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About 15% of the land area in the Northern Hemisphere is currently covered by perennially frozen soil known as permafrost. But that has not always been the case. As global temperatures fluctuated in Earth’s past, patches of that frozen soil periodically thawed and refroze.

“Permafrost is a huge reservoir of CO2, and thawing comes with repercussions because it feeds back into future warming.”

A recent study in Nature Communications shows that the Arctic was mostly free of permafrost 8.7 million years ago, when the average global temperature was 4.5°C (8.1°F) higher than it is today.

“Permafrost is a huge reservoir of CO2 [carbon dioxide], and thawing comes with huge repercussions because it feeds back into future warming,” said study coauthor Sebastian Breitenbach, a paleoclimatologist at Northumbria University. Arctic permafrost currently stores twice as much carbon as the entire atmosphere, and because the region is warming faster than the global average, those soils are susceptible to thawing.

In Search of Climate Archives

Breitenbach and his colleagues studied mineral cave deposits from northern Siberia, which is currently underlain by permafrost.

Speleothems such as stalagmites and stalactites form when mineral-rich water percolates through the ground and drips into cave openings, slowly leaving behind calcium carbonate that precipitates out of the water. They can’t grow when the ground above the cave is frozen solid because no water is able to seep through the soil. Any speleothems in the region must have formed when the ground was thawed.

The study was decades in the making. In the early 2000s, Breitenbach and his international group of colleagues were studying caves in a partially frozen region in southern Siberia. At the same time, they were looking for sites with speleothems in the heart of permafrost-covered regions farther north, turning to local communities for information about caves in remote areas. “We started asking hunters, teachers, politicians, bus drivers, anyone who would be out there in the outback,” Breitenbach said. Often, the team would visit a promising area only to find there were no caves there or, when there were caves, no useful speleothems inside them.

“Most of our information for the Miocene comes from marine sediments, so finding good terrestrial archives for this period is fantastic.”

After years of following rumors farther and farther north, they finally struck gold in 2014 at the Taba-Ba’astakh cliffs along the Lena River close to the Arctic Ocean. The team collected 14 speleothems from eroded caves high up in the cliffs and along the beach below.

Using the predictable rate of the decay of uranium into lead and the amounts of each of these isotopes in the samples, the study authors found that the cave deposits were formed 8.7 million years ago, in the late Miocene period.

“Most of our information for the Miocene comes from marine sediments, so finding good terrestrial archives for this period is fantastic,” said Dominik Fleitmann, a geologist and paleoclimatologist at Universität Basel who was not involved in the study. “There are not so many sites because erosion is our enemy. Most of the older deposits are eroded or difficult to date.”

Scientists’ ability to precisely date speleothems makes them incredibly useful as climate records, said Nikita Kaushal, a geologist at the American Museum of Natural History who was not involved with the study. “When you’re looking at past records, you want really good age control on when something happened and for how long, and information on as many climate and environmental parameters as possible.”

By studying the physical and chemical properties of speleothems, scientists can reconstruct the conditions present when the speleothems formed, such as the vegetation cover above, atmospheric circulation changes, local rainfall, droughts, and temperature.

Dima Sokol’nikov surveys a cave in the Taba-Ba’astakh cliffs. Credit: Sebastian Breitenbach

Using the proportions of bonds between certain isotopes, which are affected by the atmospheric conditions present when the mineral-rich water was flowing, the study authors established that average temperatures in the region were between 6.6°C and 11.1°C (44°F and 52°F) when the speleothems formed. That’s about 19°C–23°C (34°F–42°F) warmer than it is today.

Other studies of the same period found that global temperatures were 4.5°C higher than today at the time.

“We know from meteorological data that the Arctic is warming at about 4 times the global average,” Breitenbach said. “The underlying reasons are not entirely clear.” This phenomenon, called Arctic amplification, is likely due to a complex interplay of various factors, including loss of sea ice, air temperature inversion, and ocean heat transport.

A Vulnerable Carbon Pool

As permafrost thaws, the organic matter in the soil begins to decompose, releasing carbon dioxide and methane into the atmosphere. The Intergovernmental Panel on Climate Change estimates 14–175 billion tons of CO2 could be released into the atmosphere by thawing permafrost for every 1°C of global warming.

