The Reversibility of Antarctic Sea Ice Loss Under CO2 Removal ScenariosLi, Sirui; Hu, Kaiming; Huang, Gang; Zheng, Xiao‐Tong
doi: 10.1029/2025gl116756pmid: N/A
A pronounced decline in Antarctic sea ice has been observed since 2014, with major changes in the Earth system. This study investigates whether these impacts can be reversed by removing atmospheric greenhouse gases. Using carbon dioxide removal experiments from the Coupled Model Intercomparison Project Phase 6, we identify considerable inter‐model diversity in projections of Antarctic sea ice recovery, partly driven by a positive feedback loop starting from different initial ocean stratification in the present climate. Specifically, during the CO2 increasing period, models with stronger initial stratification tend to store heat in the upper layer but not in the deeper layer in the Antarctic Ocean, accelerating sea ice melting, which in turn strengthens ocean stratification and thus impedes sea ice recovery during the CO2 decreasing period. Conversely, weaker stratification promotes sea ice recovery under carbon dioxide removal scenarios. This demonstrates that the initial ocean stratification intensity exerts a critical influence on the reversibility of Antarctic sea ice loss.
Mega‐Tripolar Precipitation Change Accompanying Water Isotopes in Holocene Asian Summer Monsoon ReanalysisNing, Liang; Xing, Fangmiao; Liu, Zhengyu; Liu, Jian; Mann, Michael E.; Wu, Fen; Lei, Lili; Wang, Yongjin; Wan, Lingfeng; Xu, Hai; Tan, Liangcheng; Bradley, Raymond S.; Yan, Mi; Sun, Weiyi; Chen, Deliang; Lu, Huayu; Wen, Qin; Chen, Kefan; Qin, Yanmin
doi: 10.1029/2025gl116451pmid: N/A
The climatic interpretations of speleothem δ18Oc records over Asian summer monsoon (ASM) region have been controversial. Here, combining speleothem δ18Oc records with the first transient Holocene simulation of an isotope‐enabled earth system model, we reconstruct a dynamically consistent spatio‐temporal evolution of the ASM precipitation using paleoclimate data assimilation. Our reconstruction finds a new mega‐tripolar pattern of precipitation variations accompanying a continental‐wide enrichment of δ18Oc from the early to late Holocene over the entire ASM continental region. Precipitation peaked in the early Holocene over South Asia, northern China and southern China, but in the late Holocene over central China. This mega‐tripolar pattern of precipitation variations can help resolve the long‐standing controversy about the timing of Holocene ASM precipitation peaks reconstructed from various proxy records.
Geomagnetic Dipole Strength During the Cretaceous Normal Superchron Recorded by Baked Sediments From Hainan (SE Asia)Chi, Yuchen; Lhuillier, Florian; Meng, Jun; Zhang, Chunyang; Shcherbakov, Valeriy P.
doi: 10.1029/2025gl116894pmid: N/A
The Cretaceous Normal Superchron constitutes an enigmatic ∼37‐Myr interval of stable polarity in the history of the Earth's magnetic field. The strength of the geomagnetic dipole moment during this interval is controversial, with absolute paleointensity determinations on crystallized volcanic rocks, volcanic glasses, and silicate crystals yielding statistically different averages. In this study, we present the first paleointensities in the mid of the superchron conducted on baked sediments from Hainan (SE Asia). This hitherto underexploited material, akin to baked clays used in archeomagnetism, produces unambiguous linear Arai‐Nagata diagrams over 60%–90% of the fraction of natural remanent magnetization. Using strict selection criteria, we show that baked sediments, volcanic glasses, and silicate crystals are consistent with a dipole moment ∼40% higher than the present‐day value. Relying on 22 independent determinations only, this combined data set leaves open the question of the dependency between geomagnetic dipole strength and reversal frequency.
