Permafrost Research Articles

Warming-induced vegetation growth cancels out soil carbon-climate feedback in the northern Asian permafrost region in the 21st century

Permafrost soils represent an enormous carbon (C) pool that is highly vulnerable to climate warming. We used the model output ensemble of the Coupled Model Intercomparison Project Phase 6 to estimate the C storage in soil, litter, and vegetation in the current extent of northern Asian permafrost during 1900–2100. The contemporary (1995–2014) C storage was estimated to be 368.1 ± 82.5 Pg C for the full column depth of the soil, 13.3 ± 4.6 Pg C in litter, and 22.2 ± 3.2 Pg C in vegetation biomass, while these C storage levels are projected to decline by 3.9 Pg C (1.1%) in soils, increase of 0.03 Pg C (0.2%) in litter, and increase by 21.1 Pg C (95.3%) in vegetation biomass by the end of the 21st century under SSP585. The total C storage was dominated by warming-induced vegetation growth. Partial correlation analysis showed that surface air temperature (TAS), soil liquid water, and soil mineral nitrogen (SMN) dominated the soil and vegetation C pools, while SMN controlled litter C during the historical period. Under future scenarios, TAS and SMN dominated the changes of soil and litter C, while TAS determined the vegetation C increase. The growing soil C loss with warming indicates positive C-climate feedback in soils; this warming-induced acceleration of soil C loss was canceled out by the enhanced vegetation C accumulation, leading to a strong C sink in the 21st century.

Behavior of large shaft sinking headframe subjected to uneven foundation settlement

Deep mining is an inevitable trend in China and the world, for which the construction of deep and large vertical shafts is the primary task. A shaft sinking headframe is a basic structure for supporting various hoisting and sinking equipment during vertical shaft construction. The design of the shaft sinking headframe is challenging due to the significant differences in the geometry and working load compared to conventional steel structures. Recently, the effect of uneven foundation settlement on the shaft sinking headframe has been of great concern when sinking shafts by the freezing sinking method or in permafrost soil areas. In this study, finite element calculations were performed to investigate the mechanical behavior of the SA-3 shaft sinking headframe under uneven foundation settlement (0.001–0.006 L) and normal working-load conditions. The results indicate that the most unfavorable condition for the stress of members is the diagonal double foundation settlement, and in the view of the geometric offset, the most unfavorable condition is the same-side double foundation settlement. The corner members near the settled foundation were changed from a state of compression to tension. Uneven foundation settlement of less than 0.001 L is acceptable for the safety and service performance of the shaft sinking headframe. These criteria can be used for reference in engineering practice.

Carbon and nitrogen cycling dynamics following permafrost thaw in the Northwest Territories, Canada

Rapid climate warming across northern high latitudes is leading to permafrost thaw and ecosystem carbon release while simultaneously impacting other biogeochemical cycles including nitrogen. We used a two-year laboratory incubation study to quantify concomitant changes in carbon and nitrogen pool quantity and quality as drivers of potential CO2 production in thawed permafrost soils from eight soil cores collected across the southern Northwest Territories (NWT), Canada. These data were contextualized via in situ annual thaw depth measurements from 2015 to 2019 at 40 study sites that varied in burn history. We found with increasing time since experimental thaw the dissolved carbon and nitrogen pool quality significantly declined, indicating sustained microbial processing and selective immobilization across both pools. Piecewise structural equation modeling revealed CO2 trends were predominantly predicted by initial soil carbon content with minimal influence of dissolved phase carbon. Using these results, we provide a first-order estimate of potential near-surface permafrost soil losses of up to 80 g C m−2 over one year in southern NWT, exceeding regional historic mean primary productivity rates in some areas. Taken together, this research provides mechanistic knowledge needed to further constrain the permafrost‑carbon feedback and parameterize Earth system models, while building on empirical evidence that permafrost soils are at high risk of becoming weaker carbon sinks or even significant carbon sources under a changing climate.

