EOS

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
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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
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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.

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As a Ph.D. student studying the impacts of coastal flooding in Annapolis, Md., Miyuki Hino heard from people familiar with the area that rain caused flooding, but the conventional method of measuring floods wasn’t picking it up.

Tide gauges located in oceans and bays, which Hino and other scientists typically use to detect coastal floods, do not necessarily reflect flooding on land, leaving researchers, city planners, and forecasters with little information about how often these floods occur. As Hino, now an environmental social scientist at the University of North Carolina at Chapel Hill, and others revealed in a new study published in Communications Earth and Environment, installing instruments in inland communities can reveal even small-scale or sunny-day flooding that can affect residents.

“The goal of our project overall is to better answer how flooding is affecting people, businesses, and communities in low-lying areas.”

In the new study, the researchers placed low-cost flood sensors on land in three coastal North Carolina communities to study how often any type of flooding—from nuisance flooding to larger events—occurs.

“The goal of our project overall is to better answer how flooding is affecting people, businesses, and communities in low-lying areas,” Hino said. The new study takes a critical first step by measuring flooding accurately, she said.

Hino and Katherine Anarde, a coauthor on the study and a coastal engineer at North Carolina State University, hope the findings motivate other scientists to think critically about how and where they measure floods in their own research, especially as sea level rise makes coastal flooding more common. 

Out with the Tide (Gauges)

Scientists typically define coastal flooding using thresholds determined by NOAA and the National Weather Service (NWS) that refer to certain tide gauge levels. These tide gauges sit in the ocean just offshore and measure the height of water as tides change. 

NWS uses these measurements to issue watches and warnings for coastal flooding of varying severities. But often, those tide gauges don’t measure “where flooding is experienced by people,” said Paul Bates, a hydrologist at the University of Bristol who was not involved in the new study.

Tide gauges don’t account for every factor that may lead to coastal flooding, such as runoff from rainfall, contributions from groundwater, and the effects of drainage infrastructure. They’re also sparse. That means tide gauge levels—and flood warnings—don’t always match what people see on the ground. 

To determine the scale of the problem, Hino, Anarde, and their colleagues installed networks of sensors and cameras near roadways and within storm drains in two towns and one unincorporated community in North Carolina: Beaufort, Carolina Beach, and Sea Level. The research team asked residents and municipal staff for the best spots to place the sensors to capture the actual flooding that the communities witness. 

After a full year of monitoring, they found that the NOAA high-tide flood threshold and the NWS minor flood threshold, which both rely on tide gauge data, were not consistent with occurrences of inland flooding. In some cases, the inland sensors picked up flooding as much as 10 times more often than the tide gauges suggested. NOAA thresholds consistently missed inland flooding, whereas NWS thresholds both overestimated and underestimated flood frequency, depending on the community. 

They also found that tide gauge data generally underestimated the duration of floods on land. One reason for the difference is that water may recede at a tide gauge fairly quickly but may take much longer to drain off land via stormwater infrastructure and groundwater infiltration. 

The results “demonstrate the many benefits of measuring water levels on land rather than relying on tide-gauge-based estimates,” the authors wrote.

“There haven’t been many studies of this local-scale surface water flooding anywhere in the world because it’s so difficult to instrument,” Bates said. The new study is “one of the best empirical demonstrations” of the fact that water levels at the coast, as measured by tide gauges, are not a good indicator of flooding experienced inland, he said. 

In their study, the researchers defined flooding as the presence of any water on a roadway, initially indicated by their sensors and confirmed by nearby cameras. When the camera view was obscured, a flood was counted when the sensors indicated water above the elevation of the roadway by at least the measurement error of their sensors. The shallowest flood measured in the study was 0.24 inch (0.6 centimeter), and the deepest was nearly 2 feet (61 centimeters).

Nuisance flooding, such as that seen here in Beaufort, N.C., is often not fully captured by tide gauges. Credit: Sunny Day Flooding Project/Flickr, CC BY-NC-ND 2.0

The study’s results may have been very different if the researchers had used a different definition of flooding, Bates pointed out. Flood events as defined in the study are very frequent and probably do not all create a nuisance for residents, he said.

The definition was chosen, Hino explained, because even small amounts of water can pose problems for some residents, depending on their needs. “We’re not in a position where we can say everybody needs to worry about flooding [at one depth], but no one needs to care [at another depth].” 

For example, she said, driving through even a small puddle of salt water can spray water onto the underside of one’s car, which can cause corrosion. Relatively shallow floods can limit land use, depress property values, rust low-lying infrastructure, and contaminate flooded areas, according to the Sunny Day Flooding Project, of which the new research was part.  

Meaningful Measurement

The sensors revealed what people across the state have been saying—that it’s flooding “all the time,” Anarde said. Because flooding is already posing problems for communities, the results increase the urgency of developing infrastructure solutions as sea levels rise, Hino said. 

“The places that we think as scientists are important to measure may not be in line with what communities are interested in keeping dry.” 

The data show that scientists aren’t always measuring the impacts of sea level rise and coastal flooding in places where such flooding affects communities, Anarde said. “The places that we think as scientists are important to measure may not be in line with what communities are interested in keeping dry.” 

She recommends that scientists studying flooding focus on installing instrumentation in places where residents see frequent flooding, which has the added benefit of facilitating trust between residents and scientists, too. 

“I don’t think our sensors are a silver bullet solution for measuring floods at every location,” Anarde said. “We can make our data useful in planning everyday activities by coming up with new ways to measure floods.”

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

Citation: van Deelen, G. (2025), Residents know when floods happen, but data must catch up, Eos, 106, https://doi.org/10.1029/2025EO250295. Published on 12 Auguste 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.

Source: Journal of Geophysical Research: Earth Surface

This is an authorized translation of an Eos article. 本文是Eos文章的授权翻译。

与单河道蜿蜒型河流相比，多河道辫状河通常处于植被稀疏、沉积物颗粒粗大且沙洲可移动的环境中。过去的研究认为，辫状河的路径随时间变化的方式是“混乱的”，因为它们的迁移取决于许多因素，包括河流形状和水位的变化。

然而，由于单个河道的迁移可能会影响洪水或侵蚀等灾害发生的可能性，因此了解这种迁移对于保护这些复杂水道周围的居民、结构和生态系统至关重要。

Li和Limaye研究了布拉马普特拉-贾木纳河（Brahmaputra-Jamuna River）长达180公里的河道，这条河位于孟加拉国，其河道已通过卫星图像得到很好的解译。

科学家们，以及生活在河道之间岛屿上的60万居民中的许多人已经知道，在夏季的季风季节，这条河的水位很高，而从1月到3月，水位一直维持在低水平。该研究团队使用了一种称为动态时间弯曲的统计方法，来绘制2001年至2021年期间河道大小、形状和路径的长期变化。这种技术使他们能够计算出河道中心线移动的程度和速度。然后，他们应用了一个现有的为蜿蜒型河流开发的模型，看看它是否也可以预测辫状河道的运动。

他们发现，布拉马普特拉-贾木纳河的迁移比以前认为的更容易预测。在研究期内，大约43%的河道是逐渐移动的，而不是突然移动的。平均而言，这些河道线比大多数蜿蜒型河流迁移得更快，每年的速度约为其宽度的30%。在某些情况下，这种迁移的速率与河道线的曲率密切相关，而在整体上，它与河道宽度的相关性较弱。

作者称，这些发现对未来研究辫状河道有重要意义。认识到至少有一些河道线是连贯迁移的，可能会为辫状河地区，特别是人口密集地区的侵蚀和洪水缓解工作提供信息。(Journal of Geophysical Research: Earth Surface, https://doi.org/10.1029/2024JF008196, 2025)

—科学撰稿人Rebecca Owen (@beccapox.bsky.social)

Read this article on WeChat. 在微信上阅读本文。

This translation was made by Wiley. 本文翻译由Wiley提供。

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

Climate models predict that rising greenhouse gas levels cool the stratosphere, while the healing of the Antarctic ozone hole—driven by the reduction of ozone-depleting substances under the Montreal Protocol since the beginning of the 21st century—should warm the Antarctic lower stratosphere. However, observations for the period from 2002 to 2022 reveal unexpected changes: warming in the Southern Hemisphere (SH) subtropical lower stratosphere and cooling over Antarctica.

Sweeney et al. [2025] identify the cause as a slowdown in stratospheric circulation that moves stratospheric air and chemicals from low to high latitudes. These circulation changes, which are most pronounced from October to December, lead to warming in the subtropical lower stratosphere of the Southern Hemisphere and cooling in the Antarctic lower stratosphere. They also mask the anticipated ozone recovery over Antarctica during this period. Accounting for these circulation changes removes the anomalous warming of the SH subtropical lower stratosphere and reveals an obvious Antarctic lower stratospheric warming and enhanced ozone recovery. These findings highlight the crucial role of the stratospheric circulation in shaping temperature and ozone changes.