Resolving Inhomogeneous Cloud Microphysics Through Cloud‐Top Observations of Blue Corona DischargesLi, Dongshuai; Luque, Alejandro; Bruning, Eric C.; Neubert, Torsten; Chanrion, Olivier; Zhu, Yanan; Gordillo‐Vázquez, F. J.; Østgaard, Nikolai
doi: 10.1029/2025gl116520pmid: N/A
Understanding cloud‐top microphysics is essential for improving weather forecasting and convection monitoring. In this study, we propose a simplified cloud scattering light model to analyze the influence of inhomogeneities in the cloud microphysical properties on the observations of blue corona discharges (BLUEs) from Atmosphere‐Space Interactions Monitor. The results show that the depth inferred from the inhomogeneous model is consistently lower than that from the homogeneous model, with the largest difference reaching 2 km. We then present a new approach to inferring inhomogeneous cloud microphysical profiles based on the optical signals from BLUEs using radio‐inferred source depths. These profiles match well with Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation lidar measurements and show a transition nearby tropopause with different exponential change rates above and below it. Our study highlights the potential of combining optical and radio observations of BLUEs to rapidly assess cloud microphysics and monitor convective activity.
Multi‐Model Future World Aridity and Groundwater Recharge Changes With and Without Stratospheric Aerosol Intervention Under High Warming ScenarioRezaei, Abolfazl; Moore, John; Tilmes, Simone; Visioni, Daniele; Hussain, Azfar
doi: 10.1029/2025gl117234pmid: N/A
Groundwater recharge (GWR) would affect by stratospheric aerosol injection (SAI)—a proposed solar geoengineering method. Using six Earth‐system models from the G6Sulfur experiment, offsetting Shared‐Socioeconomic‐pathway SSP5‐8.5 warming to SSP2‐4.5 levels, we assess aridity and GWR responses over 2070–2099. SAI reduces global aridity (+25.4% to +9.1%) but fails in GWR restoration (from −7.7% under SSP5‐8.5 to −7.6% under G6Sulfur) due to sustained evapotranspiration (+7–25%). Recharge deficits persist or intensify in the Mediterranean, northern midlatitudes, southern Africa, and northeastern Brazil, while partial gains remain in India, the Sahel, southern Arabia, western China, and southern South America, reflecting a “wetter/colder‐get‐drier and drier‐get‐wetter” pattern. GWR sensitivity to precipitation and evapotranspiration declines by 12.0% and 14.1%. CESM2‐WACCM and CNRM‐ESM2‐1 simulate the strongest partial recovery, while MPI‐ESM1.2s, IPSL‐CM6A‐LR, and UKESM1‐0‐LL show weaker or over‐suppressed responses. Results highlight regionally incomplete and model‐dependent SAI effects on GWR and the key role of CO2‐physiological forcing.
Three‐Dimensional Global Hybrid Simulations of Plasma Transport and Energy Conversion During Solar Wind‐Magnetosphere InteractionsLu, San; Guo, Jin; Lu, Quanming; Shu, Yukang; Ren, Junyi; Wang, Rongsheng; Hajra, Rajkumar
doi: 10.1029/2025gl117084pmid: N/A
Plasma transport and energy conversion during solar wind‐magnetosphere interactions under northward, southward, and radial interplanetary magnetic fields (IMFs) are examined using three‐dimensional global hybrid simulations. Energy conversion and entry of plasma and energy are weaker when the IMF is northward. After the IMF is southward, the inflow of the electromagnetic energy (the Poynting flux) increases, leading to a loading of magnetic energy. Subsequently, a strong energy conversion occurs from the magnetic field to the plasma, leading to an unloading of the magnetic energy. When the IMF is radial, strong disturbances are formed on the magnetopause, but the total ion flux, energy fluxes, and energy conversion are not pronounced. The corresponding ion enthalpy flux and bulk kinetic energy flux are also examined. These analyses allow precise and quantitative evaluations of various space weather effects.
