EOS

Coastal waters worldwide are rapidly losing oxygen, causing declines in marine life and affecting communities who rely on the health of coastal waters.

Prominent examples of low-oxygen coastal waters are found in the Baltic Sea, for instance, where oxygen loss in recent decades has led to major ecosystem changes. Potentially toxic cyanobacterial blooms have become frequent and widespread, spawning grounds for cod have been greatly reduced, and fish kills have been observed in coastal waters [Conley et al., 2009]. Similar issues have afflicted the Gulf of Mexico, the Adriatic Sea, the East China Sea, and numerous other areas.

Dead fish are seen in coastal waters near Ostend, Belgium, following a low-oxygen event in 2018. Credit: Grégoire et al. [2023], European Marine Board, CC BY 4.0

The main cause of declining coastal ocean oxygen is well-known: Since the 1950s, phosphorus and nitrogen from agricultural runoff and wastewater have flowed into coastal seas, where they stimulate phytoplankton blooms that, upon their decay, consume oxygen. This process, called eutrophication, is not the only cause of declining oxygen and so-called dead zones in coastal waters: Increasing global temperatures are contributing by reducing both the solubility of oxygen in seawater and vertical mixing of the ocean water column, thereby limiting the aeration of deeper waters [Breitburg et al., 2018].

Indeed, even coastal systems not experiencing eutrophication, such as the Gulf of St. Lawrence in Canada, may be under threat of low oxygen because of changes in ocean circulation linked to climate change [Wallace et al., 2023].

Various means of artificial reoxygenation have been suggested and studied as possible local to regional solutions to coastal oxygen loss.

Long-term reductions in nutrient inputs from land are widely acknowledged as essential to mitigate coastal eutrophication, but such reductions will take time to have an effect. Nutrients have been accumulating in many coastal systems for decades, and switching off inputs will not immediately lead to lower concentrations [Conley et al., 2009]. Moreover, reducing nutrient releases from agricultural lands in many regions is proving challenging. Attempts to curtail the global use of fossil fuels and cut greenhouse gas emissions substantially have also been less successful to date than what is required to affect ocean oxygen [Breitburg et al., 2018].

Amid the challenges of achieving global-scale solutions, various means of artificial reoxygenation have been suggested and studied as possible local to regional solutions to coastal oxygen loss [Stigebrandt et al., 2015]. Yet these approaches come with risks that must be assessed carefully before implementation [Conley et al., 2009].

Such assessments are becoming urgent with the emergence of potential new artificial reoxygenation technologies linked to green hydrogen production. This process of splitting water by electrolysis to generate hydrogen also generates oxygen [Wallace et al., 2023], which could be put to use in coastal waters, particularly where green hydrogen production facilities are located close to the sea.

Oxygen Supply Versus Demand

Coastal seas gain oxygen naturally through air-sea exchange, vertical and lateral mixing of seawater, and photosynthetic production by phytoplankton (Figure 1). They lose oxygen through respiration of organic matter in the water column and the underlying sediment. Surface waters typically remain oxygenated because of rapid air-sea exchange and primary productivity, but in deeper waters, oxygen removal may dominate, especially in systems with limited vertical mixing [Fennel and Testa, 2019].

Fig. 1. The oxygen budget for coastal ocean systems involves several main processes.

The main goal of artificial reoxygenation is to increase the supply of oxygen to deeper waters enough that the water and sediment at the seafloor surface become or remain oxygenated. The oxygen supply needed to achieve this goal depends on the local oxygen demand, which itself depends on the input of organic matter from sinking phytoplankton biomass and the eutrophication history of the system. If organic matter inputs remain high or a lot of organic matter has accumulated on the seafloor, oxygen demand may remain high for a long time. This “legacy” effect can hinder the reoxygenation of a coastal system, as shown in the Baltic Sea [Hermans et al., 2019].

A secondary goal of reoxygenation is to limit recycling of phosphorus from sediments, which, in turn, may reduce the availability of phosphorus as a nutrient for phytoplankton in surface waters. Decreasing how much organic matter is produced and then sinks to the seafloor may lower the oxygen demand for respiration and hence increase oxygen concentrations in deeper waters [Conley et al., 2009].

Inspired by methods used to reoxygenate lakes with some success, two broad approaches have been proposed for artificially reoxygenating coastal systems (Figure 2): bubbling pure oxygen or air into the ocean [Koweek et al., 2020; Wallace et al., 2023] and pumping oxygenated surface water to greater water depths, a process called artificial downwelling [Stigebrandt et al., 2015; Lehtoranta et al., 2022].

Fig. 2. Two key methods for artificially reoxygenating coastal waters include bubble diffusion (left) and downwelling (right). O2, oxygen. Credit: Adapted from Koweek et al. [2020], CC BY 4.0

Bubble diffusers have been used in lakes to oxygenate deep water directly [Koweek et al., 2020] and in shallow coastal systems to destratify and aerate the water column by inducing mixing [Harris et al., 2015]. Artificial downwelling has been tested for local applications in only a few small coastal systems [Stigebrandt et al., 2015; Lehtoranta et al., 2022].

The Imperfections of Artificial Reoxygenation

Studies to date show that artificial reoxygenation can be applied successfully in small estuaries and bays but that its effect lasts only as long as operations are maintained.

Studies to date show that artificial reoxygenation can be applied successfully in small estuaries and bays but that its effect lasts only as long as operations are maintained. This outcome was observed, for example, in two Swedish bays following their reoxygenation through pump-driven downwelling [Stigebrandt et al., 2015; Lehtoranta et al., 2022]. Similarly, when aerators were switched off in a shallow subestuary of the Chesapeake Bay after several decades of aeration, low-oxygen, or anoxic, levels returned within a day [Harris et al., 2015].

The rapid return of anoxia upon discontinuing artificial reoxygenation operations—also known from applications in lakes—illustrates that these approaches alone do not provide permanent solutions to deoxygenation because they do not address its root causes. Moreover, adding oxygen to the water column does not mitigate wider water quality problems. Nuisance algal blooms in many coastal areas will still occur if the availability of nutrients for phytoplankton remains high.

In the Baltic Sea, for example, natural decadal-scale reoxygenation of deeper waters linked to lateral inflow of oxygenated North Sea water does not lead to a removal of phosphorus in the sediment [Hermans et al., 2019]. This lack of an effect results from the highly reducing conditions in the seafloor sediment, which hinder formation of phosphorus-containing minerals. Consequently, reoxygenation of the water column in the Baltic does not necessarily decrease recycling of phosphorus [Hermans et al., 2019], which may continue to fuel cyanobacterial blooms [Conley et al., 2009].

Reoxygenation via artificial downwelling may also be unsuccessful if it causes warming of deeper waters, which is a risk, especially when surface water pumps are used to reoxygenate temperature- and density-stratified coastal waters. Transferring warm surface water to colder, denser depths near the seafloor may weaken stratification and enhance vertical mixing. Although this process may increase the downward transfer of oxygen, it can also boost upward mixing of nutrients, which may enhance biological productivity. This enhancement can ultimately increase the oxygen demand in deeper waters to such an extent that a net decrease in oxygen results [Conley et al., 2009; Lehtoranta et al., 2022].

Warming at depth can also lead to greater metabolic activity and increased respiration of organic matter, further decreasing oxygen concentrations instead of increasing them as intended.

Side Effects on Climate and Habitats

Artificial reoxygenation may have other undesirable effects as well. It can alter the dynamics of greenhouse gases in coastal waters, for example, because increased aerobic respiration increases carbon dioxide production.

Furthermore, bubbling air through shallow coastal waters can enhance upward transport of methane, a potent greenhouse gas, in the water column and its emission to the atmosphere [Lapham et al., 2022]. In eutrophic coastal systems, reoxygenation does not necessarily suppress the release of methane from sediments [Żygadłowska et al., 2024], implying that upon bubbling, methane emissions from coastal waters may be greater than without reoxygenation.

Reoxygenation operations may also alter ocean habitats and have unintended consequences for marine life. Bubbling generates underwater noise, turbulence, and gradients in oxygen pressure that differ from naturally occurring conditions. Artificial downwelling not only changes water column temperatures but also alters vertical salinity distributions, with unknown consequences for marine organisms [Conley et al., 2009; Wallace et al., 2023]. In addition, the return of bottom-dwelling animals with reoxygenation may cause increased sediment mixing that remobilizes sediment contaminants [Conley et al., 2009].

Assessing Artificial Reoxygenation as a Solution

Artificial reoxygenation, when applied, should always be only one of various measures used to improve water quality.

Taken together, the body of evidence from reoxygenation studies to date indicates that long-term improvements in the oxygen levels and quality of coastal waters require reductions in nutrient inputs and greenhouse gas emissions. Hence, artificial reoxygenation, when applied, should always be only one of various measures used to improve water quality.

In heavily managed coastal systems, reoxygenation may be a temporary solution, as illustrated by its successful application in a subestuary of the Chesapeake Bay [Harris et al., 2015]. Elsewhere, such as in the Gulf of St. Lawrence, reoxygenation might be harnessed to maintain the current oxygen state of the system [Wallace et al., 2023]. However, responses to reoxygenation in eutrophic systems with strong legacy effects, where sediments act as a source of nutrients and a sink for oxygen, are very difficult to predict [Conley et al., 2009; Hermans et al., 2019].

The dependence of reoxygenation effects, either from aeration or from pumping, on site-specific biological, chemical, and physical characteristics, which are often poorly known and differ greatly worldwide, also hinders predictions of responses. Yet accurately predicting the effects of artificial reoxygenation before implementing it is critical and consistent with the precautionary principle that in the absence of scientific certainty, we should act to avoid harm.

This principle can be interpreted to suggest that no measures should be taken in some cases and that in other cases, measures should not be postponed because delay could lead to even more harm. Thus, careful case-by-case assessments of the suitability of artificial reoxygenation at given sites are needed—as is careful monitoring when operations are implemented. Modeling studies are valuable for such assessments [e.g., Koweek et al., 2020] but must be paired and validated with field data.

The potential availability of substantial oxygen supplies to support artificial reoxygenation as a result of increasing green hydrogen production further raises the urgency of suitability assessments [Wallace et al., 2023]. If such supplies can be tapped near coastal areas, they may help make artificial aeration operations logistically more viable and sustainable.

Foundations for Responsible Reoxygenation

For areas found to be potentially well suited for artificial reoxygenation interventions, consensus best practices should be followed when initiating pilot studies or larger implementations. As informed by discussions during a recent meeting organized by the United Nations Educational, Scientific and Cultural Organization Intergovernmental Oceanographic Commission’s Global Ocean Oxygen Network, several elements are foundational to these best practices.

Relevant government bodies, such as national and local water management authorities; stakeholders, including representatives of local communities; and scientists should be involved from the outset to safeguard the interests of all parties. Field trials and implementations should consider perceived environmental benefits and risks of the intended intervention, as well as relevant ethical issues, taking into account the intrinsic value of nature.

