimated them; now, they’re helping us to do a better job for our future projections.”

In a study published earlier this year in Environmental Research: Climate, a team of cetologists, oceanographers, and climate scientists dug deep into those records and used them to show that contemporary climate models overestimate the historic extent of sea ice in the Southern Ocean.

The group relied specifically on data from humpback whaling expeditions because that species tends to skirt along the ice edge in summer, skimming krill fed in turn by algal mats that form along the underside of the ice as it thins and retreats. This behavior makes the locations of humpback harvests a useful proxy for how far north sea ice could have reached.

“I find it a paradox,” said oceanographer Marcello Vichi of the University of Cape Town in South Africa. “We decimated them; now, they’re helping us to do a better job for our future projections.” Vichi is the first author of the new study.

Icy Estimation

Accurately estimating the extent of sea ice is important for modeling because ice reflects sunlight, said Marilyn Raphael, a physical geographer at the University of California, Los Angeles, who often focuses her research on Antarctic sea ice but was not involved with the new study.

“If it doesn’t do that reflection, the large-scale [latitudinal] temperature gradient changes,” Raphael explained, “and when the temperature gradient changes, the wind changes. And when the wind changes, the climate changes.”

Sea ice also insulates parts of the Southern Ocean, limiting how much heat the water absorbs from the atmosphere.

How climate models input the historical extent of sea ice shapes how they account for Earth’s energy balance prior to the onset of climate change. More accurate historic inputs also have implications for modeled predictions about the extent of sea ice in the future.

“If you can’t get it right when you know what happened,” Raphael said, “then you’ve got to worry about if you’ll get it right when you don’t know what will happen.”

Using Catch Data to Constrain Sea Ice

Vichi and his colleagues used data acquired from the International Whaling Commission, which recorded the locations of more than 215,000 humpback catches over the first half of the 20th century, with latitude and longitude logged to the nearest degree.

They focused their study on the 1930s, a period during which whalers logged consistently high catch counts for each month of the Antarctic summer (November through February), when humpbacks feed as ice retreats. This narrowed scope left the researchers with around 13,500 records to work with, of which more than 97% had trustworthy location data.

The team compared the catch locations with the climate models that are best tuned to match today’s satellite observation data.

All the models, they found, consistently overestimate the historic extent of sea ice by an average of about 4° latitude. In some places, Vichi added, they overshoot the ice edge suggested by the whaling records by 10°.

“It’s really great to examine historical data to find ways of understanding a complex system better, especially a complex system that we don’t have a lot of observations on.”

Vichi and his colleagues don’t yet know for certain what drives the discrepancy they found. One possible explanation may be that the nature of how ice forms and behaves in the Southern Ocean has shifted, potentially entering a new regime around the 1960s.

Scientists are working with fewer than 50 years of satellite observations when it comes to sea ice, “so if there are large cycles that happen, we don’t know if that 50 year period is representative of the whole,” said climatologist Ryan Fogt of Ohio University in Athens, who wasn’t involved in the study.

Given the dearth of direct observations, this gap can be filled only with proxies like catch data. Using indirect data is an approach both Raphael and Vichi acknowledge has limitations but is crucial for better understanding the nuances of climate change.

“I think using the whaling records is a good idea,” Raphael said. “It’s important to use all the information we have to see how it matches.”

“It’s really great to examine historical data to find ways of understanding a complex system better, especially a complex system that we don’t have a lot of observations on,” said Fogt, who has also worked with historical records (though not whale catch data) to reconstruct historic sea ice extent around Antarctica. “So even though they’re imperfect, these historical sources, they have value.”

—Syris Valentine (@shapersyris.bsky.social), Science Writer

Citation: Valentine, S. (2025), Whaling records can help improve estimates of sea ice extent, Eos, 106, https://doi.org/10.1029/2025EO250251. Published on 15 July 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

A strange planet orbiting a distant star may be even weirder than we realized. Already thought to have “iron rain” and an unusual polar orbit, this ultrahot Jupiter might also have begun life far away from its star before diving into a tight 30-hour orbit.

The planet, WASP-121b, or Tylos, is about 850 light-years from Earth and was discovered in 2015. Observing the planet in October 2022 with the James Webb Space Telescope (JSWT), researchers found it hosted a surprising amount of methane and silicon monoxide. Their observations mark the first time silicon monoxide has been conclusively found on another world.

“Something weird happened dynamically in its past.”