Citation: Sweeney, A., Fu, Q., Solomon, S., Po-Chedley, S., Randel, W. J., Steiner, A., et al. (2025). Recent warming of the southern Hemisphere subtropical lower stratosphere and Antarctic ozone healing. AGU Advances, 6, e2025AV001737. https://doi.org/10.1029/2025AV001737

—Donald Wuebbles, Editor, AGU Advances

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The most severe rainfall event ever recorded in Nepal impacted about 2.6 million people, causing losses of US$370 million and about 270 lives.

Between 26 and 28 September 2024, a devastating late monsoon rainfall event in Nepal triggered hundreds of landslides. In landslide terms, this was the most serious event recorded in Nepal outside of a major earthquake – economic losses are estimated to have been 1% of the country’s GDP and about 270 people were killed or left missing.

An initial analysis (Lamichhane et al. 2025 – the paper is behind a paywall, but the link should allow you to access it) has just been published in the journal Landslides – a very welcome paper. The authors, the majority of whom are Nepali, deserve praise for the speed at which this has been compiled, its comprehensive analysis and the diligence with which they have provided location information for the major events they describe. This is a model that others should seek to follow.

A substantial part of the paper examines the rainfall event itself. In central Nepal, 25 weather stations recorded their highest ever 24 hour rainfall. One station, at Godavari in Lalitpur District, recorded 311.6 mm. Peak hourly intensities were also high by Nepal standards – Godavari recorded 26.8 mm between 7 and 8 pm on 28 September 2024 – again, an unusually high figure for Nepal. Over the three day period, Godavari recorded 366.0 mm of rainfall.

Lamichhane et al. (2025) rightly highlight that the disaster was probably the consequence of a rainfall event that occurring in the late monsoon period, when the ground is already saturated, and that then involved high rainfall intensities, a high 24 hour rainfall total and a high 72 hour rainfall total. This is a toxic combination.

Lamichhane et al. (2025) then describe some of the more serious landslide events. The greatest losses occurred were caused by the Jhyaple Khola landslide, situated on the Tribhuvan Rajpath highway. The location is [27.71146, 85.20236] – the site is shown in the Google Earth image below, with the marker showing the point at which the landslide struck the road:-

Google Earth image of the site of the Jhyaple Khola landslide in Nepal, collected on 12 December 2023.

This is a Google Earth image of the site after the landslide:-

Google Earth image of the aftermath of the Jhyaple Khola landslide in Nepal, collected on 7 June 2025.

And here is a slider to allow you to compare the two:-

This landslide occurred at about 4 am on 28 September 2024. Unfortunately, two buses were at the site, trapped behind an earlier landslide.

Both buses were struck, killing 35 people. Lamichhane et al. (2025) describe the landslide as a 3 m deep debris flow that was rich with large pieces of woody debris. They rightly point out that the failure originated about 80 m above the road, but I would also highlight that the source appears to be another section of road. It is unclear to me as to whether the failure was on the cut slope above the road or a fill slope below it. That road appears on images from 2004, so it is not new.

Lamichhane et al. (2025) detail many other examples of landslides across Central Nepal, and even these are just a fraction of the total. Whilst the rainfall was unprecedented, they rightly highlight the anthropogenic issues that were the root of the disaster:-

“Major landslides and debris flow sites were linked to intense rainfall, unregulated sand mining, poorly managed rivers, haphazard road construction, and highly weathered slopes.”

In addition, they note that the following about the aftermath of the incident:-

“Despite involvement from various agencies, the disaster response fell short, underscoring the need for a more proactive approach to mitigation and management. Public response to rainfall warnings from agencies like Nepal’s Department of Hydrology and Meteorology (DHM) was also insufficient, contributing to tragic fatalities.“

Nepal will face many more events like this in the coming years, and indeed an even larger rainfall event is probably just around the corner. Lamichhane et al. (2025) demonstrates that immediate action is needed. Sadly, I have low confidence that this occur. It feels inevitable that I will describe another event of this type on this blog in the coming years.

Reference

Lamichhane, K., Biswakarma, K., Acharya, B. et al. 2025 Preliminary assessment of September 2024 extreme rainfall–induced landslides in Central Nepal. Landslides. https://doi.org/10.1007/s10346-025-02577-w

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Source: Journal of Geophysical Research: Planets

Despite being thinner and drier than Earth’s atmosphere, Mars’s atmosphere contains clouds composed of tiny water ice crystals. And just as on Earth, these clouds influence the planet’s climate. However, most of what we know about clouds on Mars comes from data collected during the Martian afternoon, so there is still much to learn about how clouds tend to form and dissipate over a full day.

Using data from the Emirates Mars Mission Hope probe, which has orbited Mars since 2021, Atwood et al. have captured the first comprehensive view of nighttime clouds on Mars.

Hope’s high-altitude, low-inclination elliptical orbit was specifically designed to enable observation across all times of day and night and at almost all latitudes and longitudes. The researchers analyzed data collected over nearly two Martian years by the Emirates Mars Infrared Spectrometer, an instrument mounted on Hope that can detect the presence and thickness of clouds, according to how they absorb and scatter infrared light.

The analysis revealed that for much of the Martian year, nighttime clouds are, on average, thicker than daytime clouds. Peaks in cloudiness typically occurred in the early morning and the evening, separated by a midday minimum.

During the cold season on Mars, thick clouds tended to form in a band near the equator, becoming thickest just after sunrise. Also during the cold season, late-evening clouds typically formed in a broader distribution across low latitudes, while early-morning clouds mostly concentrated over a vast volcanic region known as Tharsis, which covers the equator and low latitudes.

These findings shed new light on Martian atmospheric dynamics and could help scientists validate computational models of Mars’s atmosphere, the researchers say. (Journal of Geophysical Research: Planets, https://doi.org/10.1029/2025JE008961, 2025)

—Sarah Stanley, Science Writer

Citation: Stanley, S. (2025), First complete picture of nighttime clouds on Mars, Eos, 106, https://doi.org/10.1029/2025EO250279. Published on 11 August 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
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Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Water Resources Research

Coal seam gas (CSG) is extracted by pumping out groundwater, which lowers underground pressure, can lead to shrinking of geological layers and make the ground above sink over time.

Cui et al. [2025] present a new way to understand and predict land subsidence caused by CSG extraction. The study introduces a model that links groundwater flow with how the ground moves, including both general sediment compression and the shrinkage of coal as gas is removed. It uses real-world data, such as groundwater levels, gas production, and satellite measurements, to improve the model’s accuracy. By testing this model in the Surat Basin (Queensland, Australia), the authors find that subsidence can reach up to 235 millimeters near some wells and follows a three-stage pattern: growth, stabilization, and partial recovery.

The model helps separate reversible and permanent parts of the subsidence, which is important for long-term planning. This work is especially useful for land managers and farmers concerned about how CSG production may affect agriculture and drainage. More broadly, it provides a practical tool for evaluating the environmental impacts of energy extraction.

Citation: Cui, T., Schoning, G., Gallagher, M., Aghighi, M. A., & Pandey, S. (2025). A coupled hydro-mechanical modeling framework to concurrently simulate coal seam gas induced subsidence and groundwater impacts. Water Resources Research, 61, e2024WR039280.  https://doi.org/10.1029/2024WR039280  

—Gabriel Rau, Associate Editor, Water Resources Research

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Seismic data and eye-witness reports of a displacement wave point to a large landslide at 5:30 am.

On 10 August 2025, at 5:30 am local time, the Alaska Earthquake Center detected a seismic signal that was almost certainly generated by a landslide. They have posted the record of the seismic signal to Twitter. Their posting included a record of the seismic signal, which looks fairly typical for a landslide:-

The seismic signal from Tracy Arm in Alaska, which was probably generated by a large landslide. Data released by the Alaska Earthquake Center.

There are eye witness reports of the resultant localised displacement wave. BNO News quotes a kayaker who was camping in the affected area.

“Kayaker Sasha Calvey said she and two others were camping on Harbour Island in Tracy Arm Inlet, a fjord about 45 miles south of Juneau, when a landslide or iceberg caused a tidal surge that swept away half of their gear, including one boat, personal items, and cooking equipment.

“Calvey said their gear had been stored about 25 feet above the high tide line, but the water reached it and came within an inch of sweeping away their tent. She added that they placed a radio distress call that was picked up by a boat, which transported them to Juneau.”

The mouth of Tracy Arm is at [57.7778, -133.6167]. This is the latest Planet Labs image of at least a part of the area, captured on 7 August 2025 (last Thursday):-

Satellite image of Tracy Arm inlet. Image copyright Planet Labs, used with permission. Image dated 7 August 2025.

This is steep and rugged terrain, but the image provides no obvious hint of the location of the landslide that occurred three days later, as far as I can see. Hopefully, someone will capture a satellite image in the next few days that will shed light on the location, but that will depend upon the weather. Alternatively, the location might be identified from a boat or from an aerial survey.

I will undoubtedly return to this theme in the coming days.

Reference

Planet Team 2024. Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/

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.

This is an authorized translation of an Eos article. Esta es una traducción al español autorizada de un artículo de Eos.

Los arrecifes de coral son ecosistemas vitales que sustentan la vida marina, el ecoturismo y la protección costera. Ellos también guardan algo valioso bajo su superficie: registros del pasado del océano. Bajo la capa exterior viva de los corales masivos se encuentran estructuras esqueléticas tipo roca que contienen bandas anuales, similares a los anillos de árboles. Los científicos pueden estudiar las condiciones en el momento en que estas bandas se formaron mediante la perforación, recuperación y análisis de núcleos, algunos de los cuales representan siglos de crecimiento coral.

