Permafrost thaw and thermokarst development pose urgent challenges to Arctic communities, threatening infrastructure and essential services. This study examines the reciprocal impacts of permafrost degradation and infrastructure in Point Lay (Kali), Alaska, drawing on field data from similar to 60 boreholes, measured and modeled ground temperature records, remote sensing analysis, and community interviews. Field campaigns from 2022-2024 reveal widespread thermokarst development and ground subsidence driven by the thaw of ice-rich permafrost. Borehole analysis confirms excess-ice contents averaging similar to 40%, with syngenetic ice wedges extending over 12 m deep. Measured and modeled ground temperature data indicate a warming trend, with increasing mean annual ground temperatures and active layer thickness (ALT). Since 1949, modeled ALTs have generally deepened, with a marked shift toward consistently thicker ALTs in the 21st century. Remote sensing shows ice wedge thermokarst expanded from 60% in developed areas by 2019, with thaw rates increasing tenfold between 1974 and 2019. In contrast, adjacent, undisturbed tundra exhibited more consistent thermokarst expansion (similar to 0.2% yr(-1)), underscoring the amplifying role of infrastructure, surface disturbance, and climate change. Community interviews reveal the lived consequences of permafrost degradation, including structural damage to homes, failing utilities, and growing dependence on alternative water and wastewater strategies. Engineering recommendations include deeper pile foundations, targeted ice wedge stabilization, aboveground utilities, enhanced snow management strategies, and improved drainage to mitigate ongoing infrastructure issues. As climate change accelerates permafrost thaw across the Arctic, this study highlights the need for integrated, community-driven adaptation strategies that blend geocryological research, engineering solutions, and local and Indigenous knowledge.

As a result of the research performed, the emission of CO2 from soils in the southern tundra ecosystems of the northeastern Russian Plain has been estimated using the example of the environs of Vorkuta. The soil cover of the studied area is presented by Histic Turbic Cryosol, Histic Reductaquic Glacic Cryosol, Reductaquic Glacic Cryosol, and Reductaquic Glacic Cryosol. Atypically high values of CO2 emission from soils [2.13 +/- 0.13 g C/(m2 day)] were largely due to the weather of the 2022 growing season: high air temperatures and low precipitation. About 60% of the variability in the emission value was due to the content of microbial biomass carbon and extractable soil carbon, temperature, and soil moisture. High spatial variation in the content of extractable carbon and microbial biomass carbon and parameters of hydrothermal regime of soils was found. The soils were characterized by low values of extractable organic carbon and soil microbial biomass carbon (224 +/- 18 and 873 +/- 73 mg C/kg of soil, respectively). The thickness of organic horizon of soil determines 72% of variability in the content of microbial biomass carbon and 79% of variability in the content of extractable carbon. Regular measurements of CO2 emissions from soils of tundra ecosystems in the northeast of the Russian Plain should obtain special attention, as this will improve the accuracy of assessing the global greenhouse gas flows.

Use of forest biomass may induce changes in the aerosol emissions, with subsequent impacts on the direct and indirect climate effects of these short-lived climate forcers. We studied how alternative wood use scenarios affected the aerosol emissions and consequent radiative forcing in Finland. In all alternative scenarios, the harvest level of forest biomass was increased by 10 million m3 compared to the baseline. The increased biomass harvest was assigned to four different uses: (i) to sawn wood, (ii) to pulp-based products, (iii) to energy biomass combusted in small-scale appliances or (iv) to energy biomass combusted in medium-to-large scale boilers. Aerosol emissions (black carbon (BC), organic carbon (OC) and sulphur dioxide (SO2)) under these scenarios were estimated using displacement factors (DFs). The global aerosol-climate model ECHAM-HAMMOZ was used to study instantaneous radiative forcing due to aerosol-radiation interactions (IRFARI) and effective radiative forcing (ERF), based on the differences in aerosol emissions between the alternative wood use scenarios and the baseline scenario. The results indicated that the use of sawn wood and energy biomass combusted in medium- to large-scale boilers decreased radiative forcings, implying climate cooling, whereas the increased use of pulpwood increased them. Energy biomass combustion in small-scale appliances increased IRFARI by 0.004 W m-2 but decreased ERF by -0.260 W m-2, specifically due to a strong increase in carbonaceous aerosols. Alternative use of forest biomass notably influenced aerosol emissions and their climate impacts, and it can be concluded that increased forest biomass use requires a comprehensive assessment of aerosol emissions alongside greenhouse gases (GHGs). Given the consequent reduction in radiative forcing from aerosol emissions, we conclude that the greatest overall climate benefits could be achieved by prioritising the production of long-lived wood-based products.

