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A new study reports that climate warming can increase soil carbon accumulation in boreal Sphagnum peatlands by boosting plant productivity, protecting iron, and inhibiting microbial decomposition. These responses contrast sharply with warming-enhanced soil carbon mineralization—the process by which carbon is released as CO2—in boreal forests and tundra. Together, these contrasting processes highlight the vital yet often overlooked role of Sphagnum peatlands in counteracting boreal carbon loss under future warming.

UK winters are becoming significantly wetter mainly due to warming driven by human burning of fossil fuels releasing greenhouse gases into the atmosphere, a Newcastle University study reveals. The research shows that for every degree of global or regional warming, winter rainfall increases by a compounding 7%, increasing the risk of flooding. And the scientists warn it is happening much faster than most global climate models predict.

Geologic reservoirs that trapped petroleum for millions of years are now being repurposed to store the greenhouse gas carbon dioxide. New research is improving how we monitor this storage and verify how much CO2 these reservoirs have stored.

Scientists have long known that Earth's core is mostly made of iron, but the density is not high enough for it to be pure iron, meaning lighter elements exist in the core, as well. In particular, it's suspected to be a major reservoir of hydrogen. A new study, published in Nature Communications, supports this idea with results suggesting the core contains up to 45 oceans' worth of hydrogen. These results also challenge the idea that most of Earth's water was delivered by comets early on.

Earth systems may be on the brink of long-term, irreversible destabilization, sending our planet on a “hothouse Earth” trajectory, a scenario in which long-term temperatures remain about 5°C (9°F) higher than preindustrial temperatures, according to a new paper.

In the paper, published in One Earth, scientists argue that uncertainties in climate projections mean Earth system components could be at a higher risk than we think of reaching crucial tipping points such as the melting of the Greenland Ice Sheet and the thawing of the world’s permafrost—points of destabilization that, once breached, are irreversible.

“As we move to higher temperatures, we go into higher risk zones,” said Nico Wunderling, a coauthor of the new paper and a climate scientist at the Potsdam Institute for Climate Impact Research and Goethe University Frankfurt, both in Germany. Scientists know higher temperatures will activate interactions between tipping elements, he said.

The new paper “strongly builds” on a 2018 perspective paper linking the possibility of hothouse Earth to tipping points, said Swinda Falkena, a climate scientist at Utrecht University in the Netherlands who was not involved in either publication.

Uncertain Earth Systems

Scientists use climate models—simulations of Earth systems—to project how rising emissions may impact global temperatures, weather patterns, ice sheets, ocean circulation, and more.

But those models are never perfect representations of our planet. Climate models contain uncertainties regarding the sensitivity of Earth systems to increased levels of carbon dioxide and the role of climate feedbacks, including land and ocean carbon sinks. Simulations have particular trouble modeling potential tipping points, such as weakening ocean circulation and the dieback of the Amazon rainforest, and the interactions between them, Wunderling said.

These uncertainties mean it’s virtually impossible to reliably estimate the timing of some tipping points and that some Earth system components could be closer to tipping points than scientists thought.

In recent years, scientists have noticed that the rate of climate change has outpaced some projections. In 2024, for instance, global temperatures briefly reached 1.5°C (2.7°F) above preindustrial levels, surpassing the Paris Agreement target and indicating that Earth is virtually certain to consistently break this limit in the long term. In another example of real climate change outpacing models, exceptionally high temperatures in 2023, 2024, and 2025 led experts at Berkeley Earth, a nonprofit climate research organization, to suggest scientists may need to rethink their analyses of Earth’s warming rate.

“Warming now seems to have accelerated, which is not something we expected,” Falkena said. “That gets us to think, ‘Okay, is there something we’re missing?’”

The paper identifies 16 Earth system components (such as ice sheets, permafrost, and rainforests) that could reach tipping points, 10 of which could accelerate global heating if triggered. These 10 tipping points include the collapse of major ice sheets, the collapse of Arctic sea ice, the loss of mountain glaciers, the abrupt thaw of boreal permafrost, and the dieback of the Amazon rainforest.

