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A new review published in Advances in Atmospheric Sciences sheds light on one of climate science's enduring puzzles: how the patterns of tropical ocean warming influence the behavior of tropical cyclones (TCs) in a warming world. An international team of scientists synthesizes decades of observational evidence and climate modeling advances to chart a path forward for more reliable TC projections.

As wildfires increasingly threaten lives, landscapes, and air quality across the U.S., a Stanford-led study published in AGU Advances finds that prescribed burns can help reduce risks.

A new study challenges the idea that climate change is behind the erratic wintertime behavior of the polar jet stream, the massive current of Arctic air that regulates weather for much of the Northern Hemisphere.

Lake Tahoe’s sparkling, clear water is a point of pride among locals and a draw for tourists. Although the water clarity—measured by how deep visible light can penetrate—has decreased since measurements began in 1968, conservation efforts over the past 2 decades have stabilized it.

However, a new study published last month in Limnology and Oceanography Letters shows that ultraviolet (UV) light tells a different story. The depths to which UV radiation reaches in Lake Tahoe vary dramatically between extreme wet and dry years. Because UV radiation can affect chemical and biological processes, shifting underwater light environments between years could have significant implications for Lake Tahoe’s ecosystem.

A Question of Clarity

To measure water clarity in Lake Tahoe, a 1,645-foot-deep (594-meter-deep) freshwater lake straddling the border of California and Nevada in the Sierra Nevada Mountains, scientists drop a white disk into the water and record how deep they can see it. They use a similar approach to measure UV light, but because it’s invisible to our eyes, they drop a sensor that measures different wavelengths of UV light as it sinks.

Eighteen years ago, scientists at the University of California, Davis Tahoe Environmental Research Center began collecting UV data from the lake every 2 to 3 weeks, creating a long-term record rare for lakes anywhere in the world.

“You can use satellites to look at long-term trends in water clarity, and people have done that all over the U.S. and around the world,” said Kevin Rose, a freshwater ecologist at Rensselaer Polytechnic Institute in New York, but “a multidecade record of UV radiation is a unique asset.” Rose was not involved in the study.

“We found a huge fluctuation in UV transparency year to year.”

Several studies have used data from the record, but limnologist Shohei Watanabe at the Tahoe Environmental Research Center and his colleagues wanted to do a comprehensive analysis of whether Lake Tahoe was experiencing changes in the penetration of UV light between 2006 and 2023.

Watanabe initially expected to see a gradual decrease in UV penetration over the study period, mirroring the trend in visible light. “Instead, we found a huge fluctuation in UV transparency year to year,” he said.

In drought years, such as 2014–2015, UV radiation penetrated deeper than in exceptionally wet years such as 2017, when the Sierra Nevada received its second-highest amount of precipitation since 1910.

“It’s an amazing difference,” Watanabe said. The most dramatic differences occurred during the spring and early summer, when solar radiation is at its strongest. UV radiation was 100 times stronger 10 meters (32 feet) below the surface and reached up to nearly 4 times deeper in summers during drought years.

Shohei Watanabe and other scientists have been collecting data on UV radiation in Lake Tahoe for 18 years. Credit: Karin Higgins

The phenomenon occurs because wet years wash more particulates and dissolved organic matter off the slopes of the surrounding mountains and into the lake, which blocks the UV radiation.

Visible light showed only a twofold difference in how deep it penetrated the lake between wet and dry years because the longer wavelengths of visible light are not as easily blocked by dissolved organic matter in the water. To the naked eye, visitors might notice some changes in the water clarity between years, “but it’s not like a 100-fold difference,” Watanabe said.

A Sunburn on the Ecosystem

The balance of UV light and visible light is crucial in freshwater ecosystems. UV radiation breaks down dissolved organic matter, releasing carbon dioxide into the atmosphere. Just like UV light can give us a sunburn, it can harm freshwater organisms by damaging DNA and inhibiting photosynthesis. It can also affect zooplankton behavior—these organisms actively avoid harmful UV light by migrating deeper during the day.

For the most biologically damaging UV wavelengths, including 305 and 320 nanometers, the differences from year to year in Lake Tahoe were most pronounced.

UV radiation isn’t always harmful to the ecosystem, however. Rose noted previous research showing that it prevents invasive fish, such as bluegill, from successfully reproducing in Lake Tahoe’s clear waters because larvae don’t survive high UV exposure. The fish become restricted to murky nearshore areas such as marinas.

“I really want to stress the importance of long-term monitoring for this kind of environmental study.”

Drastic shifts in UV penetration between wet and dry years therefore imply big changes in the ecosystems in the lake—and those swings could get more intense with human-caused climate change. “When we think about Lake Tahoe, now, going through precipitation cycles, that also means potential biological damage,” Rose said. Fully understanding how these communities will react will require continued monitoring.

Similar UV cycles might also occur in other clear mountain lakes worldwide, but each lake system has unique characteristics that would influence light patterns. “I really want to stress the importance of long-term monitoring for this kind of environmental study,” Watanabe said.

Watanabe and his colleagues are now planning and performing studies to determine how these UV variations affect Lake Tahoe’s carbon cycle, primary productivity, and other biological processes. “That’s the next step,” he said.