Microbial Community Compositional Stability in Agricultural Soils During Freeze-Thaw and Fertilizer Stress

Microbial activity persists in cold region agricultural soils during the fall, winter, and spring (i.e., non-growing season) and frozen condition, with peak activity during thaw events. Climate change is expected to change the frequency of freeze-thaw cycles (FTC) and extreme temperature events (i.e, altered timing, extreme heat/cold events) in temperate cold regions, which may hasten microbial consumption of fall-amended fertilizers, decreasing potency come the growing season. We conducted a high-resolution temporal examination of the impacts of freeze-thaw and nutrient stress on microbial communities in agricultural soils across both soil depth and time. Four soil columns were incubated under a climate model of a non-growing season including precipitation, temperature, and thermal gradient with depth over 60 days. Two columns were amended with fertilizer, and two incubated as unamended soil. The impacts of repeated FTC and nutrient stress on bacterial, archaeal, and fungal soil community members were determined, providing a deeply sampled longitudinal view of soil microbial response to non-growing season conditions. Geochemical changes from flow-through leachate and amplicon sequencing of 16S and ITS rRNA genes were used to assess community response. Despite nitrification observed in fertilized columns, there were no significant microbial diversity, core community, or nitrogen cycling population trends in response to nutrient stress. FTC impacts were observable as an increase in alpha diversity during FTC. Community compositions shifted across a longer time frame than individual FTC, with bulk changes to the community in each phase of the experiment. Our results demonstrate microbial community composition remains relatively stable for archaea, bacteria, and fungi through a non-growing season, independent of nutrient availability. This observation contrasts canonical thinking that FTC have significant and prolonged effects on microbial communities. In contrast to permafrost and other soils experiencing rare FTC, in temperate agricultural soils regularly experiencing such perturbations, the response to freeze-thaw and fertilizer stress may be muted by a more resilient community or be controlled at the level of gene expression rather than population turn-over. These results clarify the impacts of winter FTC on fertilizer consumption, with implications for agricultural best practices and modeling of biogeochemical cycling in agroecosystems.

Thermal Conductivity Model Analysis of Unsaturated Ice-Containing Soil

In cold locales, the thermal conductivity of soil porous media varies according to their composition and the phase state of the substance contained within the pore space. During the winter, water and other media in the soil pore space freeze-thaw, resulting in their phase state, composition, distribution, and significant thermal conductivity changes. There are some shortcomings in the current research regarding the thermal conductivity change pattern of unsaturated ice-containing soils. In this paper, the representative elementary volume (REV) selection method is given for unsaturated ice-containing soil with porosity as a representative state variable. Under the condition of freeze-thaw, two thermal conductivity REV analysis models for unsaturated ice-containing soil are established: a simplified volume-weighted average REV model and a fine volume-weighted average REV model; accordingly, a macroscopic thermal conductivity analysis model is given. The computational analysis is carried out with an actual unsaturated ice-containing soil example. The influence of the application of frozen soil in China is examined for its effect on the variation law of the thermal conductivity of porous medium. The variation characteristics of thermal conductivity of permafrost soil with related parameters (porosity, water ratio, moisture percentage, ice content, and tortuosity) are discussed. The model built in this paper provides novel concepts and methods for analyzing the thermal conductivity characteristics of unsaturated soil, as well as enhancing and advancing the analysis.

Brief communication: Improving ERA5-Land soil temperature in permafrost regions using an optimized multi-layer snow scheme

Abstract. We previously reported a notable warm bias in ERA5-Land soil temperature in permafrost regions that was supposedly being caused by an underestimation of snow density. In this study, we implemented and evaluated a new multi-layer snow scheme in the land surface scheme of ERA5-Land, i.e., HTESSEL, with revised snow densification parameterizations. We compared permafrost soil temperatures from the numerical experiments with observations and the original ERA5-Land with a single-layer snow scheme. The revised HTESSEL significantly improved the representation of soil temperature in permafrost regions compared to ERA5-Land. The daily warm bias in winter was reduced by about 0.6–3.0 ∘C across the 522 observing stations in high-latitude permafrost regions, and the resulting modeled near-surface permafrost extent was improved (11.0–12.9×106 km2 during 2001–2018), comparing reasonably with observed estimates for continuous and discontinuous permafrost areas. We therefore suggest that a better-resolved snow scheme with a multi-layer snow profile should be included in next-generation reanalyses as a first step towards improving the representation of permafrost.

Substantial non-growing season carbon dioxide loss across Tibetan alpine permafrost region.

