EOS

Mangroves are a critical component of many coastal ecosystems, serving as havens for biodiversity, carbon sinks, barriers against storm-driven winds and waves, and bulwarks against erosion. But increasing levels of erosion from sea level rise, lack of freezing, higher-intensity storms, and land development are threatening these vulnerable, valuable ecosystems. The problem is especially poignant in Louisiana, which is losing land to the sea faster than any other state.

New research has found that sand made from recycled glass could help restore coastal mangrove ecosystems near New Orleans, serving as a growing medium for new mangroves and replenishing sediment that has washed away.

“New Orleans is a city of festivals,” said Kathryn Fronabarger, an ecologist and environmental compliance specialist at Tulane University in New Orleans and a researcher on the project. “There is a ton of glass waste in the city—glass beads, glass bottles.”

“At one point, a glass bottle was just thrown on the ground, trashed, discarded, put in a landfill,” Fronabarger said. “Now we’re seeing it used as a substrate in multiple states across the United States to build back parishes, build back communities.”

“When we hold those places together,” she added, “we preserve irreplaceable cultures and identities.”

Reuse, Recycle, Restore

Louisiana has the fastest rate of land loss in the United States, losing 28 square kilometers of coastal wetlands per year. That’s the same as losing an American football field’s worth of land every 100 minutes. Climate change is intensifying storms, and the barrier islands that had softened the storms’ impacts have disappeared under rising seas. This loss of protection has sped up coastal erosion.

“It’s absolutely a positive feedback loop, and if anything, it’s an exponential one,” Fronabarger said. The more land that erodes, the more that is exposed to future erosion. And while mangrove roots are great at trapping and retaining sediment, there still has to be sediment in which they can grow.

“Sediment is running out. Eventually, the solution collapses in on of itself.”

Although local and regional efforts have sought to create artificial reefs and barrier islands to prevent coastal erosion, no statewide programs have truly been effective at holding back the tides.

What’s more, the most common method of restoring eroded coastline, dredging riverbeds and transporting that sediment to the coast, damages river ecosystems, may not be suitable for growing mangroves, and is not sustainable in the long run.

“Sediment is running out,” Fronabarger said. “Eventually, the solution collapses in on of itself.”

Seeking an alternate approach to restoring coastal mangrove ecosystems, Fronabarger’s team looked into whether glass that had been ground down to its original form—that is, sand—could sustain mangrove growth.

The team collected 15–20 black mangrove propagules each from 15 parent plants in Grand Isle in 2023. They transported the propagules to a greenhouse and planted them in three different substrates: sediment dredged from the Mississippi River, recycled glass sand, and a 50:50 blend of both. Some plants were inoculated against fungal growth while others were not.

“I was never so happy to see a null in my life.”

The results surprised the researchers. They found that mangroves grown in glass sand developed the same amount of biomass as those grown in both the dredged sediment and the substrate blend. Inoculating the mangroves increased the plants’ survival rate from 70% to 93% but didn’t change the total biomass.

“I was never so happy to see a null in my life,” Fronabarger joked.

Another surprise was that the glass-grown mangroves had different a root structure than those grown in sediment or blended substrate despite the growing mediums having similar grain sizes. The structural roots of glass-grown mangroves were 26% thicker than those of sediment-grown mangroves, but the fine roots were 55% shorter. That could change the mangroves’ long-term stability in a turbulent coastal environment, the researchers said.

The team published these results in Restoration Ecology in July and will present its findings on 15 December at AGU’s Annual Meeting 2025 in New Orleans.

This illustration depicts how a black mangrove tree might grow in either recycled glass sand or dredged river sediment. In their experiments, the researchers grew mangrove propagules in buckets filled with different substrates and measured the plants’ root properties (extraradial and intraradial) and how inoculating against fungi (mycelium hyphae) affected growth. Credit: AC Frye From Trash to Treasure

“Recycled glass sand is increasingly being identified as a potential cost-effective source of local sediment for these types of projects, and evaluation of plant performance in this type of substrate is certainly needed and novel,” said Eric Sparks, who researches coastal estuary restoration at Mississippi State University. Sparks was not involved with the new research.

“The finding that root length in glass sand was 50% lower than in dredge sand controls really highlights the potential alternations in plant morphology that sediment substrate could influence,” he added. “Differences in root morphology could potentially influence how stable these plants are in the field when exposed to environmental factors like waves.”

“There certainly seems to be a place for recycled glass sand in the coastal restoration toolbox.”

Fronabarger said that the team wants to expand this research and test how glass-grown mangroves behave in wave flume experiments and natural environments. She also hopes to apply these same restoration ideas to other coastal areas experiencing erosion, like the Chesapeake Bay.

Is recycled glass sand a scalable solution to address coastal erosion? It depends on where you go, Fronabarger said. In cities like New Orleans with a lot of glass waste from production or consumption, it can certainly play a role. Other Gulf states like Texas, Mississippi, Alabama, and Georgia are beginning to implement large-scale glass recycling programs, too. But if there is little to no local glass to recycle, the solution is not very cost-effective.

“There certainly seems to be a place for recycled glass sand in the coastal restoration toolbox,” Sparks said.

“It’s a mindset,” Fronabarger emphasized. “It’s about taking what was once considered trash and turning it into restoration practices. I challenge people to think, ‘What have I considered trash, dilapidated or unusable, that actually can be implemented into a circular solution.’”

“It gives me a lot of hope for the future,” she said.

—Kimberly M. S. Cartier (@astrokimcartier.bsky.social), Staff Writer

Citation: Cartier, K. M. S. (2025), Glass sand grows healthy mangroves, Eos, 106, https://doi.org/10.1029/2025EO250459. Published on 12 December 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.

NASA’s Artemis mission aims to put humans back on the Moon in less than 2 years, and the China National Space Administration plans to follow suit soon after.

As astronauts return to the lunar surface for increasing periods of time, they will need structures that shield them from the Moon’s intense temperature fluctuations. In a day, temperatures can swing from 121°C (249.8°F) to −131°C (−203.8°F).

“Lunar regolith has silicon, it has oxygen elements, it has carbon. We have everything that we need to build. We just have to come up with technologies to utilize it in different ways.”

A creative solution may lie in structures made from “mooncrete,” a concrete analogue made from Moon rocks. Lunar regolith concrete (LRC) can effectively regulate temperature when exposed to dramatic fluctuations, according to new research that will be presented on 15 December at AGU’s Annual Meeting 2025 in New Orleans.

“Lunar regolith has silicon, it has oxygen elements, it has carbon. We have everything that we need to build,” said coauthor Arup Bhattacharya, a building scientist at Louisiana State University in Baton Rouge. “We just have to come up with technologies to utilize it in different ways.”

Making Mooncrete

Lunar regolith is a thick layer of rocks and dust that covers the entire lunar surface. The material is packed with minerals that make it durable, including many elements used on Earth to make concrete. To turn regolith into usable building material, scientists combine it with a binding material like sulfur, which is also available on the Moon’s surface.

Because opportunities to collect Moon rocks are few and far between, all the LRC in existence was created from 40 grams of regolith acquired during the Apollo 16 mission more than 50 years ago. Most experiments today use LRC analogues made from materials available on Earth.

This 3D printed prototype shows a lunar dome habitat that could be made from lunar regolith concrete. Credit: Arup Bhattacharya

To investigate how mooncrete might react to extreme heat and cold, the research team used data from previous experiments on lunar regolith properties to simulate a dome-shaped structure made of LRC.

The simulated structure effectively maintained an indoor temperature of 22°C (71.6°F) when subjected to the harsh lunar temperature swings. In addition, the team found that mooncrete’s insulating effects were amplified when two layers were nested on top of one another, separated by a thin layer of empty space. Heat travels less efficiently in the vacuum of space than through solid materials, so separating layers of LRC with a layer of space makes it harder for either intense heat or intense cold to penetrate the walls.

A Cost-Effective Option

Bhattacharya is “very optimistic” that structures made of lunar regolith will be built on the Moon. Using regolith is also cheaper than other options: Though estimates vary depending on the type of material, sending just 1 kilogram (2.2 pounds) of supplies to the Moon could cost more than $100,000.

“It’s the most abundant material on the Moon, its thermal conductivity is relatively small, and it can produce concrete. I think these structures will definitely be produced.”

“We could save a lot of money if we could use materials found on the Moon to build these structures,” said Adhrit Maiti, a tenth grader at Baton Rouge Magnet High School in Louisiana and first author of the study.

The study fills an important gap in lunar habitat research, said Marcello Lappa, an aerospace scientist at the University of Strathclyde in the United Kingdom who was not involved in the study. Much of the current research focuses on how to collect and process lunar regolith, yet the safety of astronauts depends on how well LRC can handle intense temperature cycles.

“It’s the most abundant material on the Moon, its thermal conductivity is relatively small, and it can produce concrete,” Lappa said. “I think these structures will definitely be produced.”

—Kaia Glickman, Science Writer

Citation: Glickman, K. (2025), Astronauts could live in structures made from Moon rocks, Eos, 106, https://doi.org/10.1029/2025EO250464. Published on 12 December 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.

Want to find schools in satellite images? Researchers say you can spot them by looking at tree cover because schools stand out as rectangular holes in the urban canopy.

Even though access to nature offers a variety of health and social benefits for students, researchers at the University of California (UC), Davis have found that trees on school grounds are declining across California. Declining tree canopy at schools can raise temperatures to dangerous levels, forcing kids to miss out on the benefits of spending time outside.

The researchers also conducted a field study to show how much schoolyard trees influence temperature. “Our motivation is thinking about a kid of around 8 years old playing in the schoolyard with their friends,” said UC Davis urban forestry scientist Luisa Velasquez-Camacho. “It’s very nice, but when you translate this scenario to Sacramento or the Central Valley at 2:00 p.m. in the hottest months, this is a nightmare because they don’t have natural shade.”

“Shade Is King”

To track changes in tree cover at schools, the researchers examined CalFire (California Department of Forestry and Fire Protection) tree canopy maps for more than 7,200 urban schools in California between 2018 and 2022. By quantifying the tree cover, they found that 85% of the schools had experienced tree loss over that time span, and some Central Valley school districts lost 25% of their tree cover. Schools had less than half the tree cover of surrounding urban areas. The results were published in Urban Forestry and Urban Greening.

“I can’t say the results are surprising,” said Kevin Lanza, an assistant professor of environmental and occupational health science at UTHealth Houston who wasn’t involved in the study. He said the findings align with existing studies on urban forestry and noted that trees can be lost in schools to make way for building expansions or because the cost of maintaining them is prohibitive. “Schools are more stressed than ever,” he said.

Scientists collected data such as temperature, radiation, and wind at children’s height. Credit: Emily C. Dooley, UC Davis

The researchers wanted to do more than document the loss of tree cover in schools; they wanted to investigate the health cost of losing those trees. To that end, said Alessandro Ossola, an ecologist at UC Davis and a coauthor of the research, “we took to the streets” in the summer of 2025, spending long days collecting weather data at school playgrounds across California.

The researchers deployed sensors collecting data on air temperature, humidity, radiation, and wind placed at children’s height around each playground. Using these data, they were able to calculate the thermal index, which is a measure of how the environment feels to a human body.

Then, they walked a sensor-laden cart around each playground—racking up over 200 miles (322 kilometers) over the summer—to map out microclimates. The researchers also scanned thermal radiation from common playground surfaces, including dry and irrigated grass, mulch, asphalt, and rubber.