Daren Coker (izquierda) y Thomas DeCarlo perforan un núcleo de coral en el Mar Rojo. Crédito: Morgan Bennett-Smith

Desde la década de 1970, los estudios de núcleos de coral pueden determinar patrones de crecimiento pasados, un campo conocido como esclerocronología coralina, han producido descubrimientos científicos notables. Knutson et al. [1972] encontraron que las bandas anuales están compuestas por bandas de alta y baja densidad que reflejan patrones de crecimiento estacional. Hudson [1981] descubrió que, por lo general, las bandas de alta densidad se forman durante el crecimiento invernal más lento, mientras que las de baja densidad se forman durante el crecimiento del verano más rápido y que el crecimiento variable a largo plazo de corales están influenciadas por la calidad del agua y los efectos del desarrollo costero. Algunos núcleos también contienen “bandas de estrés” de alta densidad, formadas debido a eventos de blanqueamiento de corales u otros desafíos medioambientales [Lough, 2008]. En conjunto, estas bandas proporcionan información sobre la historia del crecimiento de coral, lo que permite a los científicos construir modelos de edad confiables de las condiciones oceánicas y climáticas pasadas.

Hoy en día, los métodos usados para investigar núcleos de corales han avanzado considerablemente. Junto con otros métodos, como los análisis de isótopos estables y de radio elementales, la tomografía computarizada (CT) desempeña un rol fundamental en la obtención de datos que ayudan a revelar los parámetros de crecimiento coralino. Los científicos pueden escanear rayos X en 2D y escaneo CT 3D para examinar las estructuras internas de núcleos coralinos, incluyendo sus bandas de densidad anual [Knutson et al., 1972; Hudson, 1981; Lough, 2008; DeCarlo et al., 2025]. En algunos casos, este análisis involucra incluso la visita de un científico a un hospital local para usar su equipo de CT – un paciente inesperado para el técnico de radiología.

Esta animación de una tomografía computarizada muestra un corte transversal de un núcleo de coral. Los pequeños círculos dentro del núcleo son coralitos, las estructuras esqueléticas individuales formadas por pólipos de coral. Crédito: USGS, Dominio público Un núcleo coralino se encuentra en la mesa de examen de un equipo de tomografía computarizada en un hospital antes de ser escaneado. Crédito: Thomas DeCarlo

Sin embargo, no se había realizado un archivo sistemático de datos de imágenes de núcleos coralinos, en parte debido a la falta de un repositorio adecuado. Esta brecha presenta el riesgo de perder imágenes valiosas e impide un intercambio ágil y transparente de las interpretaciones científicas de estas imágenes. Por lo tanto, un repositorio centralizado, virtual y de acceso abierto de imágenes de núcleos coralinos es crucial para fomentar la transparencia científica y preservar estos recursos para investigaciones futuras.

Una aplicación para organizar un repositorio

La aplicación CoralCT se desarrolló para consolidar y organizar escáneres de núcleos coralinos en un repositorio virtual que permite el archivo digital y el análisis de imágenes [DeCarlo et al., 2025]. Actualmente, el repositorio contiene más de 1,000 escaneos de corales recolectados en una amplia gama de regiones de arrecifes coralinos, que incluye la Gran Barrera de Coral, el Caribe y el Mar Rojo. Estos escaneos coralinos han sido aportados por individuos y agencias, como el Servicio Geológico de Estados Unidos (USGS, por sus siglas en inglés) y la Oficina Nacional de Administración Oceánica y Atmosférica (NOAA, por sus siglas en inglés).

Investigadores coralinos suben escaneos de rayos X o de CT a CoralCT y, cuando están listos, pueden hacer que sus datos estén públicamente disponibles para cualquier persona con una computadora y conexión a internet. Este enfoque de transparencia fomenta la colaboración entre investigadores de núcleos coralinos, quienes pueden consultar el directorio de núcleos de la aplicación y ver quién más ha recolectado núcleos en sus áreas de interés. Esto también ayuda a evitar la duplicación innecesaria de esfuerzos de investigación, lo cual es especialmente importante dada la necesidad de reducir el impacto del muestreo en los corales, muchos de los cuales son especies en peligro de extinción.

Utilizando las herramientas analíticas de la aplicación, los observadores pueden mapear las bandas de densidad anuales en núcleos coralinos para extraer datos sobre la tasa de crecimiento y la densidad esquelética. Tal como en estudios de anillos de árboles, este tipo de análisis ofrece información sobre las condiciones medioambientales pasadas, ya que el crecimiento de corales puede responder con sensibilidad a la variabilidad climática.

Por ejemplo, Barkley et al. [2018] utilizaron CoralCT para visualizar bandas de estrés de alta densidad y reconstruir la historia del blanqueamiento de corales a lo largo de seis décadas en un arrecife remoto del Océano Pacífico ecuatorial, donde el monitoreo de datos es escaso. Rodgers et al. [2021] midieron las tasas de crecimiento anual en CoralCT para rastrear la recuperación de corales frente a Kaua’i, Hawaii, en los 15 años posteriores a un evento de inundación devastadora. Más recientemente, DeCarlo et al. [2024] aprovecharon la amplitud de núcleos en CoralCT para reconstruir patrones de crecimiento coralinos en las décadas y siglos recientes a lo largo de miles de kilómetros en el Indo Pacífico.

Rescatando registros antiguos y recolectando nuevos

Archivar datos valiosos que de otro modo podrían perderse es el propósito fundamental de CoralCT. Un destacable ejemplo de cómo cumple este propósito involucra el rescate y la digitalización de imágenes de rayos X de más de 20 núcleos recolectados en el Océano Pacífico entre la década de los 1980 y principios de 2000. Las películas de rayos X, previamente guardadas por un científico jubilado, ahora están archivadas y disponibles para su análisis en CoralCT.

Colecciones más antiguas como estas pueden proporcionar información valiosa sobre el crecimiento coralino antes de que las perturbaciones medioambientales, como el blanqueamiento masivo por estrés térmico, comenzaran a afectarlos.

En un esfuerzo similar, la USGS escaneó recientemente núcleos coralinos en TC que datan de finales de la década de los 1960, algunos de los núcleos más antiguos jamás recolectados [Hudson et al., 1976]. Estos escaneos se están incorporando al repositorio para que puedan ser reanalizados por investigadores ahora y en el futuro. Colecciones más antiguas como estas pueden proporcionar información valiosa sobre el crecimiento coralino antes de que las perturbaciones medioambientales, como el blanqueamiento masivo por estrés térmico, comenzaran a afectarlos.

Además, a estas contribuciones históricas, el repositorio CoralCT continúa creciendo con la incorporación de nuevos datos. Una contribución reciente incluye escaneos de núcleos de arrecifes recolectados en la costa de Hawai’i en 2023 durante la Expedición 389 del Programa Internacional Ocean Discovery. Los núcleos de arrecifes difieren de los núcleos coralinos en composición y estructura, pero también son cruciales para entender la historia oceánica y el cambio medioambiental. Durante la expedición 389, se recolectaron núcleos de arrecifes sumergidos que una vez crecieron cerca de la superficie del océano, pero que dejaron de calcificarse a medida que se sumergían en aguas profundas. Estos núcleos de arrecifes contienen coral fragmentado, algas coralinas, microbialitos y otros materiales constructores de arrecifes, cuyas composiciones permiten a los científicos mirar milenos hacia el pasado y descubrir registros valiosos del nivel del mar y el cambio climático.

Análisis repetibles, resultados verificables

Cuando no se archivan imágenes de núcleos coralinos originales, sin procesar, el valor de las mediciones de crecimiento y otros análisis es limitado porque otros científicos no pueden verificarlos fácil e independientemente. Esto es problemático ya que la ciencia se basa fundamentalmente en la capacidad de repetir experimentos y verificar resultados, sobre todo considerando que investigadores individuales pueden introducir subjetividad y posibles sesgos incluso en interpretaciones de datos altamente sistemáticas y rigurosas. A medida que los conjuntos de datos se hacen más grandes, complejos y numerosos, mantener la transparencia es cada vez más importante, pero también cada vez más difícil.

En esta captura de pantalla de un núcleo coralino analizado en la aplicación CoralCT, las líneas naranjas en la imagen del núcleo indican dónde un observador ha mapeado las bandas de densidad anual. Crédito: Avi Strange

CoralCT aborda estos desafíos garantizando que toda la información y el contexto de un núcleo estén completamente documentados, accesibles y descargables. Esta información incluye metadatos esenciales tales como el origen del núcleo, los detalles de propiedad, la fecha de recolección, la profundidad y la identificación de especies. Y lo que es más importante, CoralCT archiva los mapas de bandas anuales definidos el usuario para derivar datos de la tasa de crecimiento [DeCarlo et al., 2025], asegurando que estos datos e interpretaciones sean totalmente reproducibles y estén abiertos a la verificaciones de otros.