It’s a process that’s already underway. According to scientists, the upper layers of permafrost were thawing in multiple areas in Svalbard, an archipelago in the Arctic Ocean, in February 2025 as a result of exceptionally high temperatures. The thawing of permafrost is also influenced by several factors beyond temperature, Breitenbach said. “The most important ones are vegetation, snow cover, and wildfire activity.”

Even using conservative estimates, the study authors calculated that the complete loss of permafrost in the Arctic region could release 130 billion tons of CO2 into the atmosphere—and that’s accounting for only short-term emissions from the top 3 meters of thawed soil. “I was quite frightened when I saw these numbers,” Breitenbach said. “4.5° warming is at the extreme end of climate models. It’s not expected to be tomorrow or in the next decades. But even half of this is still drastic.”

—Kaja Šeruga, Science Writer

Citation: Šeruga, K. (2025), Cave deposits reveal a permafrost-free Arctic, Eos, 106, https://doi.org/10.1029/2025EO250285. Published on 4 August 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 Geophysical Research: Solid Earth

The Nankai subduction zone, in southern Japan, has hosted several magnitude 8+ earthquakes over the last 300 years, including the 1707 magnitude 8.7 Hōei earthquake, which, until the 11 March 2011 magnitude 9.0 Tohoku-Oki earthquake occurred, was the largest historical earthquake in Japan. The most recent (large) earthquakes in the region were the 1944 magnitude 8.1 Tōnankai Earthquake, followed by the 1946 M8.1 Nankaido Earthquake. Under our current knowledge, the return period of these earthquakes is thought to be approximately 100-150 years.

As a consequence, the Nankai subduction zone is arguably the best instrumented and most extensively studied subduction zone in the world. An important part of this effort has been the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE), a major project of the Integrated Ocean Drilling Program (IODP). NanTroSEIZE has spent over a decade drilling, sampling, imaging, and instrumenting this margin to observe and understand the seismogenic and tsunamigenic behavior of an active subduction plate boundary system.

Stress being the driver of faulting, Schaible and Saffer [2025] use data from borehole breakouts, a technique routinely used to infer underground stresses, observed during the NanTroSEIZE experiment. Their analysis focuses on two regions that penetrate major faults along the Nankai Trough: a major out of sequence thrust fault located about 25 kilometers landward of the trench, termed the megasplay (IODP Sites C0004, C0010, and C0022), and the décollement within a few kilometers of the trench (Sites C0006 and C0024).

Their results suggest that while the toe of the prism is understressed, the megasplay fault is near failure. This single result has important consequences for possible mechanical scenarios of how a megathrust earthquake could rupture up-dip all the way to the seafloor surface and, in consequence, on the possible scenarios of earthquake related tsunami generation for southern Japan.

Citation: Schaible, K. E., & Saffer, D. M. (2025). State of stress across major faults in the Nankai subduction zone estimated from wellbore breakouts. Journal of Geophysical Research: Solid Earth, 130, e2024JB030242. https://doi.org/10.1029/2024JB030242

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

Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

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

Ecological forecasting is crucial for proactive environmental management and policy-making.

Ecological forecasting is crucial for proactive environmental management and policy-making. In 2001, Clark et al. identified ecological forecasting as an emerging imperative, providing a vision whereby predictions of the future with specified uncertainty enable the anticipation of changes in ecosystems. Ideally, forecasts are then integrated into natural resource decision-making to mitigate adverse effects, enhance resilience, and promote sustainability. Since 2001, the field of ecological forecasting has grown, highlighted by a rapidly increasing number of papers in the literature over time (Lewis et al., 2022).

To highlight both previously published and new research, we, with the support of the Ecological Forecasting Initiative, have launched a special collection titled, “Ecological Forecasting in the Earth System” that showcases advances in the field of ecological forecasting and provides guidance and inspiration for the broader research community.

The special collection brings together cutting-edge research that develops, tests, and applies models to forecast ecological dynamics across systems and scales or advances fundamental frameworks and methods associated with the iterative ecological forecast cycle (Dietze et al., 2018). The ecological systems and scales include marine, freshwater, and terrestrial ecosystems, and dynamics at the population, community, ecosystem, regional, and global scales. Forecasting applications can include, but are not limited to, biogeochemistry, ecohydrology, water quality, phenology, biodiversity conservation, invasive species, vector-borne disease, land-use, and natural climate solutions. 