Researchers walked a sensor-laden cart over 200 miles (322 kilometers) this summer while studying California playground temperatures. Credit: Jael Mackendorf, UC Davis

Although the team hasn’t fully analyzed the data yet, early results indicate that rubberized surfaces, often found around playground equipment, are particularly dangerous for reflecting radiation. “It was ridiculous for us to stay out there in the afternoon, even as adults. A kid is much closer to the ground,” Ossola said.

They saw the heat index reach 120°F (54°C) at some schools, and a single tree could drop surface temperatures by as much as 30°F (17°C) compared to direct sunlight. But while the air temperature often wasn’t dramatically different between direct Sun and shade, the thermal index dropped considerably under the shade because of the effects of radiation.

“Shade is king.”

“Shade is king,” said Lanza, and while artificial shade is better than nothing, trees can lower temperatures even more because the water vapor produced by evaporation from the tree leaves absorbs even more heat.

Once trees are lost, planting and maintaining replacement trees until they grow big enough to offer shade are a major hurdle. The researchers suggested that after their full analysis, the results could help guide schools on where to plant new trees and what species of trees will provide the greatest benefits.

Finding a Schoolyard Shade Strategy

Finding ways to manage temperatures is vital for children’s development because if temperatures rise too high, students are forced to remain inside, and for many, recess is their only chance to be in nature. Time spent in nature increases well-being and helps build healthy physical activity habits. UC Davis researchers are also conducting studies that suggest time outside can improve academic performance.

“It’s a matter of reenvisioning trees as an asset that can be budgeted.”

Lanza also noted that “low-income and Black and Latino communities are seeing larger losses of canopy than other communities,” indicating that the impacts of losing time in nature are likely not equitable across populations.

The ongoing work by universities and Green Schoolyards America, a nonprofit partner in this research, aims to use the findings to advocate for strategic investments in trees and other plants to improve students’ time spent outside. “It’s a matter of reenvisioning trees as an asset that can be budgeted,” Ossola said. “If we are negating these opportunities to be close to nature, we are missing the bus, not just for academic outcomes but also in terms of public health in the future.”

—Andrew Chapman (@andrewgchapman.bsky.social), Science Writer

This news article is included in our ENGAGE resource for educators seeking science news for their classroom lessons. Browse all ENGAGE articles, and share with your fellow educators how you integrated the article into an activity in the comments section below.

Citation: Chapman, A. (2025), California schools are feeling the heat, Eos, 106, https://doi.org/10.1029/2025EO250458. Published on 11 December 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

Around the world, phytoplankton in the upper ocean help to cycle key nutrients and regulate Earth’s climate by absorbing carbon dioxide. These photosynthesizing organisms rely on dissolved iron as an essential micronutrient, meaning that when iron levels drop, phytoplankton activity drops, too.

However, the full details of dissolved iron dynamics in the upper ocean are unclear, limiting our understanding of the effects on phytoplankton ecology, nutrient cycling, and the climate.

Now, Bates and Hawco report a new analysis of dissolved iron levels in the upper ocean near Hawaii. Between 2020 and 2023, they collected seawater samples on 21 separate research cruises to Station ALOHA (A Long-Term Oligotrophic Habitat Assessment), a marine research site located 100 kilometers north of Oahu, Hawaii. Back in the lab, they measured levels of dissolved iron and other elements in the samples and compared samples collected during different seasons.

The analysis reconfirmed a well-documented increase in dissolved iron levels at Station ALOHA in the springtime, which is caused by an annual increase in dust carried to the site by winds from Asia. However, the new data also revealed a previously undetected spike in dissolved iron in the winter that could not be explained by dust deposition.

Further analysis of the samples, including measurements of ratios between titanium and aluminum levels, suggested that the wintertime iron peak may have a far more local source: the Hawaiian Islands themselves. It is possible that increased wintertime rainfall boosts runoff of sediment from the islands, which is then transported to Station ALOHA by wintertime swells.

The researchers also used the new data to estimate that despite seasonal fluctuations in concentration, dissolved iron tends to cycle through the upper ocean at a relatively steady rate, with each molecule being replaced about every 5 months. Prior estimates reported turnover rates of anywhere from days to decades.

These findings could help improve understanding of phytoplankton’s various ecological roles, including nitrogen cycling and carbon uptake. (Geophysical Research Letters, https://doi.org/10.1029/2025GL118095, 2025)

—Sarah Stanley, Science Writer

Citation: Stanley, S. (2025), Wintertime spike in oceanic iron levels detected near Hawaii, Eos, 106, https://doi.org/10.1029/2025EO250462. Published on 11 December 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.

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

The Nankai subduction zone in southwest Japan has produced multiple M8+ earthquakes over the past 300 years, including the 1707 M8.7 Hōei earthquake, the 1944 M8.1 Tōnankai earthquake, and the 1946 M8.1 Nankaidō earthquake. As one of the most extensively studied subduction zones in the world, it has been the focus of numerous Integrated Ocean Drilling Program (IODP) expeditions aimed at improving our understanding of its seismogenic and tsunamigenic behavior.

Faulkner et al. [2025] compile all available laboratory friction data from Nankai Trough scientific drilling samples and integrate them with routine IODP mineralogical analyses. The dataset spans three transects—Kumano, Muroto, and Ashizuri—and includes material from 26 drilling sites. The experiments cover a wide range of slip velocities, from micrometers per second to meters per second, allowing systematic inversion of key frictional parameters.

This compilation shows that the frictional strength of these materials is generally lower than typical Byerlee friction and decreases with increasing clay content. However, the tendency for materials to weaken at higher slip rates—a key condition for earthquake nucleation—does not clearly correlate with clay abundance. Frictional stability analyses indicate a broad spectrum of possible fault-slip behaviors, from slow slip to earthquake-like failure, consistent with observations in nature. Overall, the findings highlight significant natural heterogeneity in frictional properties within a subduction environment and provide new constraints on the frictional characteristics of the shallow Nankai margin.

Citation: Faulkner, D. R., Zhang, J., Okuda, H., Bedford, J. D., Ikari, M. J., Schleicher, A. M., & Hirose, T. (2025). Synthesis of the laboratory frictional properties of a major shallow subduction zone: The Nankai Trough, offshore SW Japan. Journal of Geophysical Research: Solid Earth, 130, e2025JB031613. https://doi.org/10.1029/2025JB031613

—Alexandre Schubnel, Editor-in-Chief, JGR: Solid Earth

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: Water Resources Research

Using a combination of innovative approaches including observations and models, Platt and Dugan [2025] demonstrate how post-winter storm pulses of road salt lead to high concentrations of toxic substances in runoff water.

Surprisingly, the authors find that dilution is not an effective solution in this case, as discharge and snowfall magnitudes do not significantly impact concentrations. Key factors instead include the amount of road salt applied, land use, groundwater recharge and the base flow index. Thus, under conditions of increased groundwater recharge, road salt is stored in groundwater rather than running off.

However, this is not good news either, as it contributes to legacy effects. The authors use a random forest model with available data to show that smaller, ecologically important streams in the study region are at risk, providing a map of potential regions of road salt lightning strikes.

Citation: Platt, L. R. C., & Dugan, H. A. (2025). Episodic salinization of midwestern and northeastern US rivers by road salt. Water Resources Research, 61, e2024WR039496. https://doi.org/10.1029/2024WR039496

—Stefan Kollet, Editor, Water Resources Research

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.

Scientists of all stripes know the value of collecting and using data to answer research questions about everything from microscopic life to Earth system processes to space physics. But what about the value of data shedding light on peers within their own research communities?

Such data can help scientists better understand the makeup of their field and help them find and connect with colleagues. Compiled into an up-to-date, worldwide directory of researchers in a given discipline, for example, they could help people search for employment opportunities, identify possible collaborators, and suggest potential reviewers for papers and proposals.

These data can also help scientists who are early in their careers or otherwise less visible within their community to gain recognition. And they can be used to identify emerging research areas and trends indicating fields that are thriving or declining—important information not only for scientists themselves but also for funding bodies, oversight committees, and policymakers.

Researchers may have ideas of the approximate size and composition of their community, but hard numbers and comprehensive information are difficult to come by.

Researchers may have ideas of the approximate size and composition of their community based on conferences they attend and journal articles they read, but hard numbers and comprehensive information are difficult to come by. Demographic surveys conducted by professional societies or funding agencies typically provide incomplete information, because not everybody responds to them, they may cover single countries only, and they’re performed infrequently.

The need for workforce demographic data was highlighted in the recent National Academies’ Decadal Survey for Solar and Space Physics, which specifically called (in recommendation 4-1) for U.S. federal agencies to fund collection of this information to help determine the state of the profession.

An underused resource for this data collection is hiding in plain sight: the body of scientific articles produced by the research community. By combining the metadata from these articles with Open Researcher and Contributor IDs (ORCIDs) that uniquely identify authors, it is possible to extract accurate, current information about researchers and their work.

HelioIndex is a new, automated online directory that uses this approach to offer an evolving snapshot of the global community in the field of solar and heliospheric physics (SHP) [Young, 2025]. HelioIndex’s methods are generalizable and can be applied as long as researcher ORCIDs are widely used in research publications, meaning it offers a model for developing similar tools in many other scientific fields.

The Who, What, Where, and How Much of SHP

SHP includes science focused on all aspects of the Sun, from its interior through its atmosphere, out into the solar wind, and all the way to the outer edge of the heliosphere. HelioIndex currently identifies more than 2,300 active SHP researchers in about 60 countries, offering information about these scientists’ geographic distribution, institutional affiliations, areas of expertise (derived from journal article keywords), and publication records.

Figure 1 offers a glimpse of how HelioIndex can be used to consider geographic trends, for example, showing the 10 countries with the most researchers included in the directory. As of July, the United States had the largest share at 29.1%, followed by China and the United Kingdom.

Fig. 1. Tallies of HelioIndex authors located in the 10 most-represented countries in July 2025 and July 2022 are shown here, along with the corresponding percentages of the total number of authors.

Updated twice a month using freely available publication data, HelioIndex always provides the most recent data, but figures from earlier dates can be used to track changes over time. Figure 1 also compares the current numbers of researchers in HelioIndex in the top 10 countries with the corresponding numbers from 3 years earlier and shows how each country’s proportional share of the SHP community has changed during that time.

From July 2022 to July 2025, China, India, and the United States, for example, saw standout increases of 42%, 39%, and 33%, respectively, in their numbers of SHP researchers. The increases contributed to these countries’ growing shares of the global total population of SHP scientists during this 3-year period. Meanwhile, growth in several European countries in the top 10 has been smaller, leading to generally decreased shares of the overall community population.

These numbers demonstrate that overall, SHP as a field is growing. The extent of growth shown in different countries may help early-career scientists to decide where to pursue their careers. The data may also be valuable to national funding bodies for assessing their countries’ competitiveness and determining whether funding levels are appropriate.

An important function of HelioIndex is to enhance the visibility of researchers and their work, especially researchers who have few opportunities for recognition.

At the other end of the scale from the top 10 countries, almost half of the countries are represented in HelioIndex with five or fewer SHP researchers. An important function of HelioIndex is to enhance the visibility of researchers and their work, especially researchers in countries with smaller SHP research communities or who have few opportunities for recognition. Greater visibility can foster new collaborations and research directions and help researchers to prosper and develop research communities in their countries.

The publication and ORCID data used in HelioIndex also enable users to better understand publishing trends within the SHP community. For example, these data allow calculation of the average annual number of first-authored, refereed (FAR) articles per person across all HelioIndex authors.