Monitoring is important for understanding baseline conditions and assessing the effects of reoxygenation on water quality and ecology, including termination effects after an intervention ceases.

Key biological, chemical, and physical parameters of the system where the intervention will occur (as well as of a reference site) should be monitored before, during, and afterward. This monitoring is important for understanding baseline conditions and assessing the effects of reoxygenation on water quality and ecology, including termination effects after an intervention ceases. Continued measurements over years to decades are also critical to determine longer-term effects.

Finally, the results of all field trials, including failures, should be reported completely, transparently, and publicly.

Artificial reoxygenation is unlikely to be a permanent solution to declining ocean oxygen, and it cannot replace essential measures to reduce greenhouse gas emissions and nutrient inputs to ocean waters. But with science-based suitability assessments and ethical, environmentally safe practices, reoxygenation interventions might prove beneficial in some places, allowing temporary mitigation of the detrimental consequences of coastal deoxygenation.

Acknowledgments

This feature article summarizes the discussion of a workshop on marine reoxygenation organized by the Global Ocean Oxygen Network (GO2NE) on 10–11 September 2024. We thank all participants for their contributions: D. Austin, L. Bach, L. Bopp, D. Breitburg, A. Canning, D. Conley, M. Dai, B. DeWitte, H. Enevoldsen, E. Ferrar, A. Galan, V. Garcon, M. Gregoire, B. Gustafsson,, D. Gutierrez, A. Hylén, K. Isensee, R. Lamond, M. Li, K. Limburg, I. Montes, J. Sterling, A. Tan Shau Hwai, J. Testa, D. Wallace, J. Waniek, and M. Yasuhara.

References

Breitburg, D., et al. (2018), Declining oxygen in the global ocean and coastal waters, Science, 359, 1–13, https://doi.org/10.1126/science.aam7240.

Conley, D. J., et al. (2009), Tackling hypoxia in the Baltic Sea: Is engineering a solution?, Environ. Sci. Technol., 43, 3,407–3,411, https://doi.org/10.1021/es8027633.

Fennel, K., and J. M. Testa (2019), Biogeochemical controls on coastal hypoxia, Annu. Rev. Mar. Sci., 11, 105–130, https://doi.org/10.1146/annurev-marine-010318-095138.

Grégoire, M., et al. (2023), Ocean Oxygen: The Role of the Ocean in the Oxygen We Breathe and the Threat of Deoxygenation, edited by A. Rodriguez Perez et al., Future Sci. Brief 10, Eur. Mar. Board, Ostend, Belgium, https://doi.org/10.5281/zenodo.7941157.

Harris, L. A., et al. (2015), Optimizing recovery of eutrophic estuaries: Impact of destratification and re-aeration on nutrient and dissolved oxygen dynamics, Ecol. Eng., 75, 470–483, https://doi.org/10.1016/j.ecoleng.2014.11.028.

Hermans, M., et al. (2019), Impact of natural re-oxygenation on the sediment dynamics of manganese, iron and phosphorus in a euxinic Baltic Sea basin, Geochim. Cosmochim. Acta, 246, 174–196, https://doi.org/10.1016/j.gca.2018.11.033.

Koweek, D. A., et al. (2020), Evaluating hypoxia alleviation through induced downwelling, Sci. Total Environ., 719, 137334, https://doi.org/10.1016/j.scitotenv.2020.137334.

Lapham L. L., et al. (2022), The effects of engineered aeration on atmospheric methane flux from a Chesapeake Bay tidal tributary, Front. Environ. Sci., 10, 866152, https://doi.org/10.3389/fenvs.2022.866152.

Lehtoranta, J., et al. (2022), Different responses to artificial ventilation in two stratified coastal basins, Ecol. Eng., 179, 106611, https://doi.org/10.1016/j.ecoleng.2022.106611.

Stigebrandt, A., et al. (2015), An experiment with forced oxygenation of the deepwater of the anoxic By Fjord, western Sweden, Ambio, 44(1), 42–54, https://doi.org/10.1007/s13280-014-0524-9.

Wallace, D., et al. (2023), Can green hydrogen production be used to mitigate ocean deoxygenation? A scenario from the Gulf of St. Lawrence, Mitigation Adapt. Strategies Global Change, 28, 56, https://doi.org/10.1007/s11027-023-10094-1.

Żygadłowska, O. M., et al. (2024), Eutrophication and deoxygenation drive high methane emissions from a brackish coastal system, Environ. Sci. Technol., 58, 10,582–10,590, https://doi.org/10.1021/acs.est.4c00702.

Author Information

Caroline P. Slomp (caroline.slomp@ru.nl), Radboud University, Nijmegen, Netherlands; also at Utrecht University, Netherlands; and Andreas Oschlies, GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany

Citation: Slomp, C. P., and A. Oschlies (2025), Could bubbling oxygen revitalize dying coastal seas?, Eos, 106, https://doi.org/10.1029/2025EO250163. Published on 1 May 2025. Text © 2025. The authors. CC BY 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Historic wildfires broke out in South Korea in late March 2025, killing 32 people, injuring 45, and displacing about 37,000. In total, the fires burned more than 100,000 hectares (about 247,000 acres), nearly quadruple the area that burned in the country’s previous worst recorded fire season in 2000. (In comparison, the January 2025 Palisades and Eaton Fires in Southern California burned about 91,000 hectares, or 37,000 acres.)

“This study adds to a growing body of science showing how climate change is making weather conditions more favorable to dangerous wildfires.”

A new study by scientists with World Weather Attribution (WWA) suggests that atmospheric warming—caused primarily by fossil fuel burning—made the hot, dry, and windy conditions that drove the South Korean fires about twice as likely and 15% more intense.

About 5,000 buildings burned, including homes, industrial structures, farms, and cultural heritage sites such as the Gounsa Temple in Uiseong, which was originally built in 618 CE.

Credit: World Weather Attribution

“The scale and speed of the fires were unlike anything we’ve ever experienced in South Korea,” said June-Yi Lee, an atmospheric scientist at Pusan National University and the Institute for Basic Science, in a statement. “This study adds to a growing body of science showing how climate change is making weather conditions more favorable to dangerous wildfires.”

Hot, Dry, and Windy

WWA researchers examined the Hot-Dry-Windy Index (HDWI) across the entire country for the month of March. This metric calculates fire risk from temperature, humidity, and wind speed observations.

The combination of high temperatures, low humidity, and high wind speeds that occurred from 22 to 26 March were unusual, even for today’s climate, the researchers found. Such conditions are expected to occur in March only once every 340 years. But this combination of conditions would have been even rarer in a preindustrial climate, occurring only once every 744 years.

The study suggests that the trend in the HDWI was driven primarily by unseasonably high temperatures.

“From March 22–26, the daily maximum average temperature in southeastern Korea averaged around 25°C, which was 10°C higher than the normal March average,” Lee said in a press briefing. Little rain fell in the region this winter, which, combined with high temperatures, led to drier, more flammable fuels. Relative humidity was around 20% at the time of the fires, not unusual for March. Wind speeds on 25 March reached up to 25 meters per second, a short-lived spike that helped the fires spread quickly.

The WWA team also calculated that if the climate warms by another 1.3°C by 2100, the HDWI will continue to increase, with the conditions behind such fires growing another 2 times as likely.

The nature of WWA’s rapid response studies means they are not peer reviewed, but they have published peer-reviewed studies on the methodology they use in all of their analyses. The study marks the World Weather Attribution’s 100th rapid analysis since the organization formed in 2014. It is the sixth to focus on a wildfire.

Credit: World Weather Attribution A Strong Case

ClimaMeter, another project that examines how extreme weather events may have been affected by a changing climate, released a study about South Korea’s wildfires on 25 March. (As with the WWA study, it was not peer reviewed but used peer-reviewed methods.)

ClimaMeter uses a different methodology than WWA does but had similar findings, reporting that the meteorological conditions leading up to the fires were about 2°C hotter, 30% drier, and 10% windier compared with similar past events.

“For the moment, it’s more difficult to prove that climate change did not affect an event.”

Davide Faranda, a physicist with the French National Centre for Scientific Research and coordinator of ClimaMeter, pointed out that their study showed climate change strengthened the meteorological conditions conducive to fires, not necessarily that climate change caused the fires. He was not involved with the WWA study but noted that the two groups’ rapid response studies often arrive at similar or complementary findings.

“For the moment, it’s more difficult to prove that climate change did not affect an event,” he said.

“A decade ago, the influence of climate change on events was less clear. But now it’s undeniable. The wildfires in South Korea are a case in point,” said Friederike Otto, WWA colead and a climatologist at Imperial College London, in a statement.

—Emily Dieckman (@emfurd.bsky.social), Associate Editor

Citation: Dieckman, E. (2025), Climate change heightened conditions of South Korean fires, Eos, 106, https://doi.org/10.1029/2025EO250170. Published on 30 April 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
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Source: Community Science

Research shows that communities are best able to mitigate the effects of climate change when they can work alongside scientists on adaptation plans. Hanson et al. recently extended this finding to Indigenous communities in the Colorado Plateau, including members of the Navajo Nation, Hopi Tribe, and Ute Mountain Ute Tribe.

To learn more about the qualities that make climate education most accessible to these groups, the researchers conducted a series of listening circles, interviews, and consultations with Indigenous peoples and Westerners with extensive experience working in Indigenous communities. They collaborated with members of the Nature Conservancy’s Native American Tribes Upholding Restoration and Education, or NATURE, program, which aims to equip Indigenous college students with natural resource management skills.

Several themes emerged. Indigenous students are most likely to engage in climate education when they’re actively recruited for a program, when mentors are willing to learn from students as well as teach them, and when a program emphasizes the value of integrating Traditional Knowledges with Western science, for instance. Small class sizes and ample one-on-one instruction also keep students engaged.

On the basis of these findings, the researchers created a climate module that can be taught as part of a broader college-level environmental science curriculum, for example, as part of a program like NATURE. The module is “menu style,” meaning that instructors and students can choose the activities they find appealing from an array of options. One option is classroom lessons on issues that are relevant to the Colorado Plateau, such as water conservation and cattle management. Another involves field trips, such as a day trip down the Colorado River, during which guides provide insights into how climate change is altering the landscape.

Indigenous students are “uniquely positioned to engage in environmental restoration” because they have deep connections with natural systems, the researchers wrote. This collaboratively designed program could help students achieve this potential, they say. (Community Science, https://doi.org/10.1029/2023CSJ000054, 2025)

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

Citation: Sidik, S. M. (2025), Teaming up to tailor climate education for Indigenous communities, Eos, 106, https://doi.org/10.1029/2025EO250166. Published on 30 April 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.

Source: AGU Advances

Hundreds of millions of people live in areas that could be affected by volcanic eruptions. Fortunately, clues at the surface, such as earthquakes and ground deformation, can indicate movement within underground magma dikes—sheets of magma that cut across layers of rock. Scientists can use these clues to make potentially lifesaving predictions of eruptions.