We are excited to present this joint special collection between the American Geophysical Union (AGU) and the Ecological Society of America (ESA).

To encompass a wide range of environmental disciplines, we are excited to present this joint special collection between the American Geophysical Union (AGU) and the Ecological Society of America (ESA), thereby allowing contributors to submit articles to the journal that is most appropriate for their field. Instead of siloing ecological forecasting in a single journal, we aim to promote the power of forecasting across disciplines, journals, and scientific societies. 

Here, we define ecological forecasts as near-term (i.e., a day to decade ahead) predictions that include estimates of uncertainty (Dietze et al., 2018). Forecasts should be evaluated using data, which can include the use of reforecast analyses (i.e., forecasts of conditions that have already passed but using only model inputs that would have been available if the forecast had been generated in real-time). Forecast uncertainty associated with predictions should be represented and communicated in submitted manuscripts, as absolute knowledge of the future does not exist. Uncertainty can arise from various sources, including the initial starting conditions of a model, model input and drivers (e.g., ensemble weather forecast inputs for an ecological model), model parameters, model structure, and model selection (e.g., multi-model ensembles). In this special collection, if model scenario uncertainty is presented, it should be provided in addition to other sources of uncertainty.

The larger ecological forecasting enterprise encompasses model development, data-model integration, computation, decision support, and education. Manuscripts that are not themselves descriptions and evaluations of ecological forecasts are welcome, provided they highlight direct connections to forecasting. These connections could highlight novel methodologies (e.g., machine learning, process-modeling, uncertainty quantification, digital twins, inverse modeling); interdisciplinary approaches (e.g., co-produced forecasts, integration with decision science, forecast dashboard design, forecast cyberinfrastructure); approaches for forecast delivery and education; and multi-forecast syntheses to enhance the accuracy, uncertainty representation, evaluation, and applicability of ecological forecasts. 

This collection aims to inspire further research and collaboration, ultimately contributing to more informed and effective environmental stewardship.

Overall, this special issue is timely as it coincides with a growing recognition of the need for predictive science in environmental decision-making. By showcasing the latest advancements and applications in ecological forecasting, this collection aims to inspire further research and collaboration, ultimately contributing to more informed and effective environmental stewardship.

The AGU journals included in the Special Collection are Journal of Geophysical Research: Biogeosciences, Journal of Geophysical Research: Machine Learning and Computation, Water Resources Research, Journal of Advances in Modeling Earth Systems, and Journal of Geophysical Research: Oceans. The ESA journals included are Ecology, Ecological Applications, Ecological Monographs, Ecosphere, Frontiers in Ecology and the Environment, and Earth Stewardship.

To submit to an AGU journal please use the standard submission portal for the appropriate journal and select the collection title from the drop-down menu in the Special Collection field of the submission form. To submit your manuscript to an ESA publication, use the standard submission portal and indicate the collection title in the cover letter. Queries to the organizers to share your topic proposal and/or abstract prior to submission are encouraged through our inquiry form.

—R. Quinn Thomas (rqthomas@vt.edu, 0000-0003-1282-7825), Virginia Tech, United States, Associate Editor of JGR: Biogeosciences and special collection organizer; Cayelan C. Carey (0000-0001-8835-4476), Virginia Tech, United States, special collection organizer; Eric R. Sokol (0000-0001-5923-0917), National Ecological Observatory Network, United States, special collection organizer; Melissa A. Kenney (0000-0002-2121-8135), University of Minnesota, United States, special collection organizer; Michael C. Dietze (0000-0002-2324-2518), Boston University, United States, special collection organizer; and Marguerite A. Xenopoulos (0000-0003-2307-948X), Trent University, Canada, Editor-in-Chief of JGR: Biogeosciences

Citation: Thomas, R. Q., C. C. Carey, E. R. Sokol, M. A. Kenney, M. C. Dietze, and M. A. Xenopoulos (2025), Advances in ecological forecasting, Eos, 106, https://doi.org/10.1029/2025EO255024. Published on 4 August 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.