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

Citation: Chapman, A. (2025), Precipitation extremes drive swings in Lake Tahoe’s UV exposure, Eos, 106, https://doi.org/10.1029/2025EO250234. Published on 26 June 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.

Every summer, typhoons threatening the Korean Peninsula draw their energy from the warm waters of the Northwest Pacific Ocean. In recent years, the frequency and intensity of extreme weather events—such as heat waves, droughts, and heavy rains—have been increasingly linked to rising sea surface temperatures (SST).

Author(s): Ting-yu Yao, Ji-xu Gao, Miao Tian, Shun-xin Zhang, Fu-cheng Liu, Bao-quan Ai, Yan Feng, and Ya-feng He

It is demonstrated experimentally that the effective separation of bidispersed microspheres (dust particles) in the underdamped and strongly coupled regime is realized using a designed dusty plasma ratchet. Experimental findings reveal that these dust particles can undergo directional transport at v…

[Phys. Rev. E 111, 065216] Published Thu Jun 26, 2025

A major landslide has occurred in the vicinity of Altos de Oriente and Manantiales, near to Medellín and Bello, in Colombia. It is believed that about 25 people died.

On 24 June 2025 at 3:20 am, a large landslide occurred in the vicinity of Altos de Oriente and Manantiales, near to Granizal in Colombia. At the time of writing, 13 bodies have been recovered and a further 12 are missing. In total, 50 houses were destroyed.

I don’t yet have the precise location of this landslide tied down. A map on the El Colombiano news site places it at [6.30905, -75.53277], but this is yet to be confirmed.

There is very good aerial footage of it in a news report posted to Youtube by Cubrinet:-

At around 1 minute 45 seconds into this footage, this image is captured-

The 25 June 2025 landslide at Granizal in Colombia. Still from a video posted to Youtube by Cubrinet.

This image shows the crown of the landslide:-

The crown of the 25 June 2025 landslide at Granizal in Colombia. Still from a video posted to Youtube by Cubrinet.

The failure has occurred in deeply weathered regolith. It is a debris slide, with the main portion being comparatively deep-seated. It is notable that there is a considerable volume of water visible in the images:-

The upper portion of the 25 June 2025 landslide at Granizal in Colombia. Still from a video posted to Youtube by Cubrinet.

Some news sites note that a water pipe has ruptured in the landslide. The failure occurred during a period of very heavy rainfall – the El Colombiano site quotes a local resident as saying:-

“It was raining all day and all night. About 10:00 p.m. there was a downpour that cleared before 2:00 a.m. When it wasn’t even raining, we heard the noise and when we found out, we realized that the mountain had come and covered the entire neighborhood”.

Sometimes, a small failure associated with heavy rainfall can rupture a water pipe, which feeds water into the slope, triggering a much larger landslide.

Low down in the track of the landslide, it has spread and bifurcated, controlled by the topography:-

The main body of the 25 June 2025 landslide at Granizal in Colombia. Still from a video posted to Youtube by Cubrinet.

Thee are concerns about a further landslide at this site, imperiling the teams charged with recovering the victims.

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.

AbstractIn recent years, offshore tsunami observation networks equipped with ocean bottom pressure gauges (OBPGs), such as S-net, DONET, and N-net, have been deployed around Japan, enabling real-time collection of high-quality tsunami data near the source. These networks make it possible to estimate the spatiotemporal variation of the tsunami wavefield using a data assimilation approach, and to predict coastal tsunamis from the initial or current tsunami wavefield. This study proposes a novel tsunami data assimilation method that uses physics-informed neural networks (PINNs) to estimate tsunami wavefields from the observed OBPG data. The neural network was optimised by minimising the sum of the data loss, which quantifies discrepancies from the tsunami data, and the physical loss, which quantifies the satisfaction of the linear long wave equation. This was performed to ensure that the estimated results are consistent with both the observed data and the physics of tsunami propagation, even when there are limited observational data and significant noise. We first validated the effectiveness of the proposed method using synthetic S-net OBPG data from the 2011 Tohoku-oki earthquake (Mw 9.0) tsunami. The results confirmed that by using both data and physical constraints in the PINN optimisation, the PINN could adequately assimilate the spatiotemporal distribution of the tsunami wavefield from OBPG data, even for predictions outside the network coverage area. The predicted tsunami waveforms at the coastal stations, computed from the estimated initial wavefield, showed good agreement with the actual waveforms. Next, we conducted an experiment using actual S-net OBPG data from the 2016 Fukushima-oki earthquake (Mw 6.9) tsunami. The initial tsunami source estimated by PINN was in good agreement with other studies based on waveform inversion, although the maximum source amplitude and maximum coastal tsunami heights were underestimated. We also conducted an experiment using N-net OBPG data from the 2024 Hyuganada earthquake (Mw 7.0) tsunami. The PINN could accurately estimate the initial tsunami source, even though the tsunami source of this event was located outside the N-net coverage area. Finally, we have shown that incorporating tsunami observations over time into the iterative optimisation of the PINN model allows for accurate and efficient tsunami data assimilation.

