Feed aggregator

A new wave of climate research is sounding a stark warning: Human activity may be driving drought more intensely—and more directly—than previously understood.

An international team of researchers led by the University of Massachusetts Amherst has tracked changes in more than 114,000 rivers in High Mountain Asia over a 15-year period. The paper, published in AGU Advances, reported that nearly 10% of these rivers saw an increase in flow, with an increasing proportion of that water coming from glacial ice melt compared to precipitation.

Extreme rainfall in New Zealand from future cyclones could rise by up to 35%. New high-resolution modeling predicts that rainfall from tropical cyclones will significantly increase under global warming.

Researchers at The University of Alabama in Huntsville (UAH) have published a paper in Communications Earth & Environment that demonstrates for the first time that using data gathered on atmospheric particles from Chinese megacities to characterize air quality for U.S. urban centers leads to significant inaccuracies.

An international study led by Prof. Tamar Guy-Haim and Dr. Ximena Velasquez from the Israel Oceanographic and Limnological Research (IOLR) has revealed that tiny planktonic crustaceans carry a unique microbial signature that better reflects ocean currents and environmental gradients than microbes found freely in seawater.

As glaciers melt, huge chunks of ice break free and splash into the sea, generating tsunami-sized waves and leaving behind a powerful wake as they drift away. This process, called calving, is important for researchers to understand. But the front of a glacier is a dangerous place for data collection.

On May 12, 2008, the magnitude 7.9 Wenchuan earthquake shook central China, its destructive tremors spreading from the flank of the Longmen Shan, or Dragon's Gate Mountains, along the eastern margin of the Tibetan Plateau.

In the journal Nature, 21 leading scientists prescribe ways to use food systems to halt and reverse land degradation, underlining that doing so must become a top global priority to mitigate climate change and stop biodiversity loss.

For more than 50 years, scientists have debated whether a massive ice shelf—up to 1 kilometer thick—covered the entire Arctic Ocean during past ice ages, transforming the frigid water into a solid icy surface similar to Antarctica’s Ross Ice Shelf.

The hypothesis dates to the 1970s, when British glaciologist John Mercer and others proposed that during extremely cold periods, continental ice sheets would have extended far into the Arctic Ocean. It gained support in the 1990s when researchers began finding evidence of scouring on the seafloor, indicative of large, kilometer-thick ice running aground.

“We found out that even close to the Norwegian coast, there was still open water, which completely contradicts the hypothesis of a big ice shelf covering the Arctic Ocean.”

But new data published in Science Advances add evidence against such a “pan-Arctic” ice shelf, instead suggesting that seasonal sea ice, rather than a continuous ice shelf, dominated parts of the Arctic Ocean over the past 750,000 years.

“We found out that even close to the Norwegian coast, there was still open water, which completely contradicts the hypothesis of a big ice shelf covering the Arctic Ocean,” said coauthor Gerrit Lohmann, a climate modeler from the Alfred-Wegener-Institut in Germany. However, some experts argue that the results alter merely the timing and location of Arctic ice shelves.

Reading Ancient Algae

Instead of analyzing seafloor scars, the study’s authors looked at what was living in ancient seafloor sediment. They analyzed two sediment cores drilled from the Arctic Ocean between Europe and Greenland, searching for molecules produced by marine algae such as diatoms and dinoflagellates before the organisms died and sank to the seafloor.

Some species of alga grow on the underside of seasonal sea ice, and others thrive in open water. Their presence or absence within sediment deposited at a given time signals whether sea ice was present when they were living. Levels of calcium in the sediment can also indicate the production of marine organisms in surface waters.

By searching for organisms’ unique chemical signatures in dated sections of the cores, the scientists could conclude whether and when a solid ice shelf completely covered the ocean surface.

The results showed evidence of both seasonal sea ice and open water over the past 750,000 years, with one exception, around 676,000 years ago, when the chemical signature of the key marine life decreased for roughly 55,000 years.

On a train home after a funding interview, the study’s first author, Jochen Knies, was discussing the sediment core findings with Lohmann, who immediately recognized that the computational climate model he worked on, the high-resolution AWI Earth System Model, might offer additional data on the sea ice conditions during that time. “We discussed it for hours, maybe disturbing others on the train,” Lohmann said.