SummaryThe northeastern Tibetan Plateau is bounded by the left-lateral Altyn Tagh and Haiyuan faults. How crustal motion along these fault systems transitions to crustal shortening and uplift is key for deciphering the geodynamic link between the escape tectonics and the growth of the Tibetan Plateau. Here, we use the PS-InSAR observations, combined with GNSS and leveling data, to obtain a high-resolution 3D model of the present-day crustal motion in the northeastern Tibetan Plateau. The resolved deformation field covers the entire northeastern Tibetan Plateau with a spatial resolution of approximately 0.01° × 0.01 °. Our analysis of slip rates and strain partitioning reveals that crustal motion along the Altyn Tagh fault gradually diminishes eastward and is absorbed by thrusting and uplift in the Qilianshan orogenic belt within the plateau. A similar tectonic transition occurs between the Haiyuan fault and the Liupanshan orogen on the eastern margin of the plateau. Some of the eastward crustal motion is accommodated by the younger Xiangshan-Tianjingshan fault system to the north of the Haiyuan fault, indicating the ongoing northward expansion of the Tibetan Plateau. Our results align with geological evidence of crustal deformation in the past few million years, highlighting the continuing tectonic transition from eastward crustal motion along the left-lateral strike-slip faults to the growth of the Tibetan Plateau.

SummaryThe continuous NE-SW compression due to the Indo-Asian collision creates active and complex deformation in the northeastern (NE) Tibetan plateau. How the lithosphere of the NE Tibetan plateau deforms both vertically and laterally in response to the ongoing collision is still a question. Further investigations with refined lithospheric structure are required. Here we present a high-resolution radially anisotropic model of the lithosphere beneath the NE Tibetan plateau and surrounding areas that was constrained by the joint analysis of Rayleigh and Love wave dispersion at periods from 6 to 100 s using the methods of ambient noise cross-correlation for short periods and earthquake two-plane-wave for long periods. Results show relatively small regions of significant slow shear wave velocity and positive radial anisotropy (Vsh > Vsv) in the middle crust beneath the Qilian orogenic belt, suggesting the existence of partial melting and probably limited channel flow. Considering the variable lateral strength of shear wave velocity and radial anisotropy in the middle crust with large parts mechanically strong enough to pass the strain, vertical coherent lithospheric deformation could still work in the Qilian orogenic belt. Extensive low shear wave velocity anomaly in the uppermost mantle extend from the Qilian orogenic belt northward to the Alxa block and eastward to the southwestern Ordos block, implying a hot and weak mantle lithosphere. The observed negative radial anisotropy (Vsh < Vsv) in such warm mantle lithosphere beneath the Qilian orogenic belt, Alxa block and the southwestern Ordos block is ascribed to vertical deformation fabrics arising from the convergence between Indian and Asian plates. These observations imply that the lithosphere of Qilian orogenic belt, Alxa block and southwestern Ordos block deform coherently and the NE Tibetan plateau is expanding towards Alxa block and the southwestern Ordos block.

SummaryWe develop a new method for estimating the autocorrelation function (ACF) from segmented data with the assumption of stochastic stationarity. The ACF of a signal is represented as the summation of the cross terms of sub-segments of arbitrary length. To successfully remove undesired transients in the data, this method introduces a correction for the amplitude bias associated with the removal of sub-segments, based on the comparison between the expected stationary signal and the measured signal. The method reconstructs and accesses later lag times, provides finer frequency resolution, obtains a better signal-to-noise ratio, which enables the extraction of detailed temporal or spectral structures from noisy data sets. As an application, we successfully retrieved a spectrum of the Earth’s seismic hum on the vertical component with fine frequency resolution and compared it to synthetic autocorrelation for spatially isotropic and homogeneous excitation by random shear traction at the ocean bottom and random pressure at the Earth’s surface. Although both models can explain the observed fundamental spheroidal modes, shear traction is better at explaining the observed overtones above 3 mHz. From 2 to 3 mHz, the pressure source also contributes to the excitation of the overtones, and the shear traction becomes dominant again below 2 mHz. This new method is anticipated to be effective in extracting valuable information from rare records within the context of extraterrestrial seismology.

