AGU Advances最新文献

Carbon dioxide (CO₂) removal (carbon dioxide removal (CDR)) that combines decreased greenhouse gas emissions with atmospheric CO₂ reduction is needed to limit climate change. Enhanced rock weathering (ERW) of ground silicate minerals is an emerging CDR technology with the potential to decrease atmospheric CO₂. However, there are few multi-year field studies and considerable uncertainty in field-rates of ERW. We explored combining finely ground metabasaltic rock with other soil CDR technologies (compost and biochar amendments) to stimulate carbon (C) sequestration. The combined ground rock (GR), compost, and biochar amendment had the greatest increases in soil C stocks over 3 years (15.3 ± 4.8 Mg C ha⁻¹). All other treatments slowed or reversed background C losses, with GR-only treatments reducing rates of soil C loss relative to the control but still losing soil C over time. Ground rock amendments lowered nitrous oxide (N₂O) emissions by 11.0 ± 0.6 kg CO₂e ha⁻¹ yr⁻¹ and increased methane (CH₄) consumption by 9.5 ± 3.5 to 18.4 ± 4.4 kg CO₂e ha⁻¹ yr⁻¹; while noteworthy, emissions reductions were an order of magnitude smaller than organic C sequestration with compost amendments. The combined amendment yielded the greatest estimated net ecosystem benefit (3 year relative changes in soil C, estimated ERW rates, and greenhouse gas emissions) of −86.0 ± 24.7 Mg CO₂e ha⁻¹. Benefits were dominated by soil organic C gains, directly from organic amendments and indirectly from increased plant growth. Weathering rates were <10% of the theoretical potential. Combined ERW and organic amendments increased estimated weathering rates and stimulated soil organic C sequestration.

The viscosity of magma has a first-order control on the explosivity and hazards of a volcanic eruption, and the detection of diking within the subsurface may indicate an eruption is imminent. As magma approaches the surface it is highly likely it will have a non-Newtonian shear-thinning rheology (apparent viscosity decreases as shear rate increases), yet most dike models assume magma is a simple Newtonian fluid. Here we use laser light and particle image velocimetry to image flow within a scaled experimental dike hosting a shear-thinning fluid. The results show that the internal flow dynamics of shear-thinning magma in dikes are very different to Newtonian dikes. The velocity of shear-thinning flow radiates out toward the dike margin at similar magnitude across the dike plane; this is very different to the jet flow and recirculation characteristic of the Newtonian dike model at the same conditions. A linear relationship between tip velocity and inlet Reynolds number $��{\text{Re}}_{\text{in}}�$ in the viscous regime ($��{\text{Re}}_{\text{in}}�\lesssim �0.4�$) is confirmed to also apply to shear-thinning fluids, and transitional flow ($��0.4�\lesssim �{\text{Re}}_{\text{in}}�\lesssim �100�$) is generated experimentally for the first time. These findings suggest that magma rheology (Newtonian or shear-thinning) cannot be recognized from external factors, such as the dike tip velocity. These results mark a step-change in dike modeling, introducing a new physical framework to test the petrological and geochemical evidence of magma ascent dynamics in dikes leading to volcanic eruptions.

True polar wander (TPW), the rotation of the solid Earth relative to the spin axis, is driven by changes in the Earth's moment of inertia induced by mantle convection and may have influenced past climate and life. Long-term TPW is typically inferred from large polar shifts in paleomagnetic apparent polar wander paths or computed directly by rotating them in a mantle reference frame. However, most apparent polar wander paths do not incorporate uncertainties in paleomagnetic data, which may bias estimates of TPW. Here, we provide new quantitative estimates of TPW since 320 Ma by placing a recent global apparent polar wander path corrected for age bias and with improved uncertainty quantification in existing mantle reference frames. We find large amplitude (>10°) but slow TPW rotations that predominantly occurred about two equatorial axes that are approximately orthogonal. During the Triassic and Jurassic, a ∼24° TPW oscillation occurred about an axis at ∼15°W, close to the present-day TPW axis at ∼10°E. In contrast, the TPW axis was located at ∼85°E during a smaller oscillation (∼6–10°) over the past ∼80 Ma, as well as between 260 and 320 Ma. We propose that these varying TPW axes reflect changes in the distribution and flux of subduction in the Tethyan and Pacific realms. We find no evidence for previously postulated fast (>1°/Ma) TPW oscillations in the Cretaceous and Late Jurassic. Finally, we propose that calibrating mantle convection models against reconstructed TPW will improve our understanding of mantle dynamics and the drivers of TPW itself.