The presence of methane and silicon monoxide, researchers say, might mean WASP-121b initially formed much farther from its star—as far away as 30 astronomical units, about the same distance Neptune lies from our Sun. (One astronomical unit is the average distance between the Sun and Earth.) The findings were published in Nature Astronomy and The Astronomical Journal.

“Something weird happened dynamically in its past,” said Tom Evans-Soma, an astronomer at the University of Newcastle in Australia and lead author of the Nature paper. “And it may be a big factor in how it moved from far out to close in.”

Iron Rain

Hot Jupiters are a class of gas giant planets that orbit extremely close to their stars and have temperatures exceeding 1,500 K (2,200°F). Ultrahot Jupiters are even closer and hotter, sometimes reaching temperatures above 2,000 K (3,100°F).

WASP-121b is one such ultrahot world, orbiting its star (WASP 121) within 2 times the star’s radius. At this proximity, the planet is tidally locked to the star, the way the Moon is to Earth, so the same face always points to the star. Atmospheric temperatures on WASP-121b can reach more than 3,000 K (4,900°F) on the dayside and 1,100 K (1,500°F) on the nightside.

This discrepancy in temperature may help explain the concept of iron rain on WASP-121b. Metals are likely to vaporize on the fiery dayside, and as these particles blow to the nightside, the drop in temperature creates conditions for droplets of liquid metal to form and fall from the planet’s atmosphere. “The nightside temperatures drop low enough for a whole bunch of these materials to condense,” possibly within seconds, said Evans-Soma.

The planet’s proximity to its star has also stretched the world into an oblong shape, and it orbits its star in a strange 90° orientation, almost pole to pole above and below the star. The planets of our solar system, by comparison, orbit in a flat plane.

A Distant Origin

These characteristics alone had already painted WASP-121b as an unusual world, but the latest observations further add to its mystery.

The researchers used JWST to observe the planet for 40 hours and pick apart its light, revealing the presence of water, carbon monoxide, and silicon monoxide on the dayside. These compounds may have been pulled from the nightside by a powerful equatorial jet with wind speeds of up to 10 kilometers (6 miles) per second.

The team detected methane in the planet’s nightside—a surprising result because methane shouldn’t survive WASP-121b’s high temperatures.

The team also detected methane in the planet’s nightside—a surprising result because methane shouldn’t survive WASP-121b’s high temperatures at all. “People have been looking for methane in exoplanets, but generally focusing on much cooler planets,” said Evans-Soma.

The presence of methane suggests the planet has a source of the compound replenishing its atmospheric supply. The team thinks the source might be trapped methane pulled up from the planet’s interior by strong convection currents.

The presence of methane might also point to WASP-121b forming much farther from its star. At a greater distance, icy pebbles of the methane were more abundant. Here, too, the gas giant may have consumed 21 Earths’ worth of rocky material during its formation, which would explain the presence of silicon.

A Starward Migration

Richard Booth, a planet formation expert at the University of Leeds in the United Kingdom who was not involved in the research, said that in general, scientists think hot Jupiters migrate inward over time. It is unlikely the planets formed close to their stars, he explained, because the stars’ gravity would have been too strong for planets to coalesce.

“Hot Jupiters definitely don’t form in situ,” said Booth.

But finding “evidence for migration is hard,” he continued, because migration can happen quickly (at least on planetary timescales)—in just millions or even thousands of years.

The WASP-121 system is thought to have formed about 1.1 billion years ago, with its migration possibly happening as a result of a gravitational nudge from a passing star or other planets in the system. Such a nudge might also explain the planet’s odd orbit.

Future work could tell us how this seemingly strange exoplanet compares with other ultrahot Jupiters. “It’s not clear that it is particularly unusual,” said Evans-Soma. “It just happens to be one of the planets we can study in really exquisite detail.”

—Jonathan O’Callaghan, Science Writer

Citation: O’Callaghan, J. (2025), This exoplanet may have grown stranger as it journeyed starward, Eos, 106, https://doi.org/10.1029/2025EO250250. Published on 15 July 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

A new paper (Kharismalatri, Gomi & Sidle 2025) in the journal Natural Hazards uses the concepts of the inflow angle and the channel gradient to examine the behaviour of large landslides after failure.

Large landslides in areas with steep terrain that either block the valley or turn into a long runout debris flows are an increasing problem globally as the impacts of climate change accelerate. A key question for any large, potentially unstable slope is whether it will block the valley or transition into a long runout flow. Neither is good, clearly, but the risks and management approaches differ.