AbstractUnderstanding processes in the Critical Zone requires reliable information about the vadose-zone aquifer, its geometry, and spatial variability. Commonly, such information is obtained from boreholes, yet large areas might render their application prohibitively expensive. Additionally, limited geological a-priori information might bias the interpretation due to lateral geological changes smaller than the borehole sampling scale. The transient electromagnetic method (TEM) has emerged in the last decades as a well-suited method to efficiently investigate the subsurface, as required for many hydrogeological applications. The interpretation of TEM measurements relies mainly on deterministic inversions, offering only a limited insight on the uncertainty of the subsurface model. Uncertainty quantification, however, is essential for integrating TEM results into hydrogeological models. Hence, we propose a combined approach using both deterministic and stochastic inversion of TEM soundings to investigate the uncertainty of shallow (< 40 m) aquifers. Current stochastic approaches for TEM data rely on Markov chain Monte Carlo algorithms, which have to be run from scratch for each individual sounding. Alternatively, machine learning approaches, such as Bayesian Evidential Learning (BEL), can be much faster because they do not require retraining for every new data set. Hence, we investigate, in particular, the application of a single, common prior model space instead of multiple, individual prior model spaces to directly estimate the uncertainty of multiple TEM soundings. To this end, we combine forward modelling routines with the stochastic inversion approach BEL1D and assess our approach using both field data and numerical experiments.

SUMMARYThe Fennoscandian earthquake catalogue (FENCAT) assembles data on the natural seismicity in Fennoscandia, Northern Europe. We present an updated and standardized version of the catalogue originally published in the early 1990s. New instrumental data are recorded by the seismic networks of Denmark, Estonia, Finland, Norway, and Sweden, and analyzed by the Geological Survey of Denmark and Greenland, the Geological Survey of Estonia, the University of Helsinki in Finland, the University of Bergen and the NORSAR research foundation in Norway, and Uppsala University in Sweden. The updated catalogue provides the available earthquake parameters in a brief, user-friendly version: origin time, source coordinates, focal depth, macroseismic data (maximum intensity and radius of the area of perceptibility), up to three observed magnitudes, seismic moment estimate, and a standardized moment-related magnitude, mW(HEL), for each event. The standardized magnitude is defined in this paper and its relation to other magnitude scales is provided. Suspected non-earthquakes (e.g. frost events, explosions, human-induced events) have been removed. The standardized event magnitudes range from mW(HEL) -1.0 to 6.2. To enable the usage of earthquake data in a large variety of seismological, geological and earthquake engineering investigations, the data are not truncated at the low magnitude end.The updated catalogue, FENCAT (2021), contains about 23 000 earthquakes for the period 1467–2021 in an area bounded by 54–75°N latitudes and 0–45°E longitudes. The completeness and quality of the earthquake solutions is best within the areal coverage of the above-mentioned networks.

AbstractWhile modern thermal convection in rocky planets is controlled by a slow solid-state creep flow, the earliest stages of terrestrial planets likely experienced turbulent flow during which their silicate envelope was fully molten, usually called magma ocean. The main parameter separating the two regimes is the Prandtl number (Pr), which is so high for mantle convection to be usually assumed infinite, whereas magma oceans are characterized by Pr on the order of 1. We compared the results of isoviscous convection simulations performed with three codes: (GAIA, TLBM, StreamV). These codes are based on different numerical formulations and were used for modeling convection with Pr ranging from 1 to 1000, while exploring different convection intensity by varying the Rayleigh number (Ra) from 104 to 106. GAIA (Generic Automaton for planetary Interior Analysis) is a Finite Volume fluid flow and energy solver for the Navier-Stokes equations across arbitrary geometries. TLBM (Thermal Lattice Boltzmann Method) solves the mesocale momentum and energy distribution densities for colliding particles on a discrete lattice. StreamV is a Eulerian-Lagrangian Finite Volume code that solves the Navier-Stokes equations under the Boussinesq approximation. The codes are compared over 24 different simulation setups, analogue to the classical Blankenbach infinite Pr benchmark (Blankenbach et al., 1989a), but extending it to finite Pr and to two types of boundary conditions, free-slip and no-slip. We show that the results of the three codes are generally in good agreement, and discuss differences. Finite Pr solutions show a much richer dynamics varying from stable steady-state solutions, to oscillatory and chaotic ones, and converging to infinite Prandtl number solution for increasing values of Pr for larger Ra: Pr ≥ 100 is sufficient for Ra = 105 but Pr ≥ 1000 is required for Ra = 106. Our results offer a robust set of solutions useful for testing future finite Prandtl number convection codes.

SUMMARYOur viewpoint highlights the challenges faced by women in the Induced Polarization (IP) community (and elsewhere), particularly the persistent gender imbalance in scientific workshops. This underrepresentation in leadership roles, presentations, and discussions reflects broader systemic biases in academia. By sharing the experience of the 7th IP workshop, where the organizing team made deliberate efforts to prioritize gender and diversity in organizing committees, recruitment, and session formats, we demonstrate how intentional actions can create a more inclusive, gender-balanced environment. This approach is crucial not only for the IP community but for all research communities. Emphasizing diversity and inclusion fosters a welcoming atmosphere that encourages participation from all individuals, regardless their background. In turn, this enriches the research process by incorporating diverse perspectives, driving innovation, and improving scientific outcomes. We aim to inspire other academic communities to actively promote diversity and inclusivity, recognizing that such efforts not only benefit underrepresented groups but elevate the success and relevance of science as a whole.

Taking carbon out of the atmosphere is essential for slowing global warming—and a team of Cornell University researchers has estimated "huge" potential for carbon capture using a method that is low-tech, sustainable and relatively simple: burying wood, especially the debris from managed forests.