SummaryNortheast China, with its complicated regional tectonic evolution, situated within the eastern Central Asian Orogenic Belt, is a key region for understanding lithospheric deformation and mantle dynamics. However, the ongoing debate surrounding its lithospheric structure and evolutionary processes remains, largely attributed to data limitations and methodological constraints. In this study, we integrate topography, geoid height, surface heat flow, and Rayleigh wave phase velocity dispersion curves to conduct a detailed imaging of the lithospheric thermal and compositional structure in Northeast China. We find a significant east-west gradient in lithospheric thickness, ranging from approximately 60 km in the east to 140 km in the west, and a compositional transition in the lithospheric mantle from fertile peridotite in the east to refractory peridotite in the west. By integrating analyses of upper mantle anisotropy and the spatiotemporal distribution of Mesozoic basalts, we argue that the lithospheric delamination and mantle upwelling may have combined to cause the lithospheric thinning in the region. This study highlights the significance of joint inversion of multiple datasets and integrated multidisciplinary analysis.

SummaryTraditional methods for measuring geopotential difference using optical fiber frequency transfer or satellite-based time-frequency transfer, based on general relativity, require the use of two clocks and the calibration of these clocks. Here we present a simplified clock transportation experiment using a single hydrogen clock to measure the geopotential difference between two time-frequency stations, separated by 129 km with a height difference of 1,245 m, by GNSS precise point positioning time-frequency transfer. Taking the reference clock of International GNSS Service (IGS) time as a ‘bridge’, we extract the gravity frequency shift between the two stations by comparing the fractional frequency differences between the hydrogen clock and the ‘bridge’ before and after clock transportation. The determined geopotential difference between the two stations is 12075.9$\pm $118.5 m²/s², which closely aligns with the value computed by the EIGEN-6C4 global gravity field model, with a difference of -78.7 m²/s². These results validate the feasibility of geopotential difference measurements with a single clock and highlight several advantages compared to the dual-clock method: elimination of inter-clock calibration, low operational complexity and equipment cost, high data utilization efficiency but similar precision of geopotential difference measurement. Furthermore, this method can be extended to other similar techniques to measure geopotential differences, provided that they enable users to connect to a stable time-frequency reference.

SummaryShale gas extraction could produce underground stress perturbation and local seismicity, which could put a threat human casualty. The Weiyuan area in the Sichuan province, China, underwent massive gas production and a significant increase of earthquake since 2015. In this study, we focus on human-induced subsurface hydrofracturing, calculate cumulative underground Coulomb-stress changes using a 3D numerical model, and probe the main cause of recent seismic activity in the Weiyuan area based on continuous regional stress/displacement loading. The simulation reveals the regional extent of positive Coulomb stress change with fractures matches the distribution of the moderate and micro seismicity in the past ten years. Background regional tectonic stress in the vicinity of the active fault likely resulted in earthquake preparation within and around the active faults; hydraulic fracturing changes mainly the displacement and stress pattern in the vicinity of the fracturing wells, and enhanced fracturing intensity (fracture volume-to-model volume ratio (θ), causes more obvious difference; faults may be locked prior to fracturing, and even small fracturing intensity may trigger the earthquakes near faults and fracturing wells; the seismic risk will be significantly increased near the two faults and fracturing wells in the next 50 years.

Forests play a central role in the global carbon cycle as trees store carbon in their trunks, branches, roots and leaves. However, climate change and human activities can change the ability of forests to absorb carbon and the annual changes in these carbon stocks are highly variable in space and time around the globe. That's why having continuous observations of the evolution of forest biomass over a long period is important for monitoring this essential climate variable.

After a massive earthquake off the coast of Kamchatka, a peninsula in the far east of Russia, on July 30, 2025, the world watched as the resultant tsunami spread from the epicenter and across the Pacific Ocean at the speed of a jet plane.

Forests cover about 40% of the EU's land area. Between 1990 and 2022, they absorbed around 10% of the continent's man-made carbon emissions. However, the carbon dioxide absorption capacity of forests, also known as carbon sinks, is becoming increasingly weaker.