There is a very interesting paper (Kharismalatri, Gomi & Sidle 2025) in the journal Natural Hazards that uses a database of 188 large landslides from around the world to examine this issue. The paper has been published open access and using a creative commons licence (hurrah!), so please do take a look.

This diagram, from the paper, explains a key and very interesting metric in the study – the inflow angle:-

Key concepts, including the inflow angle, in the study of large landslides by Kharismalatri, Gomi & Sidle (2025).

There are two key ideas here – one is the inflow angle, which is the angle between the main axis of the landslide and the main axis of the channel, and the other is the channel gradient – the gradient of the river valley into which the landslide is moving, measured using a consistent distance scaled to the landslide length.

The most important diagram in the paper is this one, which shows the inflow angle plotted against channel gradient:-

The relationship between the inflow angle, and the channel gradient , from the study of large landslides by Kharismalatri, Gomi & Sidle (2025).

This is quite remarkable. The inflow angle plays a key controlling role in what happens when the landslide reaches the valley. If that angle is greater than about 60o, the landslide nearly always blocks the valley. If it is less, then it generally turns into a debris flow.

Similarly, if the channel gradient is less than about 10o, the landslide almost always blocks the valley. If it is less, it generally turns into a debris flow.

There are some overlaps, but the number of these cases is remarkably low.

It is also very interesting that there are no cases of landslides with both a high inflow angle and a high channel gradient (i.e. where inflow angle is >60o and channel gradient is >15o). I am not sure why this is the case.

This will be a very useful finding for those who are having to manage developing failures in large slopes. It allows a first order prediction of likely behaviour of the slope upon failure. So, for example, I wrote yesterday about a study of the potential failure of the large landslide at Joshimath in India. It would be interesting to see where on the graph that slope plots – it appears to me that the inflow angle is c.90o?

Reference

Kharismalatri, H.S., Gomi, T. & Sidle, R.C. 2025. Geomorphic thresholds for cascading hazards of debris flows and natural dam formation caused by large landslides. Natural Hazards. https://doi.org/10.1007/s11069-025-07402-0

Return to The Landslide Blog homepage Text © 2023. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Source: Journal of Geophysical Research: Biogeosciences

When sunlight hits clouds or other atmospheric particles, it scatters and becomes diffuse light. Unlike direct sunlight, diffuse light can reach deeper into shaded plant canopies, where plants have dense, layered leaves. The diffuse-light fertilization effect theory suggests that diffuse light in such environments can promote carbon uptake and influence canopy temperature and evapotranspiration. Prior research suggests that some diffuse light can also boost photosynthesis, but after an optimal point, the overall reduction in total radiation will decrease photosynthesis.

However, diffuse light is not typically measured at ground-based sites. Previous studies used indirect methods to infer its effects on plants, including running computer models and measuring atmospheric properties such as clearness. So questions remained about the optimal amount of this filtered sunlight for vegetation.

Since 2017, the National Ecological Observatory Network (NEON) has collected data on diffuse sunlight, evapotranspiration, and other ecological variables across 32 sites in the continental United States, including forests, grasslands, shrubs, and cultivated crops. Schwartz et al. used the NEON dataset combined with satellite records from the Ecosystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) to determine how diffuse sunlight connects to evapotranspiration and net ecosystem exchange, or the carbon exchange between ecosystems and the atmosphere.

Their findings suggested that across NEON sites between 2018 and 2022, evapotranspiration decreased as diffuse radiation increased, and no optimal point was observed, contrary to what previous modeling suggested. Evapotranspiration, the researchers found, may be more strongly affected by available moisture than by either direct or diffuse light.

However, diffuse sunlight did enhance net ecosystem exchange in some locations, including forests and areas with shrub or scrub vegetation. Nineteen of the 32 sites showed a positive net ecosystem exchange response to diffuse light, meaning that more carbon can be absorbed when sunlight is scattered. (Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1029/2025JG008757, 2025)

—Rebecca Owen (@beccapox.bsky.social), Science Writer

Citation: Owen, R. (2025), How plants respond to scattered sunlight, Eos, 106, https://doi.org/10.1029/2025EO250249. Published on 14 July 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Shoppers may use a plastic bag for only a few minutes before tossing it in the trash. Inefficient waste disposal, however, may allow that bag to find its way into streams and, ultimately, coastal ecosystems. There, plastic pollution can imperil marine plants and animals as well as the economic value of beachfront businesses.

“Plastic bags are designed to be single use. They’re designed to be lightweight. Even if we’re trying to properly manage them, they just get into the environment more easily than other plastics,” said Erin Murphy, ocean plastics science and research manager at the Ocean Conservancy.

