Permafrost Research Articles

Awakening: Potential Release of Dormant Chemicals from Thawing Permafrost Soils under Climate Change.

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.

Major moisture shifts in inland Northeast Asia during the last millennium

Abstract Previous paleoenvironmental data synthesis indicates that arid central Asia (“westerlies Asia”) and mid-latitude East Asia (“monsoonal Asia”) show anti-phased moisture variations over the last millennium. However, there are very few records from inland Northeast Asia, which obscures the spatial extent of or the boundary between the two domains and hinders the assessment of climate change impacts and consequences across the region. Here, we present a multi-proxy record that combines peat properties, plant macrofossils, and isotopic ratios of Sphagnum moss cellulose from a unique precipitation-fed peatland in northern Northeast China to fill this critical data gap. The results show major centennial-scale moisture anomalies at this site, with drier and wetter conditions during the Medieval Warm Period and Little Ice Age, respectively, which resemble the pattern of moisture changes in “westerlies Asia”. During the period of rapid anthropogenic warming, the site is much drier, with isotopic evidence for threshold-like summer desiccation of peat-forming Sphagnum mosses. This study provides the long-term context and identifies the large-scale pattern of moisture variability in an inland region home to carbon-rich peatlands, forests, and permafrost soils, and highlights their potential vulnerability to future warming-enhanced drying that can be transmitted widely through atmospheric teleconnection.

Freeze-thaw strength increases microbial stability to enhance diversity-soil multifunctionality relationship

Insights into the impacts of freeze-thaw processes on soil microorganisms and their related functions in permafrost regions are crucial for assessing ecological consequences imposed by the shifts in freeze-thaw patterns. Through in-situ investigations on seasonal freeze-thaw processes in the active layer of permafrost in the Qinghai-Tibet Plateau, we found that microbial richness was higher and positively correlated with soil multifunctionality during the freeze-thaw stage (freezing and thawing periods) compared to the non-freeze-thaw stage (completely frozen and thawed periods). This relationship resulted from the higher microbial stability, which was highly consistent with the lower complexity, more keystone taxa, and greater robustness of networks. Although freeze-thaw strength exacerbated the greenhouse effect on climate, it was alleviated by the enhancement of diversity-soil multifunctionality relationship. These findings have substantial implications for exploring the responses of microbial-mediated soil multifunctionality and greenhouse effect in alpine permafrost to more drastic variations of freeze-thaw processes under future warming.

Phosphorus pool distributions and adsorption-desorption characteristics of soil aggregates in cut slopes of a permafrost zone in the Qinghai-Tibetan Plateau

Soil phosphorus (P) has attracted considerable attention from researchers because of its role in the restoration and stabilization processes of cut slopes in permafrost regions. However, the soil P pool distributions and adsorption-desorption characteristics in alpine cut slopes remain unclear. In this context, we examined in this study the P pools in the aggregates of surface cut soil slopes (0‐10 cm) in areas with three permafrost types, including perennially frozen soil (PF), seasonally frozen ground (SFG), and non-frozen soil (NFS) in the Qinghai-Tibet Plateau, China. In addition, we assessed the P adsorption-desorption characteristics and their correlations with the P pools. The results showed the significant effects of the permafrost types on the contents of total P (TP), available P (AP), labile P (LP), moderately labile P (MLP) and stable P (SP). The inorganic P (IP) contents were higher than those of organic P (OP) in the cut soil slopes of the three permafrost types. In addition, H2O-Pi and NaHCO3-Pi accounted for small proportions of IP, while NaHCO3-Po accounted for the smallest proportion of OP. On the other hand, the SP contents in the soil aggregates were generally higher than those of MLP and LP. In fact, the LP contents in the PF, SFG, and NFS were 72.55, 44.68, and 49.42 mg/kg, respectively. The AP contents in the cut soil slopes of the three permafrost types were significantly correlated with the MLP and LP contents. Moreover, the P adsorption-desorption characteristics of the SFG and NFS were closely related to AP and MLP. Compared with the PF and NFS, the SFG exhibited low and high P adsorption and desorption capacities, respectively. The findings of this study provided an important theoretical basis for the restoration of cut slopes in alpine permafrost regions.

