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Ground magnetic field variations have been used to investigate ionospheric dynamics for more than a century. They are usually explained in terms of an electric circuit in the ionosphere driven by an electric field, but this is insufficient to explain how magnetic field disturbances are dynamically established. Here we explain and simulate how the ionosphere dynamically responds to magnetospheric forcing and how it leads to magnetic field deformation via Faraday's law. Our approach underscores the causal relationships, treating the magnetic field and velocity as primary variables (the B, v paradigm), whereas the electric field and current are derived, in contrast to the E, j paradigm commonly used in ionospheric physics. The simulation approach presented here could be used as an alternative to existing circuit-based numerical models of magnetosphere-ionosphere coupling.

Large constellations of small satellites will significantly increase the number of objects orbiting the Earth. Satellites burn up at the end of service life during reentry, generating aluminum oxides as the main byproduct. These are known catalysts for chlorine activation that depletes ozone in the stratosphere. We present the first atomic-scale molecular dynamics simulation study to resolve the oxidation process of the satellite's aluminum structure during mesospheric reentry, and investigate the ozone depletion potential from aluminum oxides. We find that the demise of a typical 250-kg satellite can generate around 30 kg of aluminum oxide nanoparticles, which may endure for decades in the atmosphere. Aluminum oxide compounds generated by the entire population of satellites reentering the atmosphere in 2022 are estimated at around 17 metric tons. Reentry scenarios involving mega-constellations point to over 360 metric tons of aluminum oxide compounds per year, which can lead to significant ozone depletion.

The impact of changes in global temperatures and precipitation on climate distribution remains unclear. Taking the annual global average temperatures and precipitation as the origin, this study determined the climate distribution with the distances of temperature and precipitation from their global averages as the X and Y axes. The results showed that during 1980–2019, the global temperature distribution converged toward the mean (convergence), while the precipitation distribution moved away from the mean (divergence). The combined effects of both led to a convergence in the global climate distribution. During 2025–2100, significant climate convergence is observed under two emission scenarios (SSP245 and SSP585). However, the climate convergence and the area of change in climate type remains insignificant only under SSP126, suggesting that the diversity of the global climate pattern can be maintained under a sustainable emission pathway (SSP126), whereas high emission pathways will lead to greater uniformity in global climate.

The balance of processes affecting electron density drives the dynamics of upper-atmospheric electrical events, such as sprites. We examine the detachment of electrons from negatively charged atomic oxygen (O−) via collisions with neutral molecular nitrogen (N2) leading to the formation of nitrous oxide (N2O). Past research posited that this process, even without significant vibrational excitation of N2, strongly impacts the dynamics of sprites. We introduce updated rate coefficients derived from recent experimental measurements which suggest a negligible influence of this reaction on sprite dynamics. Given that previous rates were incompatible with the observed decay of the light emissions from sprite glows, our findings support that glows actually result from electron depletion in sprite columns.

Understanding glaciers structural heterogeneity is crucial for assessing their fate. Yet, places where structure changes are strong, such as crevasses fields, are often inaccessible for direct instrumentation. To overcome this limitation, we introduce an innovative technique that transforms seismic sources, here generated by crevasses, into virtual receivers using source-to-receiver spatial reciprocity. We demonstrate that phase interference patterns between well-localized seismic sources can be leveraged to retrieve phase velocity maps using Seismic Michelson Interferometry. The obtained phase velocity exhibits sensitivity to changes in glacier structure, offering insights into the origins of mechanical property changes, with spatial resolution surpassing traditional methods by a factor of five. In particular, we observe sharp variations in phase velocity related to strongly damaged subsurface areas indicating a complex 3-D medium. Applying this method more systematically and in other contexts will enhance our understanding of the structure of glaciers and other seismogenic environments.

Air-sea interaction in late boreal winter is studied over the extratropical North Atlantic (NA) during 1960–2020 by examining the relationship between sea-surface temperature (SST) and total turbulent heat flux (THF). The two quantities are positively correlated on interannual timescales over the central-midlatitude and subpolar NA, suggesting the atmosphere on average drives SST and THF variability is independent of SST. On decadal timescales and over the central-midlatitude NA the correlation is negative, suggesting ocean processes on average drive SST and THF variability is sensitive to SST. The correlation is positive over the subpolar NA. There, interannual and decadal THF variability is governed by the North Atlantic Oscillation (NAO). During the major late 20th and early 21st century SST increase in the subpolar NA diminishing oceanic heat loss associated with a weakening NAO was observed. This study suggests that the atmosphere is more sensitive to SST over the central-midlatitude than subpolar NA.

Approximately 150 Tg of water vapor and 0.42 Tg of sulfur dioxide were injected directly into the stratosphere by the January 2022 Hunga volcanic eruption, which represents the largest water vapor injection in the satellite era. A comparison of numerical simulations to balloon-borne and satellite observations of the water-rich plume suggests that particle coagulation contributed to the Hunga aerosol's effective dry radius increase from 0.2 μm in February to around 0.4 μm in March. Our model suggests that the stratospheric aerosol effective radius is persistently perturbed for years by moderate and large-magnitude volcanic events, whereas extreme wildfire events show limited impact on the stratospheric background particle size. Our analysis further suggests that both the particle optical efficiency and the aerosols' stratospheric lifetime explain Hunga's unusually large aerosol optical depth per unit of the SO2 injection, as compared with the Pinatubo eruption.