Esta transparencia también se comparte entre los observadores dentro de la aplicación. Cuando un usuario mapea las bandas de un núcleo, este puede agregar notas y captura de pantalla que otros usuarios pueden ver mientras analizan dicho núcleo. Más aún, cuando un usuario termina de mapear las bandas de un núcleo y procesa los datos, esta información se almacena y se puede descargar para que otros científicos la consulten. Esta capacidad permite a los científicos realizar estudios con múltiples observadores, lo que puede reducir posibles sesgos introducidos por la observación individual.

Un desafío que hemos encontrado en nuestros esfuerzos para ampliar CoralCT ha sido la reticencia en algunos investigadores y programas a compartir datos.

A pesar de estas ventajas, un desafío que hemos encontrado en nuestros esfuerzos para ampliar CoralCT ha sido la reticencia en algunos investigadores y programas a compartir datos debido a la preocupación por las infracciones de propiedad intelectual y la “apropiación indebida” de datos prepublicados. Esta reticencia, que es entendible considerando la falta de transparencia y protección para los propietarios de los datos en las prácticas previas de gestión de datos, puede lamentablemente limitar los avances científicos y las colaboraciones que podrían ayudar a abordar el cambio climático, la degradación de arrecifes coralinos y otros desafíos complejos.

Para abordar estas preocupaciones, CoralCT ofrece controles privados a los propietarios de núcleos, que pueden usar para restringir el acceso a sus escaneos y a los datos derivados. Estos controles son particularmente útiles cuando los núcleos son parte de una investigación en curso que aún no se ha publicado o están sujetos a una moratoria posterior al crucero, lo que garantiza que datos sensibles permanezcan protegidos hasta que la investigación esté lista para ser compartida. Además, cada núcleo está identificado con el propietario de los datos, agradecimientos y citas relevantes.

Avanzando hacia la accesibilidad y colaboración

CoralCT también representa un camino para hacer la ciencia más inclusiva y accesible. La aplicación está diseñada con una interfaz fácil de usar e incluye recursos tales como videotutoriales y una guía de usuario paso a paso para ayudar a presentar sus funciones a un público amplio. Recientemente, también se crearon planes de clase para estudiantes de educación media y básica que guían a los estudiantes en el mapeo de las bandas de núcleos de coral en la aplicación, ofreciendo maneras accesibles de explorar las ciencias marinas.

Un estudiante de secundaria que visita el Laboratorio de Esclerocronología de la Universidad de Tulane usa un casco de realidad virtual para interactuar con núcleos coralinos en 3D durante el evento “Boys at Tulane in STEM 2025” de la universidad. Crédito: Danielle Scanlon Estudiantes de secundaria aprenden sobre núcleos de coral gracias a un holograma en un taller de la Universidad del Pacífico de Hawái. Crédito: Thomas DeCarlo

El potencial educacional de la aplicación se demostró en recientes eventos de divulgación. Utilizando tecnología de realidad virtual, estudiantes de secundaria en Nueva Orleans visualizaron escaneos 3D de núcleos de corales desde CoralCT y practicaron la identificación de bandas de densidad anual. En un evento similar, estudiantes de sexto grado en Hawái interactuaron con núcleos holográficos 3D coralinos y aprendieron cómo los científicos los extraen y estudian para comprender los patrones de crecimiento a lo largo del tiempo. Las experiencias positivas de estudiantes y profesores durante estos eventos demostraron cómo CoralCT brinda la oportunidad de interactuar de forma práctica con datos científicos reales.

La integración de IA también podría, y esto es importante, facilitar que todos los usuarios contribuyan al análisis de núcleos coralinos, independientemente de su formación académica o experiencia de campo.

De cara al futuro, existe la posibilidad de integrar inteligencia artificial (IA) en CoralCT para la identificación automatizada de patrones de bandas de coral. Si un sistema de IA se entrenara con interpretaciones humanas existentes, podría sugerir automáticamente marcas de bandas que los usuarios podrían revisar y verificar. Este avance ofrece la posibilidad de realizar análisis de núcleos coralinos más precisos y eficientes, manteniendo la supervisión humana. La integración de IA también podría, y esto es importante, facilitar que todos los usuarios contribuyan al análisis de núcleos coralinos, independientemente de su formación académica o experiencia de campo. Cada nueva contribución o análisis de un núcleo mejora la base de datos CoralCT y amplía nuestro conocimiento de los arrecifes de coral y las condiciones oceánicas pasadas.

La esclerocronología coralina es vital para comprender los cambios medioambientales en los ecosistemas de arrecifes coralinos y los impactos que estos cambios han provocado. Gracias a esta investigación, obtenemos información sobre el pasado del océano y mejoramos nuestra comprensión de los arrecifes de coral actuales. A medida que se intensifican las amenazas a los arrecifes, los grandes conjuntos de datos de acceso abierto son cada vez más esenciales para monitorear la salud de los arrecifes y predecir los impactos futuros.

Por lo tanto, CoralCT desempeña un papel importante en la preservación de valiosos registros del crecimiento de los corales y su historia medioambiental, a la vez que promueve el intercambio colaborativo, accesible y transparente de datos. Al poner la ciencia de los arrecifes de coral a disposición de investigadores y del público en general, conecta datos, ideas y personas para abordar cuestiones cruciales sobre nuestro mundo cambiante.

Agradecimientos

CoralCT se desarrolló con el apoyo de la subvención OCE-2444864 de la National Science Foundation. El uso de nombres comerciales, de empresas o de productos se realiza únicamente con fines descriptivos y no implica su respaldo por parte del gobierno de los Estados Unidos. Agradecemos al Equipo Científico de la Expedición IODP 389, al personal de apoyo del Operador Científico de ECORD (ESO), al equipo de perforación bentónica, a los topógrafos del MMA y al capitán y la tripulación del MMA Valour. La Expedición 389 del Programa Internacional de Ocean Discovery (IODP) contó con el apoyo financiero de las diversas agencias nacionales de financiación de los países participantes en el IODP. También agradecemos a todos los contribuyentes de datos hasta la fecha, entre ellos Giulia Braz, Jessica Carilli, Leticia Cavole, Ben Chomitz, Travis Courtney, Ian Enochs, Thomas Felis, Ke Lin, Malcolm McCulloch, Haojia Ren, Riccardo Rodolfo-Metalpa, Natan Pereira y al Programa de Recursos de Riesgos Costeros y Marinos del Servicio Geológico de los Estados Unidos.

Referencias

Barkley, H. C., et al. (2018), Repeat bleaching of a central Pacific coral reef over the past six decades (1960–2016), Commun. Biol., 1, 177, https://doi.org/10.1038/s42003-018-0183-7.

DeCarlo, T. M., et al. (2024), Calcification trends in long-lived corals across the Indo-Pacific during the industrial era, Commun. Earth Environ., 5, 756, https://doi.org/10.1038/s43247-024-01904-8.

DeCarlo, T. M., et al. (2025), CoralCT: A platform for transparent and collaborative analyses of growth parameters in coral skeletal cores, Limnol. Oceanogr. Methods, 23(2), 97–116, https://doi.org/10.1002/lom3.10661.

Hudson, J. H. (1981), Growth rates in Montastraea annularis: A record of environmental change in Key Largo Coral Reef Marine Sanctuary, Florida, Bull. Mar. Sci., 31(2), 444–459, www.ingentaconnect.com/content/umrsmas/bullmar/1981/00000031/00000002/art00014.

Hudson, J. H., et al. (1976), Sclerochronology: A tool for interpreting past environments, Geology, 4(6), 361–364, https://doi.org/10.1130/0091-7613(1976)4<361:SATFIP>2.0.CO;2.

Knutson, D. W., et al. (1972), Coral chronometers: Seasonal growth bands in reef corals, Science, 177(4045), 270–272, https://doi.org/10.1126/science.177.4045.270.

Lough, J. M. (2008), Coral calcification from skeletal records revisited, Mar. Ecol. Prog. Ser., 373, 257–264, https://doi.org/10.3354/meps07398.

Rodgers, K. S., et al. (2021), Rebounds, regresses, and recovery: A 15-year study of the coral reef community at Pila‘a, Kaua‘i after decades of natural and anthropogenic stress events, Mar. Pollut. Bull., 171, 112306, https://doi.org/10.1016/j.marpolbul.2021.112306.

Información de los autores

Avi Strange y Oliwia Jasnos, Universidad de Tulane, Nueva Orleans, Luisiana; Lauren T. Toth, Centro de Ciencias Costeras y Marinas de San Petersburgo, Servicio Geológico de Estados Unidos, Florida; Nancy G. Prouty, Centro de Ciencias Costeras y Marinas del Pacífico, Servicio Geológico de Estados Unidos, Santa Cruz, California; y Thomas M. DeCarlo (tdecarlo@tulane.edu), Universidad de Tulane, Nueva Orleans, Luisiana.

This translation by Daniela Navarro-Perez was made possible by a partnership with Planeteando and Geolatinas. Esta traducción fue posible gracias a una asociación con Planeteando y Geolatinas.

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.

Shrinking glaciers present some of the most visible signs of ongoing anthropogenic climate change. Their melting also alters landscapes, increases local geohazards, and affects regional freshwater availability and global sea level rise.

