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Source: Journal of Geophysical Research: Oceans

As freshwater from glacier melt, river runoff, and precipitation enters the Arctic Ocean, a circular current called the Beaufort Gyre traps it near the surface, slowly releasing the water into the Atlantic Ocean over decades. Warming global temperatures may weaken the wind patterns that keep the gyre turning, which could slow or even stop the current and release a flood of freshwater with a volume comparable to that of the Great Lakes. This deluge would cool and freshen the surrounding Arctic and North Atlantic oceans, affecting sea life and fisheries and possibly disrupting weather patterns in Europe.

Athanase et al. analyzed the Beaufort Gyre’s circulation patterns using 27 climate models from the Coupled Model Intercomparison Project Phase 6 (CMIP6), which informed the most recent Intergovernmental Panel on Climate Change (IPCC) report.

Before trying to predict the future behavior of the gyre, the researchers turned to the past. To assess how well CMIP6 models capture the gyre’s behavior, they compared records of how the gyre actually behaved to CMIP6 simulations of how it behaved, given known conditions in the ocean and the atmosphere.

Most CMIP6 models do not capture the gyre’s behavior very well, it turns out. Some models did not predict any circulation, when circulation clearly occurred. Others overestimated the area or strength of the gyre, shifted it too far north, or inaccurately estimated sea ice thickness within the gyre. Eleven of the models produced sea ice thickness estimates the researchers called “unacceptable.”

Despite these problems, the researchers pushed ahead, using the 18 CMIP6 models that most closely reflected the gyre’s true behavior to predict how circulation could change under two future emissions scenarios: intermediate and high. Most of the tested models showed that the gyre’s circulation will decline significantly by the end of this century, but their predictions for exactly when varied from the 2030s to the 2070s. Three models predicted that the gyre will not stop turning at all.

The gyre is most likely to disappear if emissions remain high, but it may stabilize as a smaller gyre if emissions are only moderate, the researchers found. Despite substantial uncertainty, the results are a reminder that when it comes to preventing the most disruptive effects of climate change, “every fraction of a degree matters,” they write. (Journal of Geophysical Research: Oceans, https://doi.org/10.1029/2024JC021873, 2025)

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

Citation: Sidik, S. M. (2025), The uncertain fate of the Beaufort Gyre, Eos, 106, https://doi.org/10.1029/2025EO250186. Published on 13 May 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.

An international research team studying fossilized oyster shells has revealed substantial annual temperature variation in sea water during the Early Cretaceous. The finding overturns the assumption that Earth's greenhouse periods are marked by universally warmer and uniformly stable temperatures.

Carbon dioxide removal (CDR) strategies use a wide range of techniques to capture CO2 from the air and store it durably, offering a frontier solution for counteracting the increasing levels of the greenhouse gas in our environment. Increasing the alkalinity of wastewater by treating it with alkaline minerals can substantially boost the CO2 sequestration abilities, finds a study appearing in Science Advances.

A "blocking" weather system lingering high above the UK has produced one of the driest, warmest and brightest starts to spring on record.

Sphalerite is a very cool mineral. It is a beautiful, complex and diverse zinc sulfide (ZnS) mineral that also hosts a treasure trove of other critical elements. These include manganese, cadmium, mercury, indium, thallium, gallium, germanium, antimony, tin, lead, silver and cobalt.

Researchers at the University of Miami are providing improved insights into how extreme heat should be defined and addressed. The findings were published in an article titled "Where heat does not come in waves: A framework for understanding and managing chronic heat" in the journal Environmental Research: Climate.

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

Arctic ponds play a key role in permafrost thaw and greenhouse gas emissions; however, their physical mixing processes remain poorly characterized. Most conceptual models assume that vertical, one-dimensional mixing—driven by surface cooling due to which water becomes denser, and sinks vertically, mixing the water mass from the top down—is the primary mechanism for deep water renewal.

Henderson and MacIntyre [2025] challenges that model by showing that two-dimensional thermal overturning circulation dominates in a shallow permafrost pond. Specifically, nighttime surface cooling in shallow areas generates cold, dense water that flows downslope along the pond bed, displacing and renewing deeper waters. Using high-resolution velocity, temperature, and other related measurements, the authors demonstrate that these gravity currents ventilate the bottom despite persistent stable stratification during nighttime. These findings reveal that lateral thermal flows can drive vertical exchange in small water bodies. The results have important implications for biogeochemical modeling and upscaling greenhouse gas fluxes across Arctic landscapes.