Deciphering the Intricate Control of Minerals on Deep Soil Carbon Stability and Persistence in Alaskan Permafrost.

Understanding the fate of organic carbon in thawed permafrost is crucial for predicting climate feedback. While minerals and microbial necromass are known to play crucial roles in the long-term stability of organic carbon in subsoils, their exact influence on carbon persistence in Arctic permafrost remains uncertain. Our study, combining radiocarbon dating and biomarker analyses, showed that soil organic carbon in Alaskan permafrost had millennial-scale radiocarbon ages and contained only 10%-15% microbial necromass carbon, significantly lower than the global average of ~30%-60%. This ancient carbon exhibited a weak correlation with reactive minerals but a stronger correlation with mineral weathering (reactive iron to total iron ratio). Peroxidase activity displayed a high correlation coefficient (p < 10-6) with Δ14C and δ13C, indicating its strong predictive power for carbon persistence. Further, a positive correlation between peroxidase activity and polysaccharides indicates that increased peroxidase activity may promote the protection of plant residues, potentially by fostering the formation of mineral-organic associations. This protective role of mineral surfaces on biopolymers was further supported by examining 1451 synchrotron radiation infrared spectra from soil aggregates, which revealed a strong correlation between mineral OH groups and organic functional groups at the submicron scale. An incubation experiment revealed that increased moisture contents, particularly within the 0%-40% range, significantly elevated peroxidase activity, suggesting that ancient carbon in permafrost soils is vulnerable to moisture-induced destabilization. Collectively, this study offers mechanistic insights into the persistence of carbon in thawed permafrost soils, essential for refining permafrost carbon-climate feedbacks.

A 14,000‐Year Sediment Record of Mercury Accumulation and Isotopic Signatures From Lake Malaya Chabyda (Siberia)

AbstractEurasian permafrost soils contain large amounts of organic carbon (OC) and mercury (Hg), sequestered by vegetation during past and present interglacial periods. Lake sediment archives may help understand past OC and Hg dynamics and how they interact with climate‐related variables. We investigated Hg accumulation, OC dynamics, and Hg and OC stable isotopes in a 14,000‐year sediment record from Lake Malaya Chabyda (Central Yakutia, Russia). Sediment Hg was correlated to OC (p value &lt; 0.01), with lower OC and Hg accumulation rates (OCAR, HgAR) during the cold Younger Dryas (YD, 12,900–11,700 cal BP), when the lake level was low. Elevated sediment Δ200Hg (0.05‰ ± 0.11‰), representing dominant HgII deposition, and low δ13C, indicates low lake primary productivity during the YD. During the early Holocene, Δ200Hg and Δ199Hg decreased, while δ13C, δ202Hg, OCAR, and HgAR increased, suggesting enhanced algal primary productivity in deeper, more turbid waters. From 4,100 cal BP to present, Hg/OC ratios and HgAR increased at constant OCAR, indicating an additional Hg source to the lake. Analysis of Hg isotopes suggests direct Hg0 uptake into lake waters, potentially driven by primary production and efficient Hg burial. Our observations suggest that the gradual climate warming since the Last Glacial Termination and into the early Holocene led to enhanced OC and Hg burial in northern lakes and watersheds. Late Holocene enhanced Hg burial, but not OC, is possibly related to a renewed increase in lake primary productivity. Continued global warming may lead to further Hg sequestration in northern aquatic ecosystems.