One of the major uncertainties for projecting permafrost carbon (C)-climate feedback is a poor representation of the non-growing season carbon dioxide (CO2 ) emissions under a changing climate. Here, combining in situ field observations, regional synthesis and a random forest model, we assessed contemporary and future soil respired CO2 (i.e., soil respiration, Rs ) across the Tibetan alpine permafrost region, which has received much less attention compared with the Arctic permafrost domain. We estimated the regional mean Rs of 229.8, 72.9 and 302.7g C m-2 year-1 during growing season, non-growing season and the entire year, respectively; corresponding to the contemporary losses of 296.9, 94.3 and 391.2Tg Cyear-1 from this high-altitude permafrost-affected area. The non-growing season Rs accounted for a quarter of the annual soil CO2 efflux. Different from the prevailing view that temperature is the most limiting factor for cold-period CO2 release in Arctic permafrost ecosystems, precipitation determined the spatial pattern of non-growing season Rs on the Tibetan Plateau. Using the key predictors, model extrapolation demonstrated additional losses of 38.8 and 74.5Tg C from the non-growing season for a moderate mitigation scenario and a business-as-usual emissions scenario, respectively. These results provide a baseline for non-growing season CO2 emissions from high-altitude permafrost areas and help for accurate projection of permafrost C-climate feedback.

Subarctic soil carbon losses after deforestation for agriculture depend on permafrost abundance

The northern circumpolar permafrost region is experiencing considerable warming due to climate change, which is allowing agricultural production to expand into regions of discontinuous and continuous permafrost. The conversion of forests to arable land might further enhance permafrost thaw and affect soil organic carbon (SOC) that had previously been protected by frozen ground. The interactive effect of permafrost abundance and deforestation on SOC stocks has hardly been studied. In this study, soils were sampled on 18 farms across the Yukon on permafrost and non-permafrost soils to quantify the impact of land-use change from forest to cropland and grassland on SOC stocks. Furthermore, the soils were physically and chemically fractionated to assess the impact of land-use change on different functional pools of SOC. On average, permafrost-affected forest soils lost 15.6 ± 21.3% of SOC when converted to cropland and 23.0 ± 13.0% when converted to grassland. No permafrost was detected in the deforested soils, indicating that land-use change strongly enhanced warming and subsequent thawing. In contrast, the change in SOC at sites without permafrost was not significant but had a slight tendency to be positive. SOC stocks were generally lower at sites without permafrost under forest. Furthermore, land-use change increased mineral-associated SOC, while the fate of particulate organic matter (POM) after land-use change depended on permafrost occurrence. Permafrost soils showed significant POM losses after land-use change, while grassland sites without permafrost gained POM in the topsoil. The results showed that the fate of SOC after land-use change greatly depended on the abundance of permafrost in the pristine forest, which was driven by climatic conditions more than by soil properties. It can be concluded that in regions of discontinuous permafrost in particular, initial conditions in forest soils should be considered before deforestation to minimize its climate impact.

The distribution and hydrological significance of intact rock glaciers in the north-west Himalaya

ABSTRACT Intact rock glaciers are common periglacial landforms that occur in cold alpine mountains and are often considered indicators of alpine permafrost. They can be both active and inactive, but both have ice in them and can be hydrologically significant. Little is known about the distribution of the rock glaciers in the Himalaya at basin-scale and content of water that can be hydrologically significant during the water-stressed months. We have found 967 intact rock glaciers covering an area of 306 km2 in the river basins of Beas, Chenab, Ravi, Sutlej, and Yamuna. Out of these, around 77% are moraine derived and the rest are talus derived. Most of them occur in the elevation between 4000 and 4500 m having a slope of 10° to 30° with a westerly and south-westerly aspect. They start occurring from 3220 to 6206 m, in places with −10°C to 10°C mean monthly temperature and within 50–100 cm of average monthly precipitation. Their alignment suggests that these rock glaciers occur in the area with low to medium incoming solar radiations. These rock glaciers are generally found where the general rock types are low-grade metamorphic rocks and feldspar-rich intrusive granites occurring beyond the Main Central Thrust in the Higher Himalaya. Finally, we calculated about 8.5 billion m3 volume of water (ice water equivalent) stored in them, considering 60% of the volume of rock glaciers is ice.

