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Publication date: Available online 20 August 2025

Source: Advances in Space Research

Author(s): Tarek Hassan, Amr Hassan

About 71% of Earth's surface is covered by the vast oceans. When winds blow over the sea surface, they transfer energy to the water, creating waves. Some of these waves, under the force of strong winds, break and produce tiny airborne droplets that become sea spray aerosols. This process happens across all oceans and is one of the world's largest sources of aerosols. Despite decades of research, scientists still do not fully understand the impact on the planet's climate, especially how much they contribute to particles that form clouds, known as cloud condensation nuclei.

A research team from the Aerospace Information Research Institute of the Chinese Academy of Sciences has developed a new method for evaluating urban sustainability, leveraging high-resolution data from the SDGSAT-1 satellite, according to a study published in Remote Sensing of Environment.

A team of geoscientists has identified a subtle but powerful force driving mountain building and compression of Earth's crust in Japan and neighboring regions. The so-called same-dip double subduction (SDDS) in nearby oceanic trenches has effects reaching hundreds and thousands of kilometers away from the zone of subduction.

Under high-emission scenarios, the Atlantic meridional overturning circulation (AMOC), a key system of ocean currents that also includes the Gulf Stream, could shut down after the year 2100. This is the conclusion of a new study, with contributions by the Potsdam Institute for Climate Impact Research (PIK). The shutdown would cut the ocean's northward heat supply, causing summer drying and severe winter extremes in northwestern Europe and shifts in tropical rainfall belts.

For decades, the Tijuana River has carried millions of gallons of untreated sewage and industrial waste across the U.S.-Mexico border. The river passes through San Diego's South Bay region before emptying into the ocean, recently leading to more than 1,300 consecutive days of beach closures and water quality concerns.

Clouds are important for Earth's energy balance because they interact with radiation in different ways. On one hand, low clouds reflect incoming solar radiation and thus cool Earth through a property known as albedo. On the other hand, clouds mainly at high altitudes prevent thermal radiation from escaping into space, which has a warming effect. Overall, the cooling effect currently dominates.

A more thorough way to estimate how much the world's boreal-Arctic wetlands and lakes contribute to current and future harmful methane emissions has been developed in part by University of Alberta researchers.

Humanity and the environment's adaptation to climate change is dependent on water, but projecting how water resources will be impacted in the future is difficult.

How Earth's atmosphere transformed from oxygen-poor to oxygen-rich over a span of about two billion years has been revealed by an international team of researchers.

An international team of scientists led by microbiologists Marc Mussmann and Alexander Loy from the University of Vienna has discovered a new microbial metabolism: so-called MISO bacteria "breathe" iron minerals by oxidizing toxic sulfide.

Greenland, despite its name, is largely blanketed in ice. And beneath that white expanse lies a world of hidden lakes. Researchers have now used satellite observations to infer that one such subglacial lake recently burst through the surface of the Greenland Ice Sheet, an unexpected and unprecedented event. By connecting this outburst with changes in the velocity and calving of a nearby glacier, the researchers helped to unravel how subglacial lakes affect ice sheet dynamics. These results were published in Nature Geoscience.

Researchers have known for decades that pools of liquid water exist beneath the Antarctic Ice Sheet, but scientific understanding of subglacial lakes in Greenland is much more nascent. “We first discovered them about 10 years ago,” said Mal McMillan, a polar scientist at Lancaster University and the Centre for Polar Observation and Modelling, both in the United Kingdom.

Subglacial lakes can exert a significant influence on an ice sheet. That’s because they affect how water drains from melting glaciers, a mechanism that in turn causes sea level rise, water freshening, and a host of other processes that affect local and global ecosystems.

McMillan is part of a team that recently studied an unusual subglacial lake beneath the Greenland Ice Sheet. The work was led by Jade Bowling, who was a graduate student of McMillan’s at the time; Bowling is now employed by Natural England.

