In the context of global climate change, changes in unfrozen water content in permafrost significantly impact regional terrestrial plant ecology and engineering stability. Through Differential Scanning Calorimetry (DSC) experiments, this study analyzed the thermal characteristic indicators, including supercooling temperature, freezing temperature, thawing temperature, critical temperature, and phase-transition temperature ranges, for silt loam with varying starting moisture levels throughout the freezing and thawing cycles. With varying starting moisture levels throughout the freezing and thawing cycles, a model describing the connection between soil temperature and variations in unfrozen water content during freeze-thaw cycles was established and corroborated with experimental data. The findings suggest that while freezing, the freezing and supercooling temperatures of unsaturated clay increased with the soil's starting moisture level, while those of saturated clay were less affected by water content. During thawing, the initial thawing temperature of clay was generally below 0 degrees C, and the thawing temperature exhibited a power function relationship with total water content. Model analysis revealed hysteresis effects in the unfrozen water content curve during freeze-thaw cycles. Both the phase-transition temperature range and model parameters were sensitive to temperature changes, indicating that the processes of permafrost freezing and thawing are mainly controlled by ambient temperature changes. The study highlights the stability of the difference between freezing temperature and supercooling temperature in clay during freezing. These results offer a conceptual framework for comprehending the thawing mechanisms of permafrost and analyzing the variations in mechanical properties and terrestrial ecosystems caused by temperature-dependent moisture changes in permafrost.

Vulnerability of peat plateaus to global warming was analyzed in northeastern European Russia. A laboratory experiment on artificial incubation of peat was carried out to analyze the resilience of organic matter of frozen peat bogs (palsas) to decomposition. The rate of mineralization of peat organic matter was calculated from data on the CO2 and CH4 emissions from the peat incubated at a temperature of +4 degrees C under artificial aerobic and anaerobic conditions during 1300 days. Peat samples were taken from the active layer (AL), transitional layer (TL), and permafrost layer (PL). The delta 13C and delta 15N isotopes and the C/N, O/C, and H/C ratios were determined as indicators of change in the decomposition rate of organic matter. By the 1300th day of the experiment under aerobic conditions, the total CO2 amount released from the analyzed samples (per 1 g of carbon) was 10.24-37.4 mg C g-1 (on average, 25.76 mg C g-1), while under anaerobic conditions, it was only 2.1-3.38 mg C g-1 (on average, 3.15 mg C g-1). The CH4 emission was detected only in the peat from the transitional layer in very small quantities. The incubation experiment results support the hypothesis that peat plateaus are resilient, especially under anaerobic conditions, regardless the ongoing climate warming.

Iron (Fe) minerals possess a huge specific surface area and high adsorption affinity, usually considered as rust tanks of organic carbon (OC), playing an important role in global carbon storage. Microorganisms can change the chemical form of Fe by producing Fe-chelating agents such as side chains and form a stable complex with Fe(III), which makes it easier for microorganisms to use. However, in seasonal frozen soil thawing, the succession of soil Fe-cycling microbial communities and their coupling relationship with Fe oxides and Fe-bound organic carbon (Fe-OC) remains unclear. We characterized changes in the Fe phase, Fe-OC, Fe-oxidizing bacteria (FeOB), and Fe-reducing bacteria (FeRB) in the subsoil and analyzed the microbial mechanism underlying Fe-OC changes in alpine grassland by constructing a composite structural equation model (SEM). We found that the Fe(III) content consistently exceeded that of Fe(II). Among the three types of Fe oxides, organically complex Fe (Fe-p) decreased from 2.54 to 2.30 gkg(-1), whereas the opposite trend was observed for poorly crystalline Fe (Fe-o). The Fe-OC content also decreased (from 10.31 to 9.47 gkg(-1); p < 0.05). Fe-cycling microorganisms were markedly affected by the thawing of frozen soil (except FeRB). Fe-p and Feo directly affected changes in Fe-OC. Soil moisture (SM) and FeOB were significant indirect factors affecting Fe-OC changes. Freeze-thaw changes in the subsoil of alpine grassland in Central Asia significantly affected FeOB and Fe oxides, thus affecting the Fe-OC content. To the best of our knowledge, this was the first study to examine the influence of Fe-cycling microorganisms on the Fe phase and Fe-OC in the soil of alpine grassland in Central Asia. Overall, our findings provide scientific clues for exploring the biogeochemical cycle process in future climate change.