“These [plastic bag bans] are effective policies, regardless of the scale of governance in which you implement them.”

While many states and municipalities have plastic bag bans or require fees for customers who want a bag, there is no national policy that aims to reduce the number of plastic bags used in the United States.

But a study published last month in Science shows some promising results: In places with bag bans and fees, the number of plastic bags found on local beaches and shorelines has dropped significantly.

“A lot of the time, communities don’t feel like they can implement policy that will directly impact their communities and directly benefit their communities. This study showed that whether it’s a town or state, these [plastic bag bans] are effective policies, regardless of the scale of governance in which you implement them,” said Murphy, who was not involved in the research.

Analyzing the Trash

Study authors Anna Papp and Kimberly Oremus examined data collected from 45,067 shoreline cleanup events between 2016 and 2023. During these events, organized by the Ocean Conservancy, participants collected trash along a beach and logged their findings into the Trash Information and Data for Education and Solutions (TIDES) database.

Plastic bags are the fifth most common item found during these shoreline cleanups, making up 4.5% of all cataloged trash. (Some of the more unusual items logged include golf balls, Mardi Gras beads, and fake nails.)

Papp and Oremus cross-checked the cleanup data with 182 plastic bag policies around the United States that were enacted between 2017 and 2023. The discrepancy between the dates of the cleanup data (starting in 2016) and the policy data (starting a year later) allowed the researchers to use the 2016 data as a control to evaluate how trends in plastic bag litter may have changed in response to local or state-level regulation.

“Comprehensive data on plastics in the environment can be challenging to find, so the cleanup data offered a new way of measuring plastic bag litter in the environment. This, combined with the wide reach of bag policies in the U.S. in recent years, made our study possible,” said Papp, an environmental economist at the Massachusetts Institute of Technology.

A Broad Spectrum of Bans

Across the country, a hodgepodge of legislation exists to manage plastic bag waste, from strict bans (like the ones implemented in New Jersey, where single-use paper bags are also limited), to partial bans (like the ones in California, targeted at large retailers), to required fees (as in Oregon, where retailers must charge at least 5 cents for a thick, presumably reusable plastic bag). In addition to statewide legislation, hundreds of municipalities have their own plastic bag policies.

“During our data collection phase, I was initially surprised by the reach of plastic bag policies. We estimate that now one in every three Americans lives in an area with some bag policy,” said Papp.

Papp and Oremus were able to document the effectiveness of such policies, regardless of their reach. In places where some form of plastic bag legislation exists, data showed a 25%–47% decrease in the proportion of plastic bags recovered in coastline cleanups. Although all policies aimed at reducing plastic bag litter were effective, researchers found that those implemented at the state level correlated most strongly to reducing the amount of plastic bag waste found during beach cleanups.

“In some ways it’s like, well, of course, if you use fewer plastic bags, you’re going to find fewer plastic bags on the beach, but it’s good that [researchers] documented that in a quantitative way,” said Susanne Brander, an ecotoxicologist at Oregon State University who was not involved in the study. “We need those data in order to convince additional lawmakers and agencies to take this seriously and to think not just about plastic bags, but about other single-use items as well.”

—Rebecca Owen (@beccapox.bsky.social), Science Writer

Citation: Owen, R. (2025), Policy success: Fees and bans on plastic bags reduce beach trash, Eos, 106, https://doi.org/10.1029/2025EO250247. Published on 14 July 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

A new paper (Dalal et al. 2025) in the journal Engineering Geology examines movement of a major landslide complex in India. It shows that the slope reactivated in 2018, probably as a result of the loss of vegetation and poor management of water.

Loyal readers will remember a series of posts that I made back in early 2023 regarding accelerated movement of the complex landslide system located beneath the town of Joshimath located in the Himalaya in Uttarakhand, India. At this time, there was a significant increase in the movement rate of the landslide, causing substantial damage to structures within the town.

Joshimath is located at [30.5526, 79.5628]. This is a Google Earth image of the town in 2022. The complex landslides in the area are quite easy to see:-

Google Earth image of the town of Joshimath in northern India.

A very nice paper (Dalal et al. 2025) has been published in the journal Engineering Geology. The authors have used InSAR to examine the long term movement pattern of the landslides – the InSAR data extends back to 2017. In it, they demonstrate that the slope did indeed undergo a phase of rapid movement in early 2023, and they link this to heavy rainfall that occurred in October 2022, which increased the pore water pressure in the slope.