The authors point out that these tipping elements are linked and even interact with each other to create feedback loops. For example, melting ice sheets would reduce Earth’s ability to reflect sunlight, amplifying warming. Melting ice sheets could also weaken the Atlantic Meridional Overturning Circulation, or AMOC (an ocean current key to regulating Earth’s temperature), which could cause the conversion of Amazon rainforest (a critical carbon sink) into dry savanna.

A Hothouse Trajectory

The higher Earth’s temperature rises, “the more likely it is to trigger self-amplifying feedbacks.”

If enough of these tipping points are reached, Earth’s climate could be steered toward a hothouse Earth scenario, the authors write. And although there is “no precise answer” to the question of whether humanity is at risk of triggering hothouse Earth, Wunderling said the 1.5°C (2.7°F) limit set by the Paris Agreement was made with tipping point thresholds in mind.

If Earth’s temperature exceeds preindustrial levels by 2°C (3.6°F), then “we certainly run into a high-risk zone for tipping elements,” Wunderling said. The higher Earth’s temperature rises, “the more likely it is to trigger self-amplifying feedbacks.”

One 2024 modeling study showed that Earth had a high risk of breaching at least one of four climate tipping elements—the Greenland Ice Sheet collapse, the West Antarctic Ice Sheet collapse, the AMOC collapse, and a dieback of the Amazon rainforest—if temperatures do not return to below the 1.5°C (2.7°F) mark. (Scientists say the prospect of lowering Earth’s temperatures with new policies or technology after exceeding this mark is slim.)

Falkena said the likelihood of a hothouse Earth trajectory is low, but the fact that such a severe scenario is plausible at all means it’s something worth the world’s concern. As models improve, scientists will be able to better quantify the risk of a hothouse Earth trajectory.

“While averting the hothouse trajectory won’t be easy, it’s much more achievable than trying to backtrack once we’re on it.”

“While averting the hothouse trajectory won’t be easy, it’s much more achievable than trying to backtrack once we’re on it,” said Christopher Wolf, a research scientist at Terrestrial Ecosystems Research Associates, a former postdoctoral scholar at Oregon State University, and a coauthor of the new study, in a press release.

The world hasn’t sufficiently cut down on emissions, though: Earth is on track to warm by about 2.8°C (5.04°F) by 2100. In 2025, global carbon emissions rose by 1.1% compared to 2024 levels, and in the United States, total emissions rose by 2.4%. The level of carbon dioxide in the atmosphere is likely higher than it has been in at least 2 million years, and average global temperatures are likely warmer than at any point in the past 125,000 years, according to the authors.

The uncertainty about when tipping points may be breached, combined with ever-higher global temperatures, should be taken as a reason for urgent action to combat or mitigate climate change, the authors write.

“In order to avoid high-end climate risks, it is necessary to go down to net zero, to mitigate as quickly as we can,” Wunderling said.

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

Citation: van Deelen, G. (2026), Earth’s climate may go from greenhouse to hothouse, Eos, 107, https://doi.org/10.1029/2026EO260057. Published on 11 February 2026. Text © 2026. 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.

Scientists say that multiple Earth system components appear closer to destabilization than previously believed, putting the planet in increased danger of following a "hothouse" path driven by feedback loops that can amplify the consequences of global warming.

The Murray-Darling Basin Authority (MDBA)—the statutory agency responsible for planning the Basin's water resources—has just shared the starkest news yet about the Basin's future: the Basin is almost certainly going to get hotter, drier, and more volatile in the future, with reduced river flows.

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.

Update, 12 February: At a press conference today, President Donald Trump announced that the EPA has revoked the 2009 Endangerment Finding.

Trump said regulations related to the finding were “crippling,” and designed to “facilitate the green new Scam.”

“Effective immediately, we are repealing the ridiculous Endangerment Finding,” he said.

AGU immediately denounced the repeal.

Revoking the finding repeals the EPA’s authority to regulate greenhouse gas emissions and removes all greenhouse gas emissions regulations for vehicles, according to the EPA.