Dissolved organic matter characterization in soils and streams in a small coastal low-Arctic catchment

Abstract. Ongoing climate warming in the western Canadian Arctic is leading to thawing of permafrost soils and subsequent mobilization of its organic matter pool. Part of this mobilized terrestrial organic matter enters the aquatic system as dissolved organic matter (DOM) and is laterally transported from land to sea. Mobilized organic matter is an important source of nutrients for ecosystems, as it is available for microbial breakdown, and thus a source of greenhouse gases. We are beginning to understand spatial controls on the release of DOM as well as the quantities and fate of this material in large Arctic rivers. Yet, these processes remain systematically understudied in small, high-Arctic watersheds, despite the fact that these watersheds experience the strongest warming rates in comparison. Here, we sampled soil (active layer and permafrost) and water (porewater and stream water) from a small ice wedge polygon (IWP) catchment along the Yukon coast, Canada, during the summer of 2018. We assessed the organic carbon (OC) quantity (using dissolved (DOC) and particulate OC (POC) concentrations and soil OC content), quality (δ13C DOC, optical properties and source apportionment) and bioavailability (incubations; optical indices such as slope ratio, Sr; and humification index, HIX) along with stream water properties (temperature, T; pH; electrical conductivity, EC; and water isotopes). We classify and compare different landscape units and their soil horizons that differ in microtopography and hydrological connectivity, giving rise to differences in drainage capacity. Our results show that porewater DOC concentrations and yield reflect drainage patterns and waterlogged conditions in the watershed. DOC yield (in mg DOC g−1 soil OC) generally increases with depth but shows a large variability near the transition zone (around the permafrost table). Active-layer porewater DOC generally is more labile than permafrost DOC, due to various reasons (heterogeneity, presence of a paleo-active-layer and sampling strategies). Despite these differences, the very long transport times of porewater DOC indicate that substantial processing occurs in soils prior to release into streams. Within the stream, DOC strongly dominates over POC, illustrated by DOC/POC ratios around 50, yet storm events decrease that ratio to around 5. Source apportionment of stream DOC suggests a contribution of around 50 % from permafrost/deep-active-layer OC, which contrasts with patterns observed in large Arctic rivers (12 ± 8 %; Wild et al., 2019). Our 10 d monitoring period demonstrated temporal DOC patterns on multiple scales (i.e., diurnal patterns, storm events and longer-term trends), underlining the need for high-resolution long-term monitoring. First estimates of Black Creek annual DOC (8.2 ± 6.4 t DOC yr−1) and POC (0.21 ± 0.20 t yr−1) export allowed us to make a rough upscaling towards the entire Yukon Coastal Plain (34.51 ± 2.7 kt DOC yr−1 and 8.93 ± 8.5 kt POC yr−1). Rising Arctic temperatures, increases in runoff, soil organic matter (OM) leaching, permafrost thawing and primary production are likely to increase the net lateral OC flux. Consequently, altered lateral fluxes may have strong impacts on Arctic aquatic ecosystems and Arctic carbon cycling.

Risk assessment of paleo-bio-contamination of landscapes resulting from permafrost degradation by the example of reindeer pastures in the Republic of Sakha (Yakutia)

The possibility of ranking agro-landscape zones (using computer modeling) according to the risks of potential epizootics and epidemics associated with bio-contamination has been demonstrated. The task of agroecological land assessment cannot be conceptually solved without taking into account all forms of contamination. Bio-contamination of agricultural landscapes, both reversible (weeds) and irreversible (for example, anthrax spores Bacillus anthracis), is considered as a form of permafrost soils degradation. The melting of glaciers and permafrost thawing influenced by global warming determine a number of challenges. In particular, the climatically-driven transformation of the Pleistocene biota leads to the release of greenhouse gases, including methane, which is an order of magnitude stronger than carbon dioxide in terms of its contribution to the greenhouse effect and significantly increases the threat of accelerating warming. This paper examines the consequences of paleobiotic nature: during “thawing of tundra” pathogenic organisms, that were previously in biospheric isolation, pose a threat. It is noted that some of them retain their vital functions when emerging from cryobiosis. Such organisms are capable of causing soil bio-contamination, both reversible and irreversible, and can cause new outbreaks of repeated epizootics. It is proposed to identify and assess the risk zones of paleo-bio-contamination by the method of geometric stratification. The method allows identification and designation of the risk zones of pathogen infestation in specific geographical regions. This paper presents an assessment of such risk zones for reindeer (Rangifer tarandus) infection with a highly pathogenic anthrax causative agent (Bacillus anthracis) in relation to the administrative units (regions) of the Republic of Sakha (Yakutia). The zoning results obtained in this way not only characterize the existing ecological situation and create the basis for its understanding, but can also serve as a basis for the development of recommendations for competent administrative decision-making on the regulation of further use of the studied landscapes.