But there is room for improvement. Eruption predictions rely on modeling magma dikes, and most models treat magma as a simple Newtonian fluid (like water) whose viscosity stays constant under stress. However, magma’s crystals and bubbles make it more likely to behave as a non-Newtonian fluid whose viscosity decreases under greater stress (known as shear thinning). That’s especially true as it approaches the surface. Ketchup behaves similarly: It pours more easily from a jar when shaken.

Lab experiments by Kavanagh et al. reveal new insights into the potential dynamics of non-Newtonian magma flow in dikes. These findings could ultimately help improve eruption prediction strategies.

To mimic magma dikes, the researchers injected various fluids into a translucent and elastic solid gelatin material representing Earth’s crust. The injected fluids contained suspended tracer particles that could be illuminated by laser light, allowing the researchers to track each fluid’s flow within the forming dike as it traveled up from the injection site to the surface, where it “erupted” from the gelatin. They compared the behaviors of two non-Newtonian shear-thinning fluids, hydroxyethyl cellulose (a thickener often found in cosmetics) and xanthan gum (a thickener often added to foods), to water, a Newtonian fluid.

The experiments showed that the flow patterns of these fluids were very different from the flow patterns of water. However, even though their internal flow patterns differed, all fluids formed dikes with a similar shape and speed as they approached the surface.

These findings suggest that the primary information currently used to predict impending eruptions—such as the shape and speed of magma dikes—does not necessarily correlate with information about magma flow dynamics within the dikes. This result is significant because flow dynamics depend on magma characteristics that can affect how explosive an eruption will be or how quickly or how far the lava will travel.

Further research could help link these findings to real-world geological evidence and explore how they might help to improve eruption forecasting, the researchers say. (AGU Advances, https://doi.org/10.1029/2024AV001495, 2025)

—Sarah Stanley, Science Writer

Citation: Stanley, S. (2025), Matching magma dikes may have different flow patterns, Eos, 106, https://doi.org/10.1029/2025EO250167. Published on 30 April 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

Supercritical fluids—hydrous silicate liquids where water and melt become fully miscible—are believed to play a key role in chemical transport and element redistribution in subduction zones. However, the atomic-scale processes underlying their high mobility are poorly understood.

Chen et al. [2025] use first-principle molecular dynamics simulations to examine the diopside–H2O system over a wide range of water contents, pressures (up to 12 gigapascals), and temperature (3000 kelvin). Their results show that water promotes the breakdown of the silicate network by converting bridging oxygens (BOs) into non-bridging oxygens (NBOs), leading to the formation of smaller, less polymerized silicate clusters with greater diffusivity and structural stability. This depolymerization enhances atomic mobility and reduces viscosity, with strong linear correlations observed between polymerization degree and transport properties. The findings identify water-induced depolymerization as the primary mechanism behind the high mobility of supercritical fluids.

These insights have broad implications for understanding magma transport dynamics and the geochemical signatures—such as uranium-thorium disequilibria—in arc lavas. The study highlights the critical role of water in regulating the structure and dynamics of silicate fluids in subduction-related magmatic and mineralizing processes.

Citation: Chen, B., Song, J., Zhang, Y., Wang, W., Zhao, Y., Wu, Z., & Wu, X. (2025). Water dissolution driving high mobility of diopside-H2O supercritical fluid. Journal of Geophysical Research: Solid Earth, 130, e2024JB030956.  https://doi.org/10.1029/2024JB030956  

—Jun Tsuchiya, Editor, JGR: Solid Earth

Text © 2025. The authors. CC BY-NC-ND 3.0
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The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.

I have frequently highlighted the growing impact of multiple landslide events triggered by extreme rainfall around the world. Whilst there is little doubt that such events are becoming more common, they have occurred through history too. I recently came across a paper (Fiorillo et al. 2019) that documented such an event in 1954. The account is fascinating.

The paper sought to use historic aerial images and topographic data to reconstruct an inventory of the landslide triggered during this event. The location is the area around the villages of Vietri sul Mare and Maiori, which are sited on the beautiful Amalfi Coast in the Campania region of southern Italy. This is the area in the vicinity of [40.67, 14.73] – the Google Earth image below shows the landscape as it is today:-

Google Earth image of the modern setting of the 1954 landslides on the Amalfi Coast in Italy.

The analysis of Fiorillo et al. (2019) indicates that in parts of this area, 500 mm of rainfall fell in the storm that triggered these landslides. They have mapped over 1,500 landslides triggered by the storm – these are shown in the map below:-

Landslides triggered during the 1954 rainfall event on the Amalfi Coast in Italy. Map by Fiorillo et al. (2019).

As the map shows, the density of landslides was extremely high in the hills above Vietri sul Mare and Maiori. The failures were mostly shallow landslides, with many transitioning into channelised debris flows.

In total, it is believed that 316 people lost their lives in this disaster. There is some archive footage of the aftermath in the Youtube video below:-

Reference

Fiorillo, F., Guerriero, L., Capobianco, L., Pagnozzi, M., Revellino, P., Russo, F., and Guadagno, F. M., 2019. Inventory of Vietri-Maiori landslides induced by the storm of October 1954 (southern Italy). Journal of Maps, 15 (2), 530–537. doi: https://doi.org/10.1080/17445647.2019.1626777

Return to The Landslide Blog homepage Text © 2023. 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.

The EPA plans to cancel 781 grants, almost all focused on environmental justice, according to a court document filed last week.

In Woonasquatucket River Watershed Council v. Department of Agriculture, a coalition of nonprofits is challenging the Trump administration’s freezing of funding from the Biden-era Inflation Reduction Act (IRA) and Bipartisan Infrastructure Law. In the recent court document, Daniel Coogan, an administrator in the Office of Mission Support for the EPA, stated that the agency completed a grant-by-grant review of its awards to ensure that grants aligned with administration priorities. Those that were not aligned were targeted for termination.

All 781 grants targeted for termination fall under programs formed by the IRA, a 2022 law that helped to promote clean energy and bolster environmental projects. Most of the grants are part of EPA programs focused on environmental justice and include projects to help some of the United States’ most environmentally disadvantaged communities be resilient to the effects of climate change and protect residents from pollution. 

According to the court document, 377 grantees have been notified that their funding has been terminated, and the remaining 404 grantees will receive notices within the next two weeks. 

Hundreds of grantees’ projects will be affected by the terminations. In one such project, San Diego nonprofit Casa Familiar expected to receive $12.7 million to help a majority-Latino community obtain low-cost, zero-emission transportation and indoor air monitors and purifiers. The group has been unable to withdraw funds for months and now awaits notification that their grant has been terminated. In another example, the community of Chiloquin, Oregon, now expects that a planned community center and disaster shelter may never be built after the EPA suspended funding for the project.

 
Related

•  EPA is Canceling Nearly 800 Environmental Justice Grants, Court Filing Reveals
•  Democrats Demand EPA Reverse Termination of Grants for Clean Air and Water
•  Court Filing From Daniel Coogan
• Get Involved: AGU Science Policy Action Center
 

The news of the cancellations comes shortly after hundreds of EPA employees working on diversity, equity, and inclusion and environmental justice issues were given notice that they would be fired or reassigned.

According to the Washington Post, experts are concerned that the EPA did not conduct the full grant-by-grant review process required to terminate ongoing grants. “They’re claiming to the court that each one of those was done on an individualized basis, even though they haven’t shown any evidence,” Jillian Blanchard, vice president of climate change and environmental justice at Lawyers for Good Government, told the Washington Post.

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

These updates are made possible through information from the scientific community. Do you have a story about how changes in law or policy are affecting scientists or research? Send us a tip at eos@agu.org. Text © 2025. AGU. CC BY-NC-ND 3.0
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In a joint statement yesterday, Mexican and U.S. officials announced that Mexico will immediately transfer some of its water reserves to the United States and also allow a larger share of the Rio Grande River to flow into the United States. This concession from Mexico, which will last through at least October, seems to have averted the threat of additional tariffs and sanctions threatened by President Trump in early April.

Mexico and the United States share several major rivers, including the Rio Grande, the Colorado, and the Tijuana. Control over how much water each country receives from these rivers was set in a 1944 treaty. Under the treaty, Mexico must deliver 1.75 million acre-feet of water to the United States from six tributaries every 5 years, or an average of 350,000 acre-feet every year (An acre-foot is the amount of water needed to cover 1 acre of land to a depth of 1 foot.)

 
Related

•  Mexico to Give U.S. More Water From Their Shared Rivers (New York Times)
•  Welcoming Mexico’s Water Deliveries to the United States and Steps to Meet 1944 Water Treaty Requirements (U.S. State Department)
•  México y los Estados Unidos anuncian acuerdo sobre las asignaciones de agua del río Bravo conforme al Tratado de 1944 (Gobierno de México)
• Get Involved: AGU Science Policy Action Center

The United States and Mexico renegotiated parts of the treaty last year under the Biden Administration, allowing Mexico to meet its treaty obligations with water from other rivers, tributaries, or reserves. Yesterday’s announcement marks a commitment from Mexico to adhere to the amended treaty, rather than striking a new deal.

As climate change has worsened drought conditions in Mexico the country has struggled to meet the obligations of the treaty while supporting its farmers. Mexico’s current water debt to the United States is roughly 1.3 million acre-feet (420 billion gallons). Mexico’s president Claudia Sheinbaum acknowledged this water debt but said that Mexico has been complying with the treaty to “to the extent of water availability.”

In 2020, tensions over these water deliveries boiled over into violence: Mexican farmers rioted and seized control of a dam near the U.S.-Mexico border to halt deliveries. Mexican officials worry that increasing water deliveries during the hottest and driest months of the year will once again spark civil unrest among farmers.

