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SummaryRevil asserted in the comment that none of Macnae’s paper is novel. The paper however introduced a novel method of chargeability prediction as the fraction of pores blocked by metallic particles rather than the prediction using limiting Maxwell effective medium estimates based on volume fractions. This reply presents an analysis of two cases where the novel chargeability prediction proves to be significantly better than earlier methods when applied to laboratory pyrite-clay mixtures and to published petrophysical data from a Co-Cu disseminated mineral deposit. Another item of novelty in the paper was emphasis that the resistivity and conductivity time-constants can differ by orders of magnitude for the high chargeabilities of economic sulphide deposits, a fact not commonly recognised in the literature. Revil asserts in the comment that the term Induced Polarization (IP) should explicitly exclude dielectric effects and analogies as discussed in the paper, an assertion inconsistent with the early literature on IP and the fact that both diffusive and dielectric effects can affect low-frequency data. The reply provides detail on the physical nature of equivalent circuits, and how they can mechanistically model the IP phenomenon and the topology of conductive paths in materials, an issue that I did not emphasize in the paper as I thought it would have been obvious to most readers.

SummaryVolcanic and geothermal areas usually feature highly rugged and variable topography, with both steep and relatively flat areas. Potential field geophysical data being very sensitive to topographic changes, it can be challenging to accurately simulate data in such regions. Traditional modeling approaches for potential field data typically involve discretizing the physical space using rectangular prisms, or alternatively using slightly more sophisticated geometries such as polyhedrons. However, in both cases, these discretizations may lead to an under- or over- estimation of topographic effect on simulated data, unless a very fine discretization around observation points is used, consequently leading to an increase in the computational burden. To address this issue, we introduce new methodological strategies to simulate potential field data in regions with rugged topography. We propose the use of a numerical integration scheme over deformable hexahedral elements that conform to topographic variations, to numerically evaluate the integral equations governing gravity and magnetic anomalies. Density and magnetization properties are defined at grid nodes and interpolated within the elements using polynomial functions. The numerical integration relies on the use of a Gaussian quadrature, combined with a local refinement of the mesh designed to simultaneously increase the precision of the numerical integrals by reducing the effect of singularities and incorporating a more precise description of the topography at the vicinity of measurement points. This refinement is coupled with a discontinuous optimization of the elevation of geometrical nodes lying at the surface of the model by minimizing the distance between the interpolated topographic surface and a point cloud provided by a high-resolution Digital Elevation Model (DEM). The predictions at each observation points are computed with different refined versions of the mesh in order to minimize computational cost. Physical properties within the refined elements are extrapolated from the nodes of the original non-refined mesh in order not to introduce additional unknown physical parameters for the later implementation of this code for the inversion of the potential field data. The approach is first validated by comparing gravity and magnetic predictions with the analytical solution for a simple rectangular prism. We further test the method with realistic simulations using the complex topography of the Krafla geothermal area in northern Iceland. Simulation results are compared against the forward gravity and magnetic responses of a high-resolution benchmark model (discretized with 2 m × 2 m rectangular prisms) computed using the open-source software Tomofast-x (Ogarko et al. 2024). Finally, we use the same high-resolution model to quantify typical errors associated with coarser rectangular prism discretizations (cell sizes of 25 m, 50 m, and 100 m). We demonstrate that these errors can be comparable in magnitude to real geophysical anomalies and are not reproduced when using our proposed numerical approach.

The circumglobal teleconnection pattern (CGT) is a key mode of atmospheric variability during boreal summer, identified by an upper-tropospheric wave train propagating along the subtropical jet. CGT is one of the critical drivers of Northern Hemisphere mid-latitude heat waves. However, how the structure of CGT responds to global warming and its effect on future heat wave characteristics remains inconclusive.

Earth system box models are essential tools for reconstructing long-term climatic and environmental evolution and uncovering Earth system mechanisms. To overcome the spatiotemporal resolution limitations of current deep-time models, a research team has developed CESM-SCION, a new-generation high-resolution climate-biogeochemistry coupled model. This model advances the spatiotemporal resolution of long-term Earth system simulations to a new level and identifies marine regression as a key driver of the Late Paleozoic Ice Age onset.

Publication date: Available online 2 January 2026

Source: Advances in Space Research

Author(s): Eman Albalawi

Publication date: Available online 2 January 2026

Source: Advances in Space Research

Author(s): Anh Ngoc Thi Do, Tuyet Anh Thi Do

Publication date: 1 January 2026

Source: Advances in Space Research, Volume 77, Issue 1

Author(s): Huseyin Er, Aykut Ozdonmez, M. Emir Kenger, Murat Tekkesinoglu, Ergun Ege

Publication date: 1 January 2026

Source: Advances in Space Research, Volume 77, Issue 1

Author(s): Shuaipeng Wang, Keke Xu, Mosi Zhang

Publication date: 1 January 2026

Source: Advances in Space Research, Volume 77, Issue 1

Author(s): R. Jayakrishnan, C.K. Fazil, L.Rahul Dev, A. Ajesh

Publication date: 1 January 2026

Source: Advances in Space Research, Volume 77, Issue 1

Author(s): Devin Huyghebaert, Juha Vierinen, Johan Kero, Ingrid Mann, Ralph Latteck, Daniel Kastinen, Sara Våden, Jorge L. Chau

Publication date: 1 January 2026

Source: Advances in Space Research, Volume 77, Issue 1

Author(s): Huseyin Er, Aykut Ozdonmez, M. Emir Kenger, B. Batuhan Gürbulak, Ilham Nasiroglu

The Atlantic Meridional Overturning Circulation (AMOC) is the system of currents responsible for shuttling warm water northward and colder, denser water to the south. This "conveyor belt" process helps redistribute heat, nutrients, and carbon around the planet.