A recent study by The Hong Kong University of Science and Technology (HKUST) reveals a looming climate crisis: the world could face heightened risks of "precipitation whiplashes"—violent swings between extreme droughts and floods—as early as 2028.

body {background-color: #D2D1D5;} Research & Developments is a blog for brief updates that provide context for the flurry of news regarding law and policy changes that impact science and scientists today.

Staff at the National Science Foundation (NSF) were notified on 25 June that the agency’s office space, located in Alexandria, Va., will be taken over by Department of Housing and Urban Development (HUD) staff, raising the question of where more than 1,800 NSF employees will work. 

One NSF employee told E&E News that they had “literally zero idea” the news was coming until word spread among staff the previous evening. Many NSF employees had relocated to Northern Virginia on short notice when return-to-work orders were issued in January. NSF only moved into the newly constructed building in 2017 from its prior location in Arlington, Va.

In front of a banner reading “The New Golden Age of HUD” at a 25 June press conference, HUD Secretary Scott Turner announced that a “staggered and thoughtful” relocation process would take place. The relocation will move forward “as quickly as possible,” Michael Peters, commissioner of the Public Buildings Service for the U.S. General Services Administration, said at the press conference.

On 24 June, Jesus Soriano, president of the American Federation of Government Employees (AGFE) Local 3403, a union representing NSF staff, sent an alert to union members informing them that “HUD will take over the NSF building” and that NSF had not been involved in the decision, according to E&E News.

Speakers at the press conference did not provide details about HUD’s plans for the space. In a statement, AGFE Local 3403 indicated that the union was told that plans would include an executive suite for Turner, the construction of a new executive dining room, exclusive use of one elevator for Turner, and a gym for Turner and his family.

 
Related

•  Press Conference: The New Golden Age of HUD
•  American Federation of Government Employees Local 3403 Statement
•  Science Agency Staff Brace for HQ Takeover
•  Get Involved: AGU Science Policy Action Center
 

“While Secretary Turner and his staff are busy enjoying private dining and a custom gym, NSF employees are being displaced with no plan, no communication, and no respect,” AGFE Local 3403 wrote in the statement.

Turner rebuked the idea that the move was about personal perks. “This is not about Scott Turner. I didn’t come to government to get nice things,” Turner said. “This is about the HUD employees.”

Turner added that unsafe working conditions at the current HUD office space in Washington, D.C. were the reason for the move. “I would hope that no leader in government or otherwise would expect staff to work in an atmosphere where the air quality is questionable, leaks are nearly unstoppable, and the HVAC is almost unworkable. It’s time for a change.”

Addressing the coming transition for NSF, Peters said, “We are going to continue to support the National Science Foundation as we support every agency across the federal government to identify space that allows them to continue to fulfill their mission.” 

In its statement, AGFE Local 3403 pointedly questioned the merit of the relocation plan: “At a time when they claim to be cutting government waste, it is unbelievable that government funding is being redirected to build a palace-like office for the Secretary of Housing and Urban Development. The hypocrisy is truly dumbfounding.”

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

These updates are made possible through information from the scientific community. Do you have a story about how changes in law or policy are affecting scientists or research? Send us a tip at eos@agu.org. 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 a first-of-its-kind study, Stanford researchers have measured how the abundance of ocean life has changed over the past half-billion years of Earth's history.

As Britain's first heat wave of 2025 hits with temperatures climbing above 30°C, Yorkshire has joined the northwest in official drought status.

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

In the Arctic, one of the primary paths for water to flow is along water tracks, stream-like features that fill with and route water when the soil above permafrost thaws in the summer. While these water tracks are important for water and nutrient movement, little is known about their formation and how they might change in the future.

A new study in Reviews of Geophysics explores our current understanding of water tracks and what aspects are still unclear. Here, we asked the authors to give an overview of water tracks, the leading theories about their formation, and what questions remain.

What are water tracks and where do they form?

Remote sensing image of tundra water tracks in northern Russia. Credit: Del Vecchio and Evans [2025], Figure 1a

Water tracks are stream-like features that concentrate water flow in cold places where the ground is frozen in the winter. Since frozen ground doesn’t let water soak in, any water from rain, melting snow, or ice ends up moving along the surface or just under the top layer when it thaws in the summer, like through moss or soil.

Interestingly, water tracks do not have a stream channel like a typical stream. You don’t need steep hills for water tracks to occur either; even a gentle slope is enough to get water moving. Water tracks are mostly found in places with permafrost including the Arctic, parts of Alaska, northern Canada, Siberia, and even Antarctica.

What roles do water tracks play in polar regions?

Water tracks move a surprising amount of water across frozen landscapes, especially in places with hills or gentle slopes. Because the water gets funneled into these narrow paths, it also brings along nutrients, making water tracks hotspots for plant growth and biological activity in otherwise cold and dry areas. You’ll often see greener, thicker vegetation in these zones, and they can be places where more carbon dioxide and methane are produced.

From a landscape perspective, they act like pseudo-channels for water, but interestingly, they don’t seem to carve out the land or move much sediment. However, that could change with climate shifts, and if these areas start eroding, it might reshape parts of the Arctic landscape in new ways.

How do scientists identify and monitor water tracks at different spatial scales?