After some testing, he found that the model independently predicted that the same regions covered by the core samples would have had open water and seasonal sea ice instead of a continuous ice shelf, even during the coldest periods. “I was fascinated to see that in the time slices that [Knies] was interested in, the sea ice was even partly absent in summer,” Lohmann said of the modeling results. “It was completely the opposite of other hypotheses.”

“I would have assumed that where they found open water, there should have been times when this Arctic Ocean ice shelf moved into the area, and apparently it didn’t,” said Johan Nilsson, a paleoceanographer at Stockholm University in Sweden who was not involved in the new study but has published seafloor evidence of an Arctic Ocean ice shelf.

The Debate Continues

To Nilsson, the results don’t completely refute the possibility of large Arctic Ocean ice shelves; instead, they redefine their possible boundaries. “I think for me, it pushes back the edge of Arctic Ocean ice shelves a bit further north of Svalbard,” Nilsson said.

The authors of the new study “don’t see ice shelves in the Norwegian-Greenland sea, but that doesn’t mean that they didn’t exist in the Arctic.”

Leonid Polyak, a retired paleoceanographer at the Ohio State University who was not involved in the research, said the new study reveals “a very strong set of data.” He noted, however, that the evidence for Arctic ice shelves is strong, and the debate over whether they came together into one pan-Arctic ice shelf is “a bit overblown.”

“Pretty much everyone agrees that there have been ice shelves in the Arctic Ocean. The question is, When exactly did they exist, for how long, and where?” Polyak said. The authors of the new study “don’t see ice shelves in the Norwegian-Greenland sea, but that doesn’t mean that they didn’t exist in the Arctic.”

Lohmann acknowledged that mysteries remain in the Arctic and that the pan-Arctic ice shelf debate may not be settled. “I feel the final word hasn’t been spoken,” he said.

—Andrew Chapman (@andrewchapman.bsky.social), Science Writer

Citation: Chapman, A. (2025), Arctic ice shelf theory challenged by ancient algae, Eos, 106, https://doi.org/10.1029/2025EO250298. Published on 13 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.

Source: AGU Advances

What do many baked goods and the planet Mercury have in common? They shrink as they cool.

Evidence suggests that since it formed about 4.5 billion years ago, Mercury has continuously contracted as it has lost heat. And somewhat like a fresh-baked cookie or cheesecake, Mercury also cracks as it cools: Thrust faults cut through the planet’s rocky surface to accommodate the ongoing shrinking.

By observing how faults have uplifted parts of Mercury’s surface, researchers can begin to estimate how much Mercury has contracted since it formed. However, prior estimates have varied widely, suggesting that thanks to faulting resulting from cooling, Mercury’s radius has shrunk by anywhere from about 1 to 7 kilometers.

To resolve this discrepancy, Loveless and Klimczak employed an alternative method for estimating shrinkage caused by cooling-induced faulting on Mercury.

Prior estimates all relied on a method that incorporates the length and vertical relief of uplifted landforms, but that produces different shrinkage estimates depending on the number of faults included in the dataset. In contrast, the new method’s calculations are not reliant upon the number of faults. Rather, it measures how much the largest fault in the dataset accommodates shrinkage, then scales that effect to estimate the total shrinkage.

The researchers used the new approach to analyze three different fault datasets: one including 5,934 faults, one including 653 faults, and one including just 100 faults. They found that no matter which dataset was used, their method estimated about 2 to 3.5 kilometers of shrinkage. Combining their results with prior estimates of additional shrinkage that may have been caused by cooling-induced processes other than faulting, the researchers concluded that since Mercury’s formation, the planet’s radius may have shrunk by a total of 2.7 to 5.6 kilometers.

The new estimates could help deepen the understanding of the long-term thermal history of Mercury. Meanwhile, the authors suggest, the same methodology could be used to investigate the tectonics of other planetary bodies, like Mars, that feature faults. (AGU Advances, https://doi.org/10.1029/2025AV001715, 2025)

—Sarah Stanley, Science Writer

Citation: Stanley, S. (2025), How much has Mercury shrunk?, Eos, 106, https://doi.org/10.1029/2025EO250301. Published on 13 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.