Isotopic seasonality of fluvial-derived greenhouse gases implies active layer deepening

Abstract Climate change in the northern circumpolar regions is rapidly thawing organic-rich permafrost soils, releasing substantial dissolved CO2 and CH4 into fluvial systems. This mobilization impacts local ecosystems and global climate feedback loops, playing a crucial role in the Arctic carbon cycle. Here, we analyze the stable carbon (δ13C) and radiocarbon (F14C) isotopic composition of dissolved CO2 and CH4 in the Sagavanirktok and Kuparuk River watersheds on the North Slope, Alaska. By examining spatial and seasonal variations in these isotopic signatures, we identify patterns of carbon release and transport along the river continuum. We find consistent CO2 isotopic signatures across the fluvial continuum, reflecting a mixture of geogenic and biogenic sources integrated throughout the watershed. Bayesian mixing models further demonstrate a systematic depletion in 13C and 14C signatures of dissolved CO2 sources from spring to fall, indicating increasing contributions of aged carbon as the active layer deepens seasonally. This seasonal deepening allows percolating groundwater to access deeper, older soil horizons, transporting CO2 produced by aerobic and anaerobic soil respiration to streams and rivers. In contrast, we observe no clear relationships between the 13C and 14C compositions of dissolved CH4 and landscape properties. Given the reduced solubility of CH4, which facilitates outgassing and limits its transport in aquatic systems, the isotopic signatures are likely indicative of localized contributions from streambeds, adjacent water saturated soils, and lake outflows. Our study demonstrates that dissolved greenhouse gases are sensitive indicators of the release of old carbon from thawing permafrost and serve as early warning signals for permafrost carbon feedback. It establishes a crucial baseline for understanding their role in regional carbon cycling and Arctic environmental change.&amp;#xD;

Permafrost Region Greenhouse Gas Budgets Suggest a Weak CO2 Sink and CH4 and N2O Sources, But Magnitudes Differ Between Top‐Down and Bottom‐Up Methods

AbstractLarge stocks of soil carbon (C) and nitrogen (N) in northern permafrost soils are vulnerable to remobilization under climate change. However, there are large uncertainties in present‐day greenhouse gas (GHG) budgets. We compare bottom‐up (data‐driven upscaling and process‐based models) and top‐down (atmospheric inversion models) budgets of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) as well as lateral fluxes of C and N across the region over 2000–2020. Bottom‐up approaches estimate higher land‐to‐atmosphere fluxes for all GHGs. Both bottom‐up and top‐down approaches show a sink of CO2 in natural ecosystems (bottom‐up: −29 (−709, 455), top‐down: −587 (−862, −312) Tg CO2‐C yr−1) and sources of CH4 (bottom‐up: 38 (22, 53), top‐down: 15 (11, 18) Tg CH4‐C yr−1) and N2O (bottom‐up: 0.7 (0.1, 1.3), top‐down: 0.09 (−0.19, 0.37) Tg N2O‐N yr−1). The combined global warming potential of all three gases (GWP‐100) cannot be distinguished from neutral. Over shorter timescales (GWP‐20), the region is a net GHG source because CH4 dominates the total forcing. The net CO2 sink in Boreal forests and wetlands is largely offset by fires and inland water CO2 emissions as well as CH4 emissions from wetlands and inland waters, with a smaller contribution from N2O emissions. Priorities for future research include the representation of inland waters in process‐based models and the compilation of process‐model ensembles for CH4 and N2O. Discrepancies between bottom‐up and top‐down methods call for analyses of how prior flux ensembles impact inversion budgets, more and well‐distributed in situ GHG measurements and improved resolution in upscaling techniques.

Shift in potential pathogenic bacteria during permafrost degradation on the Qinghai-Tibet Plateau