Water tracks were first spotted from the air using aerial photos, and today we still rely heavily on remote sensing to study them. On the ground, scientists can look at vegetation changes, soil wetness, and evidence of surface water flow, but because water tracks can stretch for hundreds of meters, satellite and drone imagery are super helpful. They show up well in high-resolution images and in certain types of data, like infrared, because the plants growing on water tracks are greener and more productive. Tools like LiDAR can also help track changes in elevation, which is useful for spotting subtle shifts or erosion over time. While coarser satellites like Landsat might miss them, newer ones like Sentinel or PlanetScope can pick them up much more clearly.

Appalachian State University undergraduate students Noah Caldwell, Key Hatch, and Emma Ferm walk to collect water and soil samples from a water track on the North Slope of Alaska, USA in July 2023. Credit: Thomas Tobul

What are leading theories that describe how water tracks form?

In our literature review, most studies only consider their individual water tracks, so there weren’t really generalized models of water track formation out there before our review. But from literature and our own work, we noted two main theories: one theory is that they’re the result of thawing ground ice like ice wedges that create long, linear paths for water to flow. As the ice thaws, water keeps following that path, advecting heat which causes further thawing, reinforcing the track.

The other theory is a slightly different feedback mechanism: a dip or disturbance in the permafrost table, maybe from a snowdrift, vegetation, or other small indent, collects more water, which causes more thawing and even more water to flow there, creating a self-reinforcing loop. Both theories not only help explain how water tracks form, but also why they tend to show up in regular, repeating patterns across the landscape.

How is climate change expected to influence water tracks?

This is still a big unknown, but we’re starting to get some ideas. As permafrost landscapes warm, snow melts earlier and the ground thaws deeper, which could change how and where water flows. If water starts moving through deeper, less porous soil layers, it might cause erosion in places that used to be stable, turning soft, spongy mats into channels that cut into the ground. That could release stored sediment and carbon, and even shift how water tracks connect and drain the landscape. We are also seeing signs that water tracks are drying out or consolidating into fewer, deeper gullies, which could lead to even more dramatic changes over time.

How could water tracks be used to understand the hydrosphere on Mars?

Studying water tracks helps us think differently about how water might emerge and flow on other planets.

Scientists have long compared water tracks on Earth to the dark streaks seen on Martian slopes like recurring slope lineae (RSL), especially since both appear and change seasonally in cold, dry environments. Places like Antarctica and the Canadian Arctic often serve as analogs for Mars for geoscientists, where similar streaky patterns show up seasonally, which some researchers have called water tracks. While recent research suggests these Martian features might be caused by dust and wind rather than water, Earth’s water tracks still offer clues. They show that even in frozen conditions, water can move across the surface without leaving a noticeable fingerprint of erosion, which is something that might have happened on Mars in the past. So, studying water tracks helps us think differently about how water might emerge and flow on other planets, even if it doesn’t leave obvious signs behind.

What are some of the remaining questions where additional modeling, data, or research efforts are needed?

We’ve only studied a handful of water tracks in detail, so our understanding is based on a small slice of the Arctic. There’s a big need for more field data and better remote sensing to match the huge areas where water tracks actually exist. We also need more modeling to figure out what really drives their behavior and how that will change in a warmer climate, whether it’s snow, vegetation, or water flow. Questions like how water tracks “remember” past years, or how they evolve over time, are still wide open. So, more data and better models are key to unlocking how these features work and how they might change in the future.

—Joanmarie Del Vecchio (joanmarie@wm.edu, 0000-0003-3313-6097), College of William and Mary, United States; and Sarah G. Evans (0000-0001-5383-8382), Appalachian State University, United States

Editor’s Note: It is the policy of AGU Publications to invite the authors of articles published in Reviews of Geophysics to write a summary for Eos Editors’ Vox.

Citation: Del Vecchio, J., and S. G. Evans (2025), Water tracks: the veins of thawing landscapes, Eos, 106, https://doi.org/10.1029/2025EO255021. Published on 25 June 2025. This article does not represent the opinion of AGU, Eos, or any of its affiliates. It is solely the opinion of the author(s). Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Source: AGU Advances

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

No se tienen registros suficientes en las bases de datos globales de los peligros meteorológicos extremos. Por ejemplo, los eventos donde las temperaturas son potencialmente mortales y que se ajustan a las normas climatológicas generalmente no son incluidos en los estudios de riesgos, y las inundaciones locales o regionales a menudo suelen pasar desapercibidas para los instrumentos satelitales.

En los últimos 20 años Texas ha experimentado una cantidad inusualmente alta de fenómenos climáticos extremos, incluyendo un incremento en inundaciones y olas de calor. Usando datos satelitales de fácil acceso de precipitación y temperatura tomados diariamente, Preisser y Passalacqua crearon una visión más amplia de los riesgos por inundaciones y olas de calor que han afectado al estado en los últimos años.

Al consultar los datos de precipitación del 2001 al 2020, los investigadores definieron como un evento de inundación peligrosa a aquellos que ocurren en promedio una vez cada dos años o más, lo que significa que un evento de esa magnitud ocurre en un área determinada con una frecuencia que no supera los dos años. Compararon sus resultados con los registrados en la Base de Datos de Eventos de Tormentas de la NOAA y la base de datos del Observatorio de Inundaciones de Dartmouth (DFO por sus siglas en inglés). Su análisis detectó tres veces más inundaciones que en la base de datos del DFO y se identificaron daños adicionales de $320 millones de dólares.