11 February: The Endangerment Finding is a scientific determination made by the EPA that greenhouse gases threaten public health. It is the legal underpinning for major U.S. climate rules under the Clean Air Act. Revoking the finding repeals the EPA’s authority to regulate greenhouse gas emissions and removes all greenhouse gas emissions regulations for vehicles, according to the EPA. 

“I think it’s a historic low, frankly, for EPA to be taking this stance now,” Benjamin DeAngelo, a former EPA official involved in writing the 2009 finding, told POLITICO. 

Leavitt called the planned finalization the “largest deregulatory action in American history.” She said the repeal of the finding would increase energy affordability and, especially, lower vehicle costs, allegedly saving Americans “$1.3 trillion in crushing regulations.” Businesses and groups prioritizing free markets support the administration’s claim, with the editorial board of the Washington Post writing that rescinding the Endangerment Finding will “end the federal government’s power over cars.”

President Donald Trump and EPA Administrator Lee Zeldin will make the announcement to finalize the repeal on 12 February.

The EPA based its July proposal to revoke the finding on an Energy Department report written by five climate contrarians that downplayed accepted climate science. The National Academies of Sciences, Engineering and Medicine, an independent organization meant to advise the federal government on scientific matters, conducted their own review of the report and found that the 2009 Endangerment Finding was “beyond scientific dispute.”

The science supporting the Endangerment Finding “has only gotten stronger” since 2009, DeAngelo told POLITICO. 

 
Related

•  Trump EPA to Take Its Biggest Swing Yet Against Climate Change Rules
•  EPA ‘Endangerment Finding’ Explained: 5 Facts About the Science and Health Risks
•  Public Speaks Out Against EPA Plan to Rescind Endangerment Finding
•  The EPA is Barreling Toward a Supreme Court Climate Showdown
•  AGU Denounces Trump Administration’s Repeal of the EPA Endangerment Finding
•  Get Involved: AGU Science Policy Action Center
 

In public hearings in August, hundreds of people, including children, scientists, doctors, parents, advocates, and members of Congress, spoke out against the proposal to revoke the Endangerment Finding. Many cited immediate health concerns, worry about the health and safety of future generations, and a fear that the proposal would accelerate environmental degradation.

The move by the EPA will likely be challenged in the courts—which may be one reason the Trump administration has pushed its finalization through so rapidly, according to The New York Times. Legal scholars say the current, conservative-majority Supreme Court is more likely to uphold decisions supporting deregulation while Trump is still in office. 

The administration wants “to not just do what other Republican administrations have done, which is weaken regulations. They want to take the federal government out of the business of regulation, period,” Jody Freedman, director of Harvard Law School’s Environmental and Energy Law Program, told The New York Times.

—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 © 2026. 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: Community Science

Geographic information system (GIS) maps help researchers, policymakers, and community members see how environmental risks are spread throughout a given region. These types of interactive, layered maps can be used for storytelling, education, and environmental activism. When community members are involved in their use and creation, GIS maps can also be a tool for equity.

Lively et al. outlined a project focusing on mapping the features and flooding risks at and around the Tar Creek Superfund site in Ottawa County, Okla. Ottawa County is home to 10 federally recognized Tribal Nations. Residents have experienced decades of health and environmental harm from the region’s legacy of zinc and lead mining, most of which occurred within the Quapaw Reservation. Although mining ceased in 1970, giant piles of mining waste, mine water discharges, and unstable ground have poisoned residents and made entire towns unlivable. For almost a century, floods have spread these contaminants across downstream communities.

Technical experts and community members with local knowledge worked together to build a GIS map that can be used by community members and leaders. It depicts how floodwaters run through former mining sites, which then ferry toxic waste throughout the region’s creeks and soils.

The map is viewable in various layers that show the locations of different kinds of mining waste, tribal land boundaries, and flood zones designated by the Federal Emergency Management Agency (FEMA). Users can also view layers showing soil types and the locations of aquifers, fault lines, and wells.

Between 2021 and 2023, members of the Local Environmental Action Demanded Agency (LEAD), a community-led organization, connected with GIS professionals through AGU’s Thriving Earth Exchange. This program partners local organizations with volunteer scientists and experts to address environmental or geoscience-related issues in their communities. Many members of the project team contributing to the Tar Creek project were local to the Miami, Okla., region.