Old, but Not Forgotten, Data

In the course of mining archival satellite observations of the height of the Greenland Ice Sheet, the team spotted something unusual in a 2014 dataset: An area of roughly 2 square kilometers had dropped in elevation by more than 80 meters (260 feet) between two satellite passes just 10 days apart. That deflation reflected something going on deep beneath the surface of the ice, the researchers surmised.

A subglacial lake that previously was situated at the interface between the ice and the underlying bedrock must have drained, said McMillan, leaving the ice above it hanging unsupported until it tumbled down. The team used the volume of the depression to estimate that roughly 90 million cubic meters (more than 3.1 billion cubic feet) of water had drained from the lake between subsequent satellite observations, making the event one of Greenland’s biggest subglacial floods in recorded history.

“We haven’t seen this before.”

Subglacial lakes routinely grow and shrink, however, so that observation by itself wasn’t surprising. What was truly unexpected lay nearby.

“We also saw an appearance, about a kilometer downstream, of a huge area of fractures and crevassing,” McMillan said. And beyond that lay 6 square kilometers (2.3 square miles)—an area roughly the size of lower Manhattan—that was unusually smooth.

The researchers concluded that after the subglacial lake drained, its waters likely encountered ice frozen to the underlying bedrock and were forced upward and through the surface of the ice. The water then flowed across the Greenland Ice Sheet before reentering the ice several kilometers downstream, leaving behind the polished, 6-square-kilometer expanse.

“This was unexpected,” said McMillan. “We haven’t seen this before.”

A Major Calving, a Slowing Glacier

It’s most likely that the floodwater traveled under northern Greenland’s Harder Glacier before finally flowing into the ocean.

Within the same 10-day period, Harder Glacier experienced its seventh-largest calving event in the past 3 decades. It’s impossible to know whether there’s a direct link between the subglacial lake draining and the calving, but it’s suggestive, said McMillan. “The calving event that happened at the same point is consistent with lots of water flooding out” from the glacier.

Using data from several Earth-observing satellites, scientists discovered that a huge subglacial flood beneath the Greenland Ice Sheet occurred with such force that it fractured the ice sheet, resulting in a vast quantity of meltwater bursting upward through the ice surface. Credit: ESA/CPOM/Planetary Visions

“It’s like you riding on a waterslide versus a rockslide. You’re going to slide a lot faster on the waterslide.”

The team also found that Harder Glacier rapidly decelerated—3 times more quickly than normal—in 2014. That’s perhaps because the influx of water released by the draining lake carved channels in the ice that acted as conduits for subsequent meltwater, the team suggested. “When you have normal melting, it can just drain through these channels,” said McMillan. Less water in and around the glacier means less lubrication. “That’s potentially why the glacier slowed down.”

That reasoning makes sense, said Winnie Chu, a polar geophysicist at the Georgia Institute of Technology in Atlanta who was not involved in the research. “It’s like you riding on a waterslide versus a rockslide. You’re going to slide a lot faster on the waterslide.”

Just a One-Off?

In the future, McMillan and his colleagues hope to pinpoint similar events. “We don’t have a good understanding currently of whether it was a one-off,” he said.

Getting access to higher temporal resolution data will be important, McMillan added, because such observations would help researchers understand just how rapidly subglacial lakes are draining. Right now, it’s unclear whether this event occurred over the course of hours or days, because the satellite observations were separated by 10 days, McMillan said.

It’s also critical to dig into the mechanics of why the meltwater traveled vertically upward and ultimately made it to the surface of the ice sheet, Chu said. The mechanism that this paper is talking about is novel and not well reproduced in models, she added. “They need to explain a lot more about the physical mechanism.”

But something this investigation clearly shows is the value of digging through old datasets, said Chu. “They did a really good job combining tons and tons of observational data.”