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

The Pacific Decadal Oscillation (PDO) is a slowly evolving pattern of ocean temperature anomalies in the North Pacific that can influence climate and ecosystems across the globe. The climate science community and stakeholders are increasingly interested in how well we can predict the PDO from months to years in advance, but such predictions are not equally reliable at all times of year. As the PDO is part of a coupled ocean-atmosphere system, such simulations are very resource intensive.

Meeker et al. [2025] use the Seasonal to Multi Year Large Ensemble (SMYLE)—a large ensemble of initialized decadal hindcast simulations with the fully coupled Community Earth System Model 2 (CESM2)—to show that while the PDO is predictable up to one year in advance, skill drops off most rapidly during late fall and spring, a seasonal pattern that mirrors known challenges in forecasting El Niño events in the tropical Pacific. Using a simple statistical model, the authors further show that much of the PDO’s predictability comes from persistence—the ocean’s tendency to stay in the same state for a while—but atmospheric teleconnections from the tropical Pacific also play an important role.

The results highlight that when El Niño is hard to predict, so is the PDO. Understanding when and why these prediction skill drops happen is important for improving seasonal forecasts that support fisheries, agriculture and water management. This work also shows how relatively simple linear models can help diagnose behavior in more complex models of the coupled climate system, enabling benchmarking and improvement of more advanced forecasting systems.

Citation: Meeker, E. D., Maroon, E. A., Deppenmeier, A. L., Thompson, L. A., Vimont, D. J., & Yeager, S. G. (2025). Seasonality of pacific decadal oscillation prediction skill. Geophysical Research Letters, 52, e2025GL116122. https://doi.org/10.1029/2025GL116122

—Kristopher B. Karnauskas, Editor-in-Chief, 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.

The location of this major event has now been identified. It was a major rock slope failure that ran out across the South Sawyer Glacier.

The Alaska Earthquake Center has now provided a detailed update about the 10 August 2025 landslide that occurred in the area of Tracy Arm. This work has been led by Ezgi Karasözen, one of the Earthquake Center’s research scientists, so the credit must go to them.

They have posted a very informative page that describes the seismic detection of the landslide, provides eyewitness accounts of the damage that it caused and outlines how they have gone about finding the landslide. This is unusually good public communication about a large event – so well done to them.

They have also published some imagery from their initial reconnaissance of the landslide. Meanwhile, they have also posted to Facebook a short video of the landslide itself – Wordpress won’t allow me to embed this, so this is the link:-

https://www.facebook.com/reel/2164841844024421

The footage was captured by LT Chip Baucom and CDR PJ Johansen of the U.S. Coast Guard. There are two stills that are very helpful in providing an initial view of this landslide. First, this is view of the scar and the deposit – note that the landslide has failed onto the  South Sawyer Glacier.

An initial view of the 10 August 2025 landslide onto the South Sawyer Glacier. Image from a video collected by the US Coast Guard, posted to Facebook by the Alaska Earthquake Center.

This appears to be a large, joint-controlled rock slope failure, with the appearance of a wedge (or several wedges, perhaps).

Second, the video captures the track of the landslide down the glacier towards the fjord:-

An initial view of the track of the 10 August 2025 landslide over the South Sawyer Glacier. Image from a video collected by the US Coast Guard, posted to Facebook by the Alaska Earthquake Center.

This appears to have been a landslide with high mobility – probably the consequence of a large volume and the movement over a low friction surface (ice).

The Alaska Earthquake Center highlights that the seismic instruments detected about 100 small events in the hours leading up to the final collapse. This will be a rich dataset to understand the failure process.

Return to The Landslide Blog homepage Text © 2023. 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.