Though much of the actual map building was completed by the GIS expert team member, decisions on what to include in each layer of the map were made by LEAD representatives and nonscientist community members. This coproduction defined equity not only by who built or contributed to the map but also by how it is used by the community as a key storytelling tool—helping to educate officials and residents about the ongoing environmental and health risks when flooding occurs in the region. For the team, it was important not to just make the map but also to use it: Production without activism, the researchers said, would make for an unfinished project. (Community Science, https://doi.org/10.1029/2024CSJ000077, 2026)

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

Citation: Owen, R. (2026), Making a map to make a difference, Eos, 107, https://doi.org/10.1029/2026EO260035. Published on 11 February 2026. Text © 2026. 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 and Space Science

The color of the oceans is an important diagnostic parameter as it reflects the health of oceans, monitors CO2 variability, and tracks ecosystem changes due to environmental stressors. Remote observations of the ocean color (OC) are routinely performed, but rapid changes in this parameter are difficult to capture. Geostationary platforms are uniquely suited for this purpose, because they monitor the same area and can therefore detect changes in real time. However, measurements of OC from geostationary satellites are not routinely performed.

The Tropospheric Emissions: Monitoring of Pollution (TEMPO) geostationary instrument monitors air quality and pollution over North America. Using a new approach, Fasnacht et al. [2025] apply a combination of statistical and machine learning techniques to TEMPO hyperspectral hourly measurements, and obtain OC values across the USA coastal regions and the Great Lakes.

Thus, the authors demonstrate the feasibility of capturing hourly variability of environmental parameters from deep space. This reinforces the scientific value of future dedicated geostationary ocean color missions, such as the Geosynchronous Littoral Imaging and Monitoring Radiometer (GLIMR), and the Geostationary Extended Observations (GeoXO) Ocean Color Instrument (OCX).  

Citation: Fasnacht, Z., Joiner, J., Bandel, M., Ibrahim, A., Heidinger, A., Himes, M. D., et al. (2025). Exploiting machine learning to develop ocean color retrievals from the tropospheric emissions: Monitoring of pollution instrument. Earth and Space Science, 12, e2025EA004341. https://doi.org/10.1029/2025EA004341

—Graziella Caprarelli, Editor-in-Chief, Earth and Space Science

Text © 2026. 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.

Author(s): Luisa Izquierdo, Felipe Veloso, Miguel Escalona, Vicente Valenzuela-Villaseca, Gonzalo Avaria, and Julio Valenzuela

The influence of conical wire array geometry on the formation and dynamics of pulsed-power driven plasma jets is investigated. In the experiments, the jet becomes isolated from the inflows as it passes through an aperture, allowing the study of its intrinsic evolution for different conical angles. O…

[Phys. Rev. E 113, 025203] Published Wed Feb 11, 2026

SummaryIn the last two decades, the improvement of both instruments and theory, as well as the broadened scope of applications, led to a spectacular development of the use of induced polarization. In particular, the richness of complex conductivity spectra is driving the scientific community towards vast deployment of this measurement method often referred to as Spectral Induced Polarization (SIP). In this contribution, we describe an innovative multichannel instrument that we develop for fast monitoring of critical zone processes. The spectral content of a signal with line spectrum resulting from square-wave current is exploited by injecting successively three square-wave currents with periods of 1, 10 and 100 s, covering the frequency range of 10−2 to 102 Hz in less than four minutes. One dataset consists of eight successive current injections at different depths. For each current injection, the electrical potential is simultaneously measured at seven dipoles. The time-series are recorded with a 2 kHz sampling rate, allowing to calculate by Fourier transform the amplitude and phase spectra up to 1 kHz for each quadrupole. The complex conductivity data was validated by a comparison with the commercial SIP-Fuchs instrument, despite a significant discrepancy below 0.1 Hz which may be due to a worse signal-to-noise ratio at low frequencies. The prototype version of the instrument has been installed in 2018 at a wetland at Ploemeur-Guidel hydrogeological observatory to monitor reactive processes with high spatial resolution across the top meter of soil. The instrumental device, controlled by a Gantner data acquisition system connected to a solar panel, is fully autonomous and consumes little energy. Acquisitions are made several times a day and recorded on a SD card. Seven-year continuous monitoring highlights significant temporal variations of both subsurface resistivity and phase angle. The absence of correlation between resistivity and phase variations in the continuously saturated soil thickness highlights the potential of the system to monitor and separate different types of dynamics processes, such as groundwater/surface water mixing and mineral precipitation/dissolution.