—Katherine Kornei (@KatherineKornei), Science Writer

Citation: Kornei, K. (2025), A burst of subglacial water cracked the Greenland Ice Sheet, Eos, 106, https://doi.org/10.1029/2025EO250317. Published on 28 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.

Micrometeorites, unlike their larger brethren, rarely get a spotlight at museums. But there’s plenty to learn from these extraterrestrial particles, despite the largest of them measuring just millimeters across.

Nearly 50 tons of extraterrestrial material fall on Earth every day, and the majority of that cosmic detritus is minuscule. Micrometeorites are, by definition, smaller than 2 millimeters in diameter, and they’re ubiquitous, said Fabian Zahnow, an isotope geochemist at Ruhr-Universität Bochum in Germany. “You can basically find them everywhere.”

Researchers recently analyzed fossilized micrometeorites that fell to Earth millions of years ago. They extracted whiffs of atmospheric oxygen incorporated into the particles and showed that carbon dioxide (CO2) levels during the Miocene and Cretaceous did not differ wildly from modern-day values. The results were published in Communications Earth and Environment.

Extraterrestrial Needles in Rocky Haystacks

Newly fallen micrometeorites can be swept from rooftops and dredged from the bottoms of lakes.

Zahnow and his collaborators, however, opted to turn back the clock: The team analyzed a cadre of micrometeorites that fell to Earth millions of years ago and have since been fossilized. The team sifted through more than a hundred kilograms of sedimentary rocks, mostly unearthed in Europe, to discover 92 micrometeorites rich in iron. They added eight other iron-dominated micrometeorites from personal collections to bring their sample to 100 specimens.

Metal-rich micrometeorites such as these are special, said Zahnow, because they function like atmospheric time capsules. As they hurtle through the upper atmosphere on their way to Earth, they melt and oxidize, meaning that atmospheric oxygen gets incorporated into their otherwise oxygen-free makeup.

“When we extract them from the rock record, we have our oxygen, in the best case, purely from the Earth’s atmosphere,” said Zahnow.

Ancient Carbon Dioxide Levels

And that oxygen holds secrets about the past. It turns out that atmospheric oxygen isotope ratios—that is, the relative concentrations of the three isotopes of oxygen, 16O, 17O, and 18O—correlate with the amount of photosynthesis occurring and how much CO2 is present at the time. That fact, paired with model simulations of ancient photosynthesis, allowed Zahnow and his colleagues to infer long-ago atmospheric CO2 concentrations.

“The story of the atmosphere is the story of life on Earth.”

Reconstructing Earth’s atmosphere as it was millions of years ago is important because atmospheric gases affect our planet so fundamentally, said Matt Genge, a planetary scientist at Imperial College London not involved in the work. “The story of the atmosphere is the story of life on Earth.”

But Zahnow and his collaborators first had to make sure the oxygen in their micrometeorites hadn’t been contaminated. Terrestrial water, with its own unique oxygen isotope ratios, can seep into micrometeorites that would otherwise reflect atmospheric oxygen isotope ratios from long ago. That’s a common problem, said Zahnow, given the ubiquity of water on Earth. “There’s always some water present.”

The team found that the presence of manganese in their micrometeorites was a tip-off that contamination had occurred. “Extraterrestrial metal has basically no manganese,” said Zahnow. “Manganese is really a tracer for alteration.”

Unfortunately, the vast majority of the researchers’ micrometeorites contained measurable quantities of manganese. In the end, Zahnow and his collaborators deemed that only four of their micrometeorites were uncontaminated.

Those micrometeorites, which fell to Earth during the Miocene (9 million years ago) and the Late Cretaceous (87 million years ago), suggested that CO2 levels during those time periods were, on average, roughly 250–300 parts per million. That’s a bit lower than modern-day levels, which hover around 420 parts per million.

“What we really hoped for was to get pristine micrometeorites from periods where the reconstructions say really high concentrations.”

The team’s findings are consistent with values suggested previously, said Genge, but unfortunately, the team’s numbers just aren’t precise enough to conclude anything meaningful. “You have a really huge uncertainty,” he said.