Calderas often experience extended periods of unrest that are challenging to relate to a magmatic or hydrothermal origin, making it crucial to assemble a clear picture of these dynamics. Since 2005, Campi Flegrei caldera (Italy) has experienced accelerating ground uplift, seismicity rates, and degassing. Here we conduct petrological and 4D X-ray microtomography investigations on cored rocks from a ∼3 km deep geothermal well located near the center of caldera, complemented by 3D high-resolution seismic tomography. At a depth of ∼2.5–3.0 km we identify the transition to a weak tuff layer likely to trap magmatic fluids. Simulations of magma pathways indicate that stresses generated by caldera unloading may have arrested at the limestone/tuff transition past ascending dykes, which deformed, heated, and released magmatic fluids, deteriorating the surrounding rocks. This weak layer may play a crucial role in building up overpressure, causing deformation and seismicity, thus influencing the dynamics of recent unrests, and possible future magma ascent episodes.

As Earth warms, the tropopause is expected to rise, but predictions of its temperature change are less certain. Longstanding theories employing “gray” radiation tie the tropopause temperature to outgoing longwave radiation (OLR), but this is in contrast to recent work in which simulations exhibit a Fixed Tropopause Temperature (FiTT) even as OLR increases. The FiTT is thought to result from the interaction between upper tropospheric moisture and radiation, but a predictive theory for FiTT has not yet been formulated. Here, we build on a recent explanation for the temperature of anvil clouds and argue that tropopause temperature, defined by where radiative cooling becomes negligible, is set by water vapor's maximum spectroscopic absorption and Clausius-Clapeyron scaling. This “thermospectric constraint” makes quantitative predictions for tropopause temperature that are borne out in single column and general circulation model experiments where the spectroscopy is modified and both the radiative and lapse-rate tropopause change in response. This constraint provides a theoretical foundation for the FiTT hypothesis and a more refined explanation for why the tropopause rises with surface warming, shows how tropopause temperature can decouple from OLR, suggests a way to relate the temperatures of anvil clouds and the tropopause, and shows how spectroscopy manifests in Earth's general circulation.

The extraordinary eruption of the Tonga volcano on 15 January 2022 lofted material to heights exceeding 50 km, marking the highest observed since the satellite era. This eruption caused significant disturbances spanning from the hydrosphere up to the thermosphere. Our recent investigation discovered the dramatic thermospheric responses at satellite altitudes. This study, however, provides physical insights into two main possible processes, secondary gravity waves (GWs) and Lamb waves, which may explain those observed large-scale thermospheric disturbances. The comparison between the simulations and observations suggests that the MESORAC-HIAMCM secondary GWs are consistent with GRACE-FO measured global-propagation thermospheric density disturbances in timing and amplitude. WACCM-X simulations suggest that the Lamb wave can reach the thermosphere as a sharp, narrow wave packet, and may contribute about 25% to the total disturbances at 510 km.