Understanding the evolution of permafrost extent and active layer thickness (ALT) surrounding Antarctica is critical to global climate change and ecosystem transformations in the polar regions. However, due to the remoteness and harsh environment of Antarctica, most studies lack long-term and a regional perspective on the variations of ALT in Antarctica, resulting in hindering accurate assessment of ALT dynamics. In this study, based on MODIS land surface temperature (LST) and soil climate station data, we used the Stefan model to reconstruct ALT in the ice-free area of the McMurdo Dry Valleys (MDV) in East Antarctica from 2003 to 2022. The modeled ALT was verified against ground observations showing a good correlation (R) of 0.72 (p < 0.001), with an RMSE of 12.66 cm. The results indicate that the ALT exhibits a decreasing trend from coastal to inland, ranging from a maximum of 60 cm near the coastal area to zero in the polar plateau. Furthermore, within the inland valleys, deeper ALT values are mainly distributed in the lower elevation areas, reaching up to 60 cm at the lowest altitudes. During the period from 2003 to 2022, the interannual variability in ALT was notable, especially in coastal areas, with a maximum amplitude close to 30 cm in the years 2012 and 2016. Our study proved that the Stefan model with parameters estimated by MODIS LST and soil climate station data has good potential to reconstruct large-scale ALT in the ice-free area of Antarctica.

Global climate change exerts profound effects on snow cover, with consequential impacts on microbial activities and the stability of soil organic carbon (SOC) within aggregates. Northern peatlands are significant carbon reservoirs, playing a critical role in mitigating climate change. However, the effects of snow variations on microbial-mediated SOC stability within aggregates in peatlands remain inadequately understood. Here, an in-situ field experiment manipulating snow conditions (i.e., snow removal and snow cover) was conducted to investigate how snow variations affect soil microbial community and the associated SOC stability within soil aggregates (> 2, 0.25-2, and < 0.25 mm) in a peatland of Northeast China. The results showed that snow removal significantly increased the SOC content and stability within aggregates. Compared to the soils with snow cover, snow removal resulted in decreased soil average temperatures in the topsoil (0-30 cm depth) and subsoil (30-60 cm depth) (by 1.48 and 1.34 degrees C, respectively) and increased freeze-thaw cycles (by 11 cycles), consequently decreasing the stability of aggregates in the topsoil and subsoil (by 23.68% and 6.85%, respectively). Furthermore, more recalcitrant carbon and enhanced SOC stability were present in microaggregates (< 0.25 mm) at two soil depths. Moreover, reductions in bacterial diversity and network stability were observed in response to snow removal. Structural equation modeling analysis demonstrated that snow removal indirectly promoted (P < 0.01) SOC stability by regulating carbon to nitrogen (C:N) ratio within aggregates. Overall, our study suggested that microaggregate protection and an appropriate C:N ratio enhanced carbon sequestration in response to climate change.

Climate change impacts have destabilized the permafrost in the SRYY. This study developed a MODIS land surface temperature correction equation for the SRYY, analyzed permafrost variations over 2001-2020 using the Stefan equation, the Temperature at the Top of Permafrost model (TTOP) model, and the soil thermal conductivity parameterization scheme, and applied a structural equation model to identify permafrost change drivers. Leveraging the CMIP6 data, future active layer thickness (ALT) and permafrost distribution were projected under diverse scenarios. The main conclusions are as follows: The ALT in the SRYY thickened at a rate of 1.06 cm/year, with significant changes concentrated in the Tuotuo and Damqu River basins. In the future about 2100, under SSP245, the ALT in the SRYY will increase by about 30 cm compared with the historical period, and the permafrost area will reduce by a minimum of 2 x 104 km2 and a maximum of 12.3 x 104 km2. And under the SSP585, the ALT will thicken by about 60 cm, with an average decrease in permafrost area of 16.3 x 104 km2. High-altitude permafrost exhibited stronger responses to climate change, faster warming rates mainly led to this result. Variations in moisture conditions were another important cause, in which soil water content was a key factor, and the role of precipitation deserved more consideration.