The team’s methods are solid, however, said Genge, and the researchers made a valiant effort to measure what are truly faint whiffs of ancient oxygen. “It’s a brave attempt.”

In the future, it would be valuable to collect a larger number of pristine micrometeorites dating to time periods when model reconstructions suggest anomalously high CO2 levels, said Zahnow. “What we really hoped for was to get pristine micrometeorites from periods where the reconstructions say really high concentrations.”

Confirming, with data, whether such time periods, such as the Triassic, truly had off-the-charts CO2 levels would be valuable for understanding how life on Earth responded to such an abundance of CO2.

—Katherine Kornei (@KatherineKornei), Science Writer

Citation: Kornei, K. (2025), Fossilized micrometeorites record ancient CO2 levels, Eos, 106, https://doi.org/10.1029/2025EO250319. Published on 28 August 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

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

 “Everything should be made as simple as possible, but not simpler.” This popular saying paraphrases a sentiment expressed by Einstein about the need for simplicity, though not at the expense of accuracy. Modeling of the Earth’s climate system has become an incredibly complex endeavor, especially when coupling of physics of atmospheric movement with complex and nonlinear feedbacks with the ocean and land surface and forcing by collective human actions. Such complexity can make the underlying causes of model behaviors hard to diagnose and can make it prohibitively expensive to perform targeted experiments.

Two very recent developments, the emergence of kilometer-scale simulations and the rapid growth of machine learning (ML) approaches, have further increased the computational complexity of modeling global climate. In their commentary, Reed et al. [2025] remind us of the benefits of maintaining and applying a hierarchy of models with different levels of complexity. They make a special plea not to forget the power of using idealized, or simplified, climate models for hypothesis testing, model development, and teaching. 

Citation: Reed, K. A., Medeiros, B., Jablonowski, C., Simpson, I. R., Voigt, A., & Wing, A. A. (2025). Why idealized models are more important than ever in Earth system science. AGU Advances, 6, e2025AV001716. https://doi.org/10.1029/2025AV001716

—Susan Trumbore, Editor, AGU Advances

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.

On 26 August 2025, a landslide triggered by extraordinary rainfall killed at least 34 people and injured another 20 individuals.

On 26 August 2025, extremely intense late monsoon rainfall struck parts of Jammu and Kashmir in northern India, triggering extensive flooding and landslides. Unfortunately, a significant landslide occurred on the route to the Vaishno Devi shrine, a sacred Hindu site that attracts large numbers of pilgrims. At the time of writing, the reported loss of life is 34 people, with 20 more injured.

I can find little detailed information about this landslide at present – the site is remote and access is clearly extremely difficult. However, this highlights a very major issue that India faces during the monsoon.

The Google Earth image below shows the terrain around the Vaishno Devi shrine (which is located at [33.03004, 74.948032]:-

Google Earth image showing the terrain around the Vaishno Devi shrine in northern India.

The landscape here is steep and geologically vulnerable, and the shrine is located on a remote mountain side, accessed by tracks. There is a good account of making the pilgrimage here – this person started the journey at 19:15 and they arrived at 02:00 the next day. The route is well-established but the journey is long (13 km). Most people travel on foot. According to the temple itself, over 5.2 million people have the journey so far in 2025. Travel during the monsoon is not recommended, but many people inevitably make the trip at this time.

Thus, this pilgrimage, and others that also take devotees into the Himalayas, places people in a dynamic landscape at a time when landslides are most likely. Inevitably, the vulnerability of those people is high. The tragedy at Vaishno Devi is the consequence.

Unfortunately, this event is not isolated. On 14 August, another major landslide occurred at Chasoti in Kishtwar district, also in Jammu and Kashmir, on the route of the Machail Mata Yatra pilgrimage. The final loss of life is unclear, but at least 66 people were killed and some reports suggest as many as 75 more people may be missing. There have been a number of other fatal landslides this year on Hindu pilgrimage routes.