Source: Journal of Geophysical Research: Planets

Spectacular aurorae dance and shimmer nearly continuously at Jupiter’s poles. These grand displays are driven by energetic particles that are funneled toward the poles within Jupiter’s vast magnetosphere, or the area of space affected by the planet’s magnetic field. These particles then stream down toward the Jovian surface, setting atmospheric molecules aglow. Jupiter’s aurorae occur mainly at ultraviolet wavelengths and are hundreds of times more energetic than Earth’s.

Sometimes, Jupiter’s aurorae grow much brighter for hours or days at a time. Potential causes may involve the solar wind’s influence on the magnetosphere or the dynamics of energetic particles spewed into space by Jupiter’s volcanic moon Io. However, clarifying the solar wind’s role in any one brightening event would require taking simultaneous measurements of Jupiter’s magnetosphere and aurorae and their relationship with the solar wind—a difficult undertaking.

Recently, NASA’s Juno mission has made such simultaneous measurements possible. Giles et al. used data collected by the Jupiter-orbiting spacecraft to study how the gas giant’s ultraviolet aurorae responded when its magnetosphere was temporarily but dramatically compressed to a smaller size on 6 and 7 December 2022. Compression events happen from time to time and are normal, but this one was stronger than almost any previously observed.

Data from two of Juno’s onboard instruments—the Jovian Auroral Distributions Experiment (JADE) and Waves—suggest that as Juno neared Jupiter in its elliptical orbit on 6 December, the spacecraft was overtaken by the outer edge of the shrinking magnetosphere before later reentering it closer to Jupiter.

Additional data from modeling efforts suggest that just as sometimes seen with Earth’s magnetosphere, the extreme compression was caused by a sudden intensification of the solar wind that exerted a powerful squeeze on Jupiter’s magnetosphere.

This squeeze coincided with a major spike in ultraviolet auroral emissions. Another of Juno’s instruments, its ultraviolet spectrograph, measured the aurora’s peak power at this time to be 12 terawatts—6 times its baseline power level.

Given the coincident timing of these rare events, the researchers concluded that the powerful auroral display was likely triggered by the major solar wind shock compressing the magnetosphere. Further research could clarify the mechanisms by which compression can boost the aurora and explore additional processes that could trigger brightening events. (Journal of Geophysical Research: Planets, https://doi.org/10.1029/2025JE009012, 2025)

—Sarah Stanley, Science Writer

Citation: Stanley, S. (2025), A solar wind squeeze may have strengthened Jovian aurorae, Eos, 106, https://doi.org/10.1029/2025EO250281. Published on 1 August 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.

Arctic and subarctic soils store a significant proportion of Earth’s carbon. But rising temperatures could drain these soils of nitrogen—a key nutrient. The loss could reduce plant growth, limiting the soils’ ability to store carbon and amplifying global warming, according to a new study.

High-latitude soils store vast amounts of carbon because cold temperatures slow microbial activity. Though plants produce organic matter through photosynthesis, microorganisms can’t consume it fast enough, leading to its accumulation over time. Scientists have long worried that a warmer Arctic would accelerate microbial activity, releasing stored carbon into the atmosphere as carbon dioxide (CO2). But they also hoped that warmer temperatures would stimulate plant growth, which would reabsorb some of the carbon and partially offset these emissions.

The new research shows that the latter scenario is very unlikely because warming causes soils to lose nitrogen, a loss that could inhibit plant growth.

“We didn’t expect to see nitrogen loss.”

The findings come from a decade-long experiment in a subarctic grassland near Hveragerði, Iceland. In 2008, a powerful earthquake altered geothermal water flows in the region, turning previously average patches of soil into naturally heated zones with temperature gradients ranging from 0.5°C to 40°C above previous levels. The event created a unique natural laboratory for observing how ecosystems respond to long-term warming.

Using stable nitrogen-15 isotopes to trace nutrient flows in the landscape, the researchers found that for every degree Celsius of warming, soils lost between 1.7% and 2.6% of their nitrogen. The greatest losses occurred during winter and early spring, when microbes remained active but plants were dormant. During this time, nitrogen-containing compounds such as ammonium and nitrate were released into the soil, but with plants unable to absorb them, they were lost by either leaching into groundwater or escaping into the atmosphere as nitrous oxide, a greenhouse gas nearly 300 times more potent than CO2.

The findings were published in a paper in Global Change Biology.