Knowing this average—currently 0.68, which equates to about two FAR papers every 3 years—is valuable for managing expectations in the field. It may reassure young researchers feeling pressure to publish frequently to advance in their careers that success does not necessarily require such a rapid publishing pace. Meanwhile, if a researcher submits a grant proposal claiming their project will yield 10 FAR papers in a 3-year period, the HelioIndex data suggest that a reviewer considering the proposal would have a right to be skeptical!

Fig. 2. The distribution of career ages—a metric estimated from the publication date of an author’s first first-authored, refereed paper—across all HelioIndex authors, as of July 2025, is currently weighted toward early-career-stage researchers.

A “career age” can also be estimated for each HelioIndex author, using the publication date of their first FAR paper as age 0. This leads to a plot of age distributions (Figure 2), with vertical lines indicating boundaries between early-, middle-, and senior-career categories. The current median career age of all authors in HelioIndex is 9.9 years.

The age distribution and calculated career ages seemingly skew toward younger ages, likely because ORCIDs came into use only in 2009. Whereas most articles published since then will be linked to authors’ ORCIDs and thus included in the HelioIndex data, older articles may be missing for some researchers. However, it is clear from the long tail of the distribution that many senior authors have manually updated their ORCID records.

A Community-Specific Resource

HelioIndex differs from other resources that contribute to professional networking in that it serves a particular research community.

HelioIndex differs from other resources that contribute to professional networking such as ORCID, Scopus, and LinkedIn in that it serves a particular research community.

The procedure for populating HelioIndex begins with scheduled, automatic queries of recent scholarly literature—as captured in NASA’s Astrophysics Data System (ADS) bibliographic database—for articles related to SHP. Articles are likely to be flagged if they, for example, reference prominent review papers, mention a major SHP observatory or spacecraft, or include certain keywords (e.g., “solar flare”).

For each article found by the queries, the names and ORCID identifiers of the authors are gathered and added to a master list of potential HelioIndex authors. As journals generally do not have standard formats for specifying author affiliations, HelioIndex uses custom software to extract institution names and countries from affiliation information through string matching. (Affiliations listed in HelioIndex are updated routinely based upon an author’s most recent publication.)

Authors are included in HelioIndex based on meeting specific keyword criteria and publication criteria. Most journals require authors to assign several keywords to their articles to indicate the area of research to which their work belongs. For inclusion in HelioIndex, it is required that at least 15% of an author’s keywords across all their published articles contain “solar,” “Sun,” or “interplanetary.” This approach has proven effective in distinguishing SHP scientists from scientists in neighboring fields such as stellar physics and magnetospheric physics.

The publication criteria include having at least one refereed article published within the past 3 years, at least one FAR paper in their career, a career age of at least 2, and at least six total points (authorship of a FAR paper counts as two points and coauthorship of a paper counts as one point). These criteria have been chosen so that HelioIndex, at least initially, primarily represents the community of SHP researchers who have earned a doctoral degree and are part of the professional workforce.

Of course, it is difficult to ensure that the directory includes everyone it should in the SHP community. Using the criteria above, for example, it is possible that some early-career researchers—who perhaps haven’t published enough research yet—may be unintentionally excluded. Such issues can be overcome, however, because as the directory’s creator (and part of the SHP community myself), I can readily assess its completeness and adjust query parameters as needed, and I can directly respond to questions about or requests to be added to HelioIndex.

Listed authors can also check their own data, identify omissions or errors, and request not to be listed by name (though in such cases, their geographic and publication data still count toward the general statistics, such as shown in Figures 1 and 2, to maintain completeness).

Scientists Finding Scientists

In addition to providing basic demographic data about the current community of SHP scientists, HelioIndex can serve many other functions. Students and other researchers exploring career options can quickly assess where scientists in the SHP community are concentrated (or not) and use the keyword data to determine with whom their expertise and interests match. They can also browse publication lists to determine scientists’ interests, activity levels, and collaborators.

HelioIndex can also be used to identify potential reviewers for a submitted journal article by matching authors’ keywords to those used in the article. This usage allows an author (or journal editor) to suggest reviewers they may otherwise not have considered, helping diversify the reviewer pool and raise the visibility of peers. This use of HelioIndex may also benefit program managers at funding agencies looking for scientists to sit on review panels.

In just the few months since HelioIndex was publicly announced, traffic to it has been robust and feedback from users has been largely positive. In September and October, for example, the site received a combined 14,651 unique visitors—higher-than-expected traffic considering the modest size of the SHP community. Individuals have commented, for example, that HelioIndex has revealed researchers and research they weren’t previously aware of, and that it helps scientists “grasp the global view of the community of Solar Physics and Heliophysics in the world,” in the words of one midcareer scientist. These early indications suggest that HelioIndex is providing valuable services to many in this community, and seemingly even to many outside it.

The basic mechanics and principles of HelioIndex can be readily applied to develop similar resources for other scientific fields, no matter their size or scope.

Beyond SHP, the basic mechanics and principles of HelioIndex can be readily applied to develop similar resources for other scientific fields, no matter their size or scope, although specific aspects of the literature queries and keyword criteria would need to be adjusted. The initial article search, for example, would need to be modified to cover relevant journals and keywords. The keyword search would need updating too; to distinguish volcanologists from geoscientists in neighboring fields, say, the keyword search could require “volcano.” (Requiring “Earth” as well could help exclude those who study volcanoes elsewhere, such as on Mars or Io.) Author publication criteria could also be revised if, for example, average publishing trends in other fields differ from those in SHP.

As the ADS database is not currently complete for the Earth sciences or other fields outside of astrophysics, an alternative source for publication data, such as Web of Science or Scopus, may be needed. Furthermore, the approach of designing custom software to pull affiliation information from articles into HelioIndex, which worked well for the relatively small SHP research community, may be more challenging for larger fields with many more institutions represented.

HelioIndex demonstrates that scientific article metadata are a rich resource that can be efficiently and effectively mined to complement the sporadic data collected through researcher surveys. With a baseline of consistent and reproducible demographic data, geographic, temporal, and subject matter trends can be identified, providing a variety of valuable information about and for research communities.

References

Young, P. R. (2025), HelioIndex: A directory of active researchers in solar and heliospheric physics, Sol. Phys., 300, 77, https://doi.org/10.1007/s11207-025-02488-y.

Author Information

Peter Young (peter.r.young@nasa.gov), NASA Goddard Space Flight Center, Greenbelt, Md.

Citation: Young, P. (2025), Shining a light on the people behind solar science, Eos, 106, https://doi.org/10.1029/2025EO250457. Published on 10 December 2025. Text not subject to copyright.
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

When exposed to environmental stressors like high ocean temperatures and excessive solar radiation, corals bleach and die. Coral reefs collapse, and their benefits—increased biodiversity, protection from coastal erosion, and local economic activity—also disappear.

Some researchers think stratospheric aerosol injection (SAI), one of the most well-studied methods of climate intervention, may help mitigate some of the effects coral bleaching when used in tandem with reductions in greenhouse gas emissions. SAI describes a process in which aerosols such as sulfur dioxide are injected into the stratosphere to reduce incoming solar radiation.

To find out whether SAI could help corals, researchers led by physical oceanographer Gouri Anil of Louisiana State University modeled future heat stress on shallow coral reefs with and without the intervention.

Anil and her fellow researchers found that SAI could help many vulnerable reefs survive through 2060, giving researchers and lawmakers time to develop more lasting solutions to mitigate climate change. Anil and the research team will present their results on 15 December at AGU’s Annual Meeting 2025 in New Orleans.

Cool Atmosphere, Warm Waters

Anil’s team calculated the heat stress that shallow equatorial reefs across the globe would experience under a moderate climate change scenario with surface sea temperature data from the United Nations’ World Conservation Monitoring Centre and the Community Earth System Model–Whole Atmosphere Community Climate Model version 6 (CESM-WACCM6).

The model used in the study is one of the best suited for this type of climate research, according to Alan Robock, a climatologist at Rutgers University who was not involved in the study. Built with data from volcanic eruptions, CESM2-WACCM6 is able to evaluate SAI as a similar release of sulfur dioxide into the atmosphere.

The modeling showed that without any intervention, nearly all the coral reefs studied would experience a fatal amount of heat stress by 2060. Certain coral species and coral reefs in central Polynesia and the tropical east Pacific, which are exposed to the most sunlight, were particularly vulnerable.

When the researchers simulated a scenario that included SAI, however, the sustainability of shallow equatorial reefs through 2060 improved. Every year, the models showed only 10% of the reefs’ area would be at risk of bleaching if SAI was implemented beginning in 2035.

SAI Side Effects

Though SAI may reduce heat stress on coral reefs, researchers said, it could have consequences that require more research to fully understand.

For example, sulfur dioxide can react with water and other substances in the atmosphere to form sulfuric acid aerosols. These aerosols eventually precipitate, Robock said. “It’s going to fall out of the atmosphere to produce acid rain, acid snow.”

“What we’re trying to do is get this information out to people who make these decisions so that they know exactly what could happen.”

Precipitation also means that regular injections of sulfur dioxide into the stratosphere, likely by specialized planes, would be required to maintain SAI’s cooling effect, Robock explained. “You need to put gas continually into the atmosphere—the amount that would be falling out at steady state.”

And while the new model points to SAI contributing to reduced heat stress on coral reefs, it doesn’t consider other factors that could affect their survival, including ocean acidification, according to Anil. The researchers are currently working on models that incorporate variables like this.

“What we’re trying to do is not advocate for climate intervention,” Anil said. “What we’re trying to do is get this information out to people who make these decisions so that they know exactly what could happen.”

—Albert Chern, Science Writer

10 December 2025: This article has been updated to correct the climate intervention method mentioned in the headline.

Citation: Chern, A. (2025), Could stratospheric aerosol injection help save corals from bleaching?, Eos, 106, https://doi.org/10.1029/2025EO250463. Published on 10 December 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.

Satellite images are revealing the scale of the destruction in Sri Lanka caused by landslides triggered by Cyclone Ditwah at the end of November 2025.

At the end of November 2025, a “weak” tropical cyclone, subsequently named Cyclone Ditwah, formed just offshore from Sri Lanka. Over the following day the storm tracked around the south and east coasts of Sri Lanka before moving northwards to dissipate on 3 December off the east coast of India. This was not a strong tropical cyclone, but it brought catastrophic rainfall to Sri Lanka, triggering extremely extensive landslides and floods.

The stats on the impact of Cyclone Ditwah on Sri Lanka are horrifying. The UNDP is reporting that 1,200 landslides were triggered and that about 20% of the island was affected by flooding. As of the time of writing, there are 639 known fatalities, with a further 203 people reported to be missing. The highest loss of life occurred in Kandy District, in the hilly centre of of the country. Many of the fatalities occurred in channelised debris flows.

The impact of the storm is complex – to study the landslides properly would require a PhD study or similar – but a quick inspection of the Planet Labs imagery of the centre of Sri Lanka illustrates the scale of the devastation. This image, collected on 7 September 2025, shows an area in the vicinity of [7.43518, 80.87898]:-

A satellite image of part the area affected by landslides triggered by Cyclone Ditwah in Sri Lanka. This image shows the area before the event. Image copyright Planet Labs, used with permission, dated 07 September 2025.

This image, collected on 30 November 2025, shows the same area after the passage of Cyclone Ditwah:-

A satellite image of part the area affected by landslides triggered by Cyclone Ditwah in Sri Lanka. This image shows the aftermath of the event. Image copyright Planet Labs, used with permission, dated 30 November 2025.

And here is a slider to compare the two images:

Image copyright Planet Labs.

And here is the post event image pasted onto the Google Earth DEM:-

A satellite image of part the area affected by landslides triggered by Cyclone Ditwah in Sri Lanka. This image shows the aftermath of the event. Image copyright Planet Labs, used with permission, dated 30 November 2025.