Permafrost acts as a potential pathogen reservoir. With accelerating climate change and intensifying permafrost degradation, the release of these pathogens poses significant threats to ecosystems and public health. However, the changes in pathogenic communities during permafrost degradation remain unclear. This study utilized quantitative PCR and Illumina high-throughput sequencing to analyze the composition and quantities of potential pathogenic bacteria in four types of permafrost soil on the northeast edge of the Qinghai-Tibet Plateau (QTP): sub-stable permafrost (SSP), transition permafrost (TP), unstable permafrost (UP), and extremely unstable permafrost (EUP). The results showed that during permafrost degradation, the quantity of potential pathogenic bacteria decreased from 7.8 × 106 to 3.1 × 106 copies/g. Both the Richness and Shannon indices initially declined from SSP, to TP, UP, and then began to rise when permafrost degraded to EUP. A total of 216 potential pathogenic bacterial species were identified, including 166 animal pathogens, 28 zoonotic pathogens, and 22 plant pathogens. The pathogenic community intergroup differences (ANOSIM), unique taxa, and dominant pathogen analysis indicated the significant changes in pathogenic communities during permafrost degradation. The potential pathogenic community was significantly influenced by non-pathogenic bacterial communities (Procrustes analysis), with soil moisture being the primary environmental factor, followed by TDS, soil organic carbon, and total nitrogen. SourceTracker2 analysis indicated that the majority of potential pathogenic bacteria in the soil originated from external sources, only a small portion coming from the permafrost itself. These findings suggest that a large number of pathogens were released into the environment while also preserving amount from external sources. It elucidates that each stage of permafrost degradation presents unique biosecurity risks. This study highlights the release and redistribution of pathogenic bacteria associated with the potential public health risks. It provides the crucial insights into the ecological dynamics of permafrost degradation, emphasizing the need for ongoing monitoring and proactive management strategies.

Uranium Speciation and Mobilization in Thawing Permafrost.

Uranium is a toxic and pervasive geogenic contaminant often associated with organic matter. Its abundance and speciation in organic-rich permafrost soils are unknown, thereby limiting our ability to assess risks associated with uranium mobilization during permafrost thaw. In this study, we assessed uranium speciation in permafrost soil and porewater liberated during thaw using active-layer and permafrost samples from a study area in Yukon, Canada where elevated uranium concentrations occur in bedrock and groundwater. Permafrost contained 1.1-28 wt % organic carbon and elevated uranium (range 7.6-1040 μg g-1, median 25 μg g-1) relative to local bedrock. The highest soil uranium concentrations were encountered in catchments hosting uranium-enriched bedrock and correlated positively with soil organic carbon. X-ray absorption spectroscopy, micro-X-ray fluorescence, and electron microscopy analyses revealed that solid-phase uranium predominantly occurs as uranium(VI) associated with soil organic matter. Extended X-ray absorption fine structure (EXAFS) analyses suggested the presence of uranium(VI) coordinated with carbon, consistent with bidentate-mononuclear uranyl complexation on carboxyl groups. Permafrost thaw produced circumneutral pH porewater (pH 6.2-7.5) with elevated dissolved uranium (0.5-203 μg L-1). Geochemical modeling indicated that calcium-uranyl-carbonate complexes dominated the dissolved uranium speciation. This study highlights that permafrost soil can mobilize uranium upon thaw and that uranium fate is linked to dynamic biogeochemical reactions involving organic carbon and groundwater chemistry.

Road Site Inspection and Measures to Avoid Further Deformation

Strength and stability of the roadbed and engineering structures in permafrost conditions and deep seasonal freezing of soils always remain complex scientific, technical and technological problem in construction and reconstruction of roads in northern regions. Particularly important is the spread of subgrade subsidence during construction and further operation and maintenance of roads in these regions. The road destruction is mostly caused by both global warming and geological and hydrogeological conditions.To prevent the deformation development, it is necessary to provide a number of special engineering measures to prevent thawing of permafrost soils or strengthen supra-permafrost layers of foundations. The purpose of the work is to study methods for eliminating deformation of the road bed in permafrost and choosing the main method for eliminating subsidence of the road.The article discusses several ways to solve the problem of eliminating subsidence on of the federal highway. Options for reconstruction of the roadbed are considered. These are different methods of thermal stabilization, i.e., horizontal (sloping) thermal stabilization system with inclined thermal stabilizers, temporary vertical thermal stabilizers for pre-construction freezing of foundation soils, and hybrid thermal stabilization system (horizontal and vertical thermal stabilizer in one product). A method is proposed for stabilizing the road base by installing soil-cement piles. The main advantages of and disadvantages the methods are noted and cost assessment is made. A conclusion is drawn on the effectiveness of different methods to restore the subgrade structure in order to ensure the road base stability. The main method is elimination of subsidence by stabilizing the road base with installation of soil-cement piles.

