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Publication date: Available online 19 November 2025

Source: Advances in Space Research

Author(s): Rouhe Zhang, Kang Wang, Xinran Duan, Zheng Chen

Publication date: Available online 19 November 2025

Source: Advances in Space Research

Author(s): Kimiya Masjed Jamei, A. Mahmoudian

Successive major droughts, each lasting longer than 85 years, were likely a key factor in the eventual fall of the Indus Valley Civilization, according to a paper published in Communications Earth & Environment. The findings may help explain why this major ancient civilization—a contemporary of ancient Egypt located around the modern India-Pakistan border—slowly declined, and highlights how environmental factors could shape ancient societies.

A satellite deployed to measure ocean surface heights was up to the challenge when a massive earthquake off the Kamchatka Peninsula triggered a Pacific-wide tsunami in late July.

Shallow seas serve as critical transition zones connecting land and the deep ocean, supplying essential resources for navigation, fisheries, energy exploration, and island reef development. Accurate bathymetric data form the foundation for marine engineering, channel safety, resource assessment, and ecological restoration. However, nearly 50% of global shallow-water areas still lack reliable depth information, creating a major barrier to coastal management and sustainable ocean development.

SummaryThe estimation of topographic gravity field models has attracted significant interest in recent years due to its growing relevance in Earth sciences. In this study, we present a robust methodology for the computation and comprehensive validation of global, complete spherical Bouguer and isostatic gravity anomalies that are essential for accurately interpreting subsurface mass distributions therefore geological structures. We synthesize these crucial gravitational functionals by leveraging spherical harmonic coefficients from high-resolution global gravity field models and various topographic/topographic-isostatic gravity field models. Our findings underscore the critical role of comprehensive terrain corrections in deriving physically meaningful, complete Bouguer gravity fields. The calculated global anomalies demonstrate strong coherence with established benchmark datasets, such as the World Gravity Map 2012. Residual differences are primarily attributed to variations in input Digital Terrain Models. Comparisons with regional Bouguer datasets reveal systematic biases that are largely explained by differing terrain correction methodologies. After removing this effect, there is a high level of consistency between the calculated global and published regional datasets, highlighting the utility of our global solutions, particularly in regions with sparse terrestrial data. Furthermore, the globally computed isostatic gravity anomalies exhibit significant agreement with both external global and diverse regional datasets, notably without the large systematic biases observed in Bouguer comparisons. This agreement reflects the effectiveness of the combined topographic and isostatic corrections in capturing Earth’s mass balance. This research provides valuable tools for new studies in the geoscience community by offering globally consistent and complete Bouguer and isostatic gravity field anomalies that have been rigorously validated for the ICGEM service.

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.

The U.S. Environmental Protection Agency moved this week to reduce limits on fine particulate air pollution, including soot, set by the Biden administration last year. 

The administration gave up defense of a rule which lowered the standard for air pollution particles measuring less than 2.5 micrometers in diameter, also known as PM2.5. The rule, which would have been fully implemented in 2032, took the standard from 12 micrograms of PM2.5 per cubic meter of air to 9. Such tiny particles, which come from vehicle exhaust, factories, and power plants, are especially harmful to human health because they can infiltrate the lungs and the bloodstream. 

In 2024, EPA estimated the 9-microgram standard could prevent up to 4,500 premature deaths, 2,000 hospital visits, and 800,000 cases of asthma per year. 

“An abundance of scientific evidence shows that going back to the previous standard would fail to provide the level of protection for public health required under the Clean Air Act.”

On 24 November, EPA asked the U.S. Court of Appeals for the D.C. Circuit to strike down the new standard, abandoning its defense against industry trade associations and attorneys general from conservative states that had sued Biden’s EPA over the rule.

In the court filing, EPA took the side of its challengers, stating the rule was created “without the rigorous, stepwise process that Congress required.”

“EPA now confesses error,” the filing said. Though the 9-microgram standard remains in effect currently, the EPA proposed in its filing that the standard revert to the 12-microgram rule finalized in 2020.

Environmental groups said the action undermines the agency’s obligations under the Clean Air Act. “EPA’s motion is a blatant attempt to avoid legal requirements for a rollback, in this case for one of the most impactful actions the agency has taken in recent years to protect public health,” Hayden Hashimoto, an attorney for the Clean Air Task Force, a nonprofit, told AP. “An abundance of scientific evidence shows that going back to the previous standard would fail to provide the level of protection for public health required under the Clean Air Act.”