The Distribution of Electromagnetic Power Density in the Ring Current RegionMa, Lan; Shen, Chao; Ji, Yong; Zhou, Yufei; Tan, Xin; Dunlop, M. W.; Yang, Yanyan; Gao, Lai; Cheng, Kun
doi: 10.1029/2024gl113702pmid: N/A
This study analyzes electromagnetic power density E⋅j $\mathbf{E}\cdot \mathbf{j}$ in the ring current region using MMS data and multi‐point analysis method. For the first time, we statistically examine the large‐scale distribution characteristics of E⋅j $\left\langle \mathbf{E}\cdot \mathbf{j}\right\rangle $ (〈〉 $\langle \rangle $represents statistical results) within the magnetic equatorial plane, revealing a stably particles acceleration region E⋅j>0 $\left\langle \mathbf{E}\cdot \mathbf{j}\right\rangle > 0$ on the dawn side and a dynamo region E⋅j<0 $\left\langle \mathbf{E}\cdot \mathbf{j}\right\rangle < 0$ on the dusk side. Meanwhile, the corresponding distribution of current density and net charge density are also calculated. In the predawn sector near the acceleration region, a significant accumulation of net negative charges was observed. The dusk‐side dynamo region coincides with the net positive charge accumulation. The statistical analysis of electromagnetic power and net charge accumulation implies that the electrostatic field may play an important role in the energy variation of drifting particles, providing new insights into the evolution and dynamics of the ring current.
Increasing Contribution of Condensable Particulate Matter From Stationary Combustion Sources Under Strict Control Standards in ChinaSu, Yi; Chen, Yuanzheng; Wang, Huantao; Wu, Di; Xu, Peng; Song, Xiwen; Liu, Tonghao; Cai, Runlong; Wang, Dongbin; Jiang, Jingkun; Chen, Jianmin; Li, Qing
doi: 10.1029/2025gl117794pmid: N/A
China's implementation of stringent emission control measures during 2014–2020 has effectively reduced filterable particulate matter (FPM) emissions from stationary combustion sources, while increasing the contribution of condensable particulate matter (CPM) to total PM emissions. However, the lack of CPM emission inventories hinders the assessment of atmospheric impacts. This study developed a CPM emission inventory for China using field measurements from 148 typical industrial plants/processes. CPM's contribution to total PM emissions from stationary combustion sources had surged from 48.5% to 59.9% during 2014–2020, and will reach approximately 76% by 2030 under current emission control strategies in China. Furthermore, CPM constituted 14.5 ± 8.5% of ambient PM2.5 concentrations during January 2019 in China. Within this CPM contribution, 21.8% was contributed by sulfate/ammonium from coal combustion and ammonia slip in air pollution control devices. These findings call for establishing CPM‐specific emission standards and curbing ammonia slip for further improvements in air quality.
Statistical Properties of Quasi‐Periodic Electron PrecipitationShi, Xiaofei; Blum, Lauren; Angelopoulos, Vassilis
doi: 10.1029/2025gl117206pmid: N/A
Diffuse aurora is an important phenomenon that is responsible for significant magnetospheric energy input into the ionosphere. Pulsating aurora is one distinct type of diffuse aurora, caused by quasi‐periodic electron precipitation with energies ranging from a few keV to tens of keV. Recent studies have suggested that pulsating aurora can also be accompanied by relativistic electron precipitation, which can penetrate into the E/D‐layer of the ionosphere and lead to a significant ionospheric response. However, the energy extent and occurrence rate of the relativistic, quasi‐periodic precipitation are not well understood. In this study, we perform a statistical analysis of quasi‐periodic electron precipitation events observed by the low‐altitude, polar‐orbiting ELFIN CubeSats. Our results show that these precipitation events predominantly occur in the dawn sector, and approximately 15% of them extend to relativistic energies (>500 ${ >} 500$ keV). Possible mechanisms for the quasi‐periodic relativistic precipitation are also discussed.