The mid-ocean ridge runs through the oceans like a suture. Where Earth's plates move apart, new oceanic crust is continuously formed. This is often accompanied by magmatism and hydrothermal activity. Seawater seeps into the subsurface, is heated to temperatures above 400°C, and rises again to the ocean floor.

The Huíla plateau, bounded by dramatic cliffs and chasms, stands above the arid coastal plains in the country's southwest.

Source: Global Biogeochemical Cycles

The Atlantic Meridional Overturning Circulation (AMOC) is the system of currents responsible for shuttling warm water northward and colder, denser water to the south. This “conveyor belt” process helps redistribute heat, nutrients, and carbon around the planet.

During the last ice age, occurring from about 120,000 to 11,500 years ago, millennial-scale disruptions to AMOC correlated with shifts in temperature, atmospheric carbon dioxide (CO2), and carbon cycling in the ocean—as well as changes in the signatures of carbon isotopes in both the atmosphere and the ocean. At the end of the last ice age, a mass melting of glaciers caused an influx of cold meltwater to flood the northern Atlantic, which may have caused AMOC to weaken or collapse entirely.

Today, as the climate warms, AMOC may be weakening again. However, the links between AMOC, carbon levels, and isotopic variations are still not yet well understood. New modeling efforts in a pair of studies by Schmittner and Schmittner and Boling simulate an AMOC collapse to learn how ocean carbon storage, isotopic signatures, and carbon cycling could change during this process.

Both studies used the Oregon State University version of the University of Victoria climate model (OSU-UVic) to simulate carbon sources and transformations in the ocean and atmosphere under glacial and preindustrial states. Then, the researchers applied a new method to the simulation that breaks down the results more precisely. It separates dissolved inorganic carbon isotopes into preformed versus regenerated components. In addition, it distinguishes isotopic changes that come from physical sources, such as ocean circulation and temperature, from those stemming from biological sources, such as plankton photosynthesis.

Results from both model simulations suggest that an AMOC collapse would redistribute carbon throughout the oceans, as well as in the atmosphere and on land.

In the first study, for the first several hundred years of the model simulation, atmospheric carbon isotopes increased. Around year 500, they dropped sharply, with ocean processes driving the initial rise and land carbon controlling the decline. The decline is especially prominent in the North Atlantic in both glacial and preindustrial scenarios and is driven by remineralized organic matter and preformed carbon isotopes. In the Pacific, Indian, and Southern Oceans, there was a small increase in carbon isotopes.

In the second study, model output showed dissolved inorganic carbon increasing then decreasing, causing the inverse changes in atmospheric CO2. In the first thousand years of the model simulation, this increase in dissolved inorganic carbon can be partially explained by the accumulation of respired carbon in the Atlantic. The subsequent drop until year 4,000 is primarily driven by a decrease in preformed carbon in other ocean basins. (Global Biogeochemical Cycles, https://doi.org/10.1029/2025GB008527 and https://doi.org/10.1029/2025GB008526, 2025).

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

Citation: Owen, R. (2026), What could happen to the ocean’s carbon if AMOC collapses, Eos, 107, https://doi.org/10.1029/2026EO260016. Published on 6 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.

When it rains, it pours. And that's good news for California's water supply.

SummaryThe amplitude of the ${{P}_s}$ phase relative to the direct P wave (i.e., the ${{P}_s}/P$ ratio) provides valuable information about the contrasts across the crust-mantle boundary. Understanding how these amplitudes respond to variations in subsurface parameters improve interpretation of lithospheric structures. We examined the sensitivity of eight key parameters, including compressional and shear wave velocities, lower crustal and upper mantle densities, ray parameter, and Moho depth, to receiver function (RF) amplitudes and ${{P}_s}/P$ ratios. Using the synthetic RF (synRF) code of Ammon et al. (1990), we applied a Monte Carlo approach to generate randomized parameter sets, incorporated random noise, and tested both sharp and gradational Moho structures. The results show that lower crustal shear velocity has the strongest influence on all RF amplitudes and ${{P}_s}/P$ ratios, while lower crustal ${{V}_p}$, density, and upper mantle ${{V}_s}$ have moderate effects, and upper mantel ${{V}_p}$ and density show weaker sensitivity. In both sharp and gradational models, lower crustal and upper mantle shear velocities largely control the ${{P}_s}/P$ ratio. Theoretical ${{P}_s}/P$ ratios exhibit higher correlation with observed RFs than synthetic ones. Compared with the Shen & Ritzwoller (2016) model, our analysis yields ∼10% lower uncertainties in lower crustal ${{V}_s}$ and smaller uncertainties in lower crustal density derived from ${{P}_s}/P$ ratios, with consistent results in complex regions such as the northern Rocky Mountains. This study establishes the first quantitative framework linking ${{P}_s}/P$ ratio variability to lower crustal velocity and density while explicitly quantifying parameter sensitivity and uncertainties, clarifying how Moho sharpness and noise affect amplitude stability.

