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In lush South Florida, trees and bushes grow all year round. And that means yard waste and dead trees never stop piling up. But leaving them in a landfill is a climate-warming issue. Two South Florida governments think they have a new solution—light it on fire, but in a planet-friendly way.

SummaryWe have analyzed direct S-waves of teleseismic earthquakes to investigate seismic anisotropy parameters, i.e., fast polarisation direction (FPD or φ) and splitting time delay (STD or δt) beneath southwestern Tibet (around the Karakoram Fault), that enable us to comprehend the upper mantle dynamics of the study region. To achieve this aim, we employ the Reference Station Technique, which is proven to be insensitive to source-side anisotropy; hence, it permits the use of teleseismic direct S-wave signals in splitting measurements. A total of 1,624 high-quality direct S-wave splitting measurements were obtained from 145 earthquakes (M ≥5.5) within an epicentral distance of 30○ to 90○, recorded at 31 temporarily deployed seismic stations of the Y2 network. We have found STDs ranging from 1.1 s to 1.8 s, indicating a significantly anisotropic upper mantle underneath the study region. Our splitting measurements reveal predominantly E-W FPDs in the western part of the study region, with a slight shift to the ENE-WSW direction in the eastern section. A comparison of our direct S-wave derived splitting measurements with prior SKS splitting measurements indicates a largely analogous pattern at most seismic stations. The seismic stations (WT04, WT05, WT11, and WT18), which previously lacked SKS-derived seismic anisotropy, are now complemented with new measurements with clear anisotropic signatures. Nearly E-W oriented FPDs that exhibit an oblique variation to the main strike of the southeastern segment of the Karakoram Fault (KKF) can be explained by the eastward movement of upper mantle material beneath southwestern Tibet. The significant discrepancies between the orientation of FPDs and the strike direction of KKF imply that the fault is not a lithospheric-scale fault but rather is confined to crustal depths. Integrating surface deformation derived from geodetic measurements (e.g., global positioning system data) and plate motion vectors of the Indian and Eurasian plates with splitting parameters indicates that the deduced deformation patterns result from both lithospheric deformation and sub-lithospheric mantle dynamics. The FPDs exhibit a significant deviation from GPS data, signifying a decoupling of crust and upper mantle materials beneath the study area. This suggests that mantle deformation in southwestern Tibet operates in a manner that is distinct from that of crustal deformation. Finally, our novel splitting measurements, enhanced by a greater number of direct S-wave data, provide new insights into the deformation of the upper mantle in the region, elucidating the mechanisms that have shaped the plateau over geologic millennia.

SummaryNormal modes or whole Earth oscillations serve as vital tools in the investigation of the Earth and other planets, providing large-scale seismic constrains on their globally averaged interior structure. Recently, Lognonné et al., 2023b reported their detection on Mars for the largest recorded event S1222a. However, the low signal-to-noise ratio in the normal mode frequency domain makes detection of normal modes very difficult, necessitating comprehensive data processing to extract the normal mode frequencies including deglitching, phase cross correlation, multi-tapering and phasor-walkout techniques. Here, we show that normal mode spectra for event S1222a depend on the details of deglitching technique, producing different results using either instrument response deconvolution (MPS) (Scholz et al., 2020) or the novel time-frequency polarization filtering (Brinkman et al., 2023). Furthermore, the plethora of Martian seismic models published since the InSight mission also generate strongly varying synthetic spectra, which complicates the identification of individual modes. Here, we developed a different approach in which we use spectra for the S1222a event and data for the seismically ‘quiet’ day prior to the event. We compare these observed spectra to synthetic spectra for existing seismic models for Mars in order to verify the detection of normal modes and identify models which best fit the spectra. Our research incorporates a range of different filtering and deglitching sequences and eleven post-InSight Martian seismic model families to assess their effects on both observed and synthetic spectra. We find that, the synthetic spectra consistently yield more overlapping peaks with the S1222a data spectra, than with spectra from the quiet day before S1222a. Through overlap analysis, we identify a preferred crustal structure, with an average Vs of 3.25 km/s, that aligns well with current geophysical and seismic estimates of the global Martian crust. We also find that the detection of normal modes is improved by stacking the data of S1222a with the two additional events S1000a and S1094b. On the other hand, stacking of all available long period seismic data of InSight to detect the continuous activation of normal modes by Martian atmosphere proved less effective. Nevertheless, we find consistent spectral peaks across the various data sets and stacking methods. These findings indicate that normal modes are detectable on Mars. It highlights the need for future deployment of seismometers on Mars, the moon and other planets to continue the hunt for normal modes and improve our understanding of the internal structure of terrestrial planets and moons.