Worldwide observations show that global glacier decline through the early 21st century has been historically unprecedented. Modeling research suggests that 16 kilograms of glacier ice melt for every kilogram of carbon dioxide (CO2) emitted, and other studies indicate that every centimeter of sea level rise exposes an additional 2–3 million people to annual flooding.

Science has benefited from a diverse set of spaceborne missions and strategies for estimating glacier mass changes at regional to global scales.

For more than 130 years, the World Glacier Monitoring Service and its predecessor organizations have coordinated international glacier monitoring. This effort started with the worldwide collection, analysis, and distribution of in situ observations [World Glacier Monitoring Service, 2023]. In the 20th century, remote sensing data from airborne and spaceborne sensors began complementing field observations.

Over the past 2 decades, science has benefited from a diverse set of spaceborne missions and strategies for estimating glacier mass changes at regional to global scales (see Figure 2 of Berthier et al. [2023]). However, this research is challenged by its dependence on the open accessibility of observations from scientific satellite missions. The continuation and accessibility of several satellite missions are now at risk, presenting potential major gaps in our ability to observe glaciers from space.

We discuss here the history, strengths, and limitations of several strategies for tracking changes in glaciers and how combining studies from the multiple approaches available—as exemplified by a recent large-scale effort within the research community—improves the accuracy of analyses of glacial mass changes. We also outline actions required to secure the future of long-term glacier monitoring.

The Glacier Mass Balance Intercomparison Exercise

Glaciological observations from in situ measurements of ablation and accumulation, generally carried out with ablation stakes and in snow pits, represent the backbone of glacier mass balance monitoring. For more than 30 years, glaciologists have undertaken this work at 60 reference glaciers worldwide, with some observations extending back to the early 20th century.

Researchers conduct glaciological fieldwork, using ablation stakes and other tools, on Findelengletscher in Zermatt, Switzerland, in October 2024. Credit: Andreas Linsbauer, University of Zurich

These observations provide good estimates of the interannual variability of glacier mass balance and have been vital for process understanding, model calibration, and long-term monitoring. However, because of the limited spatial coverage of in situ observations, the long-term trends they indicate may not accurately represent mass change across entire glacial regions, and some largely glacierized regions are critically undersampled.

Airborne geodetic surveys provide wider views of individual glaciers compared with point measurements on the ground, and comparing ice elevation changes in airborne data allows researchers to identify and quantify biases in field observations at the glacier scale [Zemp et al., 2013]. Meanwhile, geodetic surveys from spaceborne sensors enable many opportunities to assess glacier elevation and mass changes at regional to global scales.

The Glacier Mass Balance Intercomparison Exercise (GlaMBIE), launched in 2022, combined observations from in situ and remote sensing approaches, compiling 233 regional glacier mass change estimates from about 450 data contributors organized in 35 research teams.

The results of the Glacier Mass Balance Intercomparison Exercise show that since 2000, glaciers have lost between 2% and 39% of their mass depending on the region and about 5% globally.

The results of this community effort, published in February 2025, show that since 2000, glaciers have lost between 2% and 39% of their mass depending on the region and about 5% globally [The GlaMBIE Team, 2025]. These cumulative losses amount to 273 gigatons of water annually and contribute 0.75 millimeter to mean global sea level rise each year. Compared with recent estimates for the ice sheets [Otosaka et al., 2023], glacier mass loss is about 18% larger than the loss from the Greenland Ice Sheet and more than twice the loss from the Antarctic Ice Sheet.

GlaMBIE provided the first comprehensive assessment of glacier mass change measurements from heterogeneous in situ and spaceborne observations and a new observational baseline for global glacier change and impact assessments [Berthier et al., 2023]. It also revealed opportunities and challenges ahead for monitoring glaciers from space.

Strategies for Glacier Monitoring from Space

GlaMBIE used a variety of technologies and approaches for studying glaciers from space. Many rely on repeated mapping of surface elevations to create digital elevation models (DEMs) and determine glacier elevation changes. This method provides multiannual views of glacier volume changes but requires assumptions about the density of snow, firn, and ice to convert volume changes to mass changes, which adds uncertainty because conversion factors can vary substantially.

Optical stereophotogrammetry applied to spaceborne imagery allows assessment of glacier elevation changes across scales. Analysis of imagery from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on board Terra from 2000 to 2019 yielded elevation changes at 100-meter horizontal resolution for almost all of Earth’s glaciers [Hugonnet et al., 2021]. At the regional scale, finer spatial resolution is possible with the ongoing French Satellite pour l’Observation de la Terre (SPOT) mission series and with satellites like GeoEye, Pléiades, and WorldView.

The Glacier Mass Balance Intercomparison Exercise (GlaMBIE) used data from a fleet of satellites that monitor glaciers worldwide using optical, radar, laser, and gravity measurements. Clockwise from left in this image are illustrations of Terra, CryoSat, ICESat-2, and the twin GRACE spacecraft above a map of elevation change for the Vatnajökull ice cap in Iceland. Credit: ESA/NASA/Planetary Visions

Two spaceborne missions applying synthetic aperture radar (SAR) interferometry have been used to assess glacier elevation changes. In February 2000, the Shuttle Radar Topography Mission (SRTM) produced a near-global DEM at a spatial resolution of 30 meters. The second mission, TerraSAR-X add-on for Digital Elevation Measurement (TanDEM-X), has operated since 2010, providing worldwide DEMs at a pixel spacing of 12 meters.

Data from both missions can be used to assess glacier elevation changes in many regions [Braun et al., 2019], capitalizing on the high spatial resolution and the ability of radar signals to penetrate clouds. However, measurements using C- and X-band radar—as both SRTM and TanDEM-X have—are subject to uncertainties because of topographic complexity in high mountain terrain and because the radar signals can penetrate into snow and firn.

Laser and radar altimetry allow us to determine glacier elevation changes along ground tracks or swaths, which can be aggregated to produce regional estimates. Laser altimetry has been carried out by NASA’s Ice, Cloud and Land Elevation Satellites (ICESat and ICESat-2) and the Global Ecosystem Dynamics Investigation (GEDI) on board the International Space Station (ISS) [Menounos et al., 2024; Treichler et al., 2019].

Spaceborne gravimetry offers an alternative to elevation-focused methods, allowing scientists to estimate mass changes by measuring changes in Earth’s gravitational field.

Spaceborne radar altimetry has a long tradition of measuring ocean and land surfaces, but these missions’ large detection footprints and the challenges of mountainous terrain hampered the use of early missions (e.g., ERS, Envisat) for glacier applications. The European Space Agency’s (ESA) CryoSat-2, which launched in 2010, offered improved coverage of the polar regions, denser ground coverage, a sharper footprint, and other enhanced capabilities that opened its use for monitoring global glacier elevation changes [Jakob and Gourmelen, 2023].

Both laser altimetry and radar altimetry provide elevation change time series at monthly or quarterly resolution for regions with large ice caps and ice fields (e.g., Alaska, the Canadian Arctic, Svalbard, and the periphery of the Greenland and Antarctic Ice Sheets). However, assessing mountain regions with smaller glaciers (e.g., Scandinavia, central Europe, Caucasus, and New Zealand) remains challenging because of the complex terrain and limited spatial coverage.

Spaceborne gravimetry offers an alternative to elevation-focused methods, allowing scientists to estimate mass changes across the ocean and in water and ice reservoirs by measuring changes in Earth’s gravitational field. Two missions, the NASA/German Aerospace Center Gravity Recovery and Climate Experiment (GRACE) and the NASA/GFZ Helmholtz Centre for Geosciences GRACE Follow-on mission (GRACE-FO), have provided such measurements almost continuously since 2002.

Gravimetry offers more direct estimates of glacier mass change than other methods [Wouters et al., 2019]. However, the data must be corrected to account for effects of atmospheric drag and oceanic variability, glacial isostatic adjustment, nonglacier hydrological features, and other factors [Berthier et al., 2023].

Estimates from the GRACE and GRACE-FO missions are most relevant for regions with large areas of glacier coverage (>15,000 square kilometers) because of the relatively coarse resolution (a few hundred kilometers) of the gravity data and because of issues such as poor signal-to-noise ratios in regions with small glacier areas and related small mass changes.

Securing Glacier Monitoring over the Long Term

The work of GlaMBIE to combine observations from the diverse approaches above points to several interconnected requirements and challenges for improving the comprehensiveness of global glacier change assessments and securing the future of long-term glacier monitoring.

First, we must extend the existing network of in situ glaciological observations to fill major data gaps. Such gaps remain in many regions, including Central Asia, Karakoram, Kunlun, and the Central Andes, where glaciers are vital for freshwater availability, as well as in the polar regions, where glaciers are key contributors to sea level rise. These networks also need to be updated to provide real-time monitoring, which will improve understanding of glacier processes and help calibrate and validate remote sensing data and numerical modeling.