This is a diagram of how cold water moves at night in a pond. At night, the shallow parts of the pond (near the right edge) cool down faster than the deeper parts. This creates thin layers of cold, dense water near the shore. Because this water is denser (heavier), it sinks and flows sideways along the sloped pond bottom toward the deepest part of the pond—like a slow, underwater landslide of cold water. As this cold water flows downhill, it pushes the existing bottom water upward, creating a gentle circulation loop: surface water cools and sinks at the edges, flows along the bottom, and pushes older deep water upward toward the middle. Credit: Henderson and MacIntyre, Figure 3a

Citation: Henderson, S. M., & MacIntyre, S. (2025). Thermal overturning circulation in an Arctic pond. Geophysical Research Letters, 52, e2024GL114541. https://doi.org/10.1029/2024GL114541

—Valeriy Ivanov, Editor, Geophysical Research Letters

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): Rima Mebrek, Rachid Fermous, Moufida Benzekka, and Rabia Amour

The current study examines, using a nonextensive statistical framework satisfying the H-theorem constraint 0≤q≤2, the dynamics of dust-acoustic shock waves in complex plasmas under the influence of both gravity and microgravity within adiabatic and nonadiabatic fluctuating charge. The results highli…

[Phys. Rev. E 111, 055203] Published Tue May 13, 2025

In the modern world, a reliable supply of hydrogen gas is vital for the function of society. Fertilizer produced from hydrogen contributes to the food supply of half the global population, and hydrogen is also a key energy component in many roadmaps to a carbon-neutral future, essential if we are to prevent the worst predictions of climate change.

SummaryTeleseismic P-wave coda autocorrelation has been increasingly applied to subsurface structure characterization, given its potential to infer velocities. However, the inversion of coda autocorrelation data has not been extensively investigated regarding data processing (stacking and move-out correction), inversion approaches (Monte Carlo or metaheuristic), model parameterization, and applicability. Here, we propose an inversion method for teleseismic P-wave coda autocorrelation based on particle swarm optimization and a treatment of uncertainty. This inversion method utilizes the arrival time information of reflected (or converted) waves contained in the binned stack waveforms, demonstrating promising model adaptability and robustness. Synthetic data tests show that this method accurately inverted various geological models without prior information, such as the number of crustal layers, surface sedimentary layers, and low-velocity zones within the crust. The method was successfully applied to the QSPA station near the South Pole, revealing an ice sheet thickness of approximately 2900 m, with a 340 m thick low shear-wave velocity ice layer at the base, likely containing up to 15% water. Beneath the ice sheet, we infer a 400 m thick subglacial sediment layer. The uncertainties of the thickness of the low shear wave velocity ice and the sedimentary layer are 150 m and 10 m, respectively. These findings and the potential of the proposed method open up new directions for glacier dynamics research in the region. Additionally, we apply the method to the BOSA station near Kimberley, South Africa, which confirms clear Moho and intracrustal interfaces, consistent with receiver functions and deep seismic reflection data results. This study improves the inversion algorithm for teleseismic P-wave coda autocorrelation and expands its application scenarios.

SummaryGeophysical simulations for complex subsurface structures and material distributions require the evaluation of partial differential equations by means of numerical methods. However, the mentioned high complexity often yields computationally very costly simulations, especially for electromagnetic (EM) and seismic methods. When used in the context of parameter estimation or inversion studies, this aspect severely limits the number of simulations that are affordable. However, especially for structured model analysis methods, such as global sensitivity analyses or inversions, often thousands to millions of forward simulation runs are required. To address this challenge, we propose utilizing a physics-based machine learning method, namely the non-intrusive reduced basis method, aiming at constructing low-dimensional surrogate models to significantly reduce the computational cost associated with the numerical forward model while preserving the physical principles. We demonstrate the effectiveness and benefits of the surrogate models using broadband Magnetotelluric (MT) responses of a 2-D model that mimics a conceptual volcano-hosted geothermal system. Next to being a first such application, we also show how ML reduced basis method can be adapted to consistently treat complex-valued variables – an aspect that has been overlooked in previous studies. Additionally, reducing computation time by several orders of magnitude through the surrogate enables us to perform a global sensitivity analysis for MT applications. Despite additional insights, such an analysis has been normally deemed infeasible given the high computational burden. The methods developed here are presented in a generalized form, making this approach feasible for other electromagnetic techniques with a low-dimensional parameter space.