SummaryAzimuthal anisotropy of the upper mantle, resolved from seismic records, sheds light on the characteristics of lithospheric deformation and asthenosphere flow. However, our understanding of the three-dimensional structures of P-wave azimuthal anisotropy in the upper mantle remains limited, due to the lack of accurate and high-resolution tomography methods. Motivated by this necessity, we present a novel full-wave inversion method to simultaneously retrieve the three-dimensional structures of P-wave velocity and azimuthal anisotropy of the upper mantle. The inversion is parameterized by imposing five elastic coefficients representing Pn-wave azimuthal anisotropy on the isotropic elastic tensor based on the weak anisotropy assumption. We verify the accuracy of the full-wave sensitivity kernels of Pn waveform cross-correlation delay times to the azimuthal anisotropic coefficients. Synthetic inversions demonstrate that our method effectively resolves the anomalies of both P-wave velocity and azimuthal anisotropy including 2ψ and 4ψ terms. Moreover, we analyze the model resolution and tradeoffs using the Hessian-vector product efficiently computed by the Scattering-Integral method. This study provides a novel and powerful physics-based tool to reveal accurate and high-resolution three-dimensional structures of azimuthal anisotropy in the upper mantle, which will facilitate our understanding of the modes of lithospheric deformation and mantle convection.

Water is everywhere, from the snowpack in the mountains to the tap in our kitchens. But while we often think about rainfall and snow as the main drivers of our water supply, it turns out that something we rarely see has just as much influence: the underground structure of the landscape itself.

Accurate measurements of surface currents are crucial for coastal monitoring, rip current detection, and predicting the path of pollutants. Several methods exist to measure surface currents, some of which are costly and time-consuming. In a recent paper, researchers from Texas A&M University have compared three methods for measuring surface currents over large areas, identifying an ideal method that uses drones and wave-based current mapping.

Even as global warming causes sea levels to rise worldwide, sea levels around Greenland will likely drop, according to a new paper published in Nature Communications. "The Greenland coastline is going to experience quite a different outcome," says lead author Lauren Lewright, a Ph.D. student in geophysics working at the Lamont-Doherty Earth Observatory, which is part of the Columbia Climate School. "Sea level in Greenland is actually projected to fall."

A severe winter storm that brought crippling freezing rain, sleet and snow to a large part of the U.S. in late January 2026 left a mess in states from New Mexico to New England. Hundreds of thousands of people lost power across the South as ice pulled down tree branches and power lines, more than a foot of snow fell in parts of the Midwest and Northeast, and many states faced bitter cold that was expected to linger for days.

Gold is generally associated with pyrite (iron disulfide, FeS2), and pyrite-induced gold precipitation is critical to the formation of high-grade gold deposits. However, the role of pyrite in precipitating gold from fluids has not been well understood. Now, using in situ liquid-phase transmission electron microscopy under conditions that excluded the influence of dissolved oxygen and electron beams, scientists have achieved the first nanoscale, real-time observation of the reaction between pyrite and gold-bearing solutions, providing critical insights into gold enrichment by pyrite.

An interdisciplinary study confirms, for the first time, the oceanographic pathways that transport floating macroalgae from the coastal waters of Southwest Greenland to deep-sea carbon reservoirs, potentially playing a previously underappreciated role in global carbon storage. The work is published in the journal Science of The Total Environment.