In the foreground is a large landslide that has started at the ridgeline. It has entrained heavily along the track, and has impacted a large area of fields at the toe of the slope. Note the channelised debris flow close by. In the background are multiple shallow landslides, many of which have reached the drainage line to generate channelised debris flows. These have been devastating downstream.

The impact of these landslides will be long lasting. I have made the point before, but it is worth reiterating, that tropical cyclones are often associated with strong winds and storm surge, but a huge proportion of the damage is actually caused by rainfall. Cyclone Ditwah was, in meteorological terms, “weak”. The images above show that this is a completely inappropriate way to characterise such storms.

Acknowledgement

Images from Planet Labs 2025 – see: https://www.planet.com/. Thanks as always for their agreement that I can use their images on this blog.

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.

Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: AGU Advances

If you spin a bowling ball, the finger-holes will end up near the rotation axis because putting mass as far from the axis as possible minimizes energy. So, on planets –if there is a large mountain, it will end up at the equator; in physics terms, the axes of rotation and maximum inertia align.

Conversely, a planet that is very spherical will be rather unstable, so that the solid surface can move relative to the rotation axis, so-called true polar wander (TPW). Because of its slow rotation, Venus is extremely spherical; TPW can thus easily occur, driven for example by mantle convection, which is time-dependent. Furthermore, Venus’s axes of maximum inertia and rotation are offset, by about 0.5o.

In a new paper, Patočka et al. [2025] analyze the effect of convection on Venus’s axial offset and potential for TPW. They find TPW rates that are consistent with geologically-derived values, but that the resulting axial offset is much smaller than observed. Their conclusion is that atmospheric torques are likely responsible, as they probably are for the apparent variations in Venus’s rotation rate measured from Earth.

The angular offset between the rotation and maximum inertia axis as a function of time, driven by time-dependent convection. The mean value (0.0055o) is two orders of magnitude smaller than the observed value (0.5o). Convection cannot be causing this offset. Credit: Patočka et al. [2025], Figure 2e

Three spacecraft missions will soon be heading to Venus. Direct measurement of the effects predicted by the researchers are challenging, but the coupling between atmospheric dynamics and planetary rotation will surely form an important part of their investigations.

Citation: Patočka, V., Maia, J., & Plesa, A.-C. (2025). Polar motion dynamics on slow-rotating Venus: Signatures of mantle flow. AGU Advances, 6, e2025AV001976. https://doi.org/10.1029/2025AV001976

—Francis Nimmo, Editor, AGU Advances

Text © 2025. The authors. CC BY-NC-ND 3.0
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In 2009, Rolf Hut—then a doctoral student at Delft University of Technology in the Netherlands—hacked a $40 Nintendo Wii remote, turning it into a sensor capable of measuring evaporation in a lake.

The innovation, tested in his lab’s wave generator basin, became part of Hut’s doctoral thesis and changed the course of his career. Though he’s now an associate professor at Delft, Hut considers himself a professional tinkerer and a teacher of tinkerers.

Back in 2009, Hut and a group of fellow Ph.D. students organized a session at AGU’s annual meeting in which hydrologists could demonstrate the quirky measurement devices they’d made, hacked, scavenged, or used in a manner entirely different from what manufacturers intended.

Rolf Hut from Delft University of Technology organized the AGU 2010 MacGyver session. The session included homemade devices such as a “disdrometer” for counting raindrops and a demonstration of the “rising bubble“ method of determining canal discharge. Credit: Rolf Hut

The session, “Self-Made Sensors and Unintended Use of Measurement Equipment,” was so popular that Hut organized it again the next year and the next. In addition to Hut’s remodeled Wiimote, early sessions included an acoustic rain sensor made from singing birthday card speakers, a demonstration of how to use a handheld GPS unit to measure tidal slack in estuaries, and a giant temperature-sensing pole that showed how the room heated up after the coffee break.

Since then, the endeavor has grown from a single session to many, expanded to the annual meeting of the European Geosciences Union in addition to AGU’s, and gained a new name: “People just kept calling it ‘the MacGyver session,’” Hut said.

This year, there are five MacGyver sessions, encompassing space weather, ocean environments, the geosphere, and crowdsourced science—the biggest program yet, said Chet Udell of Oregon State University, an electrical engineer and musical composer who is convening the hydrology session.

“The MacGyver sessions are a powder keg of possibilities,” Udell said. “You never know who’s gonna talk with who and what really cool collaboration or initiative could get started that way.”

The MacGyver Spirit

The term “MacGyver” originated with the 1980s television character, a resourceful secret agent known for elegantly solving complex problems with a Swiss Army knife, a few paper clips, chewing gum, or the roll of duct tape he always kept in his back pocket.

That can-do attitude is a natural fit for science, said Udell. “The MacGyver spirit is all about empowering the curiosity that drives science to also drive instrumentation.”

“Oftentimes, [scientists] come up to the barrier of, ‘I can’t ask that question because measuring this thing would be too infeasible, too complicated, too expensive, [the sensor] doesn’t exist,’” he said.

In addition to innovation—“There are a lot of people generating new science because they’ve hacked their instrumentation”—collaboration is key to the MacGyver spirit, Udell said. The ethos is less do-it-yourself (DIY) and more do-it-together. With strong links to the open-source and makerspace traditions, community and transparency are prioritized over competition and secrecy.

“No one lab has all of the expertise, the tools, and the capacity to bring these really interesting, handmade types of DIY innovation to the sciences,” Udell said.

Until recently, the MacGyver sessions were among the only places scientists and engineers could share these kinds of innovations with others. Journal articles’ methods sections typically aren’t long enough to explain exactly how to make one of these hacked or duct-taped devices.

But in 2017, the multidisciplinary, peer-reviewed journal HardwareX was launched with the aim of accelerating the distribution of low-cost, high-quality, open-source scientific hardware. Udell is an associate editor of the journal and recently published an article there with instructions on how to build a “Pied Piper” device that senses pest insects and then lures them into a trap. Citations from HardwareX can help MacGyver scientists justify time spent tinkering, he added.

The Alchemy of Serendipity

The in-person MacGyver sessions remain the heart of the movement, said Udell. There’s a certain alchemy that happens when you bring similarly geeky people together. “You know you’ve really found your community,” said Udell. “There’s a sensation that we’re all cut from the same cloth.”

“We want people to bring the physical device they’ve made and have a nerd-on-nerd discussion about that.”

There’s a reason they’re usually poster sessions, too, added Hut. “We want people to bring the physical device they’ve made and have a nerd-on-nerd discussion about that, which is a very different sort of communication than one-to-many broadcasting your awesome work.”

The format facilitates serendipitous discovery, too. “People walk by and they’re like, ‘Hey, what’s this weird device? I didn’t know you could measure that,’” said Udell. The conversation might spark an epiphany that could help someone solve a problem they’ve been wrestling with in their own research.

Kristina Collins, an electrical engineer who has convened several MacGyver sessions, said scientists and engineers from all disciplines are welcome at any of them—not just those in their own “Hogwarts House” or discipline.

“Having open-source hardware gives people a way to exchange information across different scientific cultures,” she said. “The point of Fall Meeting is to connect with the gestalt of what’s happening at the level of your field and also across fields. I really like that. I think everything interesting happens at the interface.”

Crowdsourced Science

Collins, now a research scientist at the Space Science Institute in Boulder, stumbled upon the MacGyver sessions at her first AGU annual meeting, in 2019—when she was a graduate student and the sessions were hydrology only.

At the time, she was working on making low-cost space weather station receivers for taking Doppler measurements and working with the worldwide ham radio community to deploy them—harnessing low-cost tech and crowdsourced science to gather data from the ionosphere and provide insights into the effects of solar activity on Earth.

“We named [our first receiver] the Grape because people like to name electronics after tiny fruit, and everything else was taken,” she explained (think: kiwis, limes, raspberries, blackberries, apples). “And also, it does its best work in bunches—many, many instruments [working] as a single meta instrument.”

The following year, Collins and some colleagues organized their own MacGyver session on sensors for detecting space weather. At AGU’s Annual Meeting 2025, there will be both oral and poster space weather MacGyver sessions . Collins will present an update on the Personal Space Weather Station Network and the various instruments, including Grape monitors, that make up this distributed, crowdsourced system.

For many geoscientists, the MacGyver spirit is not just a fun side quest, but a fundamental part of the scientific process, said Udell. “The questions we ask and the things that we observe are shaped by what we can measure, and this is shaped by our instrumentation,” he said.

“And so, in a way, what we make ends up making us.”

—Kate Evans (@kategevans.bsky.social), Science Writer

Citation: Evans, K. (2025), Celebrating the MacGyver spirit: Hacking, tinkering, scavenging, and crowdsourcing, Eos, 106, https://doi.org/10.1029/2025EO250460. Published on 9 December 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.

Time travelers to the Ediacaran can forget about packing a compass. Our planet’s magnetic field was remarkably weak then, and new research suggests that that situation persisted for roughly 3 times longer than previously believed.

That negligible magnetic field likely resulted in increased atmospheric oxygen levels, which in turn could have facilitated the observed growth of microscopic organisms, researchers have now concluded. These results, which will be presented at AGU’s Annual Meeting on Wednesday, 17 December, pave the way for better understanding a multitude of life-forms.

The Ediacaran period, which spans from roughly 640 million to 540 million years ago, is recognized as a time in which microscopic life began evolving into macroscopic forms. That transition in turn paved the way for the diversification of life known as the Cambrian explosion. The Ediacaran furthermore holds the honor of being one of the most recent inductees into the International Chronostratigraphic Chart, the official geologic timescale. (Last year, the Anthropocene was rejected as an addition to the International Chronostratigraphic Chart.)

A Collapsing Field, with Implications for Life

The Ediacaran was a time of magnetic tumult. An earlier study showed that our planet’s magnetic field precipitously fell from roughly modern-day values, decreasing by as much as a factor of roughly 30.

“We have this unprecedented interval in Earth’s history where the Earth’s magnetic field is collapsing.”

“We have this unprecedented interval in Earth’s history where the Earth’s magnetic field is collapsing,” said John Tarduno, a geophysicist at the University of Rochester involved in the earlier study as well as this new work.

The strength of our planet’s magnetic field has implications for life on Earth. That’s because Earth’s magnetic field functions much like a shield, protecting our planet’s atmosphere from being pummeled by a steady stream of charged particles emanating from the Sun (the solar wind). A weaker magnetic field means that more energetic particles from the solar wind can ultimately interact with the atmosphere. That influx of charged particles can alter the chemical composition of the atmosphere and allow more DNA-damaging ultraviolet radiation from the Sun to reach Earth’s surface.

There’s accordingly a strong link between Earth’s magnetic field and our planet’s ability to support life, said Tarduno. “One of the big questions we’re interested in is the relationship between Earth’s magnetic field and its habitability.”

We’re Getting Older (Rocks)

Tarduno and his colleagues previously showed that a weak magnetic field likely persisted during the Ediacaran from 591 to 565 million years ago, a span of 26 million years.

But maybe that period lasted even longer, the team surmised. To test that idea, the researchers analyzed an assemblage of 641-million-year-old anorthosite rocks from Brazil. Those rocks date to the late Cryogenian, the period immediately preceding the Ediacaran.

Back in the laboratory, the researchers extracted pieces of feldspar from the rocks. Within that feldspar, the team homed in on tiny inclusions of magnetite, a mineral that records the strength and direction of magnetic fields.