SummaryThe triple junction between the North American, Caribbean, and Cocos plates at the Guatemala-Mexico border is not well understood. It forms a broad region from around the active Tacaná volcano up to the Guatemala City graben. Tacaná is the westernmost active volcano of the Central American volcanic arc and is located at the intersection of four major active faults: the Polochic, Motagua, Jalpatagua, and Tonalá faults. Using seismicity around the Tacaná volcano, we show that there is moderate to low tectonic seismic activity between the Guatemala City graben and the Tacaná volcano, possibly related to the ancient extremes of the Motagua and Jalpatagua faults. Therefore, we speculate that the triple junction would be located onshore, around the Tacaná volcano.We located earthquakes around the Tacaná volcano between January 2017 and October 2018, a period that includes the large Mw8.2 Tehuantepec (Chiapas) earthquake of 8 September 2017, located ∼190 km away. We identified four distinct types of seismicity, interpreted as having tectonic, hydrothermal, intermediate depth magmatic, and deep magmatic origins. The tectonic seismicity occurred at depths between ∼5 km and ∼30 km b.s.l., and may be associated with three faults around the Tacaná volcanic complex. These faults are oriented in NE-SW, aligned with the four Tacaná volcanic edifices; NW-SE, consistent with the Jalpatagua fault; and approximately EW, corresponding to the Motagua fault. The hydrothermal seismicity is observed at shallow depths, from the subsurface to about 2 km b.s.l., predominantly in the western sector of the Tacaná summit, and partially beneath the San Antonio volcano, an area known for intense hydrothermal activity. This seismicity is spatially related to the shallow portions of the same three faults described above. The intermediate depth magmatic seismicity is detected at depths between 5 and 12 km b.s.l. and is interpreted to be related to the presence of a shallow magma chamber beneath the Tacaná volcanic complex. Finally, the deep magmatic seismicity is located in the eastern part of the Tacaná, at depths ranging from 15 km to about 22 km b.s.l. This seismicity is interpreted to be due to a vertical dike intrusion that connects a deep magma reservoir located between 30 km and 40 km depth, to the hypothesized shallower magma chamber associated with the intermediate depth seismicity.

SummaryAdvance detection is a pivotal technology in tunnel construction, designed to precisely invert the velocity distribution of geological formations, thereby ensuring both construction safety and operational efficiency. The unscented hybrid simulated annealing (UHSA) algorithm is a global optimization technique that has been successfully applied to the advance detection of tunnels. However, the UHSA exhibits a slow convergence rate under complex geological conditions and is prone to getting trapped in local optima. To address this issue, we propose an improved method based on the whale optimization algorithm (WOA), referred to as MEWOA. MEWOA incorporates a population-initialization method based on the tent map and reverse learning and integrates a nonlinear convergence factor, a frequency-fluctuation mechanism, and the low-soaring strategy of the red-tailed hawk algorithm (RTH). These enhancements notably improve the accuracy and convergence speed of the algorithm. We conducted a qualitative analysis of the enhancement mechanisms in MEWOA using two functions and performed quantitative experiments on four tunnel models. The experimental results demonstrate that MEWOA outperforms UHSA, achieving higher accuracy in solving inversion problems with multiple velocity models.

A new study led by the University of Southampton and research institutes in France has uncovered the mystery of how mini sand dunes form on beaches and in deserts.

The El Niño-Southern Oscillation (ENSO) is known to have a significant impact on climate across the Pacific, including Hawai'i, and adjacent continents. However, new research led by University of Hawai'i at Mānoa atmospheric scientists revealed that the Pacific Meridional Mode (PMM), another climate pattern that operates in the eastern Pacific Ocean, plays a major role in the variability of rainfall in Hawai'i.

Have you ever imagined what Antarctica looks like beneath its thick blanket of ice? Hidden below are rugged mountains, valleys, hills and plains.

Forecasters are confident it's a particularly bad water year for the Colorado River, worrying some about a likely return to record low levels in reservoirs that are reminiscent of 2022.

Hidden beneath the Antarctic ice lies a system of lakes and watercourses. A research team, including ETH researchers, has for the first time directly observed the subglacial streams of West Antarctica. Their study, published in Nature Geoscience, shows how individual flood events influence the melting of the ice.

Human emissions of greenhouse gases have caused rapid global warming. This has made high-impact, heat extreme events around the globe more and more intense over the past 70 years. Heat extremes, such as heat waves, can cause severe damage to infrastructure by damaging bridges and railways. They also harm ecosystems, and can lead to loss of life.

Every now and then, some trees apparently just need a jolt. When struck by lightning, the large-crowned Dipteryx oleifera sustains minimal damage, whereas the trees and parasitic vines in its immediate vicinity often wither away or die altogether. That clearing out of competing vegetation results in a nearly fifteenfold boost in lifetime seed production for D. oleifera, researchers estimated.

An Instrumented Forest

“This is the only place on Earth where we have consistent lightning tracking data with the precision needed to know [whether a strike] hit a patch of forest.”