At UC Berkeley's Central Sierra Snow Laboratory, located at 6,894 feet above sea level near Donner Pass, researchers collect detailed measurements of the snowpack each day. There is still some snow on the ground to measure, but less than they usually see in late January.

It’s not easy to determine how much water there is across a landscape. A measly 1% of Earth’s freshwater is on the surface, where it can be seen and measured with relative ease. But beneath that, measurements vary massively depending on water table depth and ground porosity we can’t directly see.

“We’re operating in a situation where we don’t know how much is going into the savings account every month, and we don’t know how much is in our savings account.”

Reed Maxwell, a hydrologist at Princeton University, likes to think of rainfall, snow, and surface water as a checking account used for short-term water management needs and groundwater as a savings account, where a larger sum should, ideally, be building up over time.

“We’re operating in a situation where we don’t know how much is going into the savings account every month, and we don’t know how much is in our savings account,” he said.

But a new groundwater map by Maxwell and colleagues offers the highest-resolution estimate so far of the amount of groundwater in the contiguous United States: about 306,500 cubic kilometers. That’s 13 times the volume of all the Great Lakes combined, almost 7 times the amount of water discharged by all rivers on Earth in a year. This estimate, made at 30-meter resolution, includes all groundwater to a depth of 392 meters, the deepest for which reliable porosity data exist. Previous estimates using similar constraints have ranged from 159,000 to 570,000 cubic kilometers.

“It’s definitely a move forward from some of the previous [mapping] efforts,” said Grant Ferguson, a hydrogeologist at the University of Saskatchewan who was not involved in the research. “They’re looking at much better resolution than we have in the past and using some interesting techniques.”

Well, Well, Well

Past estimations of groundwater quantity have been based largely on well observations.

“That’s the really crazy thing about groundwater in general,” said Laura Condon, a hydrologist at the University of Arizona and a coauthor of the paper. “We have these pinpricks into the subsurface where there’s a well, they take a measurement of how deep down the water table depth is, and that’s what we have to work with.”

But not all wells are measured regularly. For obvious reasons, there tend to be more wells in places where more groundwater is present, making data on areas with less groundwater scarcer. And a well represents just one point, whereas water table depth can vary greatly over short distances.

Researchers have used these data points, as well as knowledge of the physics of how water flows underground, to model water table depth at a resolution of about 1 kilometer. They’ve also used satellite data to capture large-scale trends in water movement. But those data are of lower resolution: Data from NASA’s GRACE (Gravity Recovery and Climate Experiment) Tellus mission, for instance, have a resolution of about 300 kilometers, about 10,000 times coarser than the new map.

To demonstrate the value of high-resolution data, the team showed what happened when they decreased the resolution of their entire map from 30 meters to 100 kilometers—the spatial resolution of many global hydrologic models. The resulting more pixelated map estimated just above 252,000 cubic kilometers of water, an underestimation of 18% compared to the new map.

In addition to identifying groundwater quantities at high resolution, the new map reveals more nuanced information about known groundwater sources.

For instance, it shows that about 40% of the land in the contiguous United States has a water table depth shallower than 10 meters. “That 10-meter range is that range where you can have groundwater–plant–land surface interactions,” Condon said. “And so that’s just really pointing to how connected those systems are.”

Bias for Good

The new work used direct well measurements as well as satellite data—about a million measurements, made between 1895 and 2023—along with maps of precipitation, temperature, hydraulic conductivity, soil texture, elevation, and distance of streams. Then, the scientists used the data to train a machine learning model.

In addition to its being able to quickly sort through so many data points, Maxwell noted another benefit of the machine learning approach that might sound unexpected: its bias. Early groundwater estimates were relatively simplistic, not accounting for either hydrogeology or the fact that humans themselves pump water out of the ground. The team’s machine learning approach was able to incorporate that information because evidence of groundwater pumping was present in the data used to train it.