SummaryMacnae (2025) presented a physical interpretation of the Cole Cole Complex Conductivity model in the case of porous materials with sulphides. According to his paper, the Cole Cole parameters determined from such model can be easily interpreted in terms of underlying physics. His model is partly based on the electrochemical polarization model of Wong (1979) to explain the relationship between the chargeability and the volumetric content of sulfide. None of the statements made by Macnae (2025) are however novel. That said, we agree with Macnae (2025) that the Cole Cole complex resistivity relaxation time is quite useless in deciphering the underlying physics of the induced polarization problem.

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.

Today, top appropriators in the U.S. Senate and House of Representatives released a three-bill appropriations package for fiscal year 2026 (FY26) that largely rejects drastic cuts to federal science budgets that President Trump proposed last year. The “minibus” package, negotiated and agreed upon by both political parties, outlines a budget that preserves most, but not all, funding for key science programs related to space, weather, climate, energy, and the environment across multiple agencies.

“This is a fiscally responsible package that restrains spending while providing essential federal investments that will improve water infrastructure in our country, enhance our nation’s energy and national security, and spur scientific research necessary to maintain U.S. competitiveness,” Susan Collins (R–ME), chair of the Senate Appropriations Committee, said in a statement.

In May 2025, President Trump released a budget request to Congress that proposed slashing billions of dollars in federal science funding. However, during the many rounds of meetings throughout the year, appropriators in both chambers and on both sides of the aisle seemed disinclined to follow the proposed budget, including when it came to funding for climate research, clean energy initiatives, environmental protections, and other topics that run counter to administration priorities.

 
Related

•  Dig into the details: Three Bill Package
•  Statement and Summaries from the Majority (GOP)
• Statement and Summaries from the Minority (Democrats)
•  Review the President’s Budget Request
•  Get Involved: AGU Science Policy Action Center
 

This new three-bill package follows suit in rejecting many of the president’s more drastic cuts to science programs.

“This package rejects President Trump’s push to let our competitors do laps around us by slashing federal funding for scientific research by upwards of 50% and killing thousands of good jobs in the process,” Vice Chair Senator Patty Murray (D–WA) said in a statement. “It protects essential funding for our public lands, rejects steep proposed cuts to public safety grants that keep our communities safe, and boosts funding for key flood mitigation projects.”

Here’s how some Earth and space science agencies fare in this package:

• Department of Energy (DOE) Non-Defense: $16.78 billion, including $8.4 billion for its Office of Science, $3.1 billion for energy efficiency and renewable energy programs, and $190 million for protecting the nation’s energy grids.
• Environmental Protection Agency (EPA): $8.82 billion, preserving funding to state-level programs that protect access to clean water, drinking water, and air. The bill also retains funding for the Energy Star energy efficiency labelling program and increases funding to state and Tribal assistance grant programs.
• NASA: $24.44 billion, including $7.25 for its science mission directorate, which would have seen a 47% decrease under the President’s budget request. The bills maintain funding for 55 missions that would have been cut, as well as for STEM engagement efforts and Earth science research that similarly would’ve been cut. It also increases spending for human exploration.
• National Institute of Standards and Technology (NIST): $1.847 billion, including funds to advance research into carbon dioxide removal.
• National Oceanic and Atmospheric Administration (NOAA): $6.171 billion, including $1.46 billion to the National Weather Service to improve forecasting abilities and boost staffing. The budget also earmarks funds to preserve weather and climate satellites, and maintain climate and coastal research.
• National Park Service (NPS): $3.27 billion, with enough money to sustain FY24 staffing levels at national parks.
• National Science Foundation (NSF): $8.75 billion, including $7.18 billion for research-related activities. That would support nearly 10,000 new awards and more than 250,000 scientists, technicians, teachers, and students.
• U.S. Forest Service (USFS): $6.13 billion, with just under half of that put toward wildfire prevention and management. Funded programs not related to wildfire prevention include forest restoration, forest health management, hazardous fuels reduction, and repurposing unnecessary roads as trails.
• U.S. Geological Survey (USGS): $1.42 billion, including money to maintain active satellites and topographical mapping programs.

This is the latest, but not the last, step in finalizing science funding for FY26. The bills now head out of committee to be voted upon by the full chambers of the Senate and House, reconciled between chambers, and then signed by the president.

—Kimberly M. S. Cartier (@astrokimcartier.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 © 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.

When we think of global warming, what first comes to mind is the air: crushing heat waves that are felt rather than seen, except through the haziness of humid air. But when it comes to melting ice sheets, rising ocean temperatures may play more of a role—with the worst effects experienced on the other side of the globe.