Feed aggregator

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

China's sweeping efforts to clean up its air have delivered one of the biggest public health success stories of recent decades. Since the Air Pollution Prevention and Control Action Plan was launched in 2013, coal-fired power plants have been fitted with scrubbers, heavy industry has been modernized and pollution standards tightened, leading to an over 50% reduction in atmospheric particulate matter.

Benefits to society from coral reefs, including fisheries, tourism, coastal protection, pharmaceutical discovery and more, are estimated at about $9.8 trillion per year. For the first time, an international team led by Smithsonian researchers estimated the extent of coral bleaching worldwide during a global marine heat wave, finding that half of the world's reefs experienced significant damage. Another heat wave began in 2023 and is ongoing.

Since the beginning of January, an unusually long period of easterly winds has caused the average water level in the Baltic Sea to fall to a historic low. Measurements at the Swedish Landsort-Norra gauge show values that are the lowest since records began in 1886. Researchers at the Leibniz Institute for Baltic Sea Research Warnemünde (IOW) are currently monitoring this development very closely, as it represents a rare oceanographic situation that could lead to a large inflow of saltwater from the North Sea into the Baltic Sea. An inflow of this kind could significantly affect the physical and chemical conditions in the deep basins of the central Baltic Sea.

In terms of area, forest is the most important means of avalanche protection. It is also the most cost-effective and is naturally renewable. This insight hit home after the winter of 1951, when over 1,000 avalanches caused immense damage. The SLF began researching how protection forests could be sustainably developed.

As glaciers around the world melt at unprecedented rates, tourism in these icy landscapes is booming, adding pressure to vulnerable regions and disrupting delicate ecosystems. A collective effort, led by UNIL and published in Nature Climate Change, points to ways of balancing tourism with conservation, awareness, and social equity.

About a year ago, researchers at the University of Michigan found that the extratropical cyclones that are the biggest drivers of winter weather in the Great Lakes region are warming and trending northward. That means, outside of the northern reaches of the region, residents can expect that their winters will be warmer and wetter on average.

Around the Balkan Peninsula, the African plate is sinking beneath the European plate. A piece of deeply submerged African crust resurfaced 40 million years ago far away from the sinking zone. How this phenomenon of so-called vertical extrusion can be explained and whether the Rhodope mountain range in southern Bulgaria was formed in this way is a matter of scientific debate. Dr. Iskander Muldashev and Professor Thorsten Nagel from the TU Bergakademie Freiberg have now shown how this process works in a recent publication in the journal Geology. The formation of the Rhodopes was only 40 million years ago—the mountain range is therefore 30–50 million years younger than previously assumed.

Methane is a powerful greenhouse gas with strong heat-trapping capabilities. Although there is less methane in the atmosphere than carbon dioxide, the foremost greenhouse gas, researchers attribute 30% of modern global warming to methane. Observations show that methane levels have increased over time, but the factors driving changes in the rate of accumulation remain unclear.

Publication date: 15 March 2026

Source: Earth and Planetary Science Letters, Volume 678

Author(s):

Publication date: 15 March 2026

Source: Earth and Planetary Science Letters, Volume 678

Author(s): Yong Xu, Qing Xiong, Bin Qin, Ruohan Gao, Xiaohan Gong, Degao Zhai, D. Graham Pearson, Jingao Liu

Publication date: 15 March 2026

Source: Earth and Planetary Science Letters, Volume 678

Author(s): Sylvain Barbot

Publication date: 15 March 2026

Source: Earth and Planetary Science Letters, Volume 678

Author(s): Francesco Mosconi, Elisa Tinti, Mariano Supino, Alice-Agnes Gabriel, Emanuele Casarotti, Men-Andrin Meier, Antonio Pio Rinaldi, Domenico Giardini, Massimo Cocco

Publication date: 15 March 2026

Source: Earth and Planetary Science Letters, Volume 678

Author(s): Emma R. Stoutenburg, Razvan Caracas, Andrew J. Campbell

Publication date: 15 March 2026

Source: Earth and Planetary Science Letters, Volume 678

Author(s): Morgan T. Wolfe, Michael A. Clare, Esther J. Sumner, Veerle A.I. Huvenne, Rob A. Hall, Ian A. Kane

Publication date: 15 March 2026

Source: Earth and Planetary Science Letters, Volume 678

Author(s): D. Delle Donne, G. Lacanna, A. Aiuppa, M. Bitetto, G. Ulivieri, F. Biagioli, G. Lo Bue Trisciuzzi, M. Ripepe