El equipo también amplió el análisis sobre el calor extremo. En muchos estudios previos sobre amenazas múltiples sólo se consideraron las olas de calor, donde las temperaturas superaron un percentil, como el 90 o el 95, durante tres días seguidos. Este estudio también consideró los periodos donde la temperatura de globo de bulbo húmedo (índice WBGT) supera un umbral de salud de 30°C, en lugar de un percentil determinado. Bajo esta definición, los científicos determinaron que, entre 2003 y 2020, Texas vivió 2,517 días con eventos peligrosos de calor, lo que equivale a casi el 40% de los días dentro de este periodo. Estos eventos afectaron un total de 253.2 millones de kilómetros cuadrados.

El estudio consideró como eventos de amenazas múltiples aquellos en los que coinciden inundaciones y episodios de calor extremo. Usando el método del intervalo de recurrencia promedio, junto con la definición más amplia de peligros, los investigadores encontraron que las zonas del estado con una alta concentración de poblaciones minoritarias estaban expuestas a un mayor riesgo ante este tipo de eventos multiriesgo. Esto sugiere que los métodos más antiguos pueden subestimar tanto la magnitud de los eventos de amenaza múltiple como el impacto desproporcionado en comunidades marginadas, de acuerdo con los investigadores. (AGU Advances, https://doi.org/10.1029/2025AV001667, 2025)

—Rebecca Owen (@beccapox.bsky.social), Escritora de ciencia

This translation by translator Oscar Uriel Soto was made possible by a partnership with Planeteando y GeoLatinas. Esta traducción fue posible gracias a una asociación con Planeteando and GeoLatinas.

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.

The Arctic is experiencing the most rapid climate change on Earth as average temperatures there rise up to 4 times faster than on the rest of the planet. Among the many environmental effects of this warming, the Arctic Ocean, critically, is moving toward a “blue” state, meaning it is increasingly becoming ice free during the summer months.

This shift raises significant concerns about the region’s future. Arctic Indigenous peoples, for instance, heavily rely on stable ice conditions for traditional hunting, fishing, and travel. As ice disappears, these activities become more dangerous or impossible, threatening food security, cultural practices, and the transmission of Traditional Knowledge. Global geopolitical and economic pressures will also rise as new shipping routes open, previously inaccessible resources become available for extraction, and international competition over these resources rises.

Currently, scientists struggle to predict how an ice-free Arctic will react to and amplify a warmer global climate.

Currently, however, scientists struggle to predict how an ice-free Arctic will react to and amplify a warmer global climate. The lack of clear climate projections for the region is largely due to a shortage of key geological data describing former climatic conditions and how the Arctic has responded to past changes, as well as to difficulties interpreting the records we do have. Making sense of these data is essential for understanding how the Arctic will evolve in the coming decades.

Deep-sea sediment cores provide some of the best available archives from the Arctic Ocean. These cores, drilled and collected from sites around the region, contain sediments deposited over hundreds of thousands of years that offer clues about past ocean temperatures, sea ice and ice sheets, and ocean circulation changes. To gain insights specifically into how the Arctic may respond to future warming—and the broader implications for the planet—scientists focus on past “greenhouse” states, when Earth’s climate was warmer than it is today, such as the Last Interglacial, about 130,000 years ago.

The German R/V Polarstern, shown here during an expedition into the central Arctic Ocean in 2015, has enabled the acquisition of numerous sediment cores that archive past Arctic climate changes. Credit: Alfred Wegener Institute/Mario Hoppmann, CC BY 4.0

However, reconstructing past warm climates from deep-sea core records is challenging, particularly because the chronology of Arctic Ocean sediments has been difficult to establish. The lack of biological remains and the dissolution of calcium carbonate in these sediments complicate efforts to determine their ages (i.e., their chronostratigraphy). Furthermore, the use of different dating methods and uncertainties about sedimentation rates have led to conflicting interpretations of core records and hindered the development of a solid timeline for Arctic climate history [e.g., Stein et al., 2025].

Recent advances in research have raised questions about the accuracy of prior published ages of Arctic Ocean sediments. These developments have also highlighted ongoing uncertainties and the need to understand the abilities and limitations of different dating tools. Without this understanding, it will be difficult to identify and detail past greenhouse climates with confidence, which in turn, will limit our ability to apply knowledge of these past conditions to inform climate models.

The Arctic Ocean Stratigraphic Toolbox

In fall 2024, more than 40 scientists gathered at the ArcSTRAT conference in Tromsø, Norway, to discuss the latest research and how available methods can best be used to develop a reliable chronostratigraphic framework, or age model, for Arctic sediments. Additional goals were to foster shared understanding of the region’s climate history and to improve our ability to provide accurate data to climate modelers.

A key challenge in studying Arctic paleoclimate is that oceanic sedimentation rates are typically low across the region.

A key challenge in studying Arctic paleoclimate is that oceanic sedimentation rates are typically low across the region. In fact, the central Arctic Ocean is one of the slowest accumulating marine sedimentary environments globally because of limited sediment sources and biological productivity, suppression of sediment transport by sea ice, and sediment trapping on broad circum-Arctic continental shelves.