But there are some interesting details in this piece of work. First, the slope actually started to move in 2018, and showed a seasonal pattern of deformation until the rapid movement even in 2023. The authors link this reactivation of the landslide at Joshimath to progressive urbanisation and removal of the vegetation canopy – modelling indicates that the factor of safety of the slope has been notably reduced by this effect. This is quite surprising as the failure at Joshimath is deep-seated, where vegetation does not normall play a major role.

Second, the analysis also highlights that “mismanaged groundwater seepage and blocked drainage paths further exacerbated slope weakening.” This is a common problem in rapidly developing Himalayan communities.

Finally, and most worryingly, Dalal et al. (2025) indicate that the slope could be undergoing progressive failure towards a catastrophic collapse. They have modelled runout scenarios for the slope, which indicate that such an event would threaten the Tapovan Vishnugad hydropower project downstream.

All of this indicates that action is needed at Joshimath. If a large-scale mitigation project is not possible (and I recognise that this would be extremely expensive and very challenging), efforts should be made to manage water (and drainage) across the whole area, and the slope should be monitored in real time.

Reference

Dala, P. et al. 2025. Deformation dynamics and hazard of slow-moving landslides: The 2023 Joshimath event, Uttarakhand Himalaya. Engineering Geology, 354, 108201. Doi: https://doi.org/10.1016/j.enggeo.2025.108201

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Source: Global Biogeochemical Cycles

Whether from a forest on fire or gasoline powering a car, organic matter rarely combusts completely: Remnants such as char and soot can persist in the environment for decades. Over time, as physical and biological processes break down the scorched leftovers, some of the carbon they contain leaches into groundwater, lakes, and rivers, eventually making its way to the ocean.

This carbon, known as dissolved black carbon (DBC), represents the ocean’s largest identified reservoir of stable dissolved organic carbon. Yet the isotopic signature of DBC in the ocean does not match what rivers alone supply. This discrepancy suggests there are one or more unknown sources of DBC entering the ocean that are not accounted for in the global carbon budget.

To address this knowledge gap, Zhao et al. conducted six field surveys along China’s eastern coast, in the Jiulong, Changjiang (Yangtze), and Pearl River estuaries. By gathering samples during all four seasons, the researchers aimed to quantify changes in DBC and shed light on how it moves through coastal ecosystems toward the sea. Prior research focused only on individual estuaries and didn’t always account for how processes may vary across seasons and tide cycles.

The findings from the new study reveal submarine groundwater discharge (SGD) as a likely missing source of DBC. The scientists observed that as seawater pushed into estuaries during flood tides, DBC levels rose. Conversely, when water flowed out of the estuaries during ebb tides, DBC concentrations fell. They suggest that this pattern occurs because the salty ocean water that mixes into the estuaries during flood tides promotes the release of DBC from groundwater into the water column.

The researchers estimate that globally, SGD contributes approximately 20% of the riverine discharge of DBC that enters the ocean each year. Given the role that DBC plays in carbon sequestration and biogeochemical cycling in the ocean, the findings underscore the importance of including estuarine processes in global carbon models. (Global Biogeochemical Cycles, https://doi.org/10.1029/2025GB008532, 2025)

—Aaron Sidder, Science Writer

Citation: Sidder, A. (2025), Tracing black carbon’s journey to the ocean, Eos, 106, https://doi.org/10.1029/2025EO250248. Published on 11 July 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Marine scientist Matthew Mulrennan was piggybacking on a tourist vessel around the Antarctic Peninsula’s coasts, surveying a seabed teeming with life, when his underwater cameras came across a gray seafloor scarred with ridges.

Anchoring had churned up the sediment, leaving lifeless patches strewn with crushed sponges. The damage had narrowly missed three giant volcano sponges, which can live for up to 15,000 years and grow larger than the divers who study them.

“We saw a lot of life on the seafloor and not a lot of regulation around its protection,” said Mulrennan, founder of KOLOSSAL, an ocean exploration and conservation nonprofit in California.

Anchoring churns up the seabed, destroying life and leaving regular furrows, akin to plow marks. Credit: Matt Mulrennan/KOLOSSAL

Mulrennan’s footage, which was released alongside a recent study in Frontiers in Conservation Science, provides evidence that the seafloor impacts of anchoring now extend to remote polar waters.

A Vulnerable Ecosystem

Retreating sea ice is opening Antarctica’s coast to increasing amounts of ship traffic, including tourist cruises. “Most visitors want to see the penguins, seals, and whales,” Mulrennan said, but the seafloor, which is home to 95% of the continent’s biodiversity, “is where the real action is.”