AbstractDesert strata consist of dune and interdune deposits, and they have different magnetic properties. Contrasting magnetic properties of these two types of strata is a foundation for extracting paleoclimate information from dune-interdune strata in these eco-fragile regions, but few have done so. Here we compared magnetic properties between dune and interdune strata from the late Miocene desert deposits in the northwestern Tarim Basin. We found that interdune strata displayed enhanced magnetic properties mainly due to content increase of stable single-domain (SSD) and small pseudo single-domain magnetite (PSD) within chlorite layers. But magnetic enhancement in interdune strata does not correspond with content increase of superparamagnetic (SP) ferrimagnetic minerals. Our high-resolution transmission electron microscope results suggest pedogenic SSD and small PSD magnetite form within chlorite layers, and we propose weathering of chlorites resulted in high concentration of Fe (II) and Fe (III) ions within layers, facilitating the formation of SSD and small PSD magnetite. By contrast, dry climate in the Tarim Basin results in micropore spaces between mineral particles having limited concentration of Fe (II) and Fe (III) ions, inhibiting SP magnetite formation. This pattern is different from Chinese loess-paleosols sequence, where magnetic enhancement is accompanied with content increase of both SP and SSD or small PSD ferrimagnetic mineral content. Therefore, magnetic enhancement pattern differences (whether magnetic enhancement is accompanied with SP magnetite formation) may inform climate conditions. To infer environmental variations in arid regions using magnetic parameters, reliance on proxies that indicate the relative content of ferrimagnetic grains or content of magnetic grains with stable remanence is essential.

SUMMARYSeismology has advanced significantly with ambient noise interferometry, enhancing the extraction of surface waves for detailed Vs imaging. However, direct Vp measurements remain critical for geological and engineering applications. Guided P waves offer potential for Vp insights, yet their detection from ambient noise is challenging, especially in urban environments. This study explores the feasibility of using underground urban seismic noise, specifically tunnel traffic, for guided P wave extraction and subsurface imaging. We introduce an adaptive workflow for preprocessing and enhancing guided P wave signals, applied to data from the Zijingang Tunnel beneath the campus of the Zhejiang University. Our refined data processing workflow significantly improves the quality of retrieved empirical Green’s functions of guided P waves. The joint inversion of surface waves and guided P waves provides high-resolution Vs and Vp profiles, revealing detailed subsurface structures. We also examine the impacts of source depth and type on guided P wave retrieval. We observed distinct differences in urban ambient noise characteristics between daytime and nighttime, suggesting that daytime traffic noise, with higher frequency content, is more suitable for high-frequency guided P wave retrieval. Our results demonstrate the effectiveness of using underground urban seismic noise for guided P wave extraction, highlighting the potential applications of urban ambient noise imaging in geotechnical engineering, urban planning, and seismic hazard assessment.

SUMMARYAirborne natural source electromagnetics (EM) provide spatially densely gridded, frequency-dependent inter-site transfer function estimates referring airborne vertical and horizontal magnetic field data to the horizontal components of a ground site. Common processing schemes for airborne natural source EM data are conceptually based on approaches developed for ground-based magnetotelluric sounding curve estimation and yield statistically independent transfer function estimates for selected times windows and separately for each component of the airborne recording. However, the magnetic field is spatially smooth and, moreover, its components are mutually dependent in space. Here, we propose to exploit spatial potential field relations directly in the processing workflow to refine transfer functions. The self-consistent response function estimator is applied after a first statistical estimation of transfer functions and supports the determination of a spatially smooth and self-consistent set of vertical and horizontal magnetic transfer functions that reflects physical constraints. Self-consistency is enforced by fitting sources distributed within an equivalent sheet to a preliminary set of transfer function estimates determined on a statistical basis. Smoothness is controlled by the depth to the equivalent sources. Once estimated, the distribution of vertical and horizontal magnetic transfer functions can be predicted from the equivalent sheet at any point in the air half-space. Additionally, the scheme allows for the identification of anomalous parts of the horizontal fields at the ground site. The procedure is demonstrated on a large-scale field data set from Gobabis (Namibia). We observe that transfer functions derived by using the equivalent source layer interpolator improve processing results when compared to purely statistically determined transfer function averages.