With climate change, there will be higher requirements for monitoring storm surges (SSs) in nearshore areas. However, this capability is limited by the sparseness of tide gauge (TG) stations. Establishing and maintaining a permanent, high-spatial coverage, in situ TG network is complex and expensive. Here, we propose a joint modeling method developed from the all-site modeling data-driven framework by importing temporary TGs into coastal regions with insufficient permanent TG stations. The assessments show that this method can significantly optimize the capability of extreme SS monitoring during typhoons and hurricanes. Moreover, the evaluation based on Coupled Model Intercomparison Project Phase 6 data indicates that it will monitor extreme SSs more effectively during 2025–2050 compared with only using existing permanent in situ TGs (reducing root mean square error and absolute mean bias by ∼50%). The joint modeling method provides an applicable and sustainable solution for optimizing the SS monitoring capability in coastal areas.

Earthquakes that rupture several faults occur frequently within the shallow lithosphere but are rarely observed for intermediate-depth events (70–300 km). On 29 November 2007, the M w 7.4 Martinique earthquake struck the Lesser Antilles Island Arc near the deep end of the Wadati-Benioff-Zone. The sparse regional seismic network of 2007 previously hampered a detailed examination of this unusually complex event. Here, we combine seismic data from different studies with regional moment tensor inversion results and 3D full-waveform modeling. We show that the earthquake is a doublet consisting of dip-slip and strike-slip motion along two oblique structures, both activated under extensional stress along the strike of the slab. Comparison with tectonic reconstructions suggests that the earthquake ruptured along a re-activated ridge-transform segment of the subducted Proto-Caribbean spreading ridge. The unprecedented resolution of the source process highlights the influence of pre-existing structures on localizing slab deformation also at intermediate-depth.

This study investigates the responses of the urban atmospheric thermal environment to two distinct heat waves in Hefei, China, and explores potential changes associated with future urban expansion. During the Event 1, characterized by clear and dry conditions, the western Pacific subtropical high limits water vapor influx, resulting in a significant cooling effect in rural area due to higher surface latent heat flux. The urban heat island (UHI) intensity, calculated using surface temperature and 2-m temperature, reaches 5.2°C and 1.7°C during the Event 1, respectively. Although Event 2, characterized by cloudy and humid conditions, exhibits weaker UHI and urban dry island effects, it remains highly unfavorable for human comfort. During distinct heat waves, the vertical extent of the warming effect induced by future urban expansion varies, which can be attributed to environmental factors, such as atmospheric stability and near-surface wind speed.

Anomalous tropical longwave cloud-radiative heating of the atmosphere is generated when convective precipitation occurs, which plays an important role in the dynamics of tropical disturbances. Defining the observed cloud-radiative feedback as the reduction of top-of-atmosphere longwave radiative cooling per unit precipitation, the feedback magnitudes are sensitive to the observed precipitation data set used when comparing two versions of Global Precipitation Climatology Project, version 1.3 (GPCPv1.3) and the newer version 3.2 (GPCPv3.2). GPCPv3.2 contains larger magnitudes and variance of daily precipitation, which yields a weaker cloud-radiative feedback in tropical disturbances at all frequencies and zonal wavenumbers. Weaker cloud-radiative feedbacks occur in GPCPv3.2 at shorter zonal lengths on intraseasonal timescales, which implies a preferential growth at planetary scales for the Madden-Julian oscillation. Phase relationships between precipitation, radiative heating, and other thermodynamic variables in eastward-propagating gravity waves also change with the updated GPCPv3.2.

This study uses precipitation oxygen isotopes (δ18Op) to examine key dynamics that deliver moisture to the southern slope of central Himalayas over different seasons. Results show that the majority of pre-monsoon δ18Op values are relatively high and controlled by the westerlies and local moisture. However, some abnormally low δ18Op values coincide with higher precipitation amounts during the pre-monsoon season due to moisture driven northwards from the Bay of Bengal and Arabian Sea to central Himalayas by anomalous circulations (quasi-anticyclone, anticyclone, or/and westerlies trough). The size and location of the quasi-anticyclone also influences the magnitude of the δ18Op decrease. In comparison, the monsoon δ18Op values are lower due to the combined effects of the Indian summer monsoon and convection. Our findings indicate that researchers need to consider the signals of abnormally low δ18Op values during the pre-monsoon season when attempting to interpret ice core and tree-ring records from central Himalayas.

Fault regions inferred to be slowly slipping are interpreted to accommodate much of tectonic plate motion aseismically and potentially serve as barriers to earthquake rupture. Here, we build on prior work using simulations of earthquake sequences with enhanced dynamic fault weakening to show how fault regions that exhibit decades of steady creep or transient slow-slip events can be driven to dynamically fail by incoming earthquake ruptures. Following substantial earthquake slip, such regions can be under-stressed and locked for centuries prior to slowly slipping again. Our simulations illustrate that slow fault slip indicates that a region is sufficiently loaded to be failing about its quasi-static strength. Hence, if a fault region is susceptible to failing dynamically, then observations of slow slip could serve as an indication that the region is critically stressed and ready to fail in a future earthquake, posing a qualitatively different interpretation of slow slip for seismic hazard.