“We didn’t expect to see nitrogen loss,” said Sara Marañón, a soil scientist at the Centre for Ecological Research and Forestry Applications in Spain and the study’s first author. “The soil’s mechanisms to store nitrogen are breaking down.”

A Leaner, Faster Ecosystem

The researchers also found that warming weakened the very mechanisms that help soils retain nitrogen. In warmer plots, microbial biomass and the density of fine roots—both key to nitrogen storage—were much lower than in cooler plots. Though microbes were less abundant, their metabolism was faster, releasing more CO2 per unit of biomass. Meanwhile, plants struggled to adapt, lagging behind in both growth and nutrient uptake.

“Microbial communities are able to adapt and reach a new equilibrium with faster activity rates,” Marañón said. “But plants can’t keep up.”

“This is a not-so-optimistic message.”

Heightened microbial metabolism initially results in greater consumption of the nitrogen and carbon available in the soil. After 5 or 10 years, however, the system appears to reach a new equilibrium, with reduced levels of organic matter and lower fertility. That shift suggests that warming soils may transition to a permanently less fertile state, making it harder for vegetation to recover and leading to irreversible carbon loss.

Scientists have traditionally thought that as organic matter decays faster in a warmer climate, the nitrogen it contains will become more available, leading to increased productivity, said Erik Verbruggen, a soil ecologist at the University of Antwerp in Belgium who was not involved in the study. “This paper shows that actually, this is not happening.”

Instead, nitrogen is being leached out of the soil during the spring, making it unavailable for increased biomass production. “This is a not-so-optimistic message,” Verbruggen said.

An Underestimated Source of Greenhouse Gases

With Arctic regions warming faster than the global average, this disruption to the nutrient cycle could soon become more apparent. Nitrogen and carbon loss from cold-region soils may represent a significant and previously underestimated source of greenhouse gas emissions—one that current climate models have yet to fully incorporate.

The researchers periodically returned to the warm grassland near Hveragerði, Iceland, to measure nitrogen. Credit: Sara Marañón

The researchers plan to explore the early phases of soil warming by transplanting bits of normal soils into heated areas and also to investigate how different soil types respond to heat. Marañón noted that the Icelandic soils in the study are volcanic in origin and very rich in minerals, unlike organic peat soils common in other Artic regions.

“Arctic soils also include permafrost in places like northern Russia and parts of Scandinavia, and they are the largest carbon reservoirs in the world’s soil,” Verbruggen said. The soils analyzed in this research, on the other hand, were shallow grassland soils. “They are not necessarily representative of all Arctic soils.”

Still, Verbruggen added, the study’s findings highlight the delicate balance between productivity and nutrient loss in these systems.

Soil’s abundant carbon reserves make it a major risk if mismanaged, Marañón said. “But it can also become a potential ally and compensate for CO2 emissions.”

—Javier Barbuzano (@javibar.bsky.social), Science Writer

Citation: Barbuzano, J. (2025), As the Arctic warms, soils lose key nutrients, Eos, 106, https://doi.org/10.1029/2025EO250282. Published on 1 August 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.

Author(s): L. Ansia, P. Velarde, M. Fajardo, and G. O. Williams

Nonthermal photoionized plasmas are now established in the laboratory and require models that treat the atomic processes and electron distribution self-consistently. We investigate the effects of inelastic thermalization in iron under intense x-ray irradiation using the atomic model BigBarT, suited …

[Phys. Rev. E 112, 025201] Published Fri Aug 01, 2025

Author(s): H. P. Le, E. V. Marley, and H. A. Scott

Electron distributions in laser-produced plasmas will be driven toward a super-Gaussian distribution due to inverse bremsstrahlung absorption [Langdon, Phys. Rev. Lett. 44, 575 (1980)]. Both theoretical and experimental evidence suggest that fundamental plasma properties are altered by the super-Gau…

[Phys. Rev. E 112, 025202] Published Fri Aug 01, 2025

Terrestrial plants drove an increase in global photosynthesis between 2003 and 2021, a trend partially offset by a weak decline in photosynthesis—the process of using sunlight to make food—among marine algae, according to a study published in Nature Climate Change.