And loyal readers of this blog may remember the 2013 Kedarnath disaster, when vicious debris flows struck the route of the Chardham pilgrimage when it was packed with pilgrims. The remains of 733 victims were recovered, but 3,075 people remain missing. With a total of 3,808 victims, this was one of the worst landslide disasters of the last 30 years.

There are news reports that Jammu and Kashmir chief minister, Omar Abdullah, is questioning why the Shri Mata Vaishno Devi Shrine Board did not suspend the pilgrimage. Reports indicate that the area received 629.4 mm of rainfall in a rolling 24 hour period, exceeding the previous record (342 mm) by a huge margin. In the view of the minister, these totals should have alerted the authorities to the potential for a disaster.

Whilst this is a pertinent question, it is addressing a short term issue, rather considering the underlying problems. The reality is that peak rainfall intensities in the summer monsoon are rapidly increasing across South Asia as a result of climate change, triggering landslides (especially channelised debris flows) and floods. At the same time, huge numbers of pilgrims are travelling into the landscape, where they are extremely vulnerable.

Managing this risk is very taxing, but many more people will lose their lives if systematic action is not taken to protect the pilgrims. These levels of loss cannot be tolerable.

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.

AbstractIntradecadal variations in the length-of-day (ΔLOD) can reveal changes in angular velocity interpreted as due to Earth’s core. Previous studies have identified periodic oscillations of around 6 and 8 years. To complement widely used Fourier methods, we investigate the ΔLOD record from 1962-2025 in the time domain, seeking smooth variations using cubic B-splines. We analyse in several ways. A penalised least-squares spline fit allows isolation of coherent variations from analysing the first and second derivatives. Alternatively, a smooth curve fit with least-squares splines allows removal of the long-period behaviour of ΔLOD. From this, we fit the residual with a pure cosine-wave of varying period but examine the data fits carefully in case the signal is non-stationary (for example from impulsive forcing). All approaches show clear evidence of signals with periods around 5.9 — and in the case for the time derivatives — 8.5 years. We find that the pure 5.9-year oscillation breaks down in 2010, with a one-off peak to peak separation of around 4.7 years. After 2014, the variation is once again consistent with an approximate 6 year oscillation. Such a discontinuous, non-stationary effect is not well-characterised by frequency-domain based methods. Seeking to understand this brief interruption of the 6 year oscillation, we extend the study length using a ΔLOD series from lunar occultation data extending back to 1800, and find it suitable to repeat our spline-based analysis from 1830 onwards. From this, we find the 6 year oscillation stable throughout the entire 19th and 20th century, with the exception of 1916–1920, where we observe a similar interruption of the 6 year variation by a single 4 year oscillation. The 2010 disruption to the 6-year oscillation is contemporary with changes in geomagnetic secular variation, modelled core surface flow, and inner core seismic signature. All of these events suggest a step change in core-processes around 2010.

Supercell thunderstorms are among the most impactful weather events in Europe. They typically occur in summer and are characterized by a rotating updraft of warm, humid air that brings strong winds, large hail and heavy rain. The impact is significant and often leads to property damage, agricultural losses, traffic chaos and even threats to human safety.

A new study led by researchers from the Aerospace Information Research Institute (AIR) of the Chinese Academy of Sciences has for the first time mapped the long-term, large-scale transport pathways of PM2.5 pollution across China spanning from 2000 to 2021, providing scientific support for refining national air quality management strategies.

When water is below normal levels in Latin America, it's not just farmers and consumers who suffer. A new study finds that air pollution spikes, and thousands of people die prematurely as a result.

On August 5, a cloudburst near the Kheer Ganga river triggered a flash flood that tore through Dharali, a village in the Indian Himalayas. Within minutes, the river swelled with water, mud and debris, sweeping away homes, roads and lives.