SummaryFrom April until the end of June 2025, we deployed a dense seismic network of 271 three-component stations within an 8 km radius around Lavey-les-Bains, Switzerland, to investigate the structure of the country’s hottest known natural geothermal system. The site hosts a 3 km-deep exploration well (Lavey-1), drilled in 2022, that revealed unexpectedly low flow rates despite temperatures exceeding 120°C, prompting the suspension of the project. The site lies within the narrow Rhône Valley, characterized by steep topography, strong lateral structural heterogeneity, and elevated anthropogenic noise, complicating seismic imaging. The dense nodal array was complemented by a distributed acoustic sensing (DAS) system along a buried telecommunication cable, providing a hybrid dataset suited for passive seismic imaging. We describe the network geometry, instrumentation and deployment logistics; assess data completeness and noise characteristics and present first examples of ambient noise and earthquake recordings. Preliminary analyses demonstrate a high data quality and spatial coverage. This experiment establishes a benchmark dataset for developing advanced passive imaging techniques in complex Alpine environments.

Water is made of hydrogen and oxygen, and sometimes these atoms are slightly heavier than usual. These heavier forms are called isotopes. As water evaporates or moves through the atmosphere, the amount of these isotopes changes in predictable ways. This can act as a fingerprint, allowing researchers to trace the movement of water at global scales.

Commercial shipping not only affects the Baltic Sea on the surface, but also has a significant impact on the water column and the seabed. A study by the Leibniz Institute for Baltic Sea Research Warnemünde (IOW) and Kiel University (CAU) now shows for the first time that wake turbulence from large ships in heavily trafficked areas of the western Baltic Sea significantly alters water stratification and leads to marked sea floor erosion. The research team has therefore documented a previously underestimated human impact on shallow marine areas. The results are published in the journal Nature Communications.

Tiny, invisible gases long thought to be irrelevant in cloud formation may actually play a major role in determining whether clouds form—and possibly whether it rains.

They're all around us: sensors and satellites, radars and drones. These tools form vast remote sensing networks that collect data on the climate, the ground, the air, and the water. This information is immensely useful for research, conservation, and disaster preparedness. But, according to an interdisciplinary group of Earth science researchers in a paper led by Casey O'Hara of UC Santa Barbara, we're only just scratching the surface of understanding just how beneficial Earth science information can be.

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

The surface of Mars represents the comprehensive geochemical inventory of the interactions between the lithosphere, atmosphere, and/or hydrosphere over a period of more than four billion years. By investigating the chemical composition and variability of surface materials, we can reconstruct the planet’s evolutionary history and investigate how different geological processes shaped the surface environment of Mars over geologic time. Due to their unique properties and global distribution, reactive salts of chlorine, called oxychlorine species, constitute an important component of the Martian surface.

A new article in Reviews of Geophysics investigates the state of the knowledge and discusses potential areas of future exploration for oxychlorine species on Mars. Here, we asked the author to give an overview of oxychlorine species on Mars, how scientists study them, and what questions remain.

Why is it important to understand the composition of the surface environment of Mars?

Certain surface materials can serve as diagnostic indicators of early and contemporary aqueous activity on the Martian surface.

Certain surface materials—such as salts and hydrated minerals—can serve as diagnostic indicators of early and contemporary aqueous activity on the Martian surface. Accurately understanding the formation, evolution, and preservation of these minerals that formed in aqueous systems can provide crucial constraints on the chemistry and availability of water that are needed to evaluate habitability conditions on Mars. Furthermore, characterizing the modern surface composition is the essential first step in deconvoluting geochemical cycles as well as assessing regolith toxicity, important for future robotic, sample return, and human missions to Mars.