With large areas of the Southern Ocean unexplored, scientists estimate that as many as 17,000 species might live on the seabed.

Colorful life lies on the Antarctic seabed, including the 50-armed death star starfish and the giant volcano sponge, the oldest animal on the planet. Credit: Matt Mulrennan/KOLOSSAL

Many Antarctic species, such as the giant volcano sponge, are uniquely adapted to extreme cold and play an important ecological role, Mulrennan said. “They filter water, sequester carbon, provide food and habitat.”

“These are probably some of the most vulnerable ecosystems to anchor in in the world.”

“These are probably some of the most vulnerable ecosystems to anchor in in the world,” Mulrennan said. Although relatively fast-growing tropical reef communities may start to recover from anchoring in roughly a decade or so, “it could take hundreds or potentially thousands of years for Antarctic ecosystems to grow in the exact same way,” he said.

Mulrennan surveyed 36 sites around the Antarctic Peninsula between 2022 and 2023, finding anchor damage only at Yankee Harbour on Greenwich Island.

He showed the footage to Sally Watson, a geophysicist at Earth Sciences New Zealand and a study coauthor, who matched the characteristically uniform, curved gouges to anchor damage observed elsewhere.

Anchors can dig through 80 centimeters of sediment, but most damage is caused by the connected chain, which sweeps sideways because of winds and currents and can excavate 50 centimeters of sediment where it lies on the seafloor. From above, the scars resemble a broomstick, explained Watson, composed of one main scour stemming from the anchor connected to a series of branching gouges dug as the chain shifts in the sediment.

“Most of the really important life is within the uppermost 10 centimeters,” Watson said. “Anchoring blasts through that.”

In 2022, Watson and her colleagues published the first estimate of anchoring’s global footprint, putting its damage on par with bottom trawling.

Anchors and Icebergs

Anchoring isn’t the only thing churning up the Antarctic seafloor. Icebergs can drift into shallow water and drag along the seabed—causing well-documented impacts around the Antarctic Peninsula’s coastline, said Lloyd Peck, a marine biologist from the British Antarctic Survey who was not involved in the study.

Diver surveys show that iceberg scouring can destroy up to 99% of life on the shallow seabed. Regularly uprooted by icebergs, shallow-living species recover relatively quickly, in around a decade.

Waters deeper than 30 meters are struck less often, Peck said, allowing complex, slow-growing organisms to establish themselves. The slow growth also means these deeper areas take longer to recover.

At Yankee Harbour, Mulrennan observed the scours in waters 70 meters in depth, so he is confident they were caused by anchoring rather than by icebergs. Peck agreed, noting the large, slow-growing volcano sponges nearby. “That suggests the iceberg scouring is going to be very rare here,” he explained.

“Activities in Antarctica are bound by strict conservation rules, yet ship anchoring goes almost completely unregulated.”

Peck said that compared to iceberg scouring, anchoring will have a minor imprint across the Antarctic Peninsula. But the location of an anchoring impact is as important as its scope, he noted. “This is about disrupting sheltered areas that icebergs can’t reach.”

Species-rich areas in deeper waters, such as Yankee Harbour, could be acting as refugia, Peck explained, reseeding surrounding areas with life after they are scoured by icebergs. To avoid wider ecosystem impacts, he said, “we should be making every effort to avoid anchoring in areas of undisturbed biodiversity.”

In addition to tourist cruises, research vessels, shipping fleets, and private yachts operate in Antarctic waters. “Activities in Antarctica are bound by strict conservation rules” for all visitors, Mulrennan said, “yet ship anchoring goes almost completely unregulated.”

Watson and Mulrennan have several suggestions to mitigate anchoring impacts, including limiting time vessels spend on anchor and the use of designated anchorages, where ecological impact can be monitored and limited.

Above all, anchoring needs wider recognition as a conservation concern, not just in Antarctica but globally, Watson said. “I think we could do better, by changing the way we anchor, the gear we use, but at least understanding that this is not a no-consequences game.”

—Erin Martin-Jones, Science Writer

Citation: Martin-Jones, E. (2025), Anchoring is damaging the fragile Antarctic seabed, Eos, 106, https://doi.org/10.1029/2025EO250246. Published on 11 July 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Mud volcanoes may be less imposing and less familiar than their distant cousins, lava volcanoes, but they come with hazards of their own, and their presence can signal hidden geologic processes shaping a landscape.

