An anomalous warm weather event in the Antarctic McMurdo Dry Valleys on 18 March 2022 created an opportunity to characterize soil biota communities most sensitive to freeze-thaw stress. This event caused unseasonal melt within Taylor Valley, activating stream water and microbial mats around Canada Stream. Liquid water availability in this polar desert is a driver of soil biota distribution and activity. Because climate change impacts hydrological regimes, we aimed to determine the effect on soil communities. We sampled soils identified from this event that experienced thaw, nearby hyper-arid areas, and wetted areas that did not experience thaw to compare soil bacterial and invertebrate communities. Areas that exhibited evidence of freeze-thaw supported the highest live and dead nematode counts and were composed of soil taxa from hyper-arid landscapes and wetted areas. They received water inputs from snowpacks, hyporheic water, or glacial melt, contributing to community differences associated with organic matter and salinity gradients. Inundated soils had higher organic matter and lower conductivity (p < .02) and hosted the most diverse microbial and invertebrate communities on average. Our findings suggest that as liquid water becomes more available under predicted climate change, soil communities adapted to the hyper-arid landscape will shift toward diverse, wetted soil communities.

Understanding soil organic carbon (SOC) distribution and its environmental controls in permafrost regions is essential for achieving carbon neutrality and mitigating climate change. This study examines the spatial pattern of SOC and its drivers in the Headwater Area of the Yellow River (HAYR), northeastern Qinghai-Xizang Plateau (QXP), a region highly susceptible to permafrost degradation. Field investigations at topsoils of 86 sites over three summers (2021-2023) provided data on SOC, vegetation structure, and soil properties. Moreover, the spatial distribution of key permafrost parameters was simulated: temperature at the top of permafrost (TTOP), active layer thickness (ALT), and maximum seasonal freezing depth (MSFD) using the TTOP model and Stefan Equation. Results reveal a distinct latitudinal SOC gradient (high south, low north), primarily mediated by vegetation structure, soil properties, and permafrost parameters. Vegetation coverage and above-ground biomass showed positive correlation with SOC, while soil bulk density (SBD) exhibited a negative correlation. Climate warming trends resulted in increased ALT and TTOP. Random Forest analysis identified SBD as the most important predictor of SOC variability, which explains 38.20% of the variance, followed by ALT and vegetation coverage. These findings likely enhance the understanding of carbon storage controls in vulnerable alpine permafrost ecosystems and provide insights to mitigate carbon release under climate change.

The aerosol scattering phase function (ASPF), a crucial element of aerosol optical properties, is pivotal for radiative forcing calculations and aerosol remote sensing detection. Current detection methods for the ASPF include multi-sensor detection, single-sensor rotational detection and imaging detection. However, these methods face challenges in achieving high-resolution full-angle measurement, particularly for small forward (i.e., less than 10 degrees) or backward (i.e., more than 170 degrees) scattering angles in open path. In this work, a full-angle ASPF detection system based on the multi-field-of-view Scheimpflug lidar technique has been proposed and demonstrated. A 450 nm continuous-wave semiconductor laser was utilized as the light source and four CMOS image sensors were employed as detectors. To detect the full-angle ASPF, four receiving units capture angular scattering signals across different angle ranges, namely 0 degrees-20 degrees, 10 degrees-96 degrees, 84 degrees-170 degrees, 160 degrees-180 degrees, respectively. The influence of the relative illumination and angular response of the used image sensors have been corrected, and a signal stitching algorithm was developed to obtain a complete 0-180 degrees angular scattering signal. Atmospheric measurements have been conducted by employing the full-angle ASPF detection system in open path. The experimental results of the ASPF have been compared with the AERONET data from the Socheongcho station and simulated ASPF based on the typical aerosol models in mainland China, showing excellent agreement. The promising results demonstrated in this work have shown a great potential for detecting the full-angle ASPF in open path.

The presence of frozen volatiles (especially H2O ice) has been proposed in the permanently shadowed regions (PSRs) near the poles of the Moon, based on various remote measurements including the visible and near-infrared (VNIR) spectroscopy. Compared with the middle- and low-latitude areas, the VNIR spectral signals in the PSRs are noisy due to poor solar illumination. Coupled with the lunar regolith coverage and mixing effects, the available VNIR spectral characteristics for the identification of H2O ice in the PSRs are limited. Deep learning models, as emerging techniques in lunar exploration, are able to learn spectral features and patterns, and discover complex spectral patterns and nonlinear relationships from large datasets, enabling them applicable on lunar hyperspectral remote sensing data and H2O-ice identification task. Here we present H2O ice identification results by a deep learning-based model named one-dimensional convolutional autoencoder. During the model application, there are intrinsic differences between the remote sensing spectra obtained by the orbital spectrometers and the laboratory spectra acquired by state-of-the-art instruments. To address the challenges of limited training data and the difficulty of matching laboratory and remote sensing spectra, we introduce self-supervised learning method to achieve pixel-level identification and mapping of H2O ice in the lunar south polar region. Our model is applied to the level 2 reflectance data of Moon Mineralogy Mapper. The spectra of the identified H2O ice-bearing pixels were extracted to perform dual validation using spectral angle mapping and peak clustering methods, further confirming the identification of most pixels containing H2O ice. The spectral characteristics of H2O ice in the lunar south polar region related to the crystal structure, grain size, and mixing effect of H2O ice are also discussed. H2O ice in the lunar south polar region tends to exist in the form of smaller particles (similar to 70 mu m in size), while the weak/absent 2-mu m absorption indicate the existence of unusually large particles. Crystalline ice is the main phase responsible for the identified spectra of ice-bearing surface however the possibility of amorphous H2O ice beneath optically sensed depth cannot be ruled out.