Particulate air pollution disproportionately affects Black communities and other communities of color, as well as low-income groups. One 2018 study found that people living in poverty were exposed to 35% more PM2.5 than the overall population, and Black people were exposed to 54% higher amounts.

 
Related

•  EPA to Abandon Air Pollution Rule That Would Prevent Thousands of U.S. Deaths
•  Trump EPA Moves to Abandon Rule That Sets Tough Standards for Deadly Soot Pollution
•  EPA: Health and Environmental Effects of Particulate Matter (PM)
• Some Communities Feel the Effects of Air Pollution More Than Others
•  Get Involved: AGU Science Policy Action Center

In April, a coalition of public health and community groups wrote a letter to EPA Administrator Lee Zeldin asking him to quickly implement the strengthened standard. “There is no legally viable basis for weakening it,” they wrote.

“Our communities already carry the burden of polluted air and higher rates of asthma and heart disease. Weakening soot protections will only deepen these disparities and cost more Black lives,” Yvonka Hall, executive director of the Northeast Ohio Black Health Coalition, one of the groups that signed the letter, said in a statement.

The move to vacate defense of the rule is part of a broader rollback of regulations on industrial facilities by the EPA. Earlier this year, the agency proposed repealing requirements for polluting facilities to report their greenhouse gas emissions. The EPA is expected to propose its own PM2.5 rule early next year.

—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
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

An international research team has shown that avalanches are crucial to the survival of many glaciers worldwide. The study aims to contribute to better predictions of water resources and natural hazards in the context of global warming.

It's safe to say Rhode Islanders have a symbiotic relationship with Narragansett Bay.

In Antarctica, beneath the ice, there is liquid water—and potentially a lot of it. That’s the takeaway from new research that used seismographic instruments to probe the still largely unstudied boundary between Antarctica’s bedrock and its ice sheet.

Previous hydrological studies and modeling work have found evidence of lakes and rivers beneath the Antarctic Ice Sheet, though much remains unknown about the region.

Now, using an array of seismic sensors, researchers from Stony Brook University have added more data points to the map of subglacial Antarctica, finding evidence of a layer of water-saturated sediments or rock under the ice. That layer could have implications for models of Antarctic groundwater systems, as well as for future movements of the ice sheet as it slides toward the ocean.

Looking Beneath the Ice with Earthquakes

The data, which will be presented at AGU’s 2025 Annual Meeting, come from an array of more than 600 seismic sensors strung in two long lines totaling about 600 kilometers near the South Pole, put there over the course of two field seasons in Antarctica. The sensors listen for seismic waves that travel through the upper layers of Earth and into the ice sheet.

Those waves carry the signatures of every medium through which they’ve traveled, said Weisen Shen, a geoscientist at Stony Brook University and a paper coauthor. To isolate that information, the researchers applied a mathematical technique called a receiver function to remove the waves’ source information, leaving only the signatures of what they moved through on their journey to the sensor.

In their data from beneath the South Pole, in a region known as the Pensacola-Pole Basin, the researchers found a very low velocity layer, where seismic waves travel too slowly for the conducting medium to be bedrock or ice.

While the authors can’t say exactly what this layer looks like, Shen said the best explanation is a layer of water-saturated sediments or sandstone, likely hundreds of meters thick.

“Anything we can do to try and enhance our knowledge of what’s going on…is just going to help us try and narrow down this really bizarre landscape underneath the ice.”

“We believe…there must be some aquifer system, a groundwater system, that must be preserved beneath the ice,” he said.

The water there could even be connected to groundwater elsewhere in Antarctica, Shen noted. If so, water might be moving around beneath the surface of Antarctica through hydrologically linked basins, and perhaps even out to the ocean.

That scenario could have implications for sea level rise, but, as University of Waterloo glaciologist Christine Dow pointed out, we know far too little to say for sure. In her own modeling, Dow, who wasn’t affiliated with the research, said it appears these basins aren’t connected to the ocean.

“But these are models based on our current knowledge of where’s frozen and where’s not under the Antarctic,” she said. “Perhaps this new information will change that.”

Dow welcomed new data on the mostly uncharted landscape of subglacial Antarctica, where scientists have evidence of lakes, rivers, and groundwater interacting in complex ways, but little hard evidence of the continent’s topography.