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

These updates are made possible through information from the scientific community. Do you have a story about how changes in law or policy are affecting scientists or research? Send us a tip at eos@agu.org. Text © 2025. AGU. CC BY-NC-ND 3.0
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Source: AGU Advances

This is an authorized translation of an Eos article. 本文是Eos文章的授权翻译。

人类对地球的改造如此深刻，以至于大气化学家保罗·克鲁岑（Paul Crutzen）和生物学家尤金·斯托默（Eugene Stoermer）在2000年提出，全新世已经结束，“人类世”（Anthropocene）或人类时代已经开始。然而，尽管人类活动引发了如此巨大的变化，国际地质科学联合会（IUGS）去年仍决定不将人类世正式认定为当前的地质时代。现在，参与这一过程的几位科学家发表了一篇评论文章，解释了为什么他们认为应该再给人类世一个被认定为地质时代的机会。

McCarthy等人反驳了针对该提议的两个相关批评：首先，拟议的人类世仅开始于72年前，而每个地质时代通常跨越数百万年；其次，未来不属于地质时间，因此，基于人类将在遥远的未来在地球上留下印记的预期来指定一个时代是不恰当的。

作者认为，人类世的长度无关紧要，因为从功能上讲，地球已经进入了一个前所未有的时期。自20世纪中叶以来，地球的能源消耗量是之前11700年的六倍。由此产生的结果是，全球气温急剧上升，对从海平面到生物多样性再到冰盖等方方面面都产生了广泛的影响。这些变化将是长期的，有些甚至是不可逆转的。作者说，事实上，在如此短的时间内发生如此剧烈的变化，表明地球已经进入了一个新纪元。

一些地层学家认为，划定一个以人类为中心的时代会使地质学变得政治化，但作者认为，忽视数据以维持现状同样具有政治性。同样，有报道称，这个问题在十年内不会被重新讨论，因此我们是否生活在人类世的问题在那之前是确定的，作者对此感到愤慨。“事实并非如此，”他们写道。

—科学撰稿人Saima May Sidik (@saimamay.bsky.social)

This translation was made by Wiley. 本文翻译由Wiley提供。

Read this article on WeChat. 在微信上阅读本文。

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You can’t teach an old dog new tricks, but can you teach the current generation of Earth scientists about emerging artificial intelligence and machine learning (AI/ML) methods relevant to their research? From our experience helping run a program intended to do just that at the U.S. Department of Energy’s (DOE) Pacific Northwest National Laboratory (PNNL), the answer is yes.

Earth scientists, from those focused on the atmosphere or ocean to those studying the continents or deep subsurface, often work with extremely large—sometimes global—datasets, trying to find patterns among noisy real-world observations. AI/ML is well suited for such tasks.

Relatively few Earth scientists have been trained in artificial intelligence and machine learning (AI/ML) methods, meaning unfulfilled opportunities exist to learn from the growing volumes of Earth science data available.

AI/ML approaches have recently been used, for example, to replace slow, numerical representations of rainfall in a global general circulation model [Gettelman et al., 2021]. Similarly, AI/ML image detection techniques have been used with weather radar datasets to better predict short-term rainfall [Ji and Xu, 2024]. Yet relatively few domain scientists in the field have been trained in these methods, meaning unfulfilled opportunities exist to learn from the growing volumes of Earth science data available.

Several hundred data scientists work at PNNL, and for more than a decade, the lab has developed AI/ML approaches to address critical challenges in scientific discovery, energy resilience, and national security. Recent advancements in computational techniques and methodologies have sparked renewed interest in applying AI/ML across various disciplines. However, connecting the expertise of PNNL’s data scientists to Earth science research at the lab—encompassing atmospheric, hydrological, and environmental sciences—has been a challenge.

Beginning in 2022, researchers at PNNL implemented a two-step approach—a boot camp followed by a hackathon—to prepare their colleagues to incorporate AI/ML into their research effectively. Eighty percent of those who participated in both events are now using ML techniques in their research, and the experience has boosted collaboration between the lab’s data scientists and Earth scientists. The program has also led to innovative new projects, and its initial success suggests it may be a useful model for other organizations.

Boot Camp

Prior to PNNL initiating the program, many of the lab’s Earth scientists expressed interest in learning more about AI/ML and exploring its applicability for addressing a wide variety of science questions.

Atmospheric science in particular offers ideal ground for teaching and applying ML methods because these methods are conducive to tackling many common tasks in the field. For example, they can help fill patchy datasets, such as in time series of satellite imagery [Appel, 2024]; correct biases in gridded data (e.g., overestimations of solar radiation reaching Earth in reanalysis products) [Chakraborty and Lee, 2021]; merge measurements of atmospheric properties into numerical models [Krasnopolsky, 2023]; and iteratively improve models [Irrgang et al., 2021]. Furthermore, the field is ripe with the sort of very large, high-quality datasets that are necessary for applying modern ML methods.

The staff’s interest and the clear relevance of AI/ML for their work motivated development of an initial 10-week boot camp, held in fall 2022, with weekly hybrid (online and in-person) sessions attended by 30–50 people. We enlisted 10 in-house data scientists to design lessons, hands-on tutorials, and activities covering a range of AI/ML methods and tools.

As a result of the boot camp approach, participants gained understanding and appreciation of data curation for AI/ML and the full gamut of AI/ML methods they could use in their research.

The first four sessions introduced participants to the basics of ML, with each session building upon the previous one and focusing on more state-of-the-art approaches. The remaining sessions covered popular deep learning techniques such as convolutional neural networks (CNNs), generative adversarial networks, transformers, and recurrent neural networks. They also covered topics such as how to use the ML libraries Keras and PyTorch, which offer the tools to run these models and other useful resources.

To connect the lessons to the participants’ research interests, each one featured an Earth science–relevant activity, such as using maps of monthly sea surface temperature anomaly data from NOAA satellites with unsupervised learning algorithms to detect the phases of the El Niño–Southern Oscillation (i.e., El Niño and La Niña). The instructors developed and guided participants through virtual notebook environments that included fundamental information (with references) about the topic of the activity and heavily commented model code that could be run interactively. Time was also allotted for participants to better familiarize themselves with the models by running them in parallel on their own research computing environments.

As a result of the boot camp approach, participants gained understanding and appreciation of data curation for AI/ML and the full gamut of AI/ML methods they could use in their research. One remarked that they were impressed by the diversity of applications for ML and said, “I can tell if I continue to work on this skill, it will open a lot of doors and funding opportunities in the future for me.” Another commented, “By the end, I felt my programming skills had improved as well.”

Together with colleagues, one scientist at the lab who took part in the training applied knowledge and code directly from the boot camp material in research exploring stochasticity in aerosol-cloud interactions using field campaign data [Li et al., 2024].

The instructors also reported that participating in the boot camp was worthwhile for several reasons. Each of their lessons and student demonstrations were reviewed by the other instructors, which fostered connections among peers knowledgeable in ML. According to one instructor, teaching their fellow staff also “helped provide context of how valuable my expertise is here at the lab.”

Additional hands-on opportunities were necessary to bridge the gap between learning ML and putting it into practice. So we organized a second learning opportunity—this time a hackathon.

In addition, creating and presenting the weekly lesson plans to an audience with limited knowledge about AI/ML offered opportunities for instructors to improve their teaching skills. Furthermore, the adaptability of the instructional materials to other domain sciences supports the materials’ value, longevity, and easy reuse in future trainings and research.

One year after the boot camp, participant responses to a questionnaire indicated that though many had gained literacy in ML, most had not taken the next step to start incorporating ML methods into their research. The results also showed that additional hands-on opportunities were necessary to bridge the gap between learning ML and putting it into practice. So we organized a second learning opportunity—this time a hackathon—focused on pairing ML experts and data scientists with domain scientists who share common research interests.

The Hackathon

Twenty-five domain and data scientists, many of whom had participated in the boot camp, took part in the 6-week hackathon, which began in January 2024. The domain scientists involved work in various areas of Earth science and as part of DOE projects such as the Atmospheric Radiation Measurement user facility and the PNNL-led Addressing Challenges in Energy: Floating Wind in a Changing Climate (a DOE Energy Earthshot research center), as well as NASA’s Aerosol Cloud Meteorology Interactions over the western Atlantic Experiment project.

In preparing for the course, we discovered that these scientists often had trouble formulating research questions suited to ML methods and selecting which ML method to use. Prehackathon brainstorming sessions proved critical to success. During the first prehackathon meeting, the organizing committee gathered participants virtually to group the domain scientists by their topics of interest—vegetation-atmosphere interactions, clouds and precipitation, aerosols and aerosol-cloud interactions, hydrology, and wind energy—and to brainstorm potential research questions to address.

Each of the five groups then pitched project ideas to the participating ML experts and data scientists, who selected which team to join. With the teams assembled, each further workshopped a research question within their topic focus area—as well as which ML methods to use—that they could address within the duration of the hackathon. For example, one team chose to use a CNN model to identify open- versus closed-cell atmospheric convection in radar data, which helps explain distributions of clouds and rainfall.

During the hackathon, all the teams met weekly to discuss progress and exchange ideas for continuing work. This assessment method allowed the domain scientists to engage further with experts in the PNNL ML community, who provided feedback and answers to follow-up questions, such as how to prepare data for use in the ML models. Data preparation proved to be the most time-consuming step for the domain scientists because of the challenges of correctly formatting time series and gridded atmospheric datasets (e.g., temperature, relative humidity, and pressure) before they were fed into the models.

At the end of the 6 weeks, four of the five project groups had successfully processed their data and run them through their models to achieve results related to their initial questions. The fifth group, upon reflection, agreed that selecting an overly broad research question hindered progress on their project. Their experience underscored the importance of clearly defining a focused research question—and an appropriate ML approach—with cross-disciplinary consultation among scientists.

Soon after the hackathon concluded, a representative from each team presented their project during a seminar. A postseminar Q&A about the projects with staff who had not participated in the hackathon was positive and engaging, indicating a base level understanding of AI/ML methods within the division that was not present before the boot camp.

Fostering an AI-Literate Workforce

With growing datasets of Earth observations and ongoing computing advancements, AI/ML is an increasingly useful tool to aid in skillfully assessing conditions and processes in the Earth system.

Jingjing Tian presents results from the hackathon at the HydroML Symposium in May 2024. Her project involved training a convolutional neural network (CNN) model to detect open versus closed convection using weather radar data. Credit: Andrea Starr/Pacific Northwest National Laboratory

At PNNL, more than 20% of the research workforce is advancing AI and its applications in science. The initial goal of the recent training activities was to further grow ML expertise and implementation specifically within the lab’s Atmospheric, Climate, and Earth Sciences (ACES) division. The lessons and successes of these activities suggest that other organizations similarly seeking to expand their use of AI/ML may benefit from the model of PNNL’s approach.

The different approaches of the boot camp and the hackathon allowed instructors to meet participants at their preferred comfort level and cater to different learning styles.

The boot camp created a long-term, structured environment for a large number of staff to better understand the increasingly complex ML landscape, whereas the follow-up hackathon allowed a smaller group of eager staff to be coached in a faster-paced environment to produce deliverables. The different approaches of the boot camp and the hackathon allowed instructors to meet participants at their preferred comfort level and cater to different learning styles.

The results demonstrate that although learning new skills in AI/ML takes time, the effort is worthwhile and a collaborative, cross-disciplinary environment accelerates such learning. Staff self-reported that work done during the boot camp and hackathon had resulted in three conference presentations, including at the HydroML 2024 Symposium, and two publications (another is still in preparation).

Furthermore, PNNL reported an uptick in proposals from its Earth scientists for various internal funding opportunities focused on leveraging AI/ML methods. More proposals means more competition for funding, which should drive innovation and ultimately lead to stronger projects moving forward.

Another lesson from our experience was that sourcing instructors from within PNNL (i.e., ML experts who are already colleagues of Earth scientists in the ACES division) facilitated future collaborations between data and domain scientists and new research opportunities that wouldn’t have been possible previously. One of the participating AI/ML experts noted to us that “after the hackathon, many lab scientists reached out to me for help in implementing ML/AI algorithms into their work,” leading to multiple collaborations.