Инновационный конструкционно-теплоизоляционный бетон для изоляции и повышения устойчивости мерзлых грунтов основания

Purpose: To create highly effective heat-insulating structural concrete, recommended for insulating and preventing permafrost soil thawing. Methods: When conducting research, we used GOST (Russia State Standards) 25820-2014 “Lightweight concrete. Specifications”, GOST 25485—2019 “Cellular concrete. General technical conditions”. Determination of strength and processing of results according to GOST 10180-2012 “Concrete. Methods for determining strength upon control samples”; thermal conductivity coefficient was determined according to GOST 7076-99 “Construction materials and products. Method for determining thermal conductivity and thermal resistance at stationary thermal regime”; frost resistance of concrete according to GOST 10060-2012 “Concrete. Methods for determining frost resistance”; density of concrete in natural moisture state- according to GOST 12730.1-2020 “Concrete. Density determination methods”. It has been established experimentally that in order to create highly efficient heat-insulating-structural concrete, it is advisable to use as a filler a foam glass of fraction 1.25–2.5 mm, D250, λ ≈ 0.06 W/ m · °C, and for to create strong and reliable matrix on cement basis it’s effective to use finely dispersed microsilica in combination with complex chemical additive on polycarboxylate basis, modified with nano-dispersions of silicon dioxide, SiO2. Results of physicalmechanical studies have confirmed that it is effective to use particles of silicon dioxide together of micro- and nano-size in combination with surfactants represented by polycarboxylate polymers, meanwhile, foamed glass concrete with the best compressive strength and tensile strength at bending a rises significantly, coefficient of resistance to cracks of nanomodified foam glass concrete, Ktr. = Rbend./Rcompress. = 3.6/13.3 = 0.27, has rather high value which should provide for increased resistance to cracks and for reliability for a protective coating. In order to increase density/strength without deteriorating heat-insulating indicators it is advisable to use additionally a finely-ground blast-furnace slag as a filler which a rises cohesion of foam glass concrete mixture and strength of foam glass concrete. Practical significance: Rational ratio of components of nanomodified foam glass concrete mixture ensures the creation of highly mobile foam glass concrete mixture with good workability, and on the mixture basis, a unique heat-insulating-structural material is formed with the following characteristics: D900; λ = 0.14 W/m·°C, B12, Btb2.9 F1300 that defines it as a thermal insulation material of increased reliability and durability, which is advisable for recommendation for the Arctic harsh regions.

The Indicator Role of Algae in Assessing the Organic Pollution in the Lena River Delta, the Russian Arctic

The Lena River forms a delta, one of the largest in the world. The entire territory of the delta is part of the Ust-Lensky State Natural Reserve. The delta is located beyond the Arctic Circle in a continuous permafrost zone. The delta is crossed by numerous channels and has lakes, streams, hollows, and swamps. In the Russian Arctic sector, ambitious plans for the development of the oil industries are being implemented. This study goal was to determine the species composition of algae in the Lena River delta and to use their properties as indicators of organic water pollution as evidence of water ecosystem stress. The results of the study revealed 700 species from 10 phyla. Statistical analysis indicate that hydrological conditions are the main factor, which can be a stressor too regulating the spatial structure of the species composition of algal communities in the Lena River delta. The distribution of groups of indicators of organic pollution, trophic state, and type of nutrition of algal cells along the main water channels suggests that now a possible source of organic pollution may be the effect of mixing river and saline waters during high tide. It is evidenced by an increase in the number of mixotrophic organisms and indicators of increased trophic state. Therefore, the integral bioindication as a method that reveals hidden connections in the ecosystem can be useful for monitoring in the period of the accentuated development of the oil industries in this Arctic region.