A sequence of aerial photographs taken in 1980 from about 11,000-meter altitude of Grey Glacier in the Southern Patagonian Ice Field (top) was used to generate a 3D model of the glacier (bottom). Credit: 3D reconstruction by Livia Piermattei and Camilo Rada using images from the Servicio Aerofotogramétrico de la Fuerza Aérea de Chile (SAF)

Second, we must continue unlocking historical archives of airborne and spaceborne missions to expand the spatiotemporal coverage of the observations used in glacier mass change assessments. Data from declassified spy satellites, such as CORONA and Hexagon, have provided stereo observing capabilities at horizontal resolutions of a few meters and offer potential to assess glacier elevation changes back to the 1960s and 1970s. Aerial photography has provided unique opportunities to reconstruct glacier changes since the early 20th century, such as in Svalbard, Greenland, and Antarctica. Beyond individual and institutional studies, we need open access to entire national archives of historical images to safeguard records of past glacier changes on a global scale.

We must ensure the continuation of space-based glacier monitoring with open-access and high-resolution sensors.

Third, we must ensure the continuation of space-based glacier monitoring with open-access and high-resolution sensors, following the examples of the Sentinel missions, SPOT 5, and Pléiades. For optical sensors, there is an urgent need for new missions collecting open-access, high-resolution stereo imagery. The French space agency’s forthcoming CO3D (Constellation Optique en 3D) mission, scheduled for launch in 2025, will help meet this need if its data are openly available. But with the anticipated decommissioning of ASTER [Berthier et al., 2024] and the suspended production of new ArcticDEM and REMA (Reference Elevation Model of Antarctica) products from WorldView satellite data as a result of recent U.S. funding cuts, additional replacement missions are needed to observe elevation changes over individual glaciers.

For radar imaging and altimetry, the SAR mission TanDEM-X and the radar altimeter CryoSat-2 are still operating with expected mission extensions into the late 2020s, and ESA’s SAR-equipped Harmony mission is expected to launch in 2029. With the planned launch of the Copernicus Polar Ice and Snow Topography Altimeter (CRISTAL) in 2027, ESA aims to establish a long-term, cryosphere-specific monitoring program.

The challenge with CRISTAL will be to ensure that its sensor and mission specifications are tailored for application over glaciers—a difficult task because of glaciers’ relatively small sizes, steep slopes, and distribution in mountain terrain. In the event of a gap between the end of CryoSat-2 and the start of CRISTAL, a bridging airborne campaign, similar to NASA’s Operation IceBridge between ICESat and ICESat-2, will be needed.

Grosser Aletschgletscher in Switzerland, seen in October 2015. Credit: Jürg Alean, SwissEduc, Glaciers online

For laser altimetry, we may face gaps in observations as well, as no follow-on is planned for the current ICESat-2 and GEDI science missions. ICESat-2, which measures Earth’s glacier topography and provides validation and coregistration points for other altimetry missions, is projected to run until the early to mid-2030s, but continuing missions must be initiated now. Future missions should combine high accuracy with full coverage over individual glaciers. Proposed concepts with swath lidar, such as EDGE (Earth Dynamics Geodetic Explorer) and CASALS (Concurrent Artificially-Intelligent Spectrometry and Adaptive Lidar System), could be game changers for repeated mapping because they would provide full coverage of glacier topography. Advancing Surface Topography and Vegetation (STV) as a targeted observable for NASA missions, as recommended by the National Academies’ 2017–2027 Decadal Survey, could extend such observations beyond the current science missions.

For gravimetry, we also face a potential gap in observations, depending on when GRACE-FO is decommissioned and when approved follow-up missions—GRACE-C and NGGM (Next Generation Gravity Mission)—launch. Regardless of launch dates, the usefulness of future missions for monitoring glacier mass changes across regions will strongly depend on the spatial resolution of their data and on the ability to separate glacier and nonglacier signals. Cofounded gravity missions such as the Mass-Change and Geosciences International Constellation (MAGIC), a planned joint NASA-ESA project with four satellites operating in pairs, could significantly improve the spatial and temporal resolution of the gravity data and their utility for glacier monitoring.

Bringing It All Together

Glaciers worldwide are diminishing at alarming rates, affecting everything from geohazards to freshwater supplies to sea level rise.

Glaciers worldwide are diminishing with global warming, and they’re doing so at alarming rates, affecting everything from geohazards to freshwater supplies to sea level rise. Understanding as well as possible the details of glacier change from place to place and how these changes may affect different communities requires combining careful observations from a variety of field, airborne, and—increasingly—spaceborne approaches.

In light of major existing and impending observational gaps, the scientific community along with government bodies and others should work together to expand access to relevant historical data and extend present-day monitoring capabilities. Most important, space agencies and their sponsor nations must work rapidly to replace and improve upon current satellite missions to ensure long-term glacier monitoring from space. Given the climate crisis, we also call for open scientific access to data from commercial and defense missions to fill gaps and complement civil missions.

As the work of GlaMBIE reiterated, the more complete the datasets we have, the better positioned we will be to comprehend and quantify glacier changes and related downstream impacts.

Acknowledgments

We thank Etienne Berthier, Dana Floricioiu, and Noel Gourmelen for their contributions to this article and all coauthors and data contributors of GlaMBIE for constructive and fruitful discussions during the project, which built the foundation to condense the information presented here. This article was enabled by support from ESA projects GlaMBIE (4000138018/22/I-DT) and The Circle (4000145640/24/NL/SC), with additional contributions from the International Association of Cryospheric Sciences (IACS).

References

Berthier, E., et al. (2023), Measuring glacier mass changes from space—A review, Rep. Prog. Phys., 86(3), 036801, https://doi.org/10.1088/1361-6633/acaf8e.

Berthier, E., et al. (2024), Earth-surface monitoring is at risk—More imaging tools are urgently needed, Nature, 630(8017), 563, https://doi.org/10.1038/d41586-024-02052-x.

Braun, M. H., et al. (2019), Constraining glacier elevation and mass changes in South America, Nat. Clim. Change, 9(2), 130–136, https://doi.org/10.1038/s41558-018-0375-7.

Hugonnet, R., et al. (2021), Accelerated global glacier mass loss in the early twenty-first century, Nature, 592(7856), 726–731, https://doi.org/10.1038/s41586-021-03436-z.

Jakob, L., and N. Gourmelen (2023), Glacier mass loss between 2010 and 2020 dominated by atmospheric forcing, Geophys. Res. Lett., 50(8), e2023GL102954, https://doi.org/10.1029/2023GL102954.

Menounos, B., et al. (2024), Brief communication: Recent estimates of glacier mass loss for western North America from laser altimetry, Cryosphere, 18(2), 889–894, https://doi.org/10.5194/tc-18-889-2024.

Otosaka, I. N., et al. (2023), Mass balance of the Greenland and Antarctic Ice Sheets from 1992 to 2020, Earth Syst. Sci. Data, 15(4), 1,597–1,616, https://doi.org/10.5194/essd-15-1597-2023.

The GlaMBIE Team (2025), Community estimate of global glacier mass changes from 2000 to 2023, Nature, 639, 382–388, https://doi.org/10.1038/s41586-024-08545-z.

Treichler, D., et al. (2019), Recent glacier and lake changes in high mountain Asia and their relation to precipitation changes, Cryosphere, 13(11), 2,977–3,005, https://doi.org/10.5194/tc-13-2977-2019.

World Glacier Monitoring Service (2023), Global Glacier Change Bulletin No. 5 (2020–2021), edited by M. Zemp et al., 134 pp., Zurich, Switzerland, https://wgms.ch/downloads/WGMS_GGCB_05.pdf.

Wouters, B., A. S. Gardner, and G. Moholdt (2019), Global glacier mass loss during the GRACE satellite mission (2002–2016), Front. Earth Sci., 7, 96, https://doi.org/10.3389/feart.2019.00096.

Zemp, M., et al. (2013), Reanalysing glacier mass balance measurement series, Cryosphere, 7(4), 1,227–1,245, https://doi.org/10.5194/tc-7-1227-2013.

Author Information

Michael Zemp (michael.zemp@geo.uzh.ch), University of Zurich, Switzerland; Livia Jakob, Earthwave Ltd., Edinburgh, U.K.; Fanny Brun, Université Grenoble Alpes, Grenoble, France; Tyler Sutterley, University of Washington, Seattle; and Brian Menounos, University of Northern British Columbia, Prince George, Canada

Citation: Zemp, M., L. Jakob, F. Brun, T. Sutterley, and B. Menounos (2025), Glacier monitoring from space is crucial, and at risk, Eos, 106, https://doi.org/10.1029/2025EO250290. Published on [DAY MONTH] 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.

The 21 July 2025 rock avalanche is generating a lake that could have a volume of 86 million cubic metres at the point of overtopping. This poses a threat to at least seven downstream communities in east Taiwan.

Yesterday, I posted about the enormous 21 July 2025 rock avalanche in the Matia’an valley, in Wanrong township in eastern Taiwan. Coincidentally, etaiwan.news has posted an article about the landslide that includes some images of it, and that highlights the growing concerns about the potential hazard from the landslide dammed lake.

So, let’s start with the images. This is the headscarp area:

The headscarp area of the 21 July 2025 landslide in the Matia’an valley in Taiwan. Image by etaiwan.news.