In simple terms, what are oxychlorine species and where have they been found on Mars?

Oxychlorine species are chemical compounds composed of chlorine and oxygen, ranging from stable salts like perchlorate and chlorate to reactive gases and transient intermediates. This diversity arises from the multiple oxidation states of chlorine, which vary from -1 in chloride (Cl-) to +7 in perchlorate (ClO4-). While perchlorate and chlorate (ClO3-) have been identified on Mars, highly reactive intermediates are also likely to exist, at least transiently, during oxychlorine formation and destruction processes.

These compounds are widely distributed across the Martian surface. The Phoenix lander first detected them in the northern plains, while the Curiosity and Perseverance rovers have confirmed their presence in soil, sediment, and rock samples within the Gale and Jezero craters, respectively. Furthermore, oxychlorine salts have been identified as inclusions within pristine Martian meteorites. These widespread detections suggest that oxychlorines are a global component of the Martian regolith, influencing the planet’s geochemical and environmental evolution.

The locations of oxychlorine detections on the surface of Mars. Credit: Mitra [2025], Figure 2

How do scientists detect and sample oxychlorine species?

Scientists have successfully employed various analytical techniques to identify oxychlorine species on the surface of Mars. The Phoenix lander used ion selective electrodes in the Wet Chemistry Laboratory (WCL) to detect perchlorate anions in the Martian regolith. Additional measurements from the Thermal and Evolved Gas Analyzer (TEGA) and the Surface Stereo Imager (SSI) also confirmed the presence of perchlorate anions. At Gale Crater, the Curiosity rover’s Sample Analysis at Mars (SAM) instrument identified these species by heating samples and measuring the evolution of oxygen and chlorine-bearing gases, such as HCl.

More recently, the Perseverance rover used its Raman and X-ray fluorescence spectroscopy instruments—SHERLOC, SuperCam, and PIXL— to detect oxychlorine species within altered rock assemblages at Jezero Crater. Beyond in situ analysis, orbital instruments like CRISM can be used to detect hydrated oxychlorine salts using visible and near-infrared spectroscopy. Finally, multiple analytical methods in terrestrial laboratories can detect oxychlorine species using spectroscopy, chromatography, and diffraction techniques.

What are recent advances in our understanding of oxychlorine formation and destruction on Mars?

Early research focused on atmospheric production, but the low abundance of oxygen-bearing gases in the Martian atmosphere failed to explain the high concentrations of perchlorate on Mars. Recent studies have identified three additional formation mechanisms: plasma redox chemistry during electrostatic discharges, heterogeneous reactions between chlorine-bearing salts and energetic radiation, and aqueous processes. Among these, the irradiation of chloride minerals and ices by ultraviolet light or galactic cosmic rays is particularly effective on contemporary Mars because the thin atmosphere allows radiation to interact directly with the surface.

Regarding destruction, perchlorate salts can degrade into chlorate when exposed to galactic cosmic radiation. Furthermore, chlorate can be effectively consumed by dissolved ferrous iron or ferrous minerals at temperatures as low as 273 K. While perchlorate remains kinetically stable in the presence of most redox-sensitive materials, reactive intermediates like hypochlorite (ClO–) and ClO2 gas readily react with organic compounds, leading to their mutual destruction.

Oxychlorine cycle on Mars. Credit: Mitra [2025], Figure 5

What does the presence of oxychlorine tell us about Mars’ history?

Oxychlorine species record the unique environmental history of Mars. Chlorine isotope data and detections in meteorites, such as Tissint and EETA79001, suggest an active oxychlorine cycle spanning 4 billion years, indicating that oxidizing fluids have been widespread throughout Martian history. Unlike Earth, where the nitrate-to-perchlorate ratio is high (~104), the ratio on Mars is less than one, except for inclusion in EETA79001. This discrepancy highlights fundamentally different geochemical fixation processes and nitrogen-chlorine cycles between the two planets.