Microbiome assembly in thawing permafrost and its feedbacks to climate.

The physical and chemical changes that accompany permafrost thaw directly influence the microbial communities that mediate the decomposition of formerly frozen organic matter, leading to uncertainty in permafrost–climate feedbacks. Although changes to microbial metabolism and community structure are documented following thaw, the generality of post‐thaw assembly patterns across permafrost soils of the world remains uncertain, limiting our ability to predict biogeochemistry and microbial community responses to climate change. Based on our review of the Arctic microbiome, permafrost microbiology, and community ecology, we propose that Assembly Theory provides a framework to better understand thaw‐mediated microbiome changes and the implications for community function and climate feedbacks. This framework posits that the prevalence of deterministic or stochastic processes indicates whether the community is well‐suited to thrive in changing environmental conditions. We predict that on a short timescale and following high‐disturbance thaw (e.g., thermokarst), stochasticity dominates post‐thaw microbiome assembly, suggesting that functional predictions will be aided by detailed information about the microbiome. At a longer timescale and lower‐intensity disturbance (e.g., active layer deepening), deterministic processes likely dominate, making environmental parameters sufficient for predicting function. We propose that the contribution of stochastic and deterministic processes to post‐thaw microbiome assembly depends on the characteristics of the thaw disturbance, as well as characteristics of the microbial community, such as the ecological and phylogenetic breadth of functional guilds, their functional redundancy, and biotic interactions. These propagate across space and time, potentially providing a means for predicting the microbial forcing of greenhouse gas feedbacks to global climate change.

Tree growth is connected with distribution and warming-induced degradation of permafrost in southern Siberia.

Hemiboreal and boreal forests growing at the southern margin of the permafrost distribution are vulnerable to climate warming. However, how climate warming threatens the growth of dominant tree species that are distributed on permafrost remains to be determined, particularly in synchrony with warming-induced permafrost degradation. Tree growth in the permafrost region of southern Siberia was hypothesized to be highly sensitive to temperature increasing and warming-induced permafrost degradation. To test this hypothesis, we sampled the tree ring width of 535 trees of dominant species, larch (including Larix gmelinii and L. sibirica) and white birch (Betula platyphylla), in ten hemiboreal to boreal forest plots within different permafrost zones. The relationships between the tree ring basal area index (BAI) and temperature, precipitation, and the Palmer drought severity index (PDSI) were compared among plots located in two permafrost zones. In the isolated permafrost zone, white birch grows better than larch and is not drought-stressed (p < .05). We suggest that the deep-rooted white birch benefits from the water from thawing permafrost, while the growth of the shallow-rooted larch is stressed by drought. In the sporadic discontinuous permafrost zone, both white birch and larch benefited from permafrost melting, but the sensitivity of larch growth to PDSI is still significant (p < .05), indicating drought is still an important climatic factor limiting the growth of larch. Our results imply that the permafrost degradation caused by climate warming affects tree growth by creating the root layer additional water source. In the future, it is necessary to focus on monitoring permafrost degradation to better predict forest dynamics at the southern margin of the permafrost distribution.

RETRACTED ARTICLE: The Impact of Climate Change on Permafrost Soils in Norilsk: Based on the Analysis of Geothermal Data

RETRACTED ARTICLE: The Impact of Climate Change on Permafrost Soils in Norilsk: Based on the Analysis of Geothermal Data

Changes in Unfrozen Water Contents in Warming Permafrost Soils

Climate warming in the Arctic, accompanied by changes in permafrost soil properties (mechanical, thermal, filtration, geophysical), is due to increasing unfrozen pore water content. The liquid component in frozen soils is an issue of key importance for permafrost engineering that has been extensively studied since the beginning of the 20th century. We suggest a synthesis and new classification of various experimental and calculation methods for the determination of unfrozen water content. Special focus is placed on the method of applying measurements to the water potential, which reveals the impact of permafrost warming on unfrozen water content. This method was applied to natural soil samples collected from shallow permafrost from northern West Siberia affected by climate change, and confirms the revealed trends. The obtained results confirm that unfrozen water content is sensitive not only temperature but also particle size distribution, salinity, and the organic matter content of permafrost soils.