By analyzing the last 50-60 years of climate changes in Arctic and Subarctic Yakutia, we have identified three distinct periods of climate development. The cold (1965-1987), pre-warming (1988-2004), and modern warming (2005-2023) periods are clearly identifiable. Yakutia's Arctic and Subarctic regions have experienced mean annual air temperature increases of 2.5 degrees C and 2.2 degrees C, respectively, compared to the cold period. The thawing index rose by an average of 171-214 degrees C-days, while the freezing index dropped by an average of 564-702 degrees C-days. During the pre-warming period, all three characteristics show a minor increase in warmth. Global warming intensified between 2005 and 2023, resulting in elevated permafrost temperatures and a deeper active layer. Monitoring data from the Tiksi site show that warming has been increasing at different depths since the mid-2000s. As a result, the permafrost temperature increased by 1.7 degrees C at a depth of 10 m and by 1.1 degrees C at a depth of 30 m. Soil temperature measurements at meteorological stations and observations at CALM sites both confirm the warming of the permafrost. A permafrost-climatic zoning study was conducted in Arctic and Subarctic Yakutia. Analysis identified seven regions characterized by similar responses to modern global warming. These study results form the foundation for future research on global warming's effects on permafrost and on how northern Yakutia's environment and economy adapt to the changing climate.

Background:A shallow active layer of soil above the permafrost thaws during the summer months which promotes microbial growth and releases previously confined pathogens which result in bacterial epidemics in circumpolar regions. Furthermore, these permafrost sources harbor several antibiotic resistance genes (ARGs) which may disseminate and pose a challenge for pharmacologists worldwide.Aims:The authors examined the potential association between climate change-induced permafrost thawing, and the resulting release of antibiotic-resistant pathogens, as well as the potential impact this can have on global healthcare systems in the long run.Methodology:A cursory abstract screening was done to rule out any articles that did not have to do with viral pathogens caused by melting permafrost. Articles that were not available in English or that our institutions library did not have full-text access were weeded out by a secondary screen.Results:A comprehensive analysis of 13 relevant studies successfully revealed a wide variety of bacterial genera, including Staphylococcus spp., Pseudomonas spp., Acinetobacter spp., and Achromobacter spp., along with a total of 1043 antibiotic resistance genes (ARGs), with most pertaining to aminoglycosides and beta-lactams, offering resistance via diverse mechanisms such as efflux pumps and enzymatic modifications, within the permafrost isolates. Additionally, mobile genetic elements (MGEs) housing antibiotic resistance genes (ARGs) and virulence factor genes (VFGs), including plasmids and transposons, were also discovered.Conclusion:Permafrost thawing is an underrated healthcare challenge warranting the need for further articles to highlight it alongside concerted efforts for effective mitigation.

The degradation of permafrost in the Northern Hemisphere is expected to persist and potentially worsen as the climate continues to warm. Thawing permafrost results in the decomposition of organic matter frozen in the ground, which stores large amounts of soil organic carbon (SOC), leading to carbon being emitted into the atmosphere in the form of carbon dioxide and methane. This process could potentially contribute to positive feedback between global climate change and permafrost carbon emissions. Accurate projections of permafrost thawing are key to improving our estimates of the global carbon budget and future climate change. Using data from the latest generation of climate models (CMIP6), this paper explores the challenges involved in assessing the annual active layer thickness (ALT), defined as the maximum annual thaw depth of permafrost, and estimated carbon released under various Shared Socioeconomic Pathway (SSP) scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5). We find that the ALT estimates derived from CMIP6 model soil temperatures show significant deviations from the observed ALT values. This could lead to inconsistent estimates of carbon release under climate change. We propose a simplified approach to improve the estimate of the changes in ALT under future climate projections. These predicted ALT changes, combined with present-day observations, are used to estimate vulnerable carbon under future climate projections. CMIP6 models project ALT changes of 0.1-0.3 m per degree rise in local temperature, resulting in an average deepening of approx. 1.2-2.1 m in the northern high latitudes under different scenarios. With increasing temperatures, permafrost thawing starts in Southern Siberia, Northern Canada, and Alaska, progressively extending towards the North Pole by the end of the century under high emissions scenarios (SSP5-8.5). Using projections of ALT changes and vertically resolved SOC data, we estimate the ensemble mean of decomposable carbon stocks in thawed permafrost to be approximately 115 GtC (gigatons of carbon in the form of CO2 and CH4) under SSP1-2.6, 180 GtC under SSP2-4.5, 260 GtC under SSP3-7.0, and 300 GtC under SSP5-8.5 by the end of the century.

Permafrost is a crucial part of the Earth's cryosphere. These millennia-old frozen soils not only are significant carbon reservoirs but also store a variety of chemicals. Accelerated permafrost thaw due to global warming leads to profound consequences such as infrastructure damage, hydrological changes, and, notably, environmental concerns from the release of various chemicals. In this perspective, we metaphorically term long-preserved substances as dormant chemicals that experience an awakening during permafrost thaw. We begin by providing a comprehensive overview and categorization of these chemicals and their potential transformations, utilizing a combination of field observations, laboratory studies, and modeling approaches to assess their environmental impacts. Following this, we put forward several perspectives on how to enhance the scientific understanding of their ensuing environmental impacts in the context of climate change. Ultimately, we advocate for broader research engagement in permafrost exploration and emphasize the need for extensive environmental chemical studies. This will significantly enhance our understanding of the consequences of permafrost thaw and its broader impact on other ecosystems under rapid climate warming.