Hackathon participant Sha Feng’s comments offer additional, anecdotal evidence of the success of PNNL’s program: “Participating in the hackathon has been a transformative experience,” Feng said. “By bridging the gap between atmospheric science and data science, we have created a foundation for future projects that leverage the strengths of both fields.”

We plan to continue to bridge such gaps at PNNL—and we support other organizations doing the same—to advance applications of AI/ML to address crucial questions about our planet, from the atmosphere to the ocean to the solid Earth.

Acknowledgments

We acknowledge the instructors who took part in the boot camp and hackathon: Peishi Jiang, Tirthankar “TC” Chakraborty, Andrew Geiss, Sing-Chun “Sally” Wang, Robert Hetland, Rachel Hu and Danielle Robinson from Amazon Web Services, Erol Cromwell, Maruti Mudunuru, Robin Cosbey, Samuel Dixon, and Melissa Swift. We also acknowledge the work of colleagues who contributed to this article and supported these efforts: Sing-Chun “Sally” Wang, Court Corley, Larry Berg, Timothy Scheibe, Ian Kraucunas, and Rita Steyn.

References

Appel, M. (2024), Efficient data-driven gap filling of satellite image time series using deep neural networks with partial convolutions, Artif. Intell. Earth Syst., 3, e220055, https://doi.org/10.1175/AIES-D-22-0055.1.

Chakraborty, T. C., and X. Lee (2021), Using supervised learning to develop BaRAD, a 40-year monthly bias-adjusted global gridded radiation dataset, Sci. Data, 8(1), 238, https://doi.org/10.1038/s41597-021-01016-4.

Gettelman, A., et al. (2021), Machine learning the warm rain process, J. Adv. Model. Earth Syst., 13(2), e2020MS002268, https://doi.org/10.1029/2020MS002268.

Irrgang, C., et al. (2021), Towards neural Earth system modelling by integrating artificial intelligence in Earth system science, Nat. Mach. Intell., 3, 667–674, https://doi.org/10.1038/s42256-021-00374-3.

Ji, C., and Y. Xu (2024), trajPredRNN+: A new approach for precipitation nowcasting with weather radar echo images based on deep learning, Heliyon, 10(18), e36134, https://doi.org/10.1016/j.heliyon.2024.e36134.

Krasnopolsky, V. (2023), Review: Using machine learning for data assimilation, model physics, and post-processing model outputs, Off. Note 513, 32 pp., Natl. Cent. for Environ. Predict., College Park, Md., https://doi.org/10.25923/71tx-4809.

Li, X.-Y., et al. (2024), On the prediction of aerosol-cloud interactions within a data-driven framework, Geophys. Res. Lett., 51, e2024GL110757, https://doi.org/10.1029/2024GL110757.

Author Information

Lexie Goldberger, Peishi Jiang, Tirthankar “TC” Chakraborty, Andrew Geiss, and Xingyuan Chen (xingyuan.chen@pnnl.gov), Pacific Northwest National Laboratory, Richland, Wash.

Citation: Goldberger, L., P. Jiang, T. Chakraborty, A. Geiss, and X. Chen (2025), A two-step approach to training Earth scientists in AI, Eos, 106, https://doi.org/10.1029/2025EO250160. Published on 29 April 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Journal of Advances in Modeling Earth Systems

Climate models are essential tools for understanding and predicting our planet, but accurately setting their many internal parameters is complex and has been a labor-intensive manual task in the past.

Elsaesser et al. [2025] showcase a method using machine learning to automatically tune, or “calibrate,” the NASA GISS climate model against real-world observations. The authors develop a neural network surrogate of GISS ModelE to efficiently explore different parameter settings, creating a collection of well-performing model versions known as a calibrated physics ensemble. A key success was significantly improving the model’s simulation of challenging features such as shallow cumulus clouds and Amazon rainfall—longstanding modeling challenges—without negatively impacting, for example, radiation fields.

This work represents an important advance, moving automated calibration techniques from theoretical research into practical application for large-scale climate modeling. It brings us an essential step closer to more trustworthy climate predictions. 

Citation: Elsaesser, G. S., van Lier-Walqui, M., Yang, Q., Kelley, M., Ackerman, A. S., Fridlind, A. M., et al. (2025). Using machine learning to generate a GISS ModelE calibrated physics ensemble (CPE). Journal of Advances in Modeling Earth Systems, 17, e2024MS004713. https://doi.org/10.1029/2024MS004713

—Tapio Schneider, Editor, JAMES 

Text © 2025. The authors. CC BY-NC-ND 3.0
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Where do meteorites come from? A new analysis of 75 fall events suggests that meteorites with different geologies travel from different places in the asteroid belt, which separates Mars and Jupiter. Researchers traced some types of meteorites to particular asteroid families, creating a geologic map of meteorite origins. Most meteorites were generated by just a few recent collisions between asteroids.

“Understanding the asteroid belt is really looking into the past, into the formation of the solar system, and into all the dynamics that happened at that time,” said Peter Jenniskens, coauthor on the new analysis and a meteorite astronomer at the SETI Institute in Mountain View, Calif. Those early interactions and collisions matter because much of the water on Earth and a lot of the organics likely came from primitive asteroids, he added.

Tracking Falls

Spacecraft have returned small volumes of material from the Moon, comets, and asteroids, but meteorites remain the primary way that scientists get their hands on space rocks.

“By reconstructing where specific meteorite types formed, we gain a clearer picture of the compositional and thermal gradients that existed when the solar system was young,” said Michaël Marsset, an astronomer at the European Southern Observatory in Santiago, Chile. “This has major implications for understanding how habitable environments emerge, not just here but potentially in other planetary systems as well.” Marsset studies small solar system objects and Earth impactors and was not involved in the new study.

But matching a meteorite to the asteroid it came from is a tall task.

“Asteroids in space look quite a bit different than the meteorites that we have in our laboratories.”

“Asteroids in space look quite a bit different than the meteorites that we have in our laboratories, because the asteroids in space are covered by regolith and debris and they are exposed to solar radiation and solar wind,” Jenniskens said. A meteorite might come from an asteroid’s interior, which could look entirely different from its surface. That makes it challenging to use astronomical observations alone to match meteorites to their asteroid parents.

When someone witnesses a meteorite falling to Earth, scientists can try to backtrack its orbit to a point of origin. Combining this information with the meteorite’s geochemistry, mineralogical structure, and age, they can then figure out which asteroid or asteroid family—a group of asteroids that originate from the same collision event—sent it hurtling toward Earth.

The trouble is that meteorites fall more or less at random, Jenniskens explained. It has taken a while to document enough falls to spot patterns, he said. Just 6 years ago, there were fewer than 40 meteorite falls with well-measured trajectories.

“The number of falls has doubled since that time,” Jenniskens said.

Meteorite researchers have set up more than 2 dozen global camera networks that have detected many of these recent falls—roughly 14 falls per year. Also, the rising popularity of dash cameras and doorbell cameras has contributed to the surge of recent detections.

In the new analysis, about 36 of the 75 falls were recorded by residential security cameras, Jenniskens said. People report fireball sightings and submit videos for analysis. “We really depend on the citizen science.”

Meteorite Ancestry

Jenniskens and his colleague Hadrien Devillepoix of Curtin University in Perth, Australia, reviewed the trajectories, geochemistry, mineralogy, and size of 75 meteorites. They also looked at the meteorites’ ages, calculated on the basis of how long a rock’s surface has been exposed to cosmic rays.

Though a few asteroids are suspected sources of certain meteorite types, a meteorite’s age was often the key factor in figuring out which asteroid family produced the meteorite. The positions and movements of asteroids within a family evolve in a predictable way over time, and if this so-called dynamical age matched a meteorite’s cosmic ray age, that family was more likely to be the meteorite’s source.

NASA’s Dawn spacecraft orbited asteroid 4 Vesta and mapped its surface geology and chemistry. Debris from impacts that made some of these craters makes it way to Earth as HED meteorites. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA, Public Domain

Most of the meteorites originated from a handful of asteroid families, and different classes of meteorites could be traced to different parts of the asteroid belt.

Jenniskens and Devillepoix confirmed that very low iron LL-type meteorites, such as the Chelyabinsk meteorite, originated from the extensive Flora family in the inner asteroid belt. They tracked H-type chondrites to debris clusters in the Koronis, Massalia, and Nele families. They also traced low-iron L chondrites to the Hertha asteroid family, rather than to the previously determined Massalia family.

“Hertha is covered by dark rocks that were shock blackened, indicative of an unusually violent collision,” Jenniskens said. “The L chondrites experienced a very violent origin 468 million years ago when these meteorites showered Earth in such numbers that they can be found in the geologic record.”

“It turns out that, yes, our HED meteorites seem to come from Vesta, not from its family.”

Marsset has also worked to trace meteorites to their asteroid origins, though his team used astronomical observations of asteroids and numeral modeling, rather than meteorite data. “Even with these different approaches, we’re mostly converging on similar conclusions,” Marsset said. “Where we disagree, well, that’s part of the fun! For example, I’d gladly bet a pint with Dr. Jenniskens and Dr. Devillepoix that L chondrites come from the Massalia family, not Hertha,” he joked.

The team also looked at howardite, eucrite, and diogenite (HED) meteorites, achondrites that have long been tied to the Vesta asteroid family. According to the new analysis, the volume of HED material that made its way to Earth must have come from a collision so large that it only could have happened on Vesta itself. (Vesta is the second-largest object in the asteroid belt.) What’s more, the cosmic ray exposure ages of HED meteorites closely match the ages of particular impact craters on Vesta’s surface that were mapped by NASA’s Dawn spacecraft.

“It turns out that, yes, our HED meteorites seem to come from Vesta, not from its family,” Jenniskens said.

Decoding Solar System History

“What’s remarkable about this work is the broader picture it starts to paint,” Marsset said. “We are finally able to map specific classes of meteorites that fall on Earth to distinct regions in the asteroid belt and to specific asteroid families.… That’s a major step toward understanding the compositional structure of the asteroid belt and, ultimately, how our solar system formed and evolved.”

But it’s just as important to understand where meteorites aren’t coming from, he pointed out.

“While one might expect the meteorite flux to represent a broad sampling of material from across the entire asteroid belt, we now know that it is actually dominated by a few recent fragmentation events,” Marsset said. “This insight helps us better understand the natural sampling bias in the meteorites we collect on Earth, and it also highlights which asteroid populations are underrepresented. That, in turn, can guide the targets of future space missions aimed at filling in those missing pieces.”

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

Citation: Cartier, K. M. S. (2025), A geologic map of the asteroid belt, Eos, 106, https://doi.org/10.1029/2025EO250165. Published on 28 April 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: Global Biogeochemical Cycles

Glaciers provide a unique opportunity for researchers to measure levels of atmospheric carbon deposition. Unlike other terrestrial ecosystems, these slow-moving rivers of ice do not have other large reservoirs of soil or vegetation that might obscure how much carbon they receive from the atmosphere.