The microbiome of cryospheric ecosystems

The melting of the cryosphere is among the most conspicuous consequences of climate change, with impacts on microbial life and related biogeochemistry. However, we are missing a systematic understanding of microbiome structure and function across cryospheric ecosystems. Here, we present a global inventory of the microbiome from snow, ice, permafrost soils, and both coastal and freshwater ecosystems under glacier influence. Combining phylogenetic and taxonomic approaches, we find that these cryospheric ecosystems, despite their particularities, share a microbiome with representatives across the bacterial tree of life and apparent signatures of early and constrained radiation. In addition, we use metagenomic analyses to define the genetic repertoire of cryospheric bacteria. Our work provides a reference resource for future studies on climate change microbiology.

Qinghai‐Tibet Plateau Permafrost at Risk in the Late 21st Century

AbstractGlobal warming has led to permafrost degradation worldwide. The Qinghai‐Tibet Plateau (QTP) hosts most of the world's alpine permafrost, yet its impending changes remain largely unclear, thereby affecting regional hydrological and ecological processes and the global carbon budget. By employing a land surface model adapted to simulate frozen ground, and using state‐of‐the‐art multi‐model and multi‐scenario data from the Coupled Model Intercomparison Project Phase 6, changes in permafrost distribution and its thermal regimes on the QTP are systematically predicted under various shared socioeconomic pathways (SSPs). Projections for SSP2‐4.5, SSP3‐7.0, and SSP5‐8.5 show that most of the continuous permafrost region of the QTP will persist through 2050. Much of the permafrost is likely to degrade in the late 21st century, with projected area losses of 44 ± 4%, 59 ± 5%, and 71 ± 7%, respectively, by 2100. In particular, the Three Rivers Source region in the central eastern part of the QTP is a key area of permafrost degradation, where permafrost is most vulnerable and degradation occurs earliest. The mean annual ground temperature of QTP permafrost will increase by 0.8 ± 0.2°C, 2.0 ± 0.3°C, and 2.6 ± 0.3°C under SSP2‐4.5, SSP3‐7.0, and SSP5‐8.5, respectively, and the active layer thickness will increase by 0.7 ± 0.1 m, 1.5 ± 0.3 m, and 3.0 ± 1.0 m, respectively. The surviving permafrost under SSP3‐7.0 and SSP5‐8.5 will be thermally unstable, which is a clear warning sign of complete disappearance. The analysis of permafrost sensitivity to climate change signifies that alpine permafrost on the QTP has low resilience to climate change, in contrast to permafrost in pan‐Artic high latitudes.

Ground deformation as a result of the foundation of a new module in the Spanish Antarctic Base Gabriel de Castilla, Deception Island, Antarctica

Since its inauguration in the 1989/90 campaign, the Spanish Antarctic Base Gabriel de Castilla (BAEGC) has supported an increasing volume of scientific projects, stimulating the expansion of its facilities. The permafrost soil on which they are located is affected by changing thermal and periglacial conditions that disturb its mechanical and physical characteristics. This paper analyzes the foundation behavior of a building (18.5x6.5x2.7 m length – width – height, around 104 kg in operation supported on 16 posts) through the geomechanical study (stresses and deformations) of the ground during the winter and southern summer seasons, supported by three types of foundations: piles, footings and slabs. These are commonly recommended as support elements inperiglacial soils affected by thermal-seasonal variations. The geotechnical properties have been obtained from stress-tests on soil samples collected in the surroundings of the BAEGC, General Marvá Army Engineers Laboratory (INTA). Considering the thermal variations in the tests on frozen and unfrozen samples, the geotechnical column type has been established and extended along the profile of the 2D domain. The stationary stress-strain equations with a constitutive Mohr-Coulomb rupture model have been solved using finite elements in MIDAS GTS-NX, for each season and each foundation, discretizing with a triangular or quadrangular mesh adapted to the 2D domain geometry with the foundation. The numerical results show that, in any tested case, there is no critical ground failure, and the foundation with the smallest displacement (about 0.036 m), both in summer and winter, is the 1.2 m foundation placed at 0.5 m depth on permafrost.