A team of geologists has now made a global map of submarine mud volcanoes, which they hope will help further the understanding of these little-known landforms. The study, published earlier this year in Scientific Data, mapped more than a thousand mud volcanoes in shallow seas. A million more may sit undiscovered deep in the world’s oceans.

No one had put all the mapped mud volcanoes in a single dataset until now, said study author Daniele Spatola, a marine geologist at Sapienza Università di Roma. Patterns that Spatola and his colleagues spotted in the dataset were published in another study appearing in the Journal of Marine Science and Engineering.

Hazards and Emissions

Mud volcanoes erupt when the pressure of gas trapped in rock becomes so strong that the rock is not able to hold it anymore, Spatola explained. Instead of lava, mud volcanoes spew a mix of gas, sediment, dissolved minerals, organic matter, water, and other fluids.

Fields of mud volcanoes are found in different geologic settings around the world, including in oil and gas fields, above mantle hot spots, near active faults, and at the edge of tectonic plates. Their presence and activity can give scientists important clues about tectonic and volcanic activity, said Nils Asp, a marine geologist at the Universidade Federal do Pará in northern Brazil who was not involved in the research.

“Mud volcanoes can be really dangerous.”

The unstable ground mud volcanoes create can put oil rigs, telecom cables, and other subsurface infrastructure at risk. “Mud volcanoes can be really dangerous,” Spatola said, particularly those on land.

They are also a not-insignificant source of methane and can also spew oxide-rich material and gases like carbon dioxide. “Carbon balances and climate models don’t take these emissions into account, and locally, they can be a problem in terms of increasing water acidity,” Asp said.

Having a global inventory of what submarine mud volcanoes look like and where they occur could help scientists estimate how much methane is bubbling through these vents and reveal where hazards lie.

Digging Through Records

Spatola and his colleagues gathered data from earlier published studies for roughly 1,100 submarine mud volcanoes—the majority in water no deeper than about 200 meters (650 feet). For 700 of them, the researchers either had full size, shape, and location information or had location information and were able to estimate geometry.

From these data, Spatola’s team created a freely available and downloadable database.

Most of the mud volcanoes in the database (65%) are located in the Mediterranean Sea. This distribution may reflect sampling bias, according to the authors. Areas in the eastern Mediterranean are often prospected for oil and gas, for example, and had more data available for the researchers to mine.

Other regions are less well mapped. “Probably, the number of mud volcanoes in the Atlantic is higher than what [appears in] the database, for example,” Spatola said.

Roughly 60% of mud volcanoes in the database are medium sized, with an area of 0.5–9 square kilometers. Small (<0.5 square kilometer) and large (>9 square kilometers) volcanoes together make up less than a third of the mapped volcanoes.

Giant mud volcanoes (defined as those covering an area larger than 20 square kilometers) are the rarest features in the database, making up about 4.5% of the mapped and classified total. Most of the very large or giant mud volcanoes are found in an area southeast of Japan where the Pacific and Philippine tectonic plates meet.

An initial analysis of the database showed that the more small-sized volcanoes a region has, the fewer large or giant volcanoes there are. This kind of pattern, known as a power law, is recognizable in many geologic processes, including earthquake distribution. The researchers also found that the size of a mud volcano is not necessarily related to how deep it sits below the sea surface.

The database could help inform regional health and safety measures, the study suggests, as the morphology of a mud volcano influences its geohazard potential. Tall and narrow volcanoes, for instance, are the most hazardous because they are more prone to instability.

Deep Challenges

Asp said that the database is “a solid starting point to be extended upon in further studies.”

Researchers don’t know how many submarine mud volcanoes there are because only a small portion of the ocean floor has been mapped.

“We need the help of the scientific community to improve this dataset. The more information we put into it, the better it will be.”

“In many areas, there might be a dozen kilometers of distance between one mapped stretch and another,” Asp said. “So we have no information of what is in that [unmapped] part of the seafloor.”

Some satellite imagery can penetrate a few dozen meters below the surface but not the deep ocean floor. To look that deep, marine researchers need ships capable of bathymetric mapping, but such instrumentation, including sonar and lidar equipment, is often prohibitively expensive.

The new study is a first attempt to create a database of submarine mud volcanoes, one that can be refined as more data are contributed. “We need the help of the scientific community to improve this dataset,” said Spatola. “The more information we put into it, the better it will be.”