In most terrestrial ecosystems, dissolved organic matter comes from plants and soil and can contain both organic carbon and black carbon (the sooty black product from wildfires and burning fossil fuels). In glaciers, organic matter is predominately derived from in situ microbial production and atmospheric deposition. Both can contribute to downstream food webs and broader biogeochemical cycling.

Understanding how glaciers get their carbon, including how much comes from atmospheric deposition, can help scientists understand how human activity affects the glacier carbon cycle and ecosystems.

Holt et al. investigated dissolved organic matter in the meltwater from 10 glaciers across Alaska, Switzerland, Kyrgyzstan, and Ecuador. By examining dissolved organic carbon and black carbon isotopes, as well as molecular-level composition, researchers found that anthropogenic pollutants significantly influenced the composition of dissolved organic matter in glaciers and that this influence varied by region.

The researchers collected samples from each glacier outflow stream and determined the age of the dissolved organic carbon in the samples. These ages offered an isotopic signature of their sources. For instance, younger samples might originate from wildfire material and microbial activity on the glacier surface, whereas older material more likely originated from ancient carbon sources, namely, fossil fuels.

Each region displayed different amounts of dissolved organic carbon linked to anthropogenic atmospheric pollution, ranging from 12% to 91%, with a median of 50%. Carbon from fossil fuels was more prevalent in the dissolved organic matter of the Alaskan glacier. In Ecuador, there was a higher relative contribution of carbon from biomass burning, such as wildfires, and in situ microbial activity. The exact source, age, and makeup of dissolved organic carbon and dissolved black carbon varied between different glaciers outflows. But overall, the researchers say, fossil fuels are affecting the carbon content in glacier outflow globally, with implications for the ecosystems that depend on them. (Global Biogeochemical Cycles, https://doi.org/10.1029/2024GB008359, 2025)

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

Citation: Owen, R. (2025), Glaciers offer clues into the path of fossil fuel pollution, Eos, 106, https://doi.org/10.1029/2025EO250161. Published on 28 April 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: Earth’s Future 

Coral atoll islands are particularly vulnerable to sea level rise and climate change. In rural islands where active coastal sediments processes are occurring, wave-driven sediment deposition can raise islands’ crest on their oceanward side.

Roelvink et al. [2025] show that coastal morphodynamic models are now able to provide quantitative insight into these phenomena. Specifically, they show that in the natural islands of Fiyoaree (Maldives), the sediment accumulation on the island crests can mitigate the projected increase of overwash during extreme wave events by a factor of three. Their modeling framework also confirms the benefits of adaptation measures aiming at protecting corals, particularly in reducing incoming wave energy. As climate is warming due to anthropogenic greenhouse gas emissions, increasing sea surface temperatures are causing widespread bleaching and mortality of corals, raising the urgent question of limits to coral adaptation, even at 2 degrees Celsius of global warming.

Hence, the study opens the way for future research exploring these limits in a quantitative manner, while also reminding us about the urgency of mitigating climate change to avoid irreversible losses and damages.

Citation: Roelvink, F. E., Masselink, G., Stokes, C., & McCall, R. T. (2025). Climate adaptation for a natural atoll island in the Maldives – predicting the long-term morphological response of coral islands to sea level rise and the effect of hazard mitigation strategies. Earth’s Future, 13, e2024EF005576. https://doi.org/10.1029/2024EF005576

—Gonéri Le Cozannet, Associate Editor, Earth’s Future

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

The stratosphere, one of the Earth’s atmospheric layers, is essential to understand due to its significant influence on the global climate system. Given that the composition of the stratosphere is highly influenced by air transport and circulation, scientists have developed a measure called “age of air” to quantify how long air has been in transport.

A new article in Reviews of Geophysics explores the development and use of this stratospheric age of air metric. Here, we asked the lead author to give an overview of the stratosphere, how scientists use the age of air metric, and what questions remain.

In simple terms, what is the stratosphere and what makes it a particularly interesting layer of the atmosphere to study?

The stratosphere is the second layer of the atmosphere from the ground, at about 20 to 50 kilometers high. Below, in the troposphere, temperatures decrease with height, but in the stratosphere, it gets warmer when moving higher up. This is mostly because of the stratospheric ozone layer, which absorbs high-energy sunlight that warms the stratosphere, and, at the same time, protects us from harmful UV radiation.

The dynamics of the stratosphere are very interesting: the stable stratification (i.e., temperature increase with height) inhibits the formation of “weather”, as we know, it in the troposphere. Nevertheless, the stratosphere is not boring. Certain atmospheric waves formed in the troposphere can propagate upward, and drive a gigantic heat pump in the stratosphere, transporting air upward in the tropics, poleward, and downward over the poles. The existence of such a circulation was first postulated in the 1940s and 1950s and has been named after its proposers the “Brewer-Dobson circulation”.

How does the “Brewer-Dobson circulation” help us to understand the composition of the stratosphere?

Hemisphere-wide transport circulation is important to understand how trace gases are distributed in the stratosphere.

The hemisphere-wide transport circulation is important to understand how trace gases are distributed in the stratosphere. For example, ozone is formed by photochemistry, thus primarily in the tropics, where most sunlight is available. However, ozone concentrations maximize at mid- to high latitudes, and this is thanks to transport by the Brewer-Dobson circulation. Indeed, when Brewer and Dobson took observations of ozone and water vapor in the stratosphere, the only way they could explain them was by a large-scale poleward circulation. However, at this time it was not clear how this circulation could be driven physically, and it took the science community another few decades to understand the dynamical driving of the circulation.

What is the “age of air” and how can it be observed and measured?

One of the problems with the Brewer-Dobson circulation is that it is difficult to observe it directly, since the mean velocities associated with the slow upward motion in the tropics are on the order of millimeters/second. Furthermore, processes other than the slow overturning circulation are important for understanding total transport of air masses, like fast mixing of air between tropics and extra tropics.

One way to quantify this total transport circulation is by average transport times, i.e., measuring how long it takes air to move from its entry into the stratosphere in the tropics to another point in the stratosphere. This transport time is commonly known as “age of stratospheric air”.

One advantage of age of air is that it can be deduced from certain observable trace gases. Specifically, if the concentration of a trace gas rises steadily in the troposphere, one can measure the delay of concentrations in the troposphere versus in the stratosphere. This delay equals the age of air, but strictly only if the trace gas has ideal properties of a linear increase in concentration and no chemical sinks or sources. In the real world, we have some tracers that almost fulfill those conditions, but not exactly, one example being carbon dioxide. Correcting for the non-ideal properties of tracers when deriving age of air from observations is possible, but it is a bit of an art, as we summarize in our new review paper.

How has data on the age of air advanced understanding of processes in the stratosphere?

Many trace gas measurements have been collected via aircraft, balloon, or satellite observations, and we can use them to deduce age of stratospheric air.

Over the last few decades, many trace gas measurements have been collected via aircraft, balloon or satellite observations, and we can use them to deduce age of stratospheric air. This puts us in a situation that we now have a good observational data base on how “old” the air is in the stratosphere on average. As described above, age of air is a measure of the total transport strength in the stratosphere, including many different processes. This is both good and bad: on the one hand, age of air is very well suited to test if global climate models do a good job in simulating transport. On the other hand, solely based on age of air, it is difficult to say which process is how important for the total transport time. Coming up with additional diagnostics of how we can better disentangle the role of different processes for total transport, i.e., for age of air, has been a focus of research in recent years, with good progress.

How is age theory being applied beyond the stratosphere?

The concept of age of air as a measure of transport times from a defined surface to a certain point in a fluid can be used for many geophysical circulations systems. For example, it is commonly used by oceanographers to measure when a water parcel was last in contact with the surface – in this case, the age is considerably longer, on the order of centuries or even millennia, compared to a few years for air in the stratosphere.

Why is understanding stratospheric circulation important for projecting the impacts of climate change?

Changes in the concentration of trace gases in the troposphere under climate change, such as carbon dioxide, methane or nitrous oxides, will be communicated to the stratosphere via the transport circulation. There, those trace gases can have effects on stratospheric temperature via radiation, but also on chemistry, leading to changes in the stratospheric ozone layer or stratospheric water vapor.

Stratospheric circulation and its changes are important in order to understand how the stratospheric ozone layer will be influenced by climate change.

Moreover, there is a long-standing consensus between climate models that the stratospheric Brewer-Dobson circulation will speed up in response to climate change, with consequences for how fast trace gases are transported into and through the stratosphere. Thus, stratospheric circulation and its changes are important in order to understand how the stratospheric ozone layer will be influenced by climate change, directly impacting our UV shield. Moreover, changes in the concentrations of ozone and water vapor, particularly in the lower stratosphere, lead to changes in the overall radiation, directly impacting climate change on the surface.

What are some of the remaining questions where additional modeling, data or research efforts are needed?

A topic of much debate over the last decades is whether the acceleration of the Brewer-Dobson circulation simulated by climate models can be detected in observations. The problem here is that the trends are on the order of a few percent per decade, so we need very high precision data for many decades to detect a trend. Given many uncertainties in deducing age of air from trace gas measurements, at the moment we must conclude that our database is not good enough to derive long-term trends in age of air, at least in the middle stratosphere. Thus, continuous collection of high-quality data of stratospheric trace gases will be necessary to make progress on detecting long-term changes in the stratospheric circulation.

—Hella Garny (hella.garny@dlr.de; 0000-0003-4960-2304), Institute of Atmospheric Physics, German Aerospace Center (DLR), Germany

Citation: Garny, H. (2025), An air parcel’s journey through the stratosphere, Eos, 106, https://doi.org/10.1029/2025EO255014. Published on 25 April 2025. This article does not represent the opinion of AGU, Eos, or any of its affiliates. It is solely the opinion of the author(s). Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

This is an authorized translation of an Eos article. Esta es una traducción al español autorizada de un artículo de Eos.

Después de 5 años de organizar el TierraFest, un evento anual que celebra las ciencias de la Tierra en México, una de las cosas que Raiza Piltowsky Gruner ha aprendido es que cuando se trata de comunicar el conocimiento sobre nuestro ambiente, “nosotros los científicos no somos las personas con la mayor autoridad. Todos vivimos en este planeta”.

“Hay muchas otras formas de generar conocimiento, para validarlo y vivirlo”.

Ella explicó esto durante la conferencia de prensa del evento, donde además anunció el tema del festival para este año: “Juntxs contra la tormenta”. Los organizadores del TierraFest no querían transmitir la idea de que los científicos eran la única fuente de soluciones a problemas como el cambio climático, dijo Pilatowsky Gruner. Este ha sido uno de los valores bases de Planeteando, la asociación sin fines de lucro detrás del TierraFest.

Aunque el método científico es válido e importante, “hay muchas otras formas de generar conocimiento, para validarlo y vivirlo”, añadió Pilatowsky Guner. Ella cree que esta filosofía ha hecho del TierraFest un espacio seguro para la diversidad en un escenario político incierto.