“Anything we can do to try and enhance our knowledge of what’s going on…is just going to help us try and narrow down this really bizarre landscape underneath the ice,” she said.

More Questions Than Answers

One question the new data raise is where the heat energy needed to melt the water comes from, noted Hanxiao Wu, a Ph.D. candidate at Stony Brook University and the paper’s first author. It could come from geothermal heat from below, friction caused by the movement of ice at the surface, or some combination of both.

One takeaway from the research is that estimates of geothermal heat flux below Antarctica may need to be bumped upward, Dow said. Models of ice sheet movement and evolution may also need to change to accommodate hundreds of meters of water-saturated sediments. “That’s a game changer,” Dow said.

Should there turn out to be more water beneath Antarctica than previously thought, and should that water move greater distances and in greater amounts, sea levels could rise beyond current predictions, Shen said. It’s too early, however, to estimate any of these probabilities with much certainty, he cautioned.

Right now, Shen and his fellow researchers are focused on improving their dataset and seeking collaborations with other geophysicists to map out the implications of their findings. Wu traveled back to Antarctica for the 2025–2026 field season, where the team is adding another line of seismic sensors to increase coverage and working on tracking the array to better understand changes in snow surface elevation.

In the future, they hope to add additional data from satellites, magnetotelluric surveys, and fiber-optic cables for a more comprehensive look at the ice pack and its underbelly, perhaps as part of the 5th International Polar Year in 2032.

What the scientists will find is unknown. But with millions of square miles of land underneath the ice, the potential for discovery is appropriately vast.

—Nathaniel Scharping (@nathanielscharp), Science Writer

Citation: Scharping, N. (2025), The land beneath Antarctica’s ice might be full of water, Eos, 105, https://doi.org/10.1029/2025EO250435. Published on 26 November 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.

Powerful summertime thunderstorms are injecting particulate matter from wildfires and additional moisture into the stratosphere—a layer of the atmosphere scientists have long thought was mostly pristine.

“The lower stratosphere almost looked more like a smoke cloud.”

A new study, published in Nature Geoscience, detailed these findings, which could have implications for Earth’s ozone layer and atmospheric circulation, especially as the climate continues to warm.

“We as atmospheric scientists have this preconceived notion that [the stratosphere] is a really stable, clean area of our atmosphere. We don’t think about it being perturbed all that often,” said Dan Cziczo, an atmospheric scientist at Purdue University and a coauthor of the new study. 

But in the new observations, “the lower stratosphere almost looked more like a smoke cloud,” he said.

Stratospheric Science

North America’s monsoon season starts when warm, moisture-laden air from the Gulf of Mexico collides with the Rocky Mountains. This process can create powerful summer storms familiar to those living in the U.S. Midwest.

If those storms get powerful enough, some clouds “overshoot,” or extend multiple kilometers above the troposphere and into the stratosphere—a cold, thin layer of Earth’s atmosphere beginning at about 12,000 meters (39,000 feet) above sea level.

This overshoot happens often in the United States: There are about 50,000–100,000 overshooting storms each summer, though some last only a minute or two, said Ken Bowman, an atmospheric scientist at Texas A&M University and a coauthor of the new study. 

Bowman is the lead scientist of a 6-year project called Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) that is investigating these overshooting storms. 

To study overshooting storms, DCOTSS researchers use a unique aircraft called Earth Resources 2, or ER-2, which was built by NASA and flies as high as 22,860 meters (75,000 feet)—higher than 95% of the Earth’s atmosphere. Cziczo and his team used DCOTSS data from 31 May to 27 June 2022, an active fire season in the United States, for their new study. The data came from flights over the U.S. Midwest and Great Plains that specifically targeted overshooting storms. 

Their observations showed an unexpected amount of biomass-burning particles in the lower stratosphere during periods affected by overshooting clouds.

“Once we got the aircraft into the stratosphere, we just found it to be littered with these biomass-burning particles, particles from wildfires,” Cziczo said. There had been previous evidence from flights in 2002 that biomass-burning particles existed in the stratosphere, but not to this extent—Cziczo and his team found particles as high as 4 kilometers into the stratosphere, about 4 times higher than previous detection.

The new study “is really the first time people have seen a really large contribution from smoke in the lower stratosphere,” said Brian Toon, an atmospheric scientist at the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder who was not involved in the new study. 