—Meghie Rodrigues (@meghier.bsky.social), Science Writer

Citation: Rodrigues, M. (2025), Mapping mud volcanoes in shallow seas, Eos, 106, https://doi.org/10.1029/2025EO250245. Published on 10 July 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Perspectives of Earth and Space Scientists

Our modern society is increasingly reliant on multiple technologies that are vulnerable to the adverse effects of space weather. This necessitates effective public communication and awareness of various space weather phenomena as well as increased public engagement and preparedness for risk mitigation.

Chabanski et al. [2025] advocate for the development and implementation of a standardized naming convention of geomagnetic storms, along the lines of existing naming conventions in meteorology, astronomy, and geography.

The authors surveyed the top 50 geomagnetic storms over the past 47 years (since 1978), of which only five had names assigned by the scientific community. Drawing on lessons learned in other scientific disciplines, they propose the possible formation of an international working team comprised of International Space Weather Coordination Forum participants. This international team would implement a theoretical framework and a unified international standard for defining the criteria, protocols, and procedures for naming and cataloguing geomagnetic storms based on their minimum Disturbance Storm Time (Dst) indices and their solar origins.

This proposed initiative is about not only assigning names to geomagnetic storms but also empowering the public with the knowledge necessary to navigate the challenges of the 21st-century space environment.

Citation: Chabanski, S., de Montety, F., Lilensten, J., Poedts, S., & Spogli, L. (2025). The power of a name: Toward a unified approach to naming space weather events. Perspectives of Earth and Space Scientists, 6, e2025CN000285. https://doi.org/10.1029/2025CN000285

—Andrew Yau, Editor, Perspectives of Earth and Space Scientists

Text © 2025. The authors. CC BY-NC-ND 3.0
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The Independent Review Board has released its report into a 6 million cubic metre landslide in Canada. It indicates that an initial rotational failure triggered a flow slide that travelled 1,400 metres.

On 24 June 2024, a very large landslide affected a heap leach facility (HLF) at the Eagle Gold Mine in Yukon, Canada. I wrote about this event at the time. The failure was of sufficient scale to force the mine into administration – creating a very big pile of problems (if you’ll excuse the pun) for the government. The administrator is PWC, which has now released a report by the Independent Review Board established to understand what happened. The report can be downloaded as a PDF and makes interesting reading. As expected, it is a comprehensive piece of work.

This was a large landslide – the IRB report indicates a volume of 5,946,000 m3 (about 12.3 million tonnes) with a runout distance of 1,400 m. The report includes some nice imagery of the failure, including this picture of the main body of the landslide:-

Figure 1: The main flow slide at the Eagle Gold Mine. Image from the IRB report.

Also included is this image of the upper portions of the landslide:-

Figure 2: The upper portions of the landslide at the Eagle Gold Mine. Image from the IRB report.

The IRB report provides a detailed understanding of the sequence of events that led to the failure. In creating the HLF, the operators created an oversteepened section of ore (locally the slope angle as 36.5o), which was vulnerable to failure. The system for collecting the fluids that were being circulated through the HLF was deficient, allowing the water table to rise within the ore body, and this section of the HLF had low permeability, impeding drainage. Starting in mid-April, the operator increased the level of irrigation within the HLF, allowing the water table to rise until the factor of safety reduced to one.

On 24 June 2024, a rotational failure occurred in the oversteepened section of the HLF at the Eagle Gold Mine. This can be clearly seen in Figure 1. This was a rotational failure which remained within the HLF – see the intact benches in Figure 2.

Within 10 seconds, this triggered a flow slide through static liquefaction, which rapidly moved down the slope (as shown in Figure 2). In Appendix A2, it is estimated that the landslide moved at 9 to 18 metres per second, suggesting that the total time duration of the failure was 1.5 to 2.5 minutes.

I speculated at the time that this was a rotational failure that transitioned into a flowslide.

The IRB report into the Eagle Gold Mine landslide makes a series of recommendations (see page 123 and the following pages). These seem sensible – I can only hope that they are adopted. There has been a long succession of investigations into mining landslides that have also made very sensible recommendations, but failures continue to occur.

But, I would also highlight from an external perspective that some of these recommendations seem surprising. Thus, for example, the IRB recommends that the such facilities should have independent review boards; that a single individual (a “Responsible Person”) should be in place to monitor on-site activities; that there should be a detailed monitoring and surveillance system in in place to ensure that design assumptions are correctly satisfied; and that there should be active monitoring of the performance of the HLF.

All very sensible indeed, and it is impossible to disagree, but it is deeply shocking that such recommendations are needed for a large-scale mining facility in a properly regulated country with very extensive experience of mining.

Return to The Landslide Blog homepage Text © 2023. The authors. CC BY-NC-ND 3.0
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