Introduction: Permafrost and seasonally frozen soil are widely distributed on the Qinghai-Tibetan Plateau, and the freezing-thawing cycle can lead to frequent phase changes in soil water, which can have important impacts on ecosystems.Methods: To understand the process of soil freezing-thawing and to lay the foundation for grassland ecosystems to cope with complex climate change, this study analyzed and investigated the hydrothermal data of Xainza Station on the Northern Tibet from November 2019 to October 2021.Results and Discussion: The results showed that the fluctuation of soil temperature showed a cyclical variation similar to a sine (cosine) curve; the deep soil temperature change was not as drastic as that of the shallow soil, and the shallow soil had the largest monthly mean temperature in September and the smallest monthly mean temperature in January. The soil water content curve was U-shaped; with increased soil depth, the maximum and minimum values of soil water content had a certain lag compared to that of the shallow soil. The daily freezing-thawing of the soil lasted 179 and 198 days and the freezing-thawing process can be roughly divided into the initial freezing period (November), the stable freezing period (December-early February), the early ablation period (mid-February to March), and the later ablation period (March-end of April), except for the latter period when the average temperature of the soil increased with the increase in depth. The trend of water content change with depth at all stages of freezing-thawing was consistent, and negative soil temperature was one of the key factors affecting soil moisture. This study is important for further understanding of hydrothermal coupling and the mechanism of the soil freezing-thawing process.

Climate change has regulated cryosphere-fed rivers and altered interannual and seasonal sediment dynamics, with significant implications for terrestrial material cycles and downstream aquatic ecosystems. However, there has been a notable scarcity of research focusing on the patterns of water-sediment transport within these permafrost zones. Integrating 6 years (2017-2022) of in-situ observational data from FengHuoShan basin with the partial least squares-structural equation modelling (PLS-SEM) method, we analyse the driving factors, characteristics and seasonal patterns of the water-sediment transport process. We observed a gradual increase in both suspended sediment flux (SSF, Mt/yr) and runoff (Q, km(3)/yr) within the basin, with annual growth rates of 1.34%/yr and 0.75%/yr, respectively. It is worth noting that these growth rates exhibit seasonal variations, with the highest values observed in spring (SSF: 1.76%/yr, Q: 1.71%/yr). This indicates that the response to climate change is more pronounced in spring compared with summer and autumn. Through mathematical statistics and the PLS-SEM model, we found that temperature plays a predominant role in the dynamics of water-sediment in both spring and autumn, whereas rainfall exerts a more significant impact during the summer. Most suspended sediment concentration (SSC, kg/m(3)) peak events throughout the year are primarily driven by rainfall. Affected by the freeze-thaw cycle of permafrost, SSC and discharge (Q, m(3)/s) exhibit distinct seasonality. SSC and Q demonstrate a clockwise trend; both Q and SSC begin to increase from May and peak in August before declining. The insights gleaned from this study hold significant implications for water resource management and soil conservation strategies in the region, particularly in the face of ongoing climatic changes characterized by warming and increased humidity.

Progressive climate change may have unpredictable consequences for the Arctic environment. Permafrost catchments off the west coast of Svalbard, described as thin and warm, are particularly sensitive to climate change. The interdisciplinary research on the hydrochemical response of surface and underground water functioning within a small permafrost catchment area focused on the determination of the impact of meteorological conditions (temperature (T), precipitation (P)) on the mean daily discharge (Q), and the lowering of the groundwater table (H). We determined physical and chemical properties (pH and SEC) and concentrations of major elements (Ca, Mg, Na, K) and 23 trace elements (i.a. Cd, Cu, Hg, Pb, Zn) in 280 water samples. The results of the correlation matrix showed that an increase in the average air temperature in the summer of 2021 had a significant impact on the hydrochemistry of both types of waters operating in the catchment. In response to increase in T, the lowering of the H (0.52 < r < 0.66) and a decrease in Q (-0.66 < r < -0.68) were observed what in consequence also leads to changes in water chemistry. The principal component analysis (CA) indicates that chemical weathering and binding of elements to DOC are processes influencing water chemistry. Results of statistical analysis showed that the resultant of the hydrometeorological conditions that prevailed in that season and the type of geological formations on which they were located had a significant impact on the water chemistry at individual measurement points. Significant differences in the concentrations of elements between points on the same geological formations were also found.