This study examines the optical and chemical characteristics of south Asian outflow across the northern Indian Ocean during the northern hemispheric winter of the year 2018, as part of the Integrated Campaign for Aerosols, gases, and Radiation Budget (ICARB) experiment. Our observations reveal a significant influence of anthropogenic aerosols on columnar aerosol optical depth (AOD) in the equatorial Indian Ocean, with anthropogenic AOD accounting for approximately 46 % of the composite aerosol load. Water-soluble anthropogenic ions (WSAI) emerge as the primary contributor to columnar AOD across most oceanic regions of the northern Indian Ocean, attributed to their high scaling distance compared to other dominant species such as organic carbon (OC) and black carbon (BC). The assessment of speciated aerosol radiative forcing indicates the primary contribution of BC to surface forcing in coastal regions, with WSAI (followed by BC and OC) exerting dominance in far oceanic areas. Overall, anthropogenic forcing, primarily from WSAI, OC, and BC, accounts for a substantial portion of the total forcing at the top of the atmosphere (72 %) and surface (89 %) over most of the cruise regions of the southeast Arabain Sea and the equatorial Indian Ocean, with atmospheric heating predominantly attributed to BC (84 %) exhibiting highest atmospheric absorbing efficiency of 13.38. Our findings highlight the significant role of anthropogenic aerosols from south Asian outflow in shaping optical and radiative properties over the equatorial Indian Ocean and emphasize the need for further research to understand their broader climatic and environmental implications.

Understanding the mechanical behaviour of water ice-bearing lunar soil is essential for future lunar exploration and construction. This study employs discrete element method (DEM) simulations, incorporating realistic particle shapes and a flexible membrane, to investigate the effects of ice content, initial packing density, and gravitational conditions on lunar soil behaviour. Initially, we calibrated DEM model parameters by comparing triaxial tests on lunar soil without ice to physical experiments and the angle of repose simulations, validating the accuracy of our approach. Building on this, we conducted simulations on water ice-bearing lunar soil, examining stress-strain responses, shear strain, bond breakage, deviatoric fabric, and N-ring structures. DEM simulations demonstrate that increasing ice content from 0 % to 10 % elevates peak strength from 85 kPa to 240 kPa in loose samples and from 0.2 MPa to 1.62 MPa in dense samples. This strengthening aligns with microstructural stabilization evidenced by 5-ring configurations and narrowed branch vector distributions. Strain field analysis reveals greater deformation magnitudes in icy regolith, suggesting a trade-off between enhanced load-bearing capacity and reduced ductility. These quantified mechanical responses, including strength gain, structural stabilization, and strain localization, reveal the dual engineering implications of water ice in lunar soil.

This study analyzes the aerosol and precipitable water vapor (PWV) properties at six sites in the Indo-Gangetic Plains (IGP), a densely populated and highly polluted region. The main objective is to explore how the columnar PWV is related to the attenuation of shortwave solar radiation (SWR), as well as the combined role of aerosol properties and PWV on radiative forcing based on AERONET data and model (SBDART) simulations. The analysis revealed high aerosol optical depth (AOD) values (0.4-0.6) throughout the year in all the sites, associated with increased PWV (4-5 cm) during the summer monsoon. Comprehensive investigation shows that changes in PWV levels also affect aerosols' size distribution, optical properties and radiation balance in a similar way - but in different magnitudes - between the examined sites. The water vapor radiative effect (WVRE) is highly dependent on aerosol presence, with its magnitude for both surface (-130 to -140 Wm(-2)) and atmospheric forcing becoming higher under clean atmospheres (without aerosols). Aerosol presence is also considered in the computations of the WVRE. In that case, the WVRE becomes more pronounced at the top of the atmosphere (TOA) (30 to 35 Wm(-2)) but exhibits a lower forcing impact on the surface (about -45 Wm(-2)) and within the atmosphere (70-80 Wm(-2)), suggesting important aerosol-PWV interrelations. The atmospheric heating rate due to PWV is more than double (3.5-4.5 K Day(-1)) that of aerosols (1-1.9 K Day(-1)), highlighting its essential role in radiative effects and climate implications over the IGP region. The radiative impacts of PWV and aerosols are further examined as a function of the single scattering albedo, solar zenith angle, and absorbing AOD at the different sites, revealing dependence on both astronomical and atmospheric variables related to aerosol absorption, thus unravelling the combined role of aerosols and PWV in climate implications.