Climate change is reducing snowpack across temperate regions with negative consequences for human and natural systems. Because forest canopies create microclimates that preserve snowpack, managing forests to support snow refugia-defined here as areas that remain relatively buffered from contemporary climate change over time that sustain snow quality, quantity, and/or timing appropriate to the landscape-could reduce climate change impacts on snow cover, sustaining the benefits of snow. We review the current understanding of how forest canopies affect snow, finding that while closed-conifer forests and snow interactions have been extensively studied in western North America, there are knowledge gaps for deciduous and mixed forests with dormant season leaf loss. We propose that there is an optimal, intermediate zone along a gradient of dormant season canopy cover (DSCC; the proportion of the ground area covered by the canopy during the dormant season), where peak snowpack depth and the potential for snow refugia will be greatest because the canopy-mediated effects of snowpack sheltering (which can preserve snowpack) outweigh those of snowfall interception (which can limit snowpack). As an initial test of our hypothesis, we leveraged snowpack measurements in the northeastern United States spanning the DSCC gradient (low, 50% DSCC), including from 2 sites in Old Town, Maine; 12 sites in Acadia National Park, Maine; and 30 sites in the northern White Mountains of New Hampshire. Medium DSCC forests (typically mature mixed coniferous-deciduous forests) exhibited the deepest peak snowpacks, likely due to reduced snowfall interception compared to high DSCC forests and reduced snowpack loss compared to low DSCC forests. Many snow accumulation or snowpack studies focus on the contrast between coniferous and open sites, but our results indicate a need for enhanced focus on mixed canopy sites that could serve as snow refugia. Measurements of snowpack depth and timing across a wider range of forest canopies would advance understanding of canopy-snow interactions, expand the monitoring of changing winters, and support management of forests and snow-dependent species in the face of climate change.

Climate change has been a strong driving force impacting the distribution of global water resources over the past few decades, especially in cold regions at high latitudes. Hydrological models are essential to analyse complex changing cold region's processes, such as permafrost, seasonally frozen soil, and snow cover, which are prevalent across much of Canada and the pan-Arctic basins. Here, we utilize the Hydrological Predictions for the Environment (HYPE) model with seven discretized vertical soil layers to assess climate change response to different water balance portioning components and permafrost extent. The study also explores seasonal and interannual shifts, examining the implications of model uncertainty associated with streamflow generation for the Nelson Churchill River Basin (NCRB). The calibrated HYPE model is run with a suite of fourteen GCMs and two RCPs (RCP 4.5 and RCP 8.5) scenarios representing 87% of the variability of 154 climate scenarios to discern the relationship between climate projections and water balance components. Increasing precipitation and temperature are anticipated in the future, but reduced, or balanced runoff is projected due to the dominant impact of rising temperature on evapotranspiration from thawing soil layers. Under an extreme scenario (RCP 8.5) 82% reduction in permafrost degradation is projected by the mid-future period (2050s). In this study, the future projections of streamflow, soil moisture, permafrost projection, and interrelationships of water balance processes at a continental scale are presented to aid in large-scale planning and implementation of sustainable development principles and guidelines for decision-making in the NCRB. Le changement climatique a & eacute;t & eacute; une force motrice majeure influen & ccedil;ant la r & eacute;partition des ressources en eau & agrave; l'& eacute;chelle mondiale au cours des derni & egrave;res d & eacute;cennies, en particulier dans les r & eacute;gions froides des hautes latitudes. Les mod & egrave;les hydrologiques sont essentiels pour analyser les processus complexes en & eacute;volution dans les r & eacute;gions froides, tels que le perg & eacute;lisol, les sols gel & eacute;s de mani & egrave;re saisonni & egrave;re et le couvert neigeux, qui sont r & eacute;pandus dans une grande partie du Canada et des bassins pan-arctiques. Dans cette & eacute;tude, nous utilisons le mod & egrave;le Hydrological Predictions for the Environment (HYPE), qui comprend sept couches de sol verticales discr & eacute;tis & eacute;es, pour & eacute;valuer la r & eacute;ponse au changement climatique des composantes du bilan hydrique et de l'& eacute;tendue du perg & eacute;lisol. L'& eacute;tude explore & eacute;galement les variations saisonni & egrave;res et interannuelles, en examinant les implications de l'incertitude du mod & egrave;le associ & eacute;e & agrave; la g & eacute;n & eacute;ration des d & eacute;bits fluviaux dans le bassin de la rivi & egrave;re Nelson Churchill (NCRB). Le mod & egrave;le HYPE calibr & eacute; est ex & eacute;cut & eacute; avec une s & eacute;rie de quatorze mod & egrave;les climatiques globaux (GCM) et deux sc & eacute;narios RCP (RCP 4.5 et RCP 8.5), repr & eacute;sentant 87 % de la variabilit & eacute; de 154 sc & eacute;narios climatiques, afin d'analyser la relation entre les projections climatiques et les composantes du bilan hydrique. Une augmentation des pr & eacute;cipitations et des temp & eacute;ratures est anticip & eacute;e dans le futur, mais un ruissellement r & eacute;duit ou & eacute;quilibr & eacute; est projet & eacute; en raison de l'impact dominant de la hausse des temp & eacute;ratures sur l'& eacute;vapotranspiration provenant des couches de sol en d & eacute;gel. Dans un sc & eacute;nario extr & ecirc;me (RCP 8.5), une r & eacute;duction de 82 % de la d & eacute;gradation du perg & eacute;lisol est projet & eacute;e d'ici la p & eacute;riode du milieu du si & egrave;cle (ann & eacute;es 2050). Cette & eacute;tude pr & eacute;sente des projections futures du d & eacute;bit fluvial, de l'humidit & eacute; du sol, de la d & eacute;gradation du perg & eacute;lisol et des interrelations des processus du bilan hydrique & agrave; l'& eacute;chelle continentale afin de soutenir la planification & agrave; grande & eacute;chelle et la mise en oeuvre de principes de d & eacute;veloppement durable pour & eacute;clairer la prise de d & eacute;cision dans le NCRB.