The slow sediment accumulation results in thin sediment layers that can make it difficult to obtain clear chronological data. Dissolution of calcium carbonate from deposited sediments, which can occur where deep seawater is undersaturated with respect to the mineral, further reduces the possibility of finding datable microfossils in the sedimentary record.

In some areas, biostratigraphy (the distribution of ancient life in sedimentary rocks) and stable isotope geochronology (which compares ratios of nonradioactive isotopes of, e.g., carbon or oxygen) can be used to refine age models. In other areas, alternative methods are needed to provide age constraints. Such methods include magnetostratigraphy, which dates sediment layers by correlating their magnetism to the record of Earth’s magnetic field reversals; amino acid racemization, which measures the time-dependent breakdown of proteins in fossils too old for radiocarbon dating; luminescence dating, which measures radiation that builds up in materials as they age; and radionuclide dating.

Fig. 1. Age models of Arctic Ocean sediments can incorporate data from many analytical methods. The sediment core seen here (brown bands at far left) is from Lomonosov Ridge near the geographic North Pole. Photographs of the upper 4 meters of the core are shown beside microfossil (planktic foraminifera) abundance in blue and the concentration of the cosmogenically derived isotope beryllium-10 (10Be) in yellow [Spielhagen et al., 1997]. Increases in either parameter are commonly associated with past interglacials. The global benthic (deep-water) oxygen-18 curve (δ18O) shows the ratio of oxygen-18 to oxygen-16 over time [Lisiecki and Raymo, 2005], highlighting the timing of interglacial marine isotope stages (MIS; red numbers near bottom) over the past 1 million years. This curve is shown above the geomagnetic polarity timescale, which shows the most recent magnetic reversal—from the Matuyama epoch to the Brunhes epoch—at roughly 781,000 years ago. Two end member age models have been commonly applied in the past: a high sedimentation rate (SR) scenario and low sedimentation rate scenario. These models produce widely varying age estimates for the same sedimentary layer. Some of the key new data (in red) being used to evaluate the age model options come from advances in biostratigraphy (notably, the discovery of Pseudoemiliania lacunosa, a calcareous nanofossil that went extinct during MIS 12) [Razmjooei et al., 2023], radiometric dating of bulk sediments using the uranium decay series isotopes protactinium-231 (231Pa) and thorium-230 (230Th) [Hillaire-Marcel et al., 2017], and amino acid racemization measured in the fossilized shells of planktic and benthic foraminifera [West et al., 2023]. Click image for larger version.

Recent breakthroughs, particularly in applying radionuclide methods, have shown promise in improving the accuracy of Arctic Ocean sediment age models (Figure 1). For example, novel applications of uranium series isotopes (e.g., thorium-230 and protactinium-231) have been used to propose new age constraints for marine sediment sequences from important topographic regions, such as the Mendeleev-Alpha and Lomonosov Ridges, where low sedimentation and poor preservation of fossil material have hampered previous attempts to date these sequences [Hillaire-Marcel et al., 2017]. These isotopes decay predictably over time, allowing scientists to date past interglacial periods more confidently, including the Last Interglacial and others occurring around 200,000 years ago.

These new radionuclide-based age constraints are supported in part by recent applications of more traditional dating methods like biostratigraphy. Specifically, a newly revised Arctic sediment chronology for the late Pleistocene (400,000–10,000 years ago) established on the basis of analyses of calcareous nanoplankton, although not perfectly aligned, showed less uncertainty in the identification of interglacial periods in the central Arctic Ocean [Razmjooei et al., 2023]. Tracking changes in the concentration of cosmogenic radionuclides, like beryllium-10, in Arctic sediments has also provided new insights into the timing of interglacials [Spielhagen et al., 1997].

The Need for a Multimethod Approach

Some methods are better suited than others for studying sediments from given locations because environmental conditions across the Arctic differ.

The generally low sedimentation rates across the Arctic Ocean produce thin sediment layers that require precise sampling and, because not every dating method works well everywhere, careful selection of analytical methods. Some methods are better suited than others for studying sediments from given locations because environmental conditions across the Arctic differ, contributing to variable sedimentation rates, variable preservation of fossils, and disturbances like erosion and bioturbation (the reworking of sediment layers by living organisms).

Whereas relying on a single method to study sediments from across the Arctic Ocean may lead to inaccuracies and gaps in understanding, different methods can complement each other, providing a fuller, more robust picture of the past. Discussions during the ArcSTRAT conference highlighted the importance of using a multimethod approach, combining the various available stratigraphic and isotopic dating methods.

The challenge lies in carefully selecting appropriate methods to study cores from different regions to minimize errors and uncertainties and provide a reliable reconstruction of past Arctic environments. In areas where calcium carbonate is well preserved (e.g., topographic highs), for example, biostratigraphy and isotope geochronology are extremely useful. In areas where it is not (e.g., deep basins), litho- and magnetostratigraphy combined with radionuclide dating might be better options.

The past few decades have seen the development and application of a veritable toolbox of different techniques for dating Arctic Ocean sediments. These tools must now be integrated and applied to study newly collected sediment archives.