Team member Jack Schneider, a geologist at the University of Rochester, used a scanning electron microscope to observe individual needle-shaped bits of magnetite measuring just millionths of a meter long and billionths of a meter wide. “We can see the actual magnetic recorders,” said Schneider.

Working in a room shielded from Earth’s own magnetic field, Schneider measured the magnetization of feldspar crystals containing those magnetite needles. To ensure that the magnetite needles were truly reflecting Earth’s magnetic field 641 million years ago rather than a more recent magnetic field, the team focused on single-domain magnetite. A single domain refers to a region of uniform magnetization, which is much more difficult to overprint with a new magnetic field than a region magnetized in multiple directions. “We make sure that they’re good samples for us to use,” said Schneider.

Don’t Blame Reversals

The average field strength that the team recorded was consistent with zero, with an upper limit of just a couple hundred nanoteslas. “Those are the type of numbers you measure on solar system bodies today where there’s no magnetic field,” said Tarduno. For comparison, Earth’s magnetic field today is several tens of thousands of nanoteslas.

Given the weak magnetic field strengths dating to 565 million years ago and 591 million years ago and these new measurements of rocks from 641 million years ago, there might have been a roughly 70-million-year span in which Earth’s magnetic field was unusually feeble and possibly nonexistent, the team concluded.

And magnetic reversal—the periodic switching of Earth’s north and south magnetic poles—isn’t the likely culprit, the researchers suggest. It’s true that the planet’s magnetic field drops to very low levels during some parts of a magnetic reversal, but that situation persists for at most a few thousand years, said Tarduno. That’s far too short a time to show up in this dataset—the rocks that the team measured all cooled over tens of thousands of years, so the magnetic fields they recorded are an average over that time span.

Take a Deep Breath

If it’s true that Earth’s magnetic field was anomalously weak for about 70 million years, cascading effects might have helped prompt the transition from microscopic to macroscopic life, the team suggests. That shift, known as the Avalon explosion, preceded the better-known Cambrian explosion.

In particular, a weak magnetic field would have allowed the solar wind to impinge more on our planet’s atmosphere, a process that would have preferentially kicked out lighter inhabitants of the atmosphere such as hydrogen. Such a depletion of hydrogen would have, in turn, boosted the relative concentration of an important atmospheric species: oxygen.

“If you’re removing hydrogen, you’re actually increasing the oxygenation of the planet, particularly in the atmosphere and the oceans,” explained Tarduno. And because oxygen plays such a key role for so many species across the animal kingdom, it’s not too much of a stretch to imagine that the important life shift that occurred soon thereafter—miniscule creatures evolving into ones that measured centimeters or even meters in size—owes something to the invisible actor that is our planet’s magnetic field, the team concluded. “We passed a threshold that allowed things to get big,” said Tarduno.

It’s difficult to test this hypothesis by measuring ancient atmospheric oxygen levels, the team admits. (The ice cores that famously record atmospheric gases stretch back in time just about a million years, give or take.)

But this idea that the planet’s magnetic field may have triggered atmospheric changes that in turn played a role in animals growing larger makes sense, said Shuhai Xiao, a geobiologist at Virginia Tech not involved in the research. “If the oxygen concentration is low, you simply cannot grow very big.”

In the future, it will be important to fill in our knowledge of the magnetic field during the Ediacaran with more measurements, added Xiao. “One data point could change the story a lot.”

Cathy Constable, a geophysicist at the Scripps Institution of Oceanography not involved in the research, echoed that thought. “The data are sparse,” she said. But this investigation is clearly a step in the right direction, she said. “I think this is exciting work.”

—Katherine Kornei (@KatherineKornei), Science Writer

Citation: Kornei, K. (2025), The long and the weak of it—The Ediacaran magnetic field, Eos, 106, https://doi.org/10.1029/2025EO250454. Published on 9 December 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.

The public has long been educated to respond to the threat of a tsunami by moving away from the coast and to higher ground. This messaging has created the impression that tsunami impacts are always potentially significant and has conditioned many in the public toward strong emotional responses at the mere mention of the word “tsunami.”

Indeed, in more general usage, “tsunami” is often used to indicate the arrival or occurrence of something in overwhelming quantities, such as in the seeming “tsunami of data” available in the digital age.

The prevailing messaging of tsunami risk communications is underscored by roadside signs in vulnerable areas, such as along the U.S. West Coast, that point out tsunami hazard zones or direct people to evacuation routes. The ubiquity and straightforward message of these signs, which typically depict large breaking waves (sometimes looming over human figures), reinforce the notion that tsunamis pose life-threatening hazards and that people should evacuate the area.

The disparity between the scientific definition of tsunamis and their common portrayal in risk communications and general usage creates room for confusion in public understanding.

Of course, sometimes they do present major risks—but not always.

The current scientific definition of a tsunami sets no size limit. According to the Intergovernmental Oceanographic Commission (IOC) [2019], a tsunami is “a series of travelling waves of extremely long length and period, usually generated by disturbances associated with earthquakes occurring below or near the ocean floor.” After pointing out that volcanic eruptions, submarine landslides, coastal rockfalls, and even meteorite impacts can also produce tsunamis, the definition continues: “These waves may reach enormous dimensions and travel across entire ocean basins with little loss of energy.”

The use of “may” indicates that a tsunami, or long wave, by this definition need not be large or especially impactful. If the initiating disturbance is small, the amplitude of the generated long wave will also be small.

The disparity between the scientific definition of tsunamis and their common portrayal in risk communications and general usage creates room for additional confusion in public understanding and potentially wasted effort and resources in community responses. We thus propose revising the definition of tsunami to include an amplitude threshold to help clarify when and where incoming waves pose enough of a hazard for the public to take action.

A Parting of the Waves

Tsunami wave amplitudes can vary substantially not only from one event to another but also within a single event. Following the magnitude 8.8 earthquake off the Kamchatka Peninsula in July, for example, tsunami waves upward of 4 meters hit nearby parts of the Russian coast, whereas amplitudes were much lower at distant sites across the Pacific.

Meanwhile, other disturbances create waves that although technically tsunamis, simply tend to be smaller. Prevailing public messaging about tsunami threats can complicate communications about such smaller waves, including those from meteotsunamis, for example.

Meteotsunamis are long waves generated in a body of water by a sudden atmospheric disturbance, usually a rapid change in barometric pressure [e.g., Rabinovich, 2020]. They are often reported after the fact as coastal inundation events for which no other obvious explanation can be found.

Once a meteotsunami is formed, the factors that govern its propagation, amplitude, and impact are the same as for other tsunamis. However, meteotsunami wave amplitudes are typically smaller than those of long waves generated by large seismic events.

Updating the scientific definition of a tsunami to include a low-end amplitude threshold could help avoid scenarios where oceanic long waves may be coming but evacuation is not required.

As coastal inundations are amplified by sea level rise and thus are becoming more frequent, a greater need to communicate about all coastal inundation events, including from meteotsunamis, is emerging. And with recent progress in understanding meteotsunamis, it is becoming feasible to develop operational warning systems for them (although to date, only a few countries—Korea being one [Kim et al., 2022]—have such systems).

Still, many meteotsunamis do not require coastal evacuations. Given the public’s understanding of the word “tsunami,” however, an announcement that a meteotsunami is on the way could cause an unnecessary response.

Updating the scientific definition of a tsunami to include a low-end amplitude threshold could help avoid such scenarios where oceanic long waves may be coming but evacuation is not required. We suggest that a long wave below that threshold amplitude should be referred to simply as an oceanic long wave or another suitable alternative, such as a displacement wave. Many meteotsunamis, as well as some long waves generated by low-magnitude seismicity and other drivers, would thus not be classified as tsunamis.

Conceptually, our proposal aligns somewhat with various tsunami magnitude scales developed to link wave heights or energies with potential impacts on land [e.g., Abe, 1979]. These scales have yet to be widely accepted by either the scientific community or operational warning centers, however, perhaps because it is difficult to assign a single value to represent the impact of a tsunami. In addition, tsunami magnitude calculations often require postevent analyses, which are too slow for use in early warnings.

We are not proposing yet another tsunami magnitude scale; rather, our idea focuses predominantly on terminology and solely on relatively low amplitude long waves.

Lessons from Meteorology

This kind of threshold classification for naming natural hazards has precedent in other scientific disciplines.

In meteorology, for example, a tropical low-pressure system is designated as a named tropical storm only if its maximum sustained wind speed is more than 63 kilometers per hour. Below that threshold, a system is called a tropical depression. A higher wind speed threshold is similarly specified before more emotive terms such as “hurricane,” “typhoon,” and “tropical cyclone” (depending on the region) are used.

Considering the effectiveness of using thresholds for tropical storm terminology, we anticipate that adopting a formal tsunami threshold could have similar benefits.

Current wind-based tropical storm naming systems have limitations, such as their focus on wind hazards over those from rainfall or storm surge [e.g., Paxton et al., 2024]. However, on the whole, using intensity thresholds for various terms has enhanced the communication of the risks of these weather systems—whether limited or life-threatening—to the public. The straightforward framework helps inform decisionmaking, allowing people in potentially affected areas to determine whether they should evacuate or take other protective measures against an approaching weather system [e.g., Lazo et al., 2010; Cass et al., 2023]. Lazo et al. [2010], for example, underscored that categorizing hurricanes is a powerful tool for easily conveying storm severity to the public, enabling faster and more confident protective action decisions.

Research into tsunami risk communication, including about best practices and regional differences, is limited compared with that related to other hazards [Rafliana et al., 2022]. However, considering the effectiveness of using thresholds for tropical storm terminology, we anticipate that adopting a formal tsunami threshold could have similar benefits for the communication of risk to the public. For example, it could inform decisions about where and when to issue evacuation orders and, equally important, when those orders could be lifted.

Open Questions to Consider

Our proposal raises important questions about the nature of a potential tsunami threshold and how it should be applied.

First, what should the threshold wave amplitude be? There is no obvious answer, and the decision would require careful consideration within the scientific and operational tsunami warning communities, although amplitude threshold–related techniques already used by tsunami warning services may offer useful insights.

For example, the Joint Australian Tsunami Warning Centre (JATWC) issues three categories of tsunami warnings: no threat, marine threat (indicating potentially dangerous waves and strong ocean currents in the marine environment), and land threat (indicating major land inundation of low-lying coastal areas, dangerous waves, and strong ocean currents). JATWC uses an amplitude of 0.4 meter measured at a tide gauge as a minimum for the confirmation of lower-level marine threat warnings [Allen and Greenslade, 2010]. That could be a possible value for our proposed threshold—or at least a starting point for discussion.

An internationally consistent threshold would be ideal, especially considering the expansive reach of tsunamis, but is not necessarily imperative. The terminology for tropical storms is not entirely consistent around the world, yet the benefits for hazard communication are still evident.

A second question is whether a wave should be considered a tsunami along its entire length once its amplitude anywhere reaches the threshold. We think not and instead propose that long waves be called tsunamis only where their amplitude is above the defined threshold. Were the threshold to be set at 0.4 meter, this provision would mean, for example, that in the hypothetical case following a large earthquake shown in Figure 1, only waves in the orange- and red-shaded regions would be considered tsunami waves.

Fig. 1. Modeled maximum amplitudes of waves propagating across the Pacific Ocean following a hypothetical magnitude 9.0 earthquake on the Japan Trench are seen here. Credit: Stewart Allen, Bureau of Meteorology

In this way, the proposed terminology for tsunamis would differ from that used for tropical low-pressure systems, which are classified as storms (or hurricanes, typhoons, etc.) in their entirety once their maximum sustained winds exceed a certain threshold—regardless of where that occurs. While tropical storms typically have localized impacts, long ocean waves can travel vast distances, even globally. However, since the destructive effects of these waves are limited to specific regions—similar to tropical storms—it is reasonable to refer to them as tsunamis only in areas where significant impact is expected.