Permafrost roughly affects half of the boreal region in Alaska and varies greatly in its thermo-physical properties and genesis. In boreal ecosystems, permafrost formation and degradation respond to complex interactions among climate, topography, hydrology, soils, vegetation, and disturbance. We synthesized data on soil thermal conditions and permafrost characteristics to assess current permafrost conditions in central Alaska, and classified and mapped soil landscapes vulnerable to future thaw and thermokarst development. Permafrost soil properties at 160 sites ranged from rocky soils in hillslope colluvium and glacial till, to silty loess, to thick peats on abandoned floodplains and bogs, across 64 geomorphic units. Ground-ice contents (% moisture) varied greatly across geomorphic units. Mean annual ground temperatures at similar to 1 m depth varied 12.5 degrees C across 77 sites with most permafrost near thawing or actively thawing. To assess the vulnerability of permafrost to climate variability and disturbance, we differentiated permafrost responses in terms of rate of thaw, potential thaw settlement, and thermokarst development. Using a rule-based model that uses geomorphic units for spatial extrapolation at the landscape scale, we mapped 10 vulnerability classes across three areas in central Alaska ranging from high potential settlement/low thaw rate in extremely ice-rich loess to low potential settlement/high thaw rate in rocky hillslope colluvium. Permafrost degradation is expected to result in 10 thermokarst landform types. Vulnerability classes corresponded to thermokarst features that developed in response to past climates. Differing patterns in permafrost vulnerability have large implications for ecosystem trajectories, land use, and infrastructure damage from permafrost thaw.

Sugar maple, an economically and ecologically important tree in the northern hardwood forest, has experienced regeneration failure that in the Northeast portion of the range has been variously attributed to soil acidification and resultant changes in soil chemistry, impacts of climate change, and effects of species composition. In a 5-year study spanning a latitudinal gradient in the state of New Hampshire, we examined evidence for these three hypotheses to explain sugar maple regeneration patterns. Overall, sugar maple seedling survival was highest in the two sites with lower sugar maple abundance. Alternatively, the two other sites with greater than 50% sugar maple relative dominance shared the following outcomes: higher seed production per area, greater foliar pest damage, lower seedling survival, lower sapling density, and higher canopy maple mortality, while the sites with lower dominance of maple had opposite outcomes. Based on field data and a common garden experiment, conspecific impacts on seedling survival were related to foliar pests and fungal pathogens rather than through soil feedbacks. These results lend support to other studies encouraging promotion of stand tree diversity and avoidance of monocultures.