The large source area is clear in the upper left of the image. Note the dust cloud from continued rockfall activity. The initial track of the landslide has left a complex topography that includes bare rock and some landslide material (especially on the right side of the image).

This image captures the lake that is forming:-

The barrier lake of the 21 July 2025 landslide in the Matia’an valley in Taiwan. Image by etaiwan.news.

Note the very substantial height difference between the lake and the top of the landslide deposit. Given that this valley was free draining before the landslide occurred, this must all be landslide material. As such it is erodable in the event of overtopping.

Finally, this is a view of the whole length of the landslide:-

The entire track of the 21 July 2025 landslide in the Matia’an valley in Taiwan. Image by etaiwan.news.

Again, note the height of the saddle formed from landslide material. The deposit appears on first inspection to be steep, which suggests it might be quite erodible.

The etaiwan.news article highlights work being undertaken by the Hualien Branch of the Forestry Conservation Department to understand the hazard. The statistics of the dam are concerning:

As of 7 August 2025At overtoppingLake volume23 million m386 million m3Lake length1,770 m2,900 m

The current freeboard is 79 m. Current inflow into the lake is 920,000 m3 per day, giving an overtopping date of mid-October at current rates (but see below).

A key issue is then the assets at risk downstream. This is a Google Earth image of the channel entering the Longitudinal Valley:-

Google Earth image of downstream assets from the landslide dam in the Matia’an Valley in Taiwan.

The article mentions that the risk will extend to:-

“will include the Matai’an Creek Bridge on the downstream Taiwan Line 9 [this is main highway on the eastern side of Taiwan], public and private river defence facilities and settlements on both sides of the river, and the administrative area covers Mingli Village, Dama Village, Daping Village, Dongfu Village in Wanrong Township, and Changqiaoli, Darongli and Shanxingli in Fenglin Township.”

Taiwan is well-placed to manage this hazard, but it is going to be a major issue in the coming weeks. Finally, as noted above, the overtopping date is estimated from current inflow rates. But, the next few weeks are the peak of the typhoon season, which can bring exceptional rainfall.

And, right on cue, Tropical Storm Podul has formed to the east of Taiwan, and is now moving westward. It is too early to tell whether this will bring heavy rainfall to the Matia’an valley (it is likely to pass by Taiwan on about 13 – 14 August), but if it does then this will accelerate the filling of the lake. Even if it does not bring heavy rainfall, the development of another typhoon that affects this area in the next two months would not be a surprise.

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Source: Journal of Geophysical Research: Biogeosciences

Earth’s atmosphere transports tiny forms of cellular life, such as fungal spores, pollen, bacteria, and viruses. On their journeys, these microorganisms encounter challenging conditions such as cold temperatures, UV radiation, and a lack of nutrient availability. Previous research showed that certain microorganisms can withstand these harsh conditions and potentially reside in dormancy until being deposited in a more favorable environment. But could the atmosphere itself also be the site of an active microbial system, harboring growing, adapted, and resident microorganisms?

The study of these floating life-forms is called aerobiology, but progress in the field is difficult to make: No standardized method exists for sampling the aeromicrobiome, it’s common for microbe samples to become contaminated, and it’s challenging to replicate atmospheric conditions in a laboratory setting.

Martinez-Rabert et al. suggest that computer modeling and theoretical approaches could help to improve understanding of the aeromicrobiome. Using known information about the metabolism and bioenergetics of microbial life—especially in harsh environments—as well as the chemistry and physics of the atmosphere, specialized modeling frameworks may be able to provide insight into the aeromicrobiome.

That bottom-up modeling approach, the researchers propose, could allow them to test how changing individual elements of Earth’s atmosphere would affect the proliferation of the microbial life it contains. For instance, are microbes better suited to a “free-living” lifestyle in atmospheric gases, inside droplets, or attached to solid particles? What energy sources are available to these microorganisms? How does the acidity of atmospheric aerosols affect the ability of atmospheric microorganisms to thrive?

The group suggests that combined with data generated through sampling measurements, experiments, and observations, theoretical modeling could help researchers to assess our atmosphere’s capacity to sustain a microbial biosphere and even to learn more about how microorganisms influence the atmosphere’s chemical makeup. This work could also someday be useful for modeling how life may exist in other planetary atmospheres, the researchers say. (Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1029/2025JG009071, 2025)

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

Citation: Owen, R. (2025), Can microorganisms thrive in Earth’s atmosphere, or do they simply survive there?, Eos, 106, https://doi.org/10.1029/2025EO250293. Published on 7 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.

In Malaysian Borneo, demand for timber, land, and palm oil has caused profound levels of deforestation. But the lack of historic data on the region’s rainforests has left scientists without much understanding of these forests’ baseline—what did they look like before industrial logging began?

Researchers have now found records hidden in an unexpected place. A new study, published in Scientific Reports, used corals from three reefs off the coast of Malaysian Borneo to build a timeline of deforestation and erosion on the island. The timeline provides valuable information for researchers and policymakers about how coral reefs are affected by deforestation as well as what Malaysian forests looked like in Earth’s past.

The study “allows us to have an idea of what the system looked like when it was relatively undisturbed,” said Walid Naciri, a geologist and lead author of the new study; he completed the research during his doctoral studies at the University of Leicester in the United Kingdom.

Coral Clues

Scientists can track deforestation trends with satellite imagery, but no such records exist before the onset of the satellite era around 1973.

Corals can be used as a proxy: They build themselves in alternating dark and light bands that, like trees, correspond to seasonal changes. As they grow, they absorb elements from seawater.

Corals’ ratio of barium, an element mostly found on land, to calcium, a common element in the ocean, can indicate the sediment content in river discharge that has reached a reef. Increased river discharge is an indicator of excess erosion, a consequence of deforestation. By analyzing the ratio of barium to calcium in a given band, scientists can determine the seawater composition in a given year.

“It’s a very well known impact of deforestation that you have less soil stability and more soil erosion ultimately arriving into the coastal ecosystem.”

Previous work by Naciri indicated that the barium-calcium ratio in corals matched river discharge data from the Baram River in Malaysian Borneo from 1985 to 2015. “We thought, okay, this is a pretty good analogue…so let’s have a look at the entirety of the record,” Naciri said.

The research team wanted to see whether they could use that ratio to construct a record of deforestation before 1985. They selected three separate reefs in the Miri-Sibuti Coral Reef National Park off the coast of Borneo. The three reefs, named Eve’s Garden, Anemone Garden, and Siwa, were located at different distances from the main sources of sediment: the Baram and Miri Rivers.

The team took cores of each reef and analyzed the ratios of barium to calcium. The resulting records were almost exactly what Naciri expected—cores from each of the three reefs showed a relatively flat trend until barium spiked beginning in the mid-20th century. The spike showed up later in the reefs farther from the island.

“We were pretty sure this was due to deforestation, because it’s a very well known impact of deforestation that you have less soil stability and more soil erosion ultimately arriving into the coastal ecosystem,” Naciri said. “But we needed a bit more proof.”

The team found archival forestry records that matched the mid-20th-century spike, indicating that the onset of industrial deforestation occurred around 1955. A previous analysis of land use across all of Southeast Asia from 1700 to 1990 showed a similar trend.

Naciri and his colleagues also ruled out other potential causes of the barium spike. They analyzed seawater at various distances from the Baram River to show that the barium was coming from the river rather than from leaching groundwater, for example.

The study’s authors did careful analytical work to rule out other interpretations of the data, said Dominik Fleitmann, a paleoclimatologist at the University of Basel in Switzerland who was not involved in the new study. Having three sites at varying distances from the island “adds confidence to the general reconstruction,” he said. 

The Far-Reaching Effects of Deforestation

The findings highlight how the impacts of on-land ecosystem degradation trickle down to coral ecosystems. Coral reefs rely on photosynthesis. Any influx of sediment into a reef clouds the water and harms coral’s ability to grow and even affects its ability to fight off diseases. 

“This is one more impact of deforestation that is really not talked about.”

“This is one more impact of deforestation that is really not talked about,” Naciri said. 

He urged other scientists studying deforestation to think outside of their usual study spaces and consider how marine ecosystems might be affected. “It’s an even worse problem than we think it is,” he said. 

Fleitmann said the results clearly show that “we are well above the natural variability in terms of soil erosion increases” and that the data could be useful to show policymakers the impacts of deforestation. 

The study could also be the beginning of a larger network of coral cores that could be used to build a more systematic reconstruction of deforestation records across larger areas of interest, such as the Australian or East African coast, he said. “What is the natural baseline, and how far away are we?”

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

Citation: van Deelen, G. (2025), Coral cores pinpoint onset of industrial deforestation, Eos, 106, https://doi.org/10.1029/2025EO250289. Published on 7 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: Journal of Geophysical Research: Solid Earth

Previous studies of the microearthquakes (MEQs) produced from Enhanced Geothermal Systems (EGSs) have focused on the initial phase of high‑pressure “stimulation.” Chamarczuk et al. [2025] track what happens during normal operation, the phase in which plants will spend most of their lives.