This location-dependent classification may raise practical challenges for warning centers, in part because details of the forcing disturbance (e.g., the earthquake depth and focal mechanism) may not be immediately available and because of uncertainties about how a long wave will interact with complex coastlines, which can amplify or attenuate waves.

On the other hand, early assessments of where and when an ocean long wave should be defined as a tsunami would benefit from the fact that once a tsunami is generated, its evolution is fairly predictable because of its linear propagation in deep water.

Using amplitude threshold–based definitions will require efforts to educate the public about basic principles and the terminology of ocean waves.

Another issue for consideration is that using amplitude threshold–based definitions will require efforts to educate the public about basic principles (e.g., what wave amplitudes are and why they vary) and the terminology of ocean waves. Ubiquitous mentions of atmospheric pressure “highs” and “lows” in weather forecasts have familiarized the public with terms like “tropical low” and with what conditions to expect when the pressure is low. However, “oceanic long wave” and other such terms are more obscure. Choosing the best term for waves that do not meet the tsunami threshold, as well as the best approaches for informing people, would require social science research and testing with the public.

Finally, how do we ensure that this tsunami threshold terminology prompts appropriate public reactions, whether that is evacuating coastal areas entirely, pursuing a limited response such as securing boats properly and staying out of the water, or taking no action at all? Scientists, social scientists, and the emergency management and civil protection communities must collaborate to address this question and to test the messaging with the public. Using official tsunami warning services to issue warnings about above-threshold events and more routine marine and coastal services, such as forecasts of sea and swell in coastal waters, to share news about below-threshold events might be an effective way to help the public understand the potential severity of different events and react accordingly.

Normalizing and Formalizing

Should the use of a tsunami amplitude threshold be adopted for risk communications, we advocate that ocean scientists should also adhere to the terminology in presentations and research publications in the same way that atmospheric scientists have adhered to the threshold-dependent terminology around tropical storms. This consistency will gradually normalize the usage and reduce confusion. Readers of a scientific publication that notes the occurrence of a tsunami, for example, would instantly know that it was an above-threshold event.

Formalizing a scientific redefinition of what constitutes a tsunami will require discussion, agreement, and coordination across multiple bodies, most notably the IOC, which supports the agencies that provide tsunami warnings, and the World Meteorological Organization (WMO), which supports the agencies that provide marine forecasts. Should this threshold proposal receive enough initial support, the next step would be to elevate the proposal to the IOC and WMO for further consideration in these forums.

Considering the potential benefits for risk communications and the well-being of coastal communities worldwide, we think these are discussions worth having.

References

Abe, K. (1979), Size of great earthquakes of 1837–1974 inferred from tsunami data, J. Geophys. Res., 84, 1,561–1,568, https://doi.org/10.1029/JB084iB04p01561.

Allen, S. C. R., and D. J. M. Greenslade (2010), Model-based tsunami warnings derived from observed impacts, Nat. Hazards Earth Syst. Sci., 10, 2,631–2,642, https://doi.org/10.5194/nhess-10-2631-2010.

Cass, E., et al. (2023), Identifying trends in interpretation and responses to hurricane and climate change communication tools, Int. J. Disaster Risk Reduct., 93, 103752, https://doi.org/10.1016/j.ijdrr.2023.103752.

Intergovernmental Oceanographic Commission (2019), Tsunami Glossary, 4th ed., IOC Tech. Ser. 85, U.N. Educ., Sci. and Cultural Organ., Paris, unesdoc.unesco.org/ark:/48223/pf0000188226.

Kim, M.-S., et al. (2022), Towards observation- and atmospheric model-based early warning systems for meteotsunami mitigation: A case study of Korea, Weather Clim. Extremes, 37, 100463, https://doi.org/10.1016/j.wace.2022.100463.

Lazo, J. K., et al. (2010), Household evacuation decision making and the benefits of improved hurricane forecasting: Developing a framework for assessment, Weather Forecast., 25(1), 207–219, https://doi.org/10.1175/2009WAF2222310.1.

Paxton, L. D., J. Collins, and L. Myers (2024), Reconsidering the Saffir-Simpson scale: A Qualitative investigation of public understanding and alternative frameworks, in Advances in Hurricane Risk in a Changing Climate, Hurricane Risk, vol. 3, edited by J. Collins et al., pp. 241–279, Springer, Cham, Switzerland, https://doi.org/10.1007/978-3-031-63186-3_10.

Rabinovich, A. B. (2020), Twenty-seven years of progress in the science of meteorological tsunamis following the 1992 Daytona Beach event, Pure Appl. Geophys., 177, 1,193–1,230, https://doi.org/10.1007/s00024-019-02349-3.

Rafliana, I., et al. (2022), Tsunami risk communication and management: Contemporary gaps and challenges, Int. J. Disaster Risk Reduct., 70, 102771, https://doi.org/10.1016/j.ijdrr.2021.102771.

Author Information

Diana J. M. Greenslade (diana.greenslade@bom.gov.au) and Matthew C. Wheeler, Bureau of Meteorology, Melbourne, Vic., Australia

Citation: Greenslade, D. J. M., and M. C. Wheeler (2025), When should a tsunami not be called a tsunami?, Eos, 106, https://doi.org/10.1029/2025EO250453. Published on 8 December 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. Commonwealth of Australia. 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: AGU Advances

In the coming decades, climate change is likely to lead to a loss of sea ice in and an influx of warmer water to the Arctic Ocean, affecting the ocean’s vertical circulation. Brown et al. recently investigated the forces that drive the Arctic Ocean’s vertical circulation to gain insight into how the circulation might change in the future.

The researchers drew on data from a range of sources, including measurements from shipborne and mooring-based instruments, ERA-Interim, the Arctic Ocean Model Intercomparison Project, and the Polar Science Center Hydrographic Climatology.

Two contrasting factors emerged as the main drivers of vertical circulation as warmer waters flow from the Atlantic Ocean into the Arctic. In the Barents Sea, hitherto the only ice-free part of the Arctic, the ocean loses heat to the atmosphere, causing some of the water to become denser and to sink. Elsewhere, centimeter-sized whirls of turbulence mix in freshwater from rivers and precipitation, resulting in lighter-weight water that remains close to the surface.

As climate change continues to melt sea ice, the balance between these surface fluxes and turbulent mixing is likely to change. More of the ocean surface will be exposed to heat loss to the atmosphere. At the same time, turbulence is likely both to increase and to become more variable. The Arctic Ocean is a source of cold, dense water that feeds the Atlantic Meridional Overturning Circulation, or AMOC, a circulation pattern that holds key influence over the weather in western Europe and North America. Determining how changing circulation patterns in the Arctic Ocean will affect the AMOC should be a focus for future research, the authors suggest. (AGU Advances, https://doi.org/10.1029/2024AV001529, 2025)

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

Citation: Sidik, S. M. (2025), Tiny turbulent whirls keep the Arctic Ocean flowing, Eos, 106, https://doi.org/10.1029/2025EO250455. Published on 8 December 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.

The Coral Triangle is a biodiversity hot spot. At least for now.

More than 600 species of coral grow in this massive area straddling the Pacific and Indian Oceans, stretching from the Philippines to Bali to the Solomon Islands. But as the oceans get hotter, coral reefs—and the ecosystems they support—are at risk. Experts predict up to 90% of coral could disappear from the world’s warming oceans by 2050.

Research institutions are racing to preserve corals, and one strategy involves placing them in a deep freeze. By archiving corals in cryobanks, biologists can buy time for research and restoration—and hopefully stave off extinction.

A new capacity-building project is training cryocollaborators in the Coral Triangle region, starting at the University of the Philippines (UP).

The initiative is “very, very urgent,” said Chiahsin Lin, a cryobiologist who is leading the project from Taiwan’s National Museum of Marine Biology and Aquarium.

Room to Grow

“We don’t have that much time to develop the techniques.”

A cryobank is like a frozen library. But instead of books, the shelves are lined with canisters of coral sperm, larvae, and even whole coral fragments chilled in liquid nitrogen.

Coral cryobanking can aid in coral preservation and future cultivation. But the process is tricky and time-consuming and requires trial and error. The temperature and timing that work for one species won’t carry over to others. Plus, it can take 30 minutes to freeze a single coral larva, said Lin.

University of the Philippines research assistant Ryan Carl De Juan works with Sun Yat-Sen University Ph.D. student Federica Buttari on vitrification and cryobanking procedures at the National Museum of Marine Biology and Aquarium laboratory in Taiwan. Credit: UP MSI Interactions of Marine Bionts and Benthic Ecosystems Laboratory

While materials from hundreds of species have been frozen, very few larvae have been successfully revived and brought to adulthood.

“We hope more and more people can be involved in this research,” Lin said. “We don’t have that much time to develop the techniques.”

The new project aims to increase the number of trained professionals who can freeze the world’s corals. UP’s Marine Science Institute is currently working to open the first cryobank in Southeast Asia. Lin has visited UP multiple times to train researchers on cryopreservation and vitrification. The UP team also traveled to Taiwan to work with samples in Lin’s lab.

The project will establish future cryobanks in Thailand, Malaysia, and Indonesia as well. Those teams will also participate in similar trainings to reach a shared goal: a network of coral cryobanks in the Coral Triangle.

Pausing the Clock

A major benefit of cryopreservation is that it pauses the clock. Some coral species spawn for only a few hours or days each year, and that window changes by species and by region. If a lab group misses the release, they may wait months before collecting materials again.

By freezing coral samples, researchers have more opportunities to experiment throughout the year.

In the past, Emmeline Jamodiong, a coral reproduction biologist in the Philippines, led coral reproduction trainings for stakeholders across the country. Logistics were complicated. People needed to travel from different regions and islands, but “we had to wait for the corals to spawn before we could conduct the training.” Now, even if it’s not spawning season, researchers could still work with coral reproduction.

A local cryobank “offers a lot of future research opportunities,” she said. “I’m very happy that we have this facility established in the Philippines.”

A new cryobank in the Philippines will focus on Pocilloporidae, a family of corals that grows fast, reproduces quickly, and is among the first to root on disturbed reefs. Like nearly all corals, though, Pocilloporidae are sensitive to coral bleaching and climate stress. Credit: UP MSI Interactions of Marine Bionts and Benthic Ecosystems Laboratory Freezing for the Future

The new project in the Coral Triangle is a helpful addition to cryobiology, said Mary Hagedorn, a senior scientist at the Smithsonian’s National Zoo and Conservation Biology Institute who developed the field of coral cryobanking.

“A real bottleneck for this field is there’s so few people that are trained as cryobiologists,” said Hagedorn. Every effort to expand the research ranks is valuable.

But cryobanks are just one part of coral conservation, she said. Aquariums that cultivate live coral are also important. Secure storage is essential to keeping samples safe from storms and power outages. Sustained government funding is needed to keep coral frozen and make sure staff are continuously trained.

“Without starting this project, there’s no hope for coral reefs.”

Some coral populations are already functionally extinct, making global collaborations like the one between Taiwan and the Philippines key.

“No one person can cryopreserve all the species of corals in the ocean,” Hagedorn said. Lin’s team has “a wonderful opportunity to get some amazing species and genetic diversity.”