Furthermore, chlorates are effective iron oxidants under Mars-relevant conditions and likely contribute to the formation of the planet’s ubiquitous ferric minerals. Additionally, as potent freezing point depressants, these salts may stabilize transient liquid brines even in modern equatorial regions. As a halogen-rich planet, Mars hosts a reactive surface chemistry where oxychlorine species play a substantially more dominant role than they do on Earth.

Is the presence of oxychlorine species helpful or harmful to human exploration and possible use of Mars?

Oxychlorine species can act as a potential hazard as well as a critical in situ resource for future human exploration.

Oxychlorine species can act as a potential hazard as well as a critical in situ resource for future human exploration. Perchlorate and chlorate salts can thermally decompose to release molecular oxygen (O2) and can thus potentially be used for human consumption. Approximately 60 kg of the Martian regolith, containing ~0.5 to 1 wt.% oxychlorine salt, could theoretically provide a single person’s daily oxygen supply. On the other hand, perchlorate is a well-known contaminant in drinking water since it interferes with thyroid functioning and can cause a goiter. Therefore, perchlorate in the Martian regolith could be a possible source of contamination for drinking water or agricultural systems. Owing to high chemical reactivity and oxidation potential, oxychlorine salts present in the Martian regolith are likely to pose persistent cleaning challenges for habitats, suits, and equipment during extra vehicular activity (EVA) on Mars. Additionally, agriculture in the oxychlorine-laden regolith might lead to contamination of plants and vegetables and could eventually lead to biomagnification in humans.

What are some of the remaining questions where additional research is needed?

While oxychlorine research has flourished over the last two decades, critical gaps remain regarding the spatial distribution and formation rates of distinct species. Recent detections of atmospheric HCl and electrostatic discharges necessitate a rigorous re-evaluation of Martian atmospheric chemistry. By leveraging emerging terrestrial models of chlorate formation, new pathways for Martian oxychlorine production can be proposed. Determining the relative contributions of atmospheric, plasma redox, and heterogeneous pathways is vital to understanding the evolution of the chlorine cycle and estimating equilibrium concentrations and residence times.

Furthermore, the chemical reactivity of transient intermediates, specifically ClO2 gas and chlorite, remains poorly understood regarding organic preservation at low temperatures. We also require precise thermodynamic data on complex salt mixtures to accurately predict brine stability. Ultimately, experimental validation of these salts as a viable in situ resource for oxygen and fuel is imperative for future human exploration and the interpretation of returned Martian samples.

—Kaushik Mitra (kaushik.mitra@utsa.edu; 0000-0001-9673-1032), The University of Texas at San Antonio, United States

Citation: Mitra, K. (2026), A double-edged sword: the global oxychlorine cycle on Mars, Eos, 107, https://doi.org/10.1029/2026EO265004. Published on 10 February 2026. 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 © 2026. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

A major part of the Atlantic Meridional Overturning Circulation (AMOC), a large-scale ocean circulation pattern, was warmer during the peak of Earth’s last ice age than previously thought, according to a new study published in Nature. 

The study’s results contrast with those from previous studies hinting that the North Atlantic was relatively cold and that AMOC was weaker when faced with major climate stress during the Last Glacial Maximum (LGM), about 19,000–23,000 years ago. 

The findings add confidence to models that scientists use to project how AMOC may change in the future as the climate warms, said Jack Wharton, a paleoceanographer at University College London and lead author of the new study.

Deepwater Data

The circulation of AMOC, now and in Earth’s past, requires the formation of dense, salty North Atlantic Deep Water (NADW), which brings oxygen to the deep ocean as it sinks and helps to regulate Earth’s climate. Scientists frequently use the climatic conditions of AMOC during the LGM as a test to determine how well climate models—like those used in major global climate assessments—simulate Earth systems. 

However, prior to the new study, few data points existed to validate scientists’ models showing the state of NADW during the LGM. Scientists in 2002 analyzed fluid in ocean bottom sediment cores from four sites in the North Atlantic, South Pacific, and Southern Oceans, with results suggesting that deep waters in all three were homogeneously cold.