Esta semana, Ciudad de México será sede de una feria de ciencia, performances en vivo y películas para gente de todas las edades para reflexionar sobre la relación que tenemos con el planeta.

Aprendizaje horizontal

Un ejemplo de diversidad en el festival de este año es el evento de apertura, dijo Carla Chávez, quien empezó en Planeteando como una estudiante de servicio social y es ahora una colaboradora regular. El 22 de abril (Día de la Tierra), el TierraFest empieza con una caminata al Parque Nacional de Los Dinamos, un bosque por donde pasa el Río Magdalena, el último río que corre libre en la capital de México.

“Creemos en el aprendizaje horizontal. Aprendemos de ellos y ellos aprenden de nosotros”.

Chávez, una bióloga de la Universidad Nacional Autónoma de México (UNAM), explicó que en Planeteando no quieren ser intrusos en la comunidad histórica de la Magdalena Atlitic, donde se llevará a cabo la caminata. “Creemos en el aprendizaje horizontal”, dijo. “Aprendemos de ellos y ellos aprenden de nosotros”.

Durante la caminata, Marisol Tovar Valentínez y su equipo de monitores comunitarios, miembros de la comunidad que hacen voluntariado para proteger sus bosques, guiarán a los participantes en su bosque, acompañados por los organizadores del TierraFest y la National Geographic Explorer Daniela Cafaggi.

Como parte del aprendizaje horizontal, los monitores comunitarios en entrenamiento se unirán a la caminata para aprender del equipo del TierraFest y practicar sus habilidades para guiar grupos. Además también compartirán su conocimiento sobre el bosque con los asistentes.

A diferencia de Pilatowsky Gruner, Tovar Valentínez dijo que piensa que, de hecho, los científicos podrían tener una voz de autoridad sobre el conocimiento del planeta. “Pero no sobre la sabiduría”, apuntó, describiendo la sabiduría como el conocimiento creado y protegido como comunidades como la suya. La sabiduría es un proceso continuo y vivo, dijo, aunque está en peligro de perderse a medida que mueren los ancianos de la comunidad.

Tovar Valentínez dijo que valora trabajar con científicos, incluyendo Cafaggi, una bióloga de la UNAM que trabaja con la comunidad Atlitic para estudiar los murciélagos en sus bosques.

Uniendo perspectivas distintas

El 24 de abril, el TierraFest continuará con el ConCervezatorio, evento en el que científicos y activistas comparten sus opiniones y perspectivas con unos tragos.

Pilatowsky Gruner explicó en la conferencia de prensa que los organizadores quieren usar el TierraFest 2025 para resaltar la importancia de unir gente de diferentes contextos, “Juntxs contra la tormenta”. Esa unidad puede ayudar a los individuos y comunidades a enfrentar el cambio climático y las tendencias globales como el extractivismo, ambas “tormentas” afectando el mundo entero.

Después de los tragos, la celebración de distintas perspectivas sobre los retos de la Tierra continúa. Chávez se meterá en la piel de Carmilla Desmondus, una drag queen inspirada en la icónica vampira lesbiana del libro Carmilla, de autor irlandes Joseph Sheridan Le Fanu y Desmondus, el género de los “murciélagos vampiros” chupa sangre.

“Dragas por la Tierra” surgió como un evento anual en el TierraFest tres años atrás, cuando se invitó a participar a la drag queen Bia Hollis. Pedro Adad Tristán Flores, biólogo detrás de Bia Hollis, fue también un estudiante de servicio social de Planeteando antes de ser un colaborador recurrente. Desde entonces, cada año su colectivo de drag queens toma inspiración de los temas del TierraFest para diseñar sus vestuarios y su maquillaje, los que ellas explican durante el show.

Este año, las actividades LGBTQ+ del TierraFest se expandirán para incluir el performance de teatro playback del colectivo Xuir, en el cual la audiencia contará sus historias personales mientras que los actores las interpretan en vivo. Los organizadores propondrán historias sobre la intersección entre el trabajo científico y las identidades LGBTQ+.

Mostrándole el mundo a los asistentes

El 26 de abril, el TierraFilme presentará otra de sus ediciones de películas sobre el planeta Tierra. Por primera vez, este evento se realizará en el Papalote Museo del Niño, un espacio dedicado a la comunicación de la ciencia para niños, y empezará con la proyección de uno de los episodios de la serie documental de National Geographic A Real Bug’s Life. Los asistentes verán cortometrajes de México y de Latinoamérica sobre temas como el efecto de la basura, la pérdida de lenguas indígenas y los impactos de la expansión urbana.

Los eventos del TierraFest terminarán el 27 de abril, cuando El Centro Cultural El Rule, la casa del festival ya por un tiempo, recibirá una vez más la Feria de Ciencia TierraFest. Activistas y científicos mostrarán su trabajo a adultos y niños en más de 20 talleres sobre el agua, el aire, la Tierra y la vida. Desde la vida en los mares paleozoicos hasta problemas contemporáneos como el impacto que las tuberías de gas subacuáticas podría tener en las ballenas, estos científicos están enfocados en entender mejor el planeta y compartir el conocimiento con todos.

—Roberto González (@ggonzalitos), Escritor de ciencia

This translation by Anthony Ramírez-Salazar (@Anthnyy) was made possible by a partnership with Planeteando y GeoLatinas. Esta traducción fue posible gracias a una asociación con Planeteando and GeoLatinas.

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.

A new executive order, issued on 24 April, aims to help private companies to mine the deep sea.

Some areas of the ocean floor host swaths of potato-sized nodules that contain coveted minerals such as cobalt and nickel. For the past decade, the International Seabed Authority (ISA) has been developing a mining code, which would govern the laws of how nations explore and exploit these resources.

But in the new executive order citing the 1980 Deep Seabed Hard Mineral Resources Act, President Trump declared that the United States—the only major global economy that is not part of the ISA—would create a process for granting companies permits to mine these minerals.

Under the Law of 1994 United Nations Convention on the Law of the Sea Treaty (which the United States did not ratify), a nation has economic rights to the resources within 200 nautical miles of its coast, but international waters fall under ISA jurisdiction.

The new order aims to establish the United States “as a global leader in seabed mineral exploration and development both within and beyond national jurisdiction,” according to text released by the White House.

 
Related

•  Unleashing America’s Offshore Critical Minerals and Resources
•  Trump Takes a Major Step Toward Seabed Mining in International Waters
• Why the U.S. is absent from international seabed mining talks
• Get Involved: AGU Science Policy Action Center
 

Dozens of nations have called for a moratorium, pause, or ban on deep-sea mining, and companies including BMW, Google, and Samsung have vowed to not use deep-sea minerals in their products until the risks of doing so are better understood. When The Metals Company, a Canadian seabed mining company, announced in March that it planned to apply for exploration and extraction permits through the U.S. government, even nations that generally support mining in international waters, such as China and Russia, condemned the company’s actions.

At the ISA Council’s session last month, Leticia Carvalho, secretary general of the ISA, expressed “deep concern” over The Metals Company’s announcement, saying that any unilateral action not taken under the ISA’s authority “would constitute a violation of international law.”

As Eos has reported, much of the concern surrounding deep sea mining comes from how little is known about ecosystems on the ocean floor, meaning mining these modules could have significant unforeseen impacts.

“There are still major gaps in understanding biodiversity and ecosystem functions at polymetallic nodule ecosystems,” Sabine Gollner, a deep-sea marine biologist at the Royal Netherlands Institute for Sea Research told Eos last year. “Once nodules are removed by mining, all biodiversity and functions directly dependent on the minerals will be lost for millions of years at the mined location.”

—Emily Dieckman (@emfurd.bsky.social), Associate Editor

These updates are made possible through information from the scientific community. Do you have a story about how changes in law or policy are affecting scientists or research? Send us a tip at eos@agu.org. Text © 2025. AGU. CC BY-NC-ND 3.0
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Neutron stars, supernova explosions, and other extremely energetic phenomena across the universe produce gamma rays, the highest-energy radiation in the electromagnetic spectrum. Closer to home, the Sun also emits gamma rays, and here on Earth, gamma ray sources include nuclear explosions, radioactive decay of certain materials (sometimes applied for medical uses), and—as we’ve known for about 30 years—lightning.

Many details of lightning-generated gamma rays, however, including how common they are, have remained uncertain over the past few decades since they were discovered. Every day, more than 3 million lightning strikes occur in thunderstorms around the planet. How many of these lightning bolts emit gamma radiation?

Such information is important for improving our understanding of the chemistry and dynamics of thunderclouds and other features, which feeds into our ability to forecast weather, including potentially hazardous conditions, more accurately.

With recent observations and research, scientists are revealing new insights into the mysteries of Earth’s atmospheric gamma rays, including that thunderclouds act as huge particle accelerators, emitting gamma rays far more often than previously thought.

Early Observations of Terrestrial Gamma Rays

The scientists involved were clearly amazed to find that such a gamma ray source existed in their own backyard.

In the early 1990s, the first observations of gamma rays in thunderstorms revealed a phenomenon known as terrestrial gamma ray flashes (TGFs). The discovery, made by the Compton Gamma Ray Observatory (CGRO), a space observatory built to study gamma rays originating in space, came as a big surprise for the scientific community. The scientists involved were clearly amazed to find that such a gamma ray source existed in their own backyard, writing that “detectors aboard the CGRO have observed an unexplained terrestrial phenomenon: brief, intense flashes of gamma rays” [Fishman et al., 1994].

The find immediately set the stage for the next 3 decades of research in the field of atmospheric electricity, with researchers intensely scrutinizing terrestrial gamma rays. However, in retrospect, it is evident that for much of this time, exploration and measurements of gamma rays were hampered by the available instrumentation. The only workable detectors for gamma ray detection at the time had been developed to study processes other than TGFs. These detectors included the Burst and Transient Source Experiment (BATSE) on CGRO and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and, more recently, the Astro Rivelatore Gamma a Immagini Leggero and the Fermi Gamma-ray Burst Monitor.

BATSE, for example, was designed to study gamma ray bursts from the universe, but because it had difficulty capturing very short (~1 millisecond) TGFs, the BATSE measurements were heavily biased toward the most intense events. Meanwhile, RHESSI measurements sometimes combined detections of TGF photons from two events into one [Grefenstette et al., 2008].

A Purpose-Built Mission

A few years before the discovery of TGFs, in 1989, the first documented cases of unexpected lightning above thunderclouds were observed. Several phenomena, collectively referred to as transient luminous events (TLEs), were characterized and given mythical names like blue jets, elves, and red sprites.

Early this century, researchers began developing a plan to study these newly identified atmospheric events from the International Space Station (ISS). With scientists at the University of Valencia in Spain and the University of Bergen (UiB) in Norway, Torsten Neubert from the Technical University of Denmark initiated the Atmosphere-Space Interactions Monitor (ASIM) project. While Neubert and his team took the lead on TLE studies, Nikolai Østgaard and his group at UiB developed an instrument specifically designed for TGF studies called the Modular X- and Gamma-ray Sensor (MXGS) as part of ASIM.