Hagedorn’s international collaborators think it may take 15–25 years to collect enough coral larvae to ensure genetic diversity for a species. Many corals still need a tailor-made recipe for freezing and thawing if they’re going to be cryobanked at all. It’s a daunting task and a tight timeline available to only a handful of institutions around the world. The Coral Triangle network will add to that number.

“Without starting this project, there’s no hope for coral reefs,” Lin said. Coral cryobanking “gives tomorrow’s ocean a better chance.”

—J. Besl (@j_besl, @jbesl.bsky.social), Science Writer

Citation: Besl J. (2025), A cryobank network grows in the Coral Triangle, Eos, 106, https://doi.org/10.1029/2025EO250451. Published on 5 December 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.

Groundwater is one of Earth’s most important natural resources—it’s the world’s biggest source of accessible freshwater, and in dry parts of the world, it supplies most of the water humans consume. In Australia, for example, where more than 70% of the landmass is semiarid or arid, groundwater is the only reliable source of freshwater, supplemented by limited seasonal or episodic rainfall.

Estimates of regional and global groundwater recharge exist, but they typically come with large uncertainties because recharge is generally measured indirectly: Scientists extrapolate from measurements of water table fluctuations or streamflow loss, or they simply estimate recharge as a percentage of rainfall. Moreover, the relationships between individual rainfall events and groundwater recharge are rarely examined because existing methodologies have focused on gathering data to estimate recharge volumes on monthly or annual timescales.

Groundwater is replenished, or recharged, when water—usually from precipitation—percolates into bedrock from the surface, raising the water table. However, scientists have relatively little knowledge of when this replenishment occurs and how much precipitation is needed to refill underground reservoirs known as aquifers.

The lack of understanding of when and how water goes from the surface to a reservoir makes it difficult to predict how groundwater recharge will change as the climate changes.

The lack of understanding of when and how water goes from the surface to a reservoir makes it difficult to predict how groundwater recharge will change as the climate changes. This difficulty will be increasingly problematic as our knowledge of past rainfall patterns becomes obsolete and no longer helps us to allocate water sustainably.

To reveal the relationship between rainfall and groundwater recharge, we can use a metric referred to as the rainfall recharge threshold. This threshold is the amount of rainfall that is needed for groundwater recharge to occur at a given location and time. We can determine this value if we can observe groundwater being recharged and we have weather data from prior to the recharge event so we know how much precipitation fell.

Measuring this threshold at different times and places allows us to assess how much rainfall is needed to recharge groundwater and how the amount varies seasonally and over time, how often that amount falls, and what weather patterns and climate processes make recharge events more likely.

Addressing these unknowns, in turn, helps us understand recharge processes in more detail and improves our ability to manage valuable groundwater resources sustainably.

Watching Groundwater Flow Fig. 1. This map of Australia, with state and territory borders demarcated, shows annual average rainfall across the continent, as well as the locations of current National Groundwater Recharge Observing System (NGROS) sites. Site 1, Capricorn Caves; site 2, Daylight Cave; site 3, Wellington Phosphate Mine; site 4, Wombeyan Caves; site 5, Yarrangobilly; site 6, Walhalla Mine; site 7, Derby mine tunnel; site 8, Marakoopa Cave; site 9, Ajax South Adit; site 10, Durham Lead Adit; site 11, Berringa Adit; site 12, Stawell Mine; site 13, Byaduk Lava Cave; site 14, Naracoorte Caves; site 15, Tantanoola Caves; site 16, Old Sleep’s Hill Tunnel; site 17, Montacute Mine; site 18, Burra Mine Adit; site 19, Elliston; site 20, Yanchep. Click image for larger version.

Our team has implemented an innovative approach to quantify rainfall recharge thresholds throughout Australia [Baker et al., 2024]. The approach involves directly detecting potential groundwater recharge using a network of automated hydrological loggers deployed as close to the water table as possible (so measurements are as representative of true recharge as possible) in underground tunnels, mines, and caves (Figure 1).

Since 2022, we have placed loggers at 20 sites, such as an abandoned train tunnel in Precambrian to Cambrian sandstone (at Old Sleep’s Hill Tunnel in South Australia; Figure 1, site 16), a heritage gold mine in Devonian metasedimentary rock (at Walhalla Mine in eastern Victoria; site 6), and a lava cave in Quaternary basalt (at Byaduk Lava Cave in western Victoria; site 13). These sensors make up Australia’s National Groundwater Recharge Observing System (NGROS), the first dedicated network for observing event-scale groundwater recharge across different geologic and surface environments, as well as across a wide range of Australian hydroclimates.

The hydrological loggers we use detect the impacts of falling water droplets that hit them, meaning they must be placed in open underground spaces, rather than buried in soil. They were originally designed to count drips falling from cave stalactites, but they count drips falling from the roof of any underground space just as well.

Sharp increases in drip rates allow us to identify the precise timing of recharge events.

In the time series datasets from replicate loggers at each site, sharp increases in drip rates allow us to identify the precise timing (and location, season, and climatic conditions) of recharge events—similar to how spikes in streamflow help identify flood episodes in river hydrographs. With this information, we can tie recharge to specific precipitation events, and by combining it with daily rainfall data, we can quantify rainfall recharge thresholds and their variability with geography and through time.

Confidently linking rainfall and recharge events also requires that water percolate from the surface toward the water table fast enough that the rainfall response is preserved. For this reason, loggers are placed where water flows predominantly—and rapidly—through features such as rock fractures rather than more slowly through tighter pore spaces. Data from NGROS therefore also shed light on recharge processes in fractured rock terrains, which have been relatively less researched than those in porous rocks and sediments.

We deliberately sited some NGROS sensors to be close to Australia’s new network of critical zone observatories to complement infrastructure that is recording stocks and flows of carbon, water, and mass from the plant canopy to the groundwater. We also chose cave sites where we plan to reconstruct records of past recharge by analyzing cave stalagmites. Our improved understanding of the climate conditions necessary for recharge to occur today will help us interpret stalagmite oxygen isotope compositions at these sites as a proxy for past periods of groundwater recharge and drought.

Heavy Rains Required

At NGROS sites where at least 1 year’s worth of data have been collected, we’ve observed that 10–20 millimeters of rainfall over 48 hours are typically needed to initiate recharge in fractured rock aquifers [Priestley et al., 2025].

We have seen a clear relationship across the sites between lower numbers of recharge events and higher rainfall thresholds.

Such rainfall events are infrequent in Australia. Between five and 18 occurred at each site in the first year the loggers were observing, with the fewest observed at Daylight Cave in eastern New South Wales (site 2) and the most at Capricorn Caves in central Queensland (site 1). These rainfall recharge events generally occurred when specific weather conditions manifested, such as the co-occurrence of cyclones or fronts with thunderstorms.

Regardless of the frequency of recharge events, we have seen a clear relationship across the sites between lower numbers of recharge events and higher rainfall thresholds. This relationship also holds despite differences in soil, vegetation, geology, and depth to the loggers, suggesting that climate is a major control on rainfall thresholds.

Most of the rainfall recharge events (86%) occurred in wetter seasons, and during these times, rainfall recharge thresholds were lower than in drier seasons: The median wet season rainfall recharge threshold was 19.5 millimeters in 48 hours, compared with 30.4 millimeters per 48 hours in the dry season [Priestley et al., 2025].

Drip loggers in the NGROS network were placed, for example, on old mining infrastructure in a former gold mine in Walhalla (left) and under an inflow zone in a gold adit in Durham Lead, near Ballarat, Victoria (right). The loggers can measure a maximum rate of four drips per second and can last roughly 3 years using internal batteries. Credit: Wendy Timms

The seasonal control on recharge is likely related to the greater amount of rainfall required to saturate soils during dry season events, although this control may be modulated by site‐specific factors such as soil conditions, unsaturated zone thickness, and vegetation. For example, sites vegetated with native woodland might be expected to have a greater unsaturated zone water demand in hot summer conditions and therefore to require more rainfall to generate recharge than more sparsely vegetated sites [Baker et al., 2024]. We will investigate the influence of these factors further as we collect longer time series of data.

Our results have also produced some surprising findings. Although we expected that antecedent weather conditions would influence the amount of rainfall needed for recharge to occur, we have not yet seen a clear relationship between preceding rainfall amounts or the time since the last recharge event and observed rainfall recharge thresholds. Longer time series of data should help to clarify the role of antecedent conditions as well.

Guiding Groundwater Management

Findings from NGROS have important implications for water management in Australia. Government groundwater management strategies, such as in the states of New South Wales and South Australia, where groundwater is the largest source of freshwater, rely on scientific data to support sustainable extraction and to protect groundwater-dependent ecosystems.

Our observations provide useful guidance for regulators setting extraction limits in the near term; they’re also useful to groundwater managers planning for changing future demands.

Our observations showing that only a handful of recharge events occur annually and that recharge requires a relatively high rainfall amount can, for example, provide useful guidance for regulators setting extraction limits in the near term. They’re also useful to groundwater managers planning for changing future demands resulting from changes in population, growth in agriculture and in mining industries supporting the green energy transition, and climate change.

Climate change is predicted to cause greater climatic variability across Australia, parts of which are already experiencing both wet and dry extremes. However, it is not yet clear to what extent changes in the climatic conditions that affect rainfall recharge thresholds will influence soil infiltration and overall groundwater recharge. The NGROS network is designed to investigate this question.

As a growing number of towns and even large cities (e.g., Perth, Western Australia [Broderick and McFarlane, 2022]) are forced to consider alternatives to shrinking groundwater resources, detailed information about regional and local recharge could help improve decisionmaking and give water managers more time to consider options.

NGROS findings also highlight that models used to inform groundwater management should factor in how recharge relates not only to rainfall amounts but also to the season and manner in which the rain is delivered (e.g., in long-duration, high-magnitude events versus intense bursts or prolonged sprinkles). This treatment conflicts with current practice, which typically quantifies recharge as a percentage, or some function, of annual rainfall. By instead considering the links between rainfall patterns and recharge, we can better identify how climate-induced changes in rainfall may impact future recharge.

Expanding the Network

NGROS data are already providing a more detailed understanding of rainfall recharge thresholds in Australia, helping refine recharge rate estimates by showing which rainfall event characteristics lead to recharge. Longer NGROS network time series, combined with other data such as groundwater level observations, will further help quantify recharge processes and reveal variability and trends over time and across the continent.

The concept of an underground groundwater recharge observing network could be applied more widely.

Beyond the 20 sites currently instrumented, the concept of an underground groundwater recharge observing network could be applied more widely, and we are continuously looking to expand the network within Australia and beyond.

Most recently, we installed loggers in sinkholes (vertical dissolution caves) on the Eyre Peninsula in South Australia, an arid region where groundwater levels have been falling. We have also commenced collaborations with colleagues in Africa, Europe, and North America, sharing our experience and know-how in setting up logger networks.

If groundwater observing networks are expanded to other parts of the world, researchers could compare recharge thresholds and processes across a wider range of climates, weather patterns, geologies, and environments to gain a more comprehensive view of when and how precipitation leads to recharge. Such knowledge would support sustainable management of vital groundwater resources not only in Australia but around the world.

Acknowledgments

Maria de Lourdes Melo Zurita (University of New South Wales, Sydney) also contributed to the underlying research project and provided feedback for this article.

References

Baker, A., et al. (2024), An underground drip water monitoring network to characterize rainfall recharge of groundwater at different geologies, environments, and climates across Australia, Geosci. Instrum. Methods Data Syst., 13(1), 117–129, https://doi.org/10.5194/gi-13-117-2024.

Broderick, K., and D. McFarlane (2022), Water resources planning in a drying climate in the south-west of Western Australia, Australas. J. Water Resour., 26(1), 72–83, https://doi.org/10.1080/13241583.2022.2078470.