New Arctic Archives

Alongside methodological developments, new Arctic sediment cores have been retrieved recently, including during the International Ocean Discovery Program’s Expedition 403. In 2024, this campaign successfully drilled more than 5 kilometers of sediment cores from the Fram Strait west of Svalbard that offer a high-resolution record of past Arctic climates [Lucchi et al., 2024].

The scientific aim of this drilling was to better understand the ocean system and cryosphere during past warm intervals and how they relate to high insolation (exposure to sunlight) and atmospheric carbon dioxide levels. This information is essential for comprehending the climatic evolution of the Northern Hemisphere and the dynamics of ice sheets, sea ice, and ocean circulation. Data from these cores will be invaluable for studying the mechanisms that lead to ice-free Arctic summers and for understanding the effects of these conditions within and beyond the Arctic.

The Norwegian icebreaker R/V Kronprins Haakon sails in the Arctic Ocean. Credit: Dimitri Kalenitchenko, UiT The Arctic University of Norway

In 2025, the European Research Council’s (ERC) Synergy Grant–funded “Into The Blue” (i2B) Arctic expedition aboard R/V Kronprins Haakon will focus on recovering additional unique sediment archives from the central Arctic Ocean. The plan is to use a combination of classical and cutting-edge techniques to explore the Arctic’s climate history as completely as possible, matching the methods to the demands of each core. Together with stratigraphic methods, these techniques include analyses of molecular biomarkers, palynology (the study of preserved pollen grains and spores), ancient DNA, radionuclides, and stable isotopes to reconstruct past sea ice conditions, ocean heat transport, and cryosphere variability during warmer-than-present climate states such as the Last Interglacial.

A Promising Start to the Work Ahead

The ArcSTRAT conference made clear that the work ahead is challenging but promising. The outcomes and consensus about coordinating multimethod approaches will provide a crucial framework for analyzing new cores from the i2B expedition and, hopefully, additional future expeditions. The meeting also helped to establish a forum for continued collaboration and knowledge exchange among Arctic stratigraphy experts—an important step toward resolving continuing disparities among dating methods and developing a robust Arctic Ocean chronostratigraphy.

As the Arctic continues changing at an unprecedented rate and advancing toward blue summers, understanding its past is more critical than ever.

As the Arctic continues changing at an unprecedented rate and advancing toward blue summers, understanding its past is more critical than ever. By piecing together the climatic history of past greenhouse states, scientists are building the foundation for more accurate climate models, which are essential for informing accurate global climate assessments that, in turn, guide policy decisions in countries and communities around the world.

With ongoing advances in the toolbox of techniques for studying ocean sediment stratigraphy, as well as the collection of new sediment records, we will be better positioned to predict how the Arctic will respond to further warming and what the far-reaching consequences of this response will be.

Acknowledgments

We thank the participants in the 2024 ArcSTRAT conference in Tromsø, Norway, especially keynote speakers Ruediger Stein, Anne de Vernal, Renata Lucchi, Jutta Wollenburg, and Stijn De Schepper. The conference was funded by the Research Council of Norway, as well as by ERC through the Synergy Grant “i2B–Into The Blue” (grant 101118519).

References

Hillaire-Marcel, C., et al. (2017), A new chronology of late Quaternary sequences from the central Arctic Ocean based on “extinction ages” of their excesses in 231Pa and 230Th, Geochem. Geophys. Geosyst., 18(12), 4,573–4,585, https://doi.org/10.1002/2017GC007050.

Lisiecki, L. E., and M. E. Raymo (2005), A Pliocene‐Pleistocene stack of 57 globally distributed benthic δ18O records, Paleoceanography, 20(1), PA1003, https://doi.org/10.1029/2004PA001071.

Lucchi, R. G., et al. (2024), Expedition 403 preliminary report: Eastern Fram Strait paleo-archive, Int. Ocean Discovery Program, https://doi.org/10.14379/iodp.pr.403.2024.

Razmjooei, M. J., et al. (2023), Revision of the Quaternary calcareous nannofossil biochronology of Arctic Ocean sediments, Quat. Sci. Rev., 321, 108382, https://doi.org/10.1016/j.quascirev.2023.108382.

Spielhagen, R. F., et al. (1997), Arctic Ocean evidence for late Quaternary initiation of northern Eurasian ice sheets, Geology, 25(9), 783–786, https://doi.org/10.1130/0091-7613(1997)025%3C0783:AOEFLQ%3E2.3.CO;2.

Stein, R., et al. (2025), A 430 kyr record of ice-sheet dynamics and organic-carbon burial in the central Eurasian Arctic Ocean, Nat. Commun., 16, 3822, https://doi.org/10.1038/s41467-025-59112-7.

West, G., et al. (2023), Amino acid racemization in Neogloboquadrina pachyderma and Cibicidoides wuellerstorfi from the Arctic Ocean and its implications for age models, Geochronology, 5(1), 285–299, https://doi.org/10.5194/gchron-5-285-2023.

Author Information

Jochen Knies (Jochen.Knies@uit.no), UiT The Arctic University of Norway, Tromsø; Matt O’Regan, Stockholm University, Sweden; and Claude Hillaire Marcel, Université du Québec à Montréal, Montreal, Canada

Citation: Knies, J., M. O’Regan, and C. H. Marcel (2025), Finding consensus on Arctic Ocean climate history, Eos, 106, https://doi.org/10.1029/2025EO250230. Published on 25 June 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
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