AbstractThis study investigates the mantle transition zone (MTZ) beneath Central and Eastern Europe using a 3D Common Conversion Point migration of P-to-S receiver functions derived from a dense regional seismic network. The analysis focuses on the major seismic discontinuities at ∼410 km, ∼520 km, and ∼660 km depth to assess their depth variations, continuity, and implications for past and ongoing geodynamic processes.Our results reveal significant spatial variations in the thickness and topography of the MTZ. In the Western Alps and central Pannonian Basin, the MTZ is thickened up to ∼280 km, deviating from the global average of ∼250 km. This thickening is attributed to the presence of stagnant slab material in the transition zone, suggesting a long-lasting influence of past subduction, particularly of the Adria Plate and Vrancea slab. In the Carpathians and Dinarides, the 410 km discontinuity is uplifted to depths as shallow as ∼400 km, while the 660 km discontinuity reaches depths of ∼670–680 km in regions affected by subducted lithosphere, further supporting the presence of cold slab remnants.Additionally, the 520 km discontinuity—often intermittent or absent in global studies—is clearly imaged in many parts of the region, and found at variable depths ranging between ∼510 and ∼540 km. These depth anomalies suggest the presence of compositional heterogeneities and thermal variations within the MTZ, possibly linked to subducted oceanic crust or recycled lithospheric material.Evidence for mantle upwellings is also observed, particularly beneath the Pannonian Basin, where low-velocity anomalies near the 410 km discontinuity are consistent with small-scale plumes or thermal anomalies. These may be associated with post-subduction processes or intraplate volcanism. Importantly, the Alpine slab itself is not clearly detected in the transition zone, indicating that it may have already sunk below the MTZ or is not well-coupled to the upper mantle structure imaged by receiver functions.By providing new constraints on the structure of the upper mantle and its transition zone, this study refines existing models of regional tectonic evolution. Our findings emphasize the interplay between surface tectonics and deep mantle dynamics and demonstrate that the observed MTZ features preserve a strong geodynamic imprint of both past subduction and intraplate processes across the Alpine-Carpathian-Pannonian-Dinarides region.

SUMMARYThe temporal variations in seismic wave velocity provide critical insights into the sources and physical mechanisms underlying diverse geophysical processes. While traditional approaches rely on measuring coda wave traveltime shifts to estimate velocity changes, the increasing availability of dense seismic networks has shifted attention toward ballistic waves for seismic velocity monitoring. Current methodologies for measuring ballistic wave time shifts predominantly employ the wavelet-transform technique, which, despite its proven reliability for coda wave analysis, introduces nonnegligible biases in ballistic wave monitoring due to the spectral leakage effect. To address this limitation, we propose a novel frequency-domain approach that estimates time shifts at each frequency, leveraging the characteristics of invariant phase shifts of ballistic waves along lag time. This method offers enhanced computational efficiency and simplicity in phase shift measurements compared to the time-frequency domain analysis. The phase velocity change is subsequently determined through a linear regression of phase time shifts along the offset. Synthetic tests validate the superior stability and accuracy of our method in estimating ballistic wave phase velocity changes. We further apply this approach to extract surface wave relative phase velocity changes from field data. Our results bring a robust and efficient method for measuring relative phase velocity changes in ballistic wave seismic monitoring.

AbstractSpectral electrical impedance tomography (sEIT) has attracted increasing interest in hydrogeology, biogeosciences, agriculture, and environmental studies. However, broadband sEIT measurements, particularly at frequencies above 50 Hz, have long been challenging due to electromagnetic (EM) coupling effects. Recent advances in instrumentation, data correction, and filtering have improved sEIT measurements at higher frequencies, yet many of these developments rely on a customized system with distributed amplifiers. Extending these advancements to more universally applicable methods is necessary, as sEIT measurements are often acquired using systems with centralized multiplexers. This study aims to bridge this gap by developing model-based data correction methods to mitigate EM coupling effects in sEIT measurements acquired with such a set-up. For this, the differences in EM coupling effects between measurements with a centralized multiplexer and distributed amplifiers were discussed, and the required correction methods in case of a centralized multiplexer were developed. The effectiveness of the developed corrections was tested using sEIT measurements acquired with a centralized multiplexer. A dataset obtained using distributed amplifiers and corrected using previously developed approaches served as a reference. Finally, inversion results of all datasets were compared. It was shown that cable capacitance dominates the capacitive coupling in the sEIT measurements acquired with a centralized multiplexer when coaxial cables are used. Improvements were observed after each correction step using the developed methods. It was concluded that broadband sEIT imaging results can be obtained using measurements with a centralized multiplexer and coaxial cables using the proposed data correction and filtering methods.

Research in the International Journal of Hydrology Science and Technology has shown that conventional approaches to measuring water storage across Europe's complex river systems may significantly underrepresent the scale and severity of changes linked to climate change.

From its olive groves to its coastal cities, the Mediterranean depends on a delicate balance of rain and sun, but climate change is tipping the scales.