Applying machine learning to continuous acoustic emissions, signals previously deemed noise, from laboratory faults and slowly slipping subduction-zone faults, demonstrates hidden signatures are emitted that describe physical details, including fault displacement and friction. However, no evidence currently exists to demonstrate that similar hidden signals occur during seismogenic stick-slip on earthquake faults—the damaging earthquakes of most societal interest. We show that continuous seismic emissions emitted during the 2018 multi-month caldera collapse sequence at the Kı̄lauea volcano in Hawai'i contain hidden signatures characterizing the earthquake cycle. Multi-spectral data features extracted from 30 s intervals of the continuous seismic emission are used to train a gradient boosted tree regression model to predict the GNSS-derived contemporaneous surface displacement and time-to-failure of the upcoming collapse event. This striking result suggests that at least some faults emit such signals and provide a potential path to characterizing the instantaneous and future behavior of earthquake faults.

The El Niño-Southern Oscillation causes anomalous atmospheric circulation, temperature and precipitation across southern polar latitudes, but the influence of Central and Eastern Pacific El Niño events on Antarctic surface mass balance and snow accumulation has not yet been assessed. Here, we use reanalysis and reanalysis-forced regional climate model output and find that Central Pacific El Niño results in significantly increased snow accumulation in the western Ross Sea sector and significantly decreased snow accumulation in the Amundsen Sea sector. Eastern Pacific El Niño is associated with similar but weaker patterns, with some regional exceptions. In some areas, like Dronning Maud Land, or the Wilkes Subglacial Basin, the effect of El Niño on snow accumulation changes from increased to reduced accumulation depending on the type of El Niño. Our results show that projecting El Niño types is important for constraining future changes in Antarctic surface mass balance.

The sediment mixed layer (SML) in the deep ocean is an important interface with a rich diversity of benthic organisms. With increasing ocean mineral exploration, and eventual mining, the effect of sediment mixing on deep ocean ecosystems has raised considerable concern. We evaluate the distribution patterns and driving factors of SML depth in deep ocean nodule fields using naturally occurring 210Pb–226Ra isotopes. Results show that average SML depth has increased in Mn-nodule fields since the end of the last century. SML processes are associated with significant desorption of 226Ra from sediments, resulting in a departure from radioactive equilibrium. By estimating possible driving factors, we conclude that anthropogenic exploration activities, rather than natural physical and/or biological drivers, are the most likely mechanism for intensified sediment mixing. 210Pb–226Ra disequilibria may be a potential tracer for quantifying the impact of human exploration on deep-ocean sediment mixing and associated biological and geochemical effects.

Positive leaders branch less frequently than negative counterpart, and the physical processes and properties of positive leader branching remain a mystery. We investigated 10 m laboratory discharges under four positive voltages using a high-speed video camera. Positive leaders differ from negative leaders by either directly splitting or connecting with floating bidirectional leaders to form branching, and the number of leader branches shows a positive correlation with the applied voltage, that is, the branched channels increased from 1 to 4 when the voltage increased by a factor of 1.5. Grounding points are positioned beneath the electrode and are more concentrated with lower voltage. During the stable progression of the leader, there is a slight increase in its development speed as the applied voltage rises. When the voltage is increased by 70%, the average breakdown time decreases by 40%. These characteristics provide insights into the branching mechanism of positive leaders.

We report results from a global simulation of the September 2017 geomagnetic storm. The global model comprises the ionospheric code SAMI3 and the atmosphere/thermosphere code WACCM-X. We show that a train of large-scale EPBs form in the Pacific sector during the storm recovery phase on 8 September 2017. The EPBs are associated with storm-induced modification of the zonal and meridional winds. These changes lead to an eastward electric field which in turn causes an upward E × B drift in the post-midnight sector. A large decrease in the Pedersen conductance caused by meridional equatorward winds leads to an increase in the growth rate of the generalized Rayleigh-Taylor instability that causes EPBs to develop. Interestingly, several EPBs reach altitudes above 3,000 km.

Damage zones are common around faults, but their effects on earthquake mechanics are still incompletely understood. Here, we investigate how damage affects rupture patterns, source time functions (STF) and ground motions in 2D fully-dynamic cycle models. We find that back-propagating rupture fronts emerge in large faults and can be triggered by residual stresses left by previous ruptures or by damage-induced pulse-to-crack transitions. Damage-induced back-propagating fronts are modulated by slip rate oscillations, amplify high-frequency radiation, and sharpen the multiple peaks in STF even in the absence of frictional heterogeneity or fault segmentation. Near-field ground motion is predominantly controlled by stress heterogeneity left by prior seismicity, and further amplified within the damage zone by trapped waves and outside it by secondary rupture fronts. This study refines our knowledge on damage zone effects on earthquake rupture and identifies their potentially observable signatures in the near and far field.