Researchers sampled 16 sediment cores from across the North Atlantic to deduce how waters may have circulated during the peak of the last ice age. Credit: Jack Wharton, UCL

“The deep-ocean temperature constraints during the [Last Glacial Maximum] were pretty few and far between,” Wharton said. And to him, the 2002 results were counterintuitive. It seemed more likely, he said, that the North Atlantic during the peak of the last ice age would have remained mobile and that winds and cold air would have cooled and evaporated surface waters, making them saltier, denser, and more prone to create NADW and spur circulation.

“This is quite new,” he remembered thinking. “What kind of good science could help show that this is believable?”

Wharton and his colleagues evaluated 16 sediment cores collected across the North Atlantic. First, they measured the ratio of trace magnesium and calcium in microscopic shells of microorganisms called benthic foraminifera. This ratio relates to the temperature at which the microorganisms lived. The results showed much warmer North Atlantic Deep Water than the 2002 study indicated. 

Wharton felt cautious, especially because magnesium to calcium ratios are sometimes affected by ocean chemistry as well as by temperature: “This is quite new,” he remembered thinking. “What kind of good science could help show that this is believable?”

The team, this time led by Emilia Kozikowska, a doctoral candidate at University College London, verified the initial results using a method called clumped isotope analysis, which measures how carbon isotopes in the cores are bonded together, a proxy for temperature. The team basically “did the whole study again, but using a different method,” Wharton said. The results aligned. 

Ratios of magnesium to calcium contained in benthic foraminifera, tiny microbes living in marine sediment, offer insights into the temperature of North Atlantic waters thousands of years ago. Credit: Jack Wharton and Mark Stanley

Analyzing multiple temperature proxies in multiple cores from a broad array of locations made the research “a really thorough and well-done study,” said Jean Lynch-Stieglitz, a paleoceanographer at the Georgia Institute of Technology who was not part of the research team but has worked closely with one of its authors. 

The results, in conjunction with previous salinity data from the same cores, allowed the team to deduce how the North Atlantic likely moved during the LGM. “We were able to infer that the circulation was still active,” Wharton said. 

Modeling AMOC

The findings give scientists an additional benchmark with which to test the accuracy of climate models, Lynch-Stieglitz said. “LGM circulation is a good target, and the more that we can refine the benchmarks…that’s a really good thing,” she said. “This is another really nice dataset that can be used to better assess what the Last Glacial Maximum circulation was really doing.”

“Our data [are] helping show that maybe AMOC was sustained.”

In many widely used climate models, North Atlantic circulation during the LGM looks consistent with the view provided by Wharton’s team’s results, indicating that NADW was forming somehow during the LGM, Lynch-Stieglitz said. However, no model can completely explain all of the proxy data related to the LGM’s climatic conditions.

“Our data [are] helping show that maybe AMOC was sustained,” which helps reconcile climate models with proxy data, Wharton said. Lynch-Stieglitz added that a perhaps equally important contribution of the new study is that it removes the sometimes difficult-to-simulate benchmark of very cold NADW during the LGM that was suggested in research in the early 2000s. “We don’t have to make the whole ocean super cold [in models],” she said.

Some climate models suggest that modern-day climate change may slow AMOC, which could trigger a severe cooling of Europe, change global precipitation patterns, and lead to additional Earth system chaos. However, ocean circulation is highly complex, and models differ in their ability to project future changes. Still, “if they could do a great job with LGM AMOC, then we would have a lot more confidence in their ability to project a future AMOC,” Lynch-Stieglitz said.

Wharton said the results also suggest that another question scientists have been investigating about the last ice age—how and why it ended—may be worth revisiting. Many hypotheses rely on North Atlantic waters being very close to freezing during the LGM, he said. “By us suggesting that maybe they weren’t so close to freezing…that sort of necessitates that people might need to rethink the hypotheses.”

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

Citation: van Deelen, G. (2026), The AMOC of the ice age was warmer than once thought, Eos, 107, https://doi.org/10.1029/2026EO260053. Published on 10 February 2026. Text © 2026. AGU. CC BY-NC-ND 3.0
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