Panama is often known for its eponymous canal. But Barro Colorado Island, in central Panama, is also home to what researchers who work in the area call “one of the best-studied patches of tropical forest on earth.” That’s because cameras and devices to measure electric fields are constantly surveying the forest from atop a series of towers, each about 40 meters high. Those instruments can reveal, among other information, the precise locations of lightning strikes. “This is the only place on Earth where we have consistent lightning tracking data with the precision needed to know [whether a strike] hit a patch of forest,” said Evan Gora, an ecologist at the Cary Institute of Ecosystem Studies and the Smithsonian Tropical Research Institute.

Such infrastructure is key to locating trees that have been struck by lightning, said Gabriel Arellano, a forest ecologist at the University of Michigan in Ann Arbor who was not involved in the research. “It’s very difficult to monitor lightning strikes and find the specific trees that were affected.”

That’s because a lightning strike to a tropical tree rarely leads to a fire, said Gora. More commonly, tropical trees hit by lightning look largely undamaged but die off slowly over a period of months.

Follow the Flashes

To better understand how large tropical trees are affected by lightning strikes, Gora and his colleagues examined 94 lightning strikes to 93 unique trees on Barro Colorado Island between 2014 and 2019. In 2021, the team traveled to the island to collect both ground- and drone-based imagery of each directly struck tree and its environs.

Gora and his colleagues recorded six metrics about the condition of each directly struck tree and its cadre of parasitic woody vines known as lianas—including crown loss, trunk damage, and percent of the crown infested with lianas. Lianas colonize the crowns of many tropical trees, using them for structure and competing with them for light. Think of someone sitting next to you and picking off half of every bite of food you take, Gora said. “That’s effectively what these lianas are doing.”

The team also surveyed the trees surrounding each directly struck tree. The electrical current of a lightning strike can travel through the air and pass through nearby trees as well, explained Gora. Where a struck tree’s branches are closest to its neighbors, “the ends of its branches and its neighbors’ will die,” Gora said. “You’ll see dozens of those locations.”

Thriving After Lightning

On average, the researchers found that about a quarter of trees directly struck by lightning died. But when the team divided up their sample by tree species, D. oleifera (more commonly known as the almendro or tonka bean tree) stood out for its uncanny ability to survive lightning strikes. The nine D. oleifera trees in the team’s sample consistently survived lightning strikes, whereas their lianas and immediate neighbors did not fare so well. “There was a pretty substantial amount of damage in the area, but not to the directly struck tree,” said Gora of the species. “This one never died.”

(Ten other species in the researchers’ cohort of trees also exhibited no mortality after being struck by lightning, but those samples were all too small—one or two individuals—to draw any robust conclusions from.)

A D. oleifera tree in Panama is shown just after being struck by lightning in 2019 (left) and 2 years later (right). The tree survived the strike, but its parasitic vines and some of its neighbors did not. Credit: Evan Gora

Gora and his collaborators estimated that large D. oleifera trees are struck by lightning an average of five times during their roughly 300-year lifespan. This species’ ability to survive those events while lianas and neighboring trees often died back should result in overall reduced competition for nutrients and sunlight, the team reasoned. Using models of tree growth and reproductive capacity, the researchers estimated that D. oleifera reaped substantial benefits from being struck by lightning—particularly in regard to fecundity, or the number of seeds produced over a tree’s lifetime. “The ability to survive lightning increases their fecundity by fourteenfold,” Gora said.

D. oleifera may be essentially evolving to be better lightning rods.

The researchers furthermore showed that D. oleifera tended to be both taller and wider at its crown than many other tropical tree species on Barro Colorado Island. Previous work by Gora and his colleagues has shown that taller trees are particularly at risk for getting struck by lightning. It’s therefore conceivable that D. oleifera are essentially evolving to be better lightning rods, said Gora. “Maybe lightning is shaping not just the dynamics of our forests but also the evolution.”

These results were published in New Phytologist.

Gora and his collaborators hypothesized that the physiology of D. oleifera must be conferring some protection against the massive amount of current imparted by a lightning strike. Previous work by Gora and other researchers has suggested that D. oleifera is more conductive than average; higher levels of conductivity mean less resistance and therefore less internal heating. “We think that how conductive a tree is is really important to whether it dies,” said Gora.

Continuing to ferret out other lightning-hardy tree species will be important for understanding how forests evolve over time. And that’s where more data will be useful, said Arellano. “I wouldn’t be surprised if we find many other species.”

—Katherine Kornei (@KatherineKornei), Science Writer

Citation: Kornei, K. (2025), Some tropical trees benefit from lightning strikes, Eos, 106, https://doi.org/10.1029/2025EO250181. Published on 12 May 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.