Using a distributed acoustic sensing (DAS) cable in a monitoring well and on‑site processing, the authors built a two‑month MEQ catalog through stimulation, crossflow testing, and five load‑following cycles. During those cycles, seismicity rose and fell with subsurface fluid pressure, then settled toward an equilibrium between injections. Event locations formed a cloud whose growth matched a simple diffusion model, which points to pressure migration as the main earthquake triggering mechanism.

These observations suggest that operators have the ability to control seismicity through careful management of injection rates and fluid pressure. They also demonstrate that affordable, real‑time monitoring is feasible for future commercial projects.

Citation: Chamarczuk, M., Ajo-Franklin, J., Nayak, A., Norbeck, J., Latimer, T., Titov, A., & Dadi, S. (2025). Insights into seismicity associated with flexibly operating enhanced geothermal system from real-time distributed acoustic sensing. Journal of Geophysical Research: Solid Earth, 130, e2025JB031634. https://doi.org/10.1029/2025JB031634

—David Dempsey, Associate Editor, JGR: Solid Earth

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On 21 July 2025, a very large rock avalanche occurred in the mountains of Hualien County, Taiwan. Initial measurements suggest that this ran out over about 6 km.

On 21 July 2025, an extremely large rock avalanche occurred in the administrative area of Wanrong Township in Hualien Count in Taiwan. This event was detected on seismic data and it has been described on Facebook by Chen-Yu Chen. In the days before the landslide, southern Taiwan had been affected by heavy rainfall associated with the passage of Tropical Storm Wipha.

The crown of the landslide is at [23.72645, 121.29021]. A rough measurement suggests that it is in the order of 6 km long and 2 km wide. The location is steep and rugged – this is a Google Earth image of the site of the landslide:-

Google Earth image of the site of the 21 July 2025 landslide in Wanrong township, Taiwan.

As the image above shows, the area affected by the rock avalanche is exceptionally steep (even by Taiwan standards) and deeply dissected, suggesting regular landslide activity. I will return to this theme in a future post.

This is a Planet Labs image of the site, draped onto the Google Earth DEM, captured on 25 July 2025. So far, this is the only image of the site that I have been able to access – this part of Taiwan is exceptionally cloudy at this time of the year. Whilst some of the landslide is covered in cloud, most is visible.

Planet Labs image, draped onto the Google Earth DEM, showing the site of the 21 July 2025 landslide in Wanrong township, Taiwan. Satellite image copyright Planet Labs, used with permission. Image dated 25 July 2025.

Of particular note is the large-scale of the event, the long runout and the large amount of dust on the adjacent slopes. Note also the lake that has started to develop – it is reported on Facebook that the hazard associated with this is being managed.

The crown of the landslide is at about 2,450 metres and the toe is at roughly 700 metres, so this has a vertical extent of about 1,750 metres.

Here is an initial slider of the before and after images of the landslide:-

This is probably the largest landslide in Taiwan by volume since the Tsaoling rock avalanche and the Chiufengershan rock avalanche, both triggered by the Ch-Chi earthquake in 1999. However, the runout of the Wanrong landslide is, I think, larger than both of these landslides. I do not have a volume estimate at this point.

In the autumn, it is likely that clear imagery will become available of this exceptional landslide. However, Taiwan is likely to be affected by further heavy rainfall in the coming weeks, so the landslide might evolve further.

Reference and acknowledgement

Many thanks to Brian Yanites of Indiana University Bloomington for highlighting this event, and for his work on the landslide.

Planet Team 2025. Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/

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Climate change warps the timing of natural processes. Scientists have evidence that flowers are blooming, trees are dropping their leaves, and animals are emerging from hibernation earlier than they did years prior.

“We’re seeing a trend towards an earlier onset.”

Now, there’s new evidence of another climate-related shift: California’s wildfire seasons are beginning as much as 46 days earlier than the typical onset 3 decades ago. The analysis, published in a paper in Science Advances, found that the trend was similar in almost all of California’s varied ecosystems.

The study defined wildfire season onset as the day when 5% of that season’s fires have occurred. “We’re seeing a trend towards an earlier onset,” said Gavin D. Madakumbura, a hydroclimatologist at the University of California, Los Angeles and lead author of the new study. “We wanted to understand what’s causing this.”

Previous work, including one landmark 2006 study, indicated that in some western U.S. forests, the wildfire season has both lengthened and started earlier.

To quantify the role of climate change in those trends, Madakumbura and his colleagues first analyzed U.S. Forest Service fire occurrence data and season start dates from 1992 to 2020 in California’s 13 ecoregions, from mountains in the north to deserts in the south. They found that since 1992, fire season has started earlier in all but one ecoregion (the Sonoran Basin and Range). The Cascades ecoregion shifted the most, with its 2020 onset occurring 46 days earlier than in 1992.

“The fact that they can see [the shift] across a broad array of ecosystems, most of them statistically significant, is noteworthy,” said LeRoy Westerling, a climate scientist at the University of California, Merced who was the lead author of the 2006 study that first indicated the shift. Westerling was not involved in the new study.

Though the shift in onset timing has been suspected for years, its magnitude is “much larger” than anticipated and “truly surprising,” wrote Virginia Iglesias, a climate scientist at the University of Colorado Boulder who was not involved in the new study, in an email.

Northern California ecoregions showed stronger trends than southern ecoregions, with the Eastern Cascades, Cascades, Central California Foothills, and Coastal Mountains showing the most significant changes. Madakumbura said the north-south difference exists because northern ecoregions’ fire seasons are more sensitive to changes in winter snowpack, which has also dwindled as the climate warms.

Climate Change’s Role

The team then evaluated the role of climate change as a driver of each ecoregion’s fire season start dates.

For each ecoregion, they determined how strongly climate-related drivers, such as how dry fuels were, influenced fire season start date compared with drivers that were not directly related to climate change, such as vegetation type. Then they compared changes observed for each of those drivers through time.

“The calendar-based boundaries we’ve long relied on for fire preparedness may no longer hold.”

The result suggested that although natural variability and severe droughts in the mid-2010s contributed to earlier fire seasons, climate change was a major driver of the earlier season in 11 of the 13 ecoregions.

“The climate, and the aridity of fuel, is the main controlling factor,” Madakumbura said.

“The paper presents compelling evidence that anthropogenic climate change is a dominant and quantifiable driver of the earlier wildfire season onset,” Iglesias wrote. “The logic is clear and the conclusions are well supported.”

As the climate continues to warm, fire seasons in California will likely start even earlier, the authors wrote. Knowing that fire seasons are trending earlier can help emergency managers prepare for longer fire seasons that burn more area, Madakumbura said.

“An earlier start to the season just taxes all these resources that much earlier,” Westerling said. “It’s the same people, the same equipment, and the same budgets that are under stress.” Fire season in California is extending later into the fall as well, he said, creating a much longer period when communities need to stay prepared for fires.

The asymmetry between northern and southern trends “highlights the need for regionally tailored fire management and climate adaptation strategies,” Iglesias wrote.

“The calendar-based boundaries we’ve long relied on for fire preparedness may no longer hold.”

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

Citation: van Deelen, G. (2025), California’s getting an earlier start to wildfire season, Eos, 106, https://doi.org/10.1029/2025EO250297. Published on 6 August 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
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Source: Global Biogeochemical Cycles

Human activity is shifting the type of nitrogen flowing out of Arctic rivers and into the Arctic Ocean, a new publication shows. The amount of organic nitrogen, which is derived from living things, is going up. Meanwhile, the amount of inorganic nitrogen, which is produced from nitrogen in the air through chemical reactions, is going down.

Ruyle et al. sampled water from sites at six Arctic rivers: the Kolyma, Lena, Ob, and Yenisey in Russia; the Mackenzie in Canada; and the Yukon in the United States. Together, these watersheds cover about two thirds of the land area that drains into the Arctic Ocean. From 2003 to 2023, researchers collected samples from the rivers five to six times per year and measured the abundance of various forms of nitrogen. In four of the six rivers (Lena, Ob, Yenisey, Mackenzie), the ratio of dissolved organic nitrogen to total nitrogen (i.e., the sum of organic and inorganic nitrogen) increased significantly during that period at a rate between 1% and 2% per year.

The team applied newly developed models to these measurements to identify environmental and climate conditions associated with changes in nitrogen composition. The amount of water flowing through rivers, the extent to which surrounding permafrost has thawed, and the prevalence of burned landscape are all key drivers of the shift from inorganic to organic nitrogen, they found. Climate change is intensifying all of these conditions, so the trend is likely to continue.

Photosynthetic organisms such as algae and cyanobacteria typically use inorganic nitrogen to fuel their growth, whereas organisms that eat other living things can use organic nitrogen. The microbes that cause harmful algae blooms are typically photosynthetic.

So in the coming years, a decrease in inorganic nitrogen in these rivers could lead to fewer harmful blooms in coastal regions where river inputs are most important. However, the overall effects of a shift from inorganic to organic nitrogen are not completely understood, and the authors suggest the shifts should be the subject of future research. (Global Biogeochemical Cycles, https://doi.org/10.1029/2025GB008639, 2025)

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

Citation: Sidik, S. M. (2025), Arctic rivers trade inorganic nitrogen for organic, Eos, 106, https://doi.org/10.1029/2025EO250292. Published on 6 August 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
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