“When you hear about bias in machine learning all the time, it’s usually in a negative connotation, right?” Maxwell said. “As it turns out, when you can’t disentangle the signal of groundwater pumping and groundwater depletion from the almost 1 million observations that we used to train this machine learning approach, it implicitly learned that bias.… It’s learned the pumping signals, it’s learned the human depletion signal.”

“Wherever you’re standing, dig down, and there’s water down there somewhere.”

Maxwell and the other researchers hope the map can be a resource for regional water management decisionmakers, as well as for farmers making decisions about irrigation. Condon added that she hopes it raises awareness of groundwater in general.

“Groundwater is literally everywhere all the time,” she said. The map is “filled in everywhere, wherever you are. Some places it’s 300 meters deep, some places it’s 1 meter deep. But wherever you’re standing, dig down, and there’s water down there somewhere.”

—Emily Gardner (@emfurd.bsky.social), Associate Editor

Citation: Gardner, E. (2026), Report: 13 Great Lakes’ worth of water underlies the contiguous United States, Eos, 107, https://doi.org/10.1029/2026EO260036. Published on 26 January 2026. Text © 2026. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

An experiment in western China over the past four decades shows that it is possible to tame the expansion of desert lands with greenery, and, in the process, pull excess carbon dioxide out of the sky.

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

A crucial source of freshwater, groundwater is vulnerable to contamination and overuse. Knowing how long groundwater has been under ground is critical for sustainable management of this resource. The Carbon-14 (14C) and Argon-39 (39Ar) isotopes are environmental tracers especially suited for dating groundwater aged between 50 and 30,000 years. However, ages obtained from previous analyses of these two tracers disagreed with each other.

Musy et al. [2025] use a quantitative framework to understand the effect of groundwater flow within the Earth’s subsurface on the age calculated from 14C and 39Ar measured in aquifers in Denmark. Reactions that affect 14C, the production of 39Ar in the subsurface, and the existence of slow and fast paths for groundwater flow, such as in fractured aquifers, explain the differences observed between age estimates. Accounting for these processes leads to more accurate estimate of groundwater residence times and supports better water resource management.

Citation: Musy, S. L., Hinsby, K., Wachs, D., Sültenfuss, J., Troldborg, L., Aeschbach, W., et al. (2025). Bridging the 39Ar–14C groundwater dating gap: A dual-permeability transport perspective based on numerical modeling and field data. Water Resources Research, 61, e2025WR040370. https://doi.org/10.1029/2025WR040370

—Sergi Molins, Associate Editor, Water Resources Research

Text © 2026. 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.

Stronger El Niño events are more likely when springtime surface waters in the western Pacific Ocean become unusually salty, a new study in Geophysical Research Letters suggests. Traditionally, scientists have focused on temperature and wind patterns to understand El Niño—periodic shifts in the tropical Pacific between warmer and cooler conditions that influence weather patterns across the globe. But researchers now show that subtle variations in ocean salinity north of the equator during boreal spring (March to May) can substantially amplify El Niño's strength and nearly double the odds of an extreme event.

This month, AFP reported from OceanXplorer, a high-tech marine research vessel owned by billionaire-backed nonprofit OceanX, as it studied seamounts off Indonesia.

A dome-fronted submersible sinks beneath the waves off Indonesia, heading down nearly 1,000 meters in search of new species, plastic-eating microbes and compounds that could one day make medicines.

A new study of climate extremes since 1988 finds that many regions have seen increases in deaths due to floods, storms and extreme temperatures. In human terms, the harm comes not just from deaths, but also from lost labor and property damage. (And this doesn't consider damage to species and ecosystems.) A new look at trends and outliers has been published in Geophysical Research Letters.

Publication date: Available online 21 January 2026

Source: Advances in Space Research

Author(s): Fabienne Seibert, Jan Thimo Grundmann, Matteo Ceriotti, Bernd Dachwald

The atmosphere is an important transport medium that carries microplastics to even the most remote parts of the world. These microplastics can be inhaled and pose a health risk to humans and animals. They can also settle out of the atmosphere and contaminate oceans and soils worldwide.