SummaryIn this study, we compare the usability of a simplified microtremor-based empirical method and a conventional microtremor method based on an inversion analysis of a subsurface velocity structure model for constructing a map of average S-wave velocity (AVS) values. In the simplified (empirical) method, the phase velocities of Rayleigh waves, which can be obtained by processing a microtremor array, at wavelengths of 13, 25, and 40 m are regarded as AVS values from the ground surface to depths of 10, 20, and 30 m (${\overline {Vs} }_{10},{\overline {Vs} }_{20},\ {\rm{and}}\ {\overline {Vs} }_{30}$), respectively. Microtremor array surveys were conducted at 173 observation points within a 15 km × 17 km area east of Aso caldera, Kyushu, Japan (target area). AVS values are obtained by applying the empirical method to the phase velocities obtained at each observation point. The AVS values at an observation point (located near the centre of the target area) with velocity logging data are verified by a comparison with those based on the velocity logging data (i.e. overestimations by 6 per cent at maximum). It is found that for the entire target area, the spatial distribution of the obtained AVS values is consistent with the geological distribution. The AVS values within areas of the Aso-3 ignimbrite are 30–40 per cent larger than those within areas of thick soil and tephra on the strongly consolidated Aso-4 ignimbrite. In addition, the AVS values of the Aso-3 deposits are more than 10 per cent larger than those of the Aso-4 deposits and about 10 per cent smaller than those of geological units older than the Aso-3 deposits. We also apply a conventional (i.e. inversion) method to the phase velocity data at each observation point to obtain a one-dimensional S-wave velocity (Vs) structure model from which we deduce AVS values. The deduced AVS values at the velocity logging point are underestimated by -8 per cent, with differences from the AVS values obtained using the empirical method reaching 13 per cent. The average systematic difference between the two methods is 15 per cent, as determined from a statistical analysis. None the less, a strong correlation is found between the methods, with an average correlation coefficient of 0.94, with no evidence showing that either method is more accurate. The empirical method can be used to construct an AVS map if overestimation is carefully considered. This analysis also reveals that the average maximum survey depths of the one-dimensional Vs structures based on the inversion method are only 23±10 m, making them often insufficient to map ${\overline {Vs} }_{20}$ and ${\overline {Vs} }_{30}$ (the ratios of the available to total numbers of data points are only 60 and 21 per cent, respectively). In contrast, the empirical method can determine ${\overline {Vs} }_{10},{\overline {Vs} }_{20},\ \ {\rm{and}}\ {\overline {Vs} }_{30}$ at more than 80 per cent of all sites. The construction of AVS maps using the empirical method is effective in terms of the simplicity and reliability of planning, observational efficiency, and simplicity of data processing, which support a practical and objective approach to seismic assessments.

SummaryIn this study we obtain 35 903 high-quality P-wave receiver functions from 1737 teleseismic events recorded at 120 dense broadband TanluArray temporary stations deployed in and around the Tanlu fault zone (TLFZ). After station azimuth and sediment correction are made, a detailed Moho depth distribution is obtained by CCP stacking. Our results show a sharp change in the Moho depth across the TLFZ from the west to east, which well corresponds to the surface geological structure. The deepest Moho (38.0 ∼ 40.0 km) occurs beneath the Dabie orogenic belt and the Sulu orogenic belt. The Moho beneath the Luxi uplift, Jiangnan orogenic belt and Jiaodong uplift is deeper (36.0 ∼ 37.0 km), whereas the Subei basin and the southern basin of the South Yellow Sea have a shallow Moho (28.0 ∼ 30.0 km). There is an obvious Moho uplift near Weifang, which corresponds to the Changle ancient volcano on the surface and may be a channel for upwelling of hot mantle material. The Moho is unclear under the fault zone near Tancheng, which is speculated to be a channel for upwelling of hot mantle material. It may be related to upwelling of hot and wet flows in the big mantle wedge above the subducted Pacific slab that is stagnant in the mantle transition zone beneath East Asia, which is a possible cause of the 1668 M8.5 Tancheng earthquake.

A new study shows that natural dust particles swirling in from faraway deserts can trigger freezing of clouds in Earth's Northern Hemisphere. This subtle mechanism influences how much sunlight clouds reflect and how they produce rain and snow—with major implications for climate projections.