“When you add lots of water vapor, it changes a lot of things.”

Cziczo explained that powerful storm clouds pick up smoke, either directly from burning areas or from smoke already mixed into the troposphere, then “spit” that smoke out into the stratosphere after clouds build up and cross the boundary between the two layers. Virtually all the observed biomass-burning particles were probably transported by overshooting storms, as there are no other likely mechanisms for the particles to enter the stratosphere, Bowman said.

The particles the team observed in the lower 4 kilometers of the stratosphere will likely stay suspended there for months.

The researchers didn’t have a way to track exactly where the particles they observed originated. But wildfires across the United States and Canada in the summer of 2022 were a likely source: “We just have to sort of infer that it was the smoke that was in the Midwest,” Cziczo said.

In addition to the biomass-burning particles, the overshooting storms brought a lot of moisture to the stratosphere. As the ER-2 aircraft flew through overshooting clouds, instruments on board detected additional water, sometimes taking the stratosphere’s usual 4 or 5 parts per million of water up to 20 or 30 parts per million. 

Such an influx of water can affect the chemistry, heating, and cooling of the stratosphere, but more research is needed to figure out exactly how. “When you add lots of water vapor, it changes a lot of things,” Bowman said.

Atmospheric Alterations

The combined forces of stronger storms and more wildfires could make the occurrence of these sooty particles in the stratosphere more likely as the climate continues to warm. 

Additional biomass-burning particles in the stratosphere could have consequences for Earth’s ozone layer. Particles provide additional surface area for the stratosphere’s gas molecules to stick to, encounter other gas particles, and react. Many of these reactions over time can damage the ozone layer, a shield of ozone molecules that protects Earth from too much ultraviolet radiation from the Sun.

“It’s important to make sure we understand this so that we can see what might happen in the future.”

“This is not a paper to panic about,” Bowman said. “But as the number of wildfires increases, which it’s likely to continue doing, we’ll get more biomass-burning particles in the stratosphere. And as the climate warms up, it’s likely that the amount of overshooting convection is going to increase, so that’s going to put more material into the stratosphere.”

The findings also raise numerous questions about how additional particles in the stratosphere might affect Earth’s other atmospheric processes. Additional dark, sooty particles could heat the atmosphere, which could change its dynamics or even blur the typically stark boundary between the troposphere and the stratosphere.

“It’s important to make sure we understand this so that we can see what might happen in the future,” Bowman said.

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

Citation: van Deelen, G. (2025), Some summer storms spit sooty particles into the stratosphere, Eos, 106, https://doi.org/10.1029/2025EO250443. Published on 26 November 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.

Canada has a marine coastline twice as long as any other country and shares four Great Lakes with the United States. A new report warns that without coordinated planning, coastal communities face increasing flooding and erosion as climate change accelerates.

SummaryDestabilization of volcanic edifices can generate debris avalanches with catastrophic impacts on their environment. We present the first high-resolution muography of Mount Unzen, Japan, conducted to characterize the structure of lava lobes formed on the volcano’s summit and flank during the 1990-1995 eruption. A multi-wire-proportional-chamber-based muon tracking system was operated for 203 days. The obtained high-resolution muographic image shows the internal density structure of Mount Unzen with a spatial resolution of 12 meters. Mean densities were respectively measured as 2,470 kg m−3 and 2,290 kg m−3 for the base rock and a fracture zone, and both were consistent with the results of prior drilling and sampling experiments. The mean density of lava lobes was measured significantly lower value of 1,570 kg m−3, indicating post-eruptive structural weakening. A comparison between the time-series of muographically measured density-lengths and daily precipitation records suggest that rainfall-induced gravitational destabilization did not occur during the observational period. This work demonstrates that long-term (multi-year) muon monitoring of the lava lobes can provide valuable complementary information for volcanic stability assessments.