Enhanced weathering has emerged as a promising natural climate solution that has the potential to remove billions of tons of carbon from the atmosphere if widely adopted in agricultural settings. Despite this potential, few field trials have been published that verify the carbon dioxide removal (CDR) potential of enhanced weathering in croplands and, until now, none had been published in grazing lands. Anthony et al. (2025, https://doi.org/10.1029/2024AV001480) conducted the first trial of enhanced weathering in a California rangeland and showed weathering of ground silicate rocks despite drought conditions in an already dry climate. Co-application of inorganic (silicate rocks) with organic (biochar and compost) amendments revealed not just additive, but synergistic effects whereby organic amendments increased rates of weathering. This is important because field CDR rates were <10% of the theoretical maximum (i.e., the rate if basalt was completely weathered); thus, methods to improve weathering rates will be necessary for this practice to scale in a meaningful way. Multi-carbon pool measurements revealed not only how co-application of soil amendments heightened net carbon benefits, but also how soil amendments complemented each other to produce net benefits for soil carbon, biomass growth, and greenhouse gas emission reductions. Anthony et al. (2025, https://doi.org/10.1029/2024AV001480) produce new insights toward our understanding of enhanced weathering as well as introduce paths for future research concerning combined amendment applications, synergistic mechanisms for carbon storage, and deployment in various agricultural contexts. While questions remain about the fate of weathering products in arid regions, Anthony et al. (2025, https://doi.org/10.1029/2024AV001480) present novel findings on the potential for significant weathering to occur even under suboptimal conditions.

High-speed electron flows (HSEFs) play a crucial role in the energy dissipation and conversion processes within the terrestrial magnetosphere and can drive various types of plasma waves and instabilities, affecting the electron-scale dynamics. The existence, spatial distribution, and general properties of HSEFs in the Earth magnetotail are still unknown. In this study, we conduct a comprehensive survey of HSEFs in the Earth magnetotail, utilizing NASA's Magnetospheric Multiscale (MMS) mission observations from 2017 to 2021. A total of 642 events characterized by electron bulk speeds exceeding 5,000 km/s are identified. The main statistical properties are: (a) The duration of almost all HSEFs are less than 4 s, and the average duration is 0.74 s. (b) HSEFs exhibit a strong dawn-dusk (30%–70%) asymmetry. (c) 39.6%, 29.0%, and 31.4% of the events are located in the plasma sheet, plasma sheet boundary layer (PSBL), and lobe region, respectively. (d) In the plasma sheet, HSEFs have arbitrary moving directions regarding the ambient magnetic field, and the events near the neutral line predominantly move along the same direction as the ion outflows, indicating outflow electrons generated by magnetic reconnection. (e) HSEFs in the PSBL and lobe mainly move along the ambient magnetic field, and 70% of HSEFs in the PSBL exhibit features of reconnection inflow. The HSEFs in lobe regions may locate near the reconnection electron edges. Our study reveals that the HSEFs in magnetotail are closely associated with magnetic reconnection, and the statistical results deepen the understanding of HSEF fundamental properties in collisionless plasma.

Characterizing the evolution of drought frequency and severity under anthropogenic global warming remains a key challenge because of the mismatch between the length of instrumental records and the long-term variability of drought features. To address this gap, we propose a modeling framework that combines river flow observations, paleo-hydrological reconstructions, and climate model simulations. Such diversity of climate information, that is bridged in a flexible approach, allows evaluating the hazard of hydrological droughts for any large catchment globally. By focusing on the specific case of Alpine regions and analyzing the information contained in an ensemble for the period 1100–2100, we show that, compared to the past nine centuries, the mean annual flow in the Po River (Italy's main water course) may decrease by about 10% during the 21st century, while the mean drought duration and severity are likely to increase by approximately 11% and 12%, respectively. Future drought conditions are likely to match, or even exceed, the driest period of the Medieval Climate Anomaly under different emissions scenarios. This indicates unprecedented drought conditions in Alpine regions in the coming decades, thus calling for an increased preparedness in managing water resources under climate change.

Addressing global challenges and advancing knowledge in the Earth and space sciences requires an equitable, diverse, and inclusive scholarly community where researchers must be freely able to conduct, collaborate on, share, review, and discuss their research on important economic and societal topics such as climate change. The current Executive Orders in the United States focus on censoring research and researchers by banning specific words, removing access to data sets, or by restricting what type of research can be funded or published, therefore compromising the knowledge that researchers are able to produce. As Editors-in-Chief of AGU publications we stand by our mission to support the publication of evidence-based, rigorously vetted research without political pressure. Collectively, our peer-reviewed journals and books provide inclusive publication outlets for the global research community to advance Earth and space sciences and to strengthen the public's trust in scientific evidence.