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Geophysical Quantification of Water Phases: Influence of Surface Conductivity and Temperature Modelling

Geophysical Journal International - Fri, 01/23/2026 - 00:00

SummaryThe quantification of frozen and unfrozen water content in porous media is essential for understanding hydrological, thermal, and mechanical processes in cold regions. Petrophysical joint inversion (PJI) frameworks that integrate seismic and electrical data offer promising tools for resolving water and ice distributions but are often limited by simplified petrophysical models. Here, we extend a PJI framework by incorporating a temperature-dependent relationship that accounts for both electrolytic and surface conduction. Using synthetic data, we show that this formulation improves modelling of frequency-dependent resistivity and enhances estimates of water content and interfacial conductivity quantified by cation exchange capacity. Our results highlight the critical role of temperature in controlling subsurface electrical properties and demonstrate that neglecting these effects can lead to substantial errors in the ice and water estimates. The extended PJI framework provides a physically consistent basis for geophysical imaging of water phase dynamics in partially frozen systems, with broad applicability to cold-region hydrology and seasonally or perennially frozen environments.

Numerical wavefield simulations with instantaneous time mirror in a 3D elastic medium

Geophysical Journal International - Fri, 01/23/2026 - 00:00

SummaryWe simulate an instantaneous time mirror (ITM), i.e., a rapid short duration change in elastic material properties, using numerical experiments in time-varying isotropic elastic media. Our implementation in the seismic wave propagation software SeisSol is based on high-order discontinuous Galerkin discretization with ADER time stepping. We develop an eigenvector-based analytical solution for time interfaces for general linear hyperbolic wave systems and apply it to analyze the energy balance at time boundaries and ITMs. The energy increases for all intermittent medium changes for all impedance scaling factors. Our numerical implementation is validated against these analytical solutions and achieves high-order convergence. Its accuracy is further corroborated by estimates of reflection and transmission coefficients and observed frequency shifts across time boundaries, and by acoustic wave speed estimates obtained from focal spots associated with ITM-generated converging P waves that are consistent with theoretical predictions and ground truth values, respectively. We use the ITM implementation to simulate the partitioning of seismic body waves excited by a point source in a spatially homogeneous elastic full space. The response to an intermittent short change in the elastic parameters yields a diverging and converging P and S wavefield. A systematic scaling of the elastic parameters is then used to steer independent ITM reflections of either P or S waves. Numerical ITM solutions as developed here can be used to synthesize converging wavefields in seismic imaging applications, and more generally to analyze the behavior and manipulation of seismic wavefields in space-time varying media.

New analysis disputes historic earthquake, tsunami and death toll on Greek island

Phys.org: Earth science - Thu, 01/22/2026 - 22:30

For decades, researchers thought that an October 1843 earthquake on the small Greek island of Chalke caused a powerful tsunami and led to the deaths of as many as 600 people. But a new analysis of primary accounts of the event by Ioanna Triantafyllou at Hellenic Mediterranean University suggests the truth was much less dramatic and destructive.

Amplifying feedbacks could drive Greenland ice sheet to near-complete disappearance

Phys.org: Earth science - Thu, 01/22/2026 - 21:10

Greenland, which has been prominently in the news in recent days, hosts a vast ice sheet. If it melts, it will become one of the largest contributors to global sea-level rise. Under a high-emissions scenario, the Greenland Ice Sheet is expected to largely disappear over time, with far-reaching consequences. This is the conclusion of a new study by Chloë Paice and colleagues, published in The Cryosphere. The Greenland Ice Sheet contains enough ice to raise global sea levels by approximately 7.4 meters and has been losing mass at an accelerating rate since the 1990s. Roughly half of this loss is due to surface melt, while the other half results from ice calving where the ice sheet meets the ocean.

Arctic cloud and ice formation affected by Russian river runoff as region studied for first time

Phys.org: Earth science - Thu, 01/22/2026 - 19:54

Organic matter carried in rivers to the Russian part of the Arctic Ocean may be creating more clouds and keeping the region cooler, a new study has found.

Coastal Coralline Algae Naturally Survive Persistent, Extreme Low pH

EOS - Thu, 01/22/2026 - 19:11

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

Ocean acidification is known to have major impacts on marine habitats under projected climate change. How vulnerable marine organisms in these habitats are to acidification largely depends on the variability of environmental conditions, such as pH, they experience naturally.

Burdett et al. [2025] provide precious time-series evidence that, unlike the open ocean, coastal ecosystems experience high natural environmental variability. For about two thirds of the year, the monitored coastal coralline algae reef was exposed to pH levels as low as those expected for the year 2100 under IPCC projections. The pH levels varied considerably throughout the day and between seasons, associated with biological activity, tidal cycling, and water temperature. Long‐term exposure to such low pH conditions and high variability may help coralline algal communities to adapt to future acidification, providing a level of optimism for the survival of this globally distributed biodiverse habitat.

Citation: Burdett, H. L., Mao, J., Foster, G. L., & Kamenos, N. A. (2025). Persistence of extreme low pH in a coralline algae habitat. Journal of Geophysical Research: Biogeosciences, 130, e2025JG009062. https://doi.org/10.1029/2025JG009062

—Xiaojuan Feng, Associate Editor, JGR: Biogeosciences

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