SummaryThe asthenosphere is a weak layer in the upper mantle that supports the movement of the overriding tectonic plates and facilitates mantle convection. In this study, we compile a global dataset of SS precursors reflected at the base of the asthenosphere, also known as the 220-km discontinuity. The global dataset includes the oceanic SS precursors from Sun & Zhou (2025a) and new measurements with bounce points in continental regions. Similar to the oceanic dataset, the continental SS precursors are observed on about 45% of the SS waves, with bounce points distributed across all tectonic regions — from orogeny belts to stable cratons. We image the depth of the discontinuity at a global scale using finite-frequency tomography. In oceanic regions, the depth of the 220-km discontinuity agree well with the previous study, with discontinuity depth structure characterized by alternating linear bands of shallow and deep anomalies that roughly follow seafloor age contours. In continental regions, the variations are not spatially oscillatory but are instead much broader, with prominent perturbations associated with convergent plate boundaries. The base of the asthenosphere is shallow along the southern border of the Eurasian plate, from the Mediterranean region to Southeast Asia. Shallow discontinuity anomalies are also observed in the continental interiors – in Eurasia, from the northern Tian Shan through Mongolia to eastern Siberia, and in North America east of the Rocky Mountains. These anomalies form a linear structure roughly parallel to the Pacific subduction zones. The average depth of the discontinuity, as well as the velocity contrast across the interface, is globally consistent across both oceans and continents, with an average depth of approximately 251 km and a velocity increase of about 7%. Given that the continental lithosphere has been cooling for much longer than the oceanic lithosphere, the observed consistency in the average depth of the discontinuity implies that secular cooling does not significantly impact the thermal structure at the base of the asthenosphere.

SummaryA very frequent approach for studying lithospheric processes is to deploy temporary seismological networks in dedicated areas and to map the mantle structures with different approaches. One of them is the well-established relative travel time body wave tomography. Different circumstances often lead to a non-uniform deployment of stations both in space and time, and a wish to combine data which have been acquired asynchronously. This is the situation in Patagonia where two distinct seismic experiments provide complementary seismic data over the region covering the Patagonia slab window. Combining these data in one regional relative body wave tomography is however problematic as the two data sets are a priori with respect to two different reference models. In this contribution, we show that the number of finite-frequency relative travel time residuals varies very strongly from station to station for this data set, violating the assumption implicit in relative travel time tomography of a unique reference model due to an even data distribution for all events. We demonstrate the superiority of the inversion using relative sensitivity kernels compared with a traditional approach with absolute kernels and event terms. A resolution test proves how this is crucial for resolving the important issue of the eastern extent of the slab window. In addition, we discuss potential issues related to interference of the direct phases with core phases when measuring finite-frequency travel time residuals by cross-correlation of waveforms in necessarily relatively large time windows. We also briefly outline our preferred strategy for performing crustal correction, keeping in mind that finite-frequency residuals require frequency-dependent crustal corrections.

SummaryP-wave receiver functions (RFs), which utilize P-wave conversions to probe subsurface structures, face significant challenges in sedimentary environments. Specifically, strong reverberations generated by ultra-low-velocity sedimentary layers distort RF waveforms and obscure crustal signals, posing challenges for robust shallow crustal imaging. We develop a novel Bayesian joint inversion framework that simultaneously utilizes three complementary datasets—reverberant receiver functions, dereverberated receiver functions, and surface wave dispersion—to address this challenge. Our approach employs Unscented Kalman Inversion, a derivative-free method that efficiently handles nonlinear joint inversion problems. Synthetic tests demonstrate that our joint inversion recovers sediment thickness and Moho depth with uncertainties of ±0.50 km and ±1.0 km, respectively. Application to real data from the Songliao Basin verifies the approach, successfully reconstructing sediment thickness and Moho depth beneath sedimentary cover. This methodology demonstrates potential for advancing crustal investigations in complex sedimentary settings, such as continental rift basins and oceanic margins, where sedimentary sequences of variable thickness often obscure deeper structures.

The next global volcanic disaster is more likely to come from volcanoes that appear dormant and are barely monitored than from the likes of famous volcanoes such as Etna in Sicily or Yellowstone in the US.

Publication date: Available online 19 November 2025

Source: Advances in Space Research

Author(s): Stephen Catsamas, Sarah Caddy, Michele Trenti, Benjamin Metha, Simon Barraclough, Robert Mearns, Airlie Chapman, Rachel Webster

Publication date: Available online 19 November 2025

Source: Advances in Space Research

Author(s): Xing-han Liu, Ming Zhu, Yi-fei Zhang, Tian Chen

Publication date: Available online 19 November 2025

Source: Advances in Space Research

Author(s): Saoussen Djeddi, Tarek Bentahar, Riad Saidi, Yacine Belhocine