Thawing-triggered slope failures and landslides are becoming an increasing concern in cold regions due to the ongoing climate change. Predicting and understanding the behaviour of frozen soils under these changing conditions is therefore critical and has led to a growing interest in the research community. To address this challenge, we present the first mesh-free smoothed particle hydrodynamics (SPH) computational framework designed to handle the multi-phase and multi-physic coupled thermo-hydro-mechanical (THM) process in frozen soils, namely the THM-SPH computational framework. The frozen soil is considered a tri-phase mixture (i.e., soil, water and ice), whose governing equations are then established based on u-p-T formulations. A critical-state elasto-plastic Clay and Sand Model for Frozen soils (CASM-F), formulated in terms of solid-phase stress, is then introduced to describe the transition response and large deformation behaviour of frozen soils due to thawing action for the first time. Several numerical verifications and demonstrations highlight the usefulness of this advanced THM-SPH computational framework in addressing challenging problems involving thawing-induced large deformation and failures of slopes. The results indicate that our proposed single-layer, fully coupled THM-SPH model can predict the entire failure process of thawing-induced landslides, from the initiation to post-failure responses, capturing the complex interaction among multiple coupled phases. This represents a significant advancement in the numerical modelling of frozen soils and their thawing-induced failure mechanisms in cold regions.

This study highlights the results of a palaeoecological analysis conducted on five permafrost peatlands in the northern tundra subzone along the Barents Sea coast in the European Arctic zone. The depth of the peat cores that were sampled was approximately 2 m. The analysis combined data on the main physical and chemical soil properties, radiocarbon dating, botanical composition, and mass fraction of polycyclic aromatic hydrocarbons (PAHs). The concentrations of 16 PAHs in peat organic layers ranged from 140 to 254 ng/g, with an average of 182 ng/g. The peatlands studied were dominated by PAHs with a low molecular weight: naphthalene, phenanthrene, fluoranthene, pyrene, chrysene. The vertical distribution patterns of PAHs along the peat profile in the active layer and permafrost were determined. PAHs migrating down the active layer profile encounter the permafrost barrier and accumulate at the boundary between active layer and permafrost layer. The deep permafrost layers accumulate large amounts of PAHs and PAH derivatives, which are products of lignin conversion during the decomposition of grassy and woody vegetation during the Holocene climate optima. The total toxic equivalency concentration (TEQ) was calculated. Peatlands from the Barents Sea coast have low toxicity for carcinogenic PAHs throughout the profile. TEQ ranged from a minimum of 0.1 ng/g to a maximum of 13.5 ng/g in all peatlands investigated. For further potential use in Arctic/sub-Arctic environmental studies, PAH indicator ratios were estimated. In all investigated sections and peatland horizons, the most characteristic ratios indicate the petrogenic (natural) origin of PAHs.

Characterizing vertical profiles of in-situ particle properties is relevant because being only based on the surface or column-integrated measurements cannot unambiguously conclude the radiative impact on aerosol. Vertical profiles of in-situ aerosol properties on-board an unmanned aerial vehicle (UAV) were measured above El Arenosillo (37.1 N,-6.7 W) in the southwest of Spain during four flight missions. Measured properties included particle number size distribution, total particle concentration and multiwavelength absorption coefficient up to 3100 m during cold season (February 4, 2022 and December 11, 2023) and warm season (September 20, 2023 and April 2, 2024). The heterogeneity of particle properties has been shown around two types of events: a mineral particle event of desert origin during cold season and a new particle formation event during warm season. During cold season, a comparison between the flight missions with and without desert dust episodes shows that mineral particles decrease the planetary boundary layer (PBL) height. This behavior is probably related to absorber particles aloft atmosphere, which traps solar radiation and heat up the upper layer of the atmosphere and deteriorates the vertical dispersion. In the literature, this effect is called as 'dome effect'. During warm season, new particle formation was observed above PBL. This event could be related to the presence of precursor gases in the residual layer, and enhanced by a low concentration of pre-existing particles. The characteristic parameter during the observed event was the fine-to-total particle volume concentration ratio close to zero. These observations highlight the necessity to establish a long-term multi-temporal monitoring of vertical profiles for atmospheric parameters onboard UAV systems and to integrate in Earth observations networks. For example, radiative forcing is usually estimated from surface data, but the heterogeneity in the vertical profiles of atmospheric particles properties, which are used to the forcing quantification, is a result of inaccuracies.