Priestley, S. C., et al. (2025), Groundwater recharge of fractured rock aquifers in SE Australia is episodic and controlled by season and rainfall amount, Geophys. Res. Lett., 52(5), e2024GL113503, https://doi.org/10.1029/2024GL113503.

Author Information

Stacey Priestley (stacey.priestley@csiro.au), Commonwealth Scientific and Industrial Research Organisation, Adelaide, SA, Australia; Andy Baker (a.baker@unsw.edu.au), University of New South Wales, Sydney, Australia; Margaret Shanafield, Flinders University, SA, Adelaide, Australia; Wendy Timms, Deakin University, Geelong Waurn Ponds, Vic, Australia; and Martin Andersen, University of New South Wales, Sydney, Australia

Citation: Priestley, S., A. Baker, M. Shanafield, W. Timms, and M. Andersen (2025), When does rainfall become recharge?, Eos, 106, https://doi.org/10.1029/2025EO250452. Published on 4 December 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: Community Science

The Xwulqw'selu Sta'lo' (Koksilah River) is a culturally important river to the Cowichan Tribes, located on traditional Quw'utsun land on Vancouver Island, British Columbia. The land, which was never ceded to Canada, is part of a watershed that faces challenges including decreasing salmon populations, low river flow, flooding, and land use changes.

Gleeson et al. are working with the Cowichan Tribes and the provincial government to collaborate on the first water sustainability plan in British Columbia. About halfway through their 5-year project, the researchers are sharing how their work is guided by five “woven statements,” representing their intentions and values. These statements include a commitment to uphold Quw'utsun rights and laws, an intention that community-based monitoring and modeling will inform water and land decisions about the river, and a commitment by researchers to share their practices and outcomes. Just like the horizontal wefts and vertical warps in traditional Coast Salish weaving practices, these statements overlap and connect with their research goals, projects, and partnerships.

The research project has three goals: to improve understanding of current and future low flows in the Xwulqw'selu Sta'lo' through community science; to promote community engagement with water science, water governance, and Indigenous Knowledge; and to examine how this community science work can be useful to shared watershed management.

To accomplish these goals, the researchers use traditional scientific practices deeply grounded in the river itself. The community science project includes hydrological monitoring, modeling of low river flows, and quantification of groundwater flows into the river. In 2024, 44 volunteers participated in the community science project.

The 5-year project is part of the larger Xwulqw'selu Connections program, which supports a shift toward water cogovernance between the Cowichan Tribes and the provincial government through the Xwulqw'selu Water Sustainability Plan. The program could inform other community science collaborations between governments and Indigenous peoples, the authors say. (Community Science, https://doi.org/10.1029/2024CSJ000120, 2025)

—Madeline Reinsel, Science Writer

Citation: Reinsel, M. (2025), Watershed sustainability project centers place-based research, Eos, 106, https://doi.org/10.1029/2025EO250439. Published on 4 December 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.

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

Reconstructing the direction and rate of motion of tectonic plates is essential for understanding deformation within and between plates and for evaluating the geodynamical drivers of plate tectonics. One debate concerns the relative importance of flow in the asthenosphere versus processes at plate boundaries in controlling the motion of tectonic plates.

Wilson and DeMets [2025] present the most detailed reconstruction of changes in motion of the Nazca Plate to date. Remarkably, their results show periods of constant motion separated by geologically short periods of rapid acceleration or deceleration. These changes coincide with changes in the dip of the Nazca plate where it subducts beneath South America, with decelerations occurring when multiple regions of the slab shallowed to anomalously low dips (“flat slab subduction”), and accelerations occurring when the slab deepened to normal dips.  These results imply that changes in the forces acting between plates are an important control on plate motion.

Citation: Wilson, D. S., & DeMets, C. (2025). Changes in motion of the Nazca/Farallon plate over the last 34 million years: Implications for flat-slab subduction and the propagation of plate kinematic changes. Journal of Geophysical Research: Solid Earth, 130, e2025JB031933. https://doi.org/10.1029/2025JB031933

—Donna Shillington, Associate Editor, JGR: Solid Earth

Text © 2025. The authors. CC BY-NC-ND 3.0
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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.

At the White House today, President Donald Trump announced his administration would “reset” vehicle fuel economy standards. Trump said the administration plans to revoke tightened standards, also known as Corporate Average Fuel Economy (CAFE) standards, set by President Joe Biden in 2024.

“We’re bringing back the car industry that was stolen from us.”

“We are officially terminating Joe Biden’s ridiculously burdensome—horrible, actually—CAFE standards that imposed expensive restrictions and all sorts of problems, all sorts of problems, to automakers,” Trump said. “We’re bringing back the car industry that was stolen from us.”

Automobile executives from Ford, General Motors (GM), and Stellantis joined federal officials, including Department of Transportation Secretary Sean Duffy, at the announcement. The administration said, without providing evidence during today’s announcement, that the current CAFE standards have increased vehicle prices and estimated that changing those standards would save American families $109 billion in total.

Vehicle fuel efficiency standards, which set the average gas mileage that vehicles must achieve, have been in place since 1975. The standards were most recently tightened in June 2024 by the Biden administration, and required automakers to ensure vehicles achieved an average fuel efficiency of about 50.4 miles per gallon by model year 2031. The Biden administration estimated that the rule would lower fuel costs by $23 billion and prevent the emission of more than 710 million metric tons of carbon dioxide by 2050. 

Fuel economy standards have significantly reduced greenhouse gas emissions from vehicles, which are one of the largest sources of carbon emissions in the United States. According to one estimate, fuel economy improvements spurred by the standards have avoided 14 billion tons of greenhouse gas emissions since 1975. 

However, Duffy said, the current standards are “completely unattainable” for automakers.

The announcement did not specify the degree to which the administration would lower the standards.

 
Related

•  Fact Sheet: President Donald J. Trump Announces the Reset of Corporate Average Fuel Economy (CAFE) Standards
•  Read about the 2024 standards: USDOT Finalizes New Fuel Economy Standards for Model Years 2027-2031
•  U.S. Fuel Economy and Greenhouse Gas Standards: What Have They Achieved and What Have We Learned?
•  Get Involved: AGU Science Policy Action Center
 

Weakening fuel economy rules for vehicles is the latest step in President Trump’s continued efforts to slow the adoption of electric vehicles and boost the fossil fuel industry. 

Trump’s One Big Beautiful Bill, the omnibus spending bill that became law in July, also eliminated fines for automakers that did not comply with fuel economy standards. The Environmental Protection Agency is also expected to weaken limits of greenhouse gas emissions from vehicles by finalizing the repeal of the 2009 Endangerment Finding, which underpins important federal climate regulations, early next year. 

Policy advocates said weakening the standards would slow the transition to electric vehicles and make the U.S. vehicle market less competitive. “While Trump tells G.M., Ford and others that they needn’t make gas-saving cars, China is telling its carmakers to take advantage of the lack of U.S. competition and accelerate their efforts to grab the world’s burgeoning clean car market,” Dan Becker, director of the Safe Climate Transport Campaign at the Center for Biological Diversity, told The New York Times. 

However, automakers supported the proposal. “As America’s largest auto producer, we appreciate President Trump’s leadership in aligning fuel economy standards with market realities,” Jim Farley, Ford’s CEO, told Fox News.

“Today is a victory of common sense and affordability,” Farley, who attended the announcement, said. 

The Transportation Department will solicit public comments about the rule and is expected to finalize it next year.

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

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As a child in Algeria in the late 1990s, Walid Ouaret remembers going to the mosque when droughts turned severe. There, he and his family would join their neighbors in a communal prayer for rain called the Salat al-Istisqāʼ. It was no informal event: The ceremony had been announced by the government.

“I was not a farmer, but I was feeling for other people from my own community,” remembered Ouaret, who’s now a Ph.D. candidate at the University of Maryland studying the intersections of climate and agriculture.

As he explored ways to improve the climate models he was using to understand the ramifications of climate change, Ouaret remembered the rain prayers. Rainfall patterns are changing globally due to climate change, but data from places like Algeria can be sparse. The Salat al-Istisqāʼ, on the other hand, is practiced across the Muslim world, which spans northern Africa, the Middle East, and Central Asia.

“I was trying to find a proxy, something that would tell me when food production was impacted or soil moisture was impacted at this regional [scale].”

“I was trying to find a proxy, something that would tell me when food production was impacted or soil moisture was impacted at this regional [scale],” he said. The call for rain prayers, he realized, could be a key data point revealing when droughts had become sufficiently severe to warrant state-led interventions.

In most instances, the ceremony is widely advertised, giving Ouaret a simple way of tracking its prevalence over time.

A New Kind of Climate Data

For research that will be presented on 18 December at AGU’s Annual Meeting 2025, Ouaret and his coauthors combed through mass media, including newspapers and websites, from Algeria, Morocco, and Tunisia from 2000 to 2024, looking for announcements of Salat al-Istisqāʼ. Then, they calculated how likely the calls for rain prayers were to correspond to drought conditions, as measured by the Standardized Precipitation Evapotranspiration Index.

Ouaret found a strong correlation between Salat al-Istisqāʼ notices and 6-month drought severity, which validated the announcement of rain prayers as a proxy for extreme weather. The environment wasn’t the only relevant influence on the calls to prayer, however. Ouaret said social unrest, as measured by conflict event data, was also associated with the announcement of rain prayers. That confluence is a sign, he said, that calls to prayer may also function as a governance tool for increasing social cohesion.

These kinds of data are valuable, as they illuminate areas of the planet with fewer reliable climate monitoring networks, said Jen Shaffer, an ecological anthropologist also at the University of Maryland, who wasn’t involved in the research.

“This sort of grassroots, bottom-up view is really valuable to get at areas where we don’t have weather stations.”

“People are getting signals of change going on in the environment that’s not easy to record with satellite data, or with all of our instruments,” Shaffer said. “This sort of grassroots, bottom-up view is really valuable to get at areas where we don’t have weather stations.”

The Maghreb and other regions of Africa are vulnerable to such lack of data, but agricultural communities around the world are beset by climate-induced challenges.

Rituals that ask for rain are common in cultures both past and present, from the kachina of the Pueblo cultures of the American Southwest to Catholic pro pluvia rogation ceremonies practiced in Spain to Days of Prayer for Rain in the State of Texas designated by the state’s governor in 2011. These practices offer both a historical record of drought and a potential input for climate models.

Adding cultural events to climate models, which are normally fed rigorously quantitative data, can be difficult, Shaffer noted. But Ouaret’s dataset benefits from the fact that a public, official announcement of rain prayers can be tied to specific dates and locations.

In the future, Ouaret believes his work could provide a potential early-warning system for drought vulnerability in specific communities, allowing more time to marshal aid to where it’s needed most. Data on the frequency of calls for rain prayers could also be a helpful tool for talking about climate change in affected communities, he said.

Communities “have been doing this in the past, but it was happening like once every 5 years. Now it’s happening every year,” Ouaret said. Incorporating calls for rain prayers into scientific models would be “validating [people’s] experience and telling them that it’s scientifically valid.”

The work also aligns with another goal for Ouaret, which is expanding the reach of open science in North Africa and other places underprioritized by Western researchers.

“Empowering people to do their science will help them so much to bring innovation to the whole community and bring a new way of addressing our traditional problems,” he said.

—Nathaniel Scharping (@nathanielscharp), Science Writer

Citation: Scharping, N. (2025), When a prayer is also a climate signal, Eos, 106, https://doi.org/10.1029/2025EO250450. Published on 3 December 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.