The finding that terrestrial gamma ray flashes (TGFs) happen before the visible flashes of lightning was crucial for establishing a theoretical framework for the sequence of events in thunderstorms.

In 2018, the ASIM payload was finally launched into space and mounted on the ISS’s Columbus module. From this vantage, more than 400 kilometers above the ground, ASIM would have a view from above of the drama unfolding during thunderstorms. Over the next few years, the scientists reported several groundbreaking observations.

For example, Østgaard et al. [2019] found that TGFs observed from space actually occur before or simultaneously with the optical (visible light) pulses of lightning. Østgaard et al. [2021] then found that the delay of the optical pulse in those cases was explained well by the scattering of light through clouds. This finding, that TGFs happen before the visible flashes of lightning, was crucial for establishing a theoretical framework for the sequence of events in thunderstorms. It means that electrons are accelerated to relativistic energies in electric fields associated with long conductive leaders and that the optical pulse we see from space is a signature of the leader discharge that follows.

In another study, Neubert et al. [2019] reported the first simultaneous observation of TGFs and TLEs known as elves (emissions of light and very low frequency perturbations), confirming previous theoretical predictions of their co-occurrence.

ALOFT Changes the Game

ASIM observations provided great insights into TGFs, but the question remained whether a significant population of TGFs that are too weak to observe from space existed. That question, addressed and discussed by Østgaard et al. [2012], motivated the Airborne Lightning Observatory for FEGS and TGFs (ALOFT) flight campaign, a collaboration between UiB and NASA, in summer 2023.

The ER-2 aircraft is seen from below during an ALOFT campaign flight on 12 July 2023. Credit: NASA/Carla Thomas

Building on their experience developing MXGS, the UiB scientists came up with a new instrument, called UiB-BGO, to measure gamma rays from NASA’s ER-2 aircraft. Although the detector and front-end electronics were similar to those in MXGS, the system used on ASIM to trigger gamma ray measurements was replaced with a data acquisition and storage system that enabled continuous data recording during flights.

The results from the Airborne Lightning Observatory for FEGS and TGFs flight campaign have turned out to be game-changing.

Ten ALOFT flights were conducted, with NASA operating the ER-2 out of MacDill Air Force Base in Florida. The aircraft visited tropical thunderstorms around the Gulf of Mexico, Central America, and the Caribbean, flying just above the thunderclouds at heights of about 20 kilometers and bringing the UiB-BGO as close as possible to the spectacular events unfolding.

Real-time telemetry of gamma ray count rates allowed scientists to recognize immediately whether the plane was flying over a gamma ray–producing storm. They could then instruct the pilot to turn and scan an area again to maximize gamma ray detections. The ER-2’s instrument payload also included lightning sensors and microwave sensors, which provided data on thundercloud characteristics.

The results from ALOFT have turned out to be game-changing. Prior to the flight campaign, terrestrial gamma rays were considered rare, and only two types—microsecond bursts of TGFs and gamma ray glows that lasted minutes at a time—had been observed. That prior understanding has now been updated significantly.

Flickering Flashes and Boiling Glows

Observations of ample gamma ray events from the ALOFT campaign suggest that TGFs occur up to 100 times more frequently than previously believed [Østgaard et al., 2024; Marisaldi et al., 2024; Bjørge-Engeland et al., 2024]. It turns out that a substantial population of TGFs is, indeed, too weak to observe from space, showing that earlier detection efforts from space had just scratched the tip of the iceberg. Further, unlike previous flight campaigns that circulated around the outskirts of thunderclouds, the ALOFT ER-2 flew directly above thunderclouds, enabling it to detect the weak TGF population.

Data from ALOFT also allowed identification of a third, previously undetected terrestrial gamma ray phenomenon named flickering gamma ray flashes (FGFs), which seem to combine characteristics of both TGFs and gamma ray glows [Østgaard et al., 2024]. FGFs begin as glows before intensifying into pulsed sequences of gamma ray emissions resembling TGFs, except that the pulses last longer (~2 milliseconds) and the sequences overall last tens to hundreds of milliseconds. As with gamma glows, but unlike TGFs, initiation of FGFs is not associated with detectable optical or radio signals, including lightning discharges.

The old picture of minutes-long gamma ray glows must be revisited too. The recent observations show that thunderclouds can actually emit gamma rays for hours and that these emissions can take place over many thousands of square kilometers. They also seem to be highly dynamic in space and time, with gamma glows popping up for 1–10 seconds at a time in different locations within the most highly convective cores of a cloud system, resembling bubbles in a boiling pot [Marisaldi et al., 2024].

Reconsidering the Role of Atmospheric Gamma Rays

Thunderclouds are, indeed, huge particle accelerators, and gamma ray emissions, hardly a rarity, are an intrinsic part of highly convective systems.

The groundbreaking results from the ALOFT campaign suggest a revised view of the role of gamma rays in the atmosphere and that we need to reconsider existing frameworks describing gamma ray phenomena. Thunderclouds are, indeed, huge particle accelerators, and gamma ray emissions, hardly a rarity, are an intrinsic part of highly convective systems.

Assessing the implications of this new knowledge will motivate additional questions and continued study of atmospheric electricity. It’s possible, for example, that gamma ray generation contributes importantly to lightning initiation, at least for a large fraction of lightning.

Considering that about 2,000 thunderstorms are active on the planet at any given moment and about 3 million lightning strikes occur each day globally, further discerning the effects of gamma ray production and propagation on thundercloud dynamics is a fundamental need for improving our understanding of and ability to forecast the planet’s weather and atmospheric environment.

References

Bjørge-Engeland, I., et al. (2024), Evidence of a new population of weak terrestrial gamma-ray flashes observed from aircraft altitude, Geophys. Res. Lett., 51(17), e2024GL110395, https://doi.org/10.1029/2024GL110395.

Fishman, G. J., et al. (1994), Discovery of intense gamma-ray flashes of atmospheric origin, Science, 264, 1,313–1,316, https://doi.org/10.1126/science.264.5163.1313.

Grefenstette, B. W., et al. (2008), Time evolution of terrestrial gamma ray flashes, Geophys. Res. Lett., 35(6), L06802, https://doi.org/10.1029/2007GL032922.

Marisaldi, M., et al. (2024), Highly dynamic gamma-ray emissions are common in tropical thunderclouds, Nature, 634, 57–60, https://doi.org/10.1038/s41586-024-07936-6.

Neubert, T., et al. (2019), A terrestrial gamma-ray flash and ionospheric ultraviolet emissions powered by lightning, Science, 367, 183–186, https://doi.org/10.1126/science.aax3872.

Østgaard, N., et al. (2012), The true fluence distribution of terrestrial gamma flashes at satellite altitude, J. Geophys. Res. Space Phys., 117, A03327, https://doi.org/10.1029/2011JA017365.

Østgaard, N., et al. (2019), First 10 months of TGF observations by ASIM, J. Geophys. Res. Atmos., 124(24), 14,024–14,036, https://doi.org/10.1029/2019JD031214.

Østgaard, N., et al. (2021), Simultaneous observations of EIP, TGF, Elve, and optical lightning, J. Geophys. Res. Atmos., 126(11), e2020JD033921, https://doi.org/10.1029/2020JD033921.

Østgaard, N., et al. (2024), Flickering gamma-ray flashes, the missing link between gamma glows and TGFs, Nature, 634, 53–56, https://doi.org/10.1038/s41586-024-07893-0.

Author Information

Arve Aksnes (Arve.Aksnes@vlfk.no), Nikolai Østgaard, Martino Marisaldi, and Ingrid Bjørge-Engeland, University of Bergen, Bergen, Norway

Citation: Aksnes, A., N. Østgaard, M. Marisaldi, and I. Bjørge-Engeland (2025), A new view of gamma rays from thunderclouds, Eos, 106, https://doi.org/10.1029/2025EO250156. Published on 25 April 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

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

The preservation of ancient Martian Valley Networks has been extensively examined to decipher the past climatic conditions and provide critical constraints for understanding the habitability of ancient Mars. However, the valleys on Alba Mons are frequently ignored in global studies due to their young Amazonian age (younger than 3 billion years).

Scheidt et al. [2025] provide a detailed mapping of the rivers that have formed on this volcano, belonging to the Tharsis volcanic province. The detailed morphological analysis of these reveals mature drainage systems, with characteristics comparable to precipitation-dominated drainage systems on Earth. The valley networks on Alba Mons are attributed to surface runoff from a combination of rainfall, snow, and ice melt. This study offers therefore intriguing insights into the Amazonian climate and the possible relationships between volcanic activity and fluvial processes.

Citation: Scheidt, S. P., Crown, D. A., & Berman, D. C. (2025). Mapping fluvial valleys on the flanks of Alba Mons: Implications for Amazonian watershed development in Northern Tharsis, Mars. Earth and Space Science, 12, e2024EA003967.  https://doi.org/10.1029/2024EA003967

—David Baratoux, Editor, Earth and Space Science

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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: Geophysical Research Letters

This is an authorized translation of an Eos article. 本文是Eos文章的授权翻译。

北大西洋冬季急流的位置反映了盆地和周围大陆上空大尺度大气环流的组织方式，这直接影响着天气，包括极端事件。因此，了解气候变化背景下决定急流偏移的相互竞争的物理机制是很重要的。其中的关键驱动因素包括：北极地区相对于其他地区的变暖程度（北极放大效应），北大西洋亚极地海面温度相对于其他地区的下降（或变暖程度较低）程度（与海洋环流密切相关），以及北大西洋亚极地至中纬度地区天气噪声对底层海洋的影响（大气对海洋的反馈）。

Yu 等人 [2025] 通过多模型实验分析了达到工业化前二氧化碳水平后的 60 年时间，探究北极海冰在二氧化碳去除后是否能恢复到工业化前的状态。他们发现，大多数模型都存在年平均海冰面积约 100 万平方公里的缺口，并且急流向赤道移动。借鉴另一项多模型实验的结果，该实验的重点是区分北极海冰损失与全球海洋变暖在诱发气候响应方面的影响，他们将冬季急流向赤道移动（与工业化前条件相比）归因于海冰面积的减少。北大西洋急流的偏移较弱，但与不同的驱动因素之间存在惊人的关联。这凸显了在专门的模型实验中研究该地区不同物理过程的重要性，尤其是研究气候变化下各种过程之间的相互作用。

Citation: Yu, H., Screen, J. A., Xu, M., Hay, S., Qiu, W., & Catto, J. L. (2025). Incomplete Arctic sea‐ice recovery under CO2 removal and its effects on the winter atmospheric circulation.  Geophysical Research Letters, 52, e2024GL113541. https://doi.org/10.1029/2024GL113541

—Gudrun Magnusdottir, Editor, Geophysical Research Letters

Text © 2024. 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.