Prospects for the use of Foam Glass Products in the Foundation of Buildings and Structures on Long Term Frozen Soils

The degradation of permafrost is the reason for the increase in deformability of the foundations of buildings and structures built on long term frozen soils. It is necessary to develop geotechnical solutions that guarantee their operational reliability in a warming climate. The introduction of foam glass for use in the cryolithozone as thermal insulation solutions making it possible to preserve the frozen state of the soils of the bases is relevant. This will make it possible to limit the use of materials with lower durability. The existing scope of application of foam glass in Russia and the prospects for the use of foam glass products in the permafrost zone are considered. The high prospects of using foam glass at the base of buildings and structures on permafrost soils are determined by its physico-mechanical and thermos-physical characteristics such as durability, low water absorption and environmental safety. These properties of foam glass make it a promising material for use in the long term frozen soils zone. The main advantages of foam glass in comparison with its analogues are also low sorption capacity and capillary absorbency, high strength, fire resistance and resistance against aggressive media. In the production of foam glass for use in the cryolithozone, it is possible to use alternative local sources of raw materials: aluminosilicate and siliceous rocks. This will reduce the cost of the material, make it more affordable and increase sales volumes.

Water budgets in an arid and alpine permafrost basin: Observations from the High Mountain Asia

Ground freeze‒thaw processes have significant impacts on infiltration, runoff and evapotranspiration. However, there are still critical knowledge gaps in understanding of hydrological processes in permafrost regions, especially of the interactions among permafrost, ecology, and hydrology. In this study, an alpine permafrost basin on the northeastern Qinghai‒Tibet Plateau was selected to conduct hydrological and meteorological observations. We analyzed the annual variations in runoff, precipitation, evapotranspiration, and changes in water storage, as well as the mechanisms for runoff generation in the basin from May 2014 to December 2015. The annual flow curve in the basin exhibited peaks both in spring and autumn floods. The high ratio of evapotranspiration to annual precipitation (>1.0) in the investigated wetland is mainly due to the considerably underestimated ‘observed’ precipitation caused by the wind-induced instrumental error and the neglect of snow sublimation. The stream flow from early May to late October probably came from the lateral discharge of subsurface flow in alpine wetlands. This study can provide data support and validation for hydrological model simulation and prediction, as well as water resource assessment, in the upper Yellow River Basin, especially for the headwater area. The results also provide case support for permafrost hydrology modeling in ungauged or poorly gauged watersheds in the High Mountain Asia.

Temperature related to the spatial heterogeneity of wetland soil total nitrogen content in a frozen zone

Changes in soil total nitrogen (N) content would affect wetland function and the global N cycle. Determination of spatial heterogeneity controlling factors of wetland soil total N content per unit mass is essential to assess responses of ecosystem N cycle to global change. However, such information is limited in permafrost zones because few soil profiles have been acquired and methods to predict spatial distributions of wetland soil total N content in large areas are inefficient, which increase uncertainty in evaluations of N cycle at national or global scales. To determine the spatial heterogeneity of wetland soil total N content at different soil depths and frozen zones and the factors controlling wetland soil total N content in the frozen zones of Northeast China, the spatial pattern of wetland soil total N content was investigated by using a random forest method that combined field samples with environmental factors. Vertically, wetland soil total N content decreased with increasing soil depth, with the highest content in the top soil layer (0–30 cm). Spatially, wetland soil total N content decreased from northwest to southeast, with relatively high total N content in a continuous permafrost zone and relatively low total N content in a seasonally frozen zone. The overall coefficient of variation of wetland soil total N content in the frozen zones of Northeast was 29.58 %, indicating moderate variation. Land surface temperature, mean annual temperature, and mean annual humidity significantly affected total N content in 0–30 and 30–60 cm soil layers, suggesting that variations in temperature and humidity altered sequestration processes of wetland soil total N content. In the 60–100 cm soil layer, compared with other environmental factors, mean annual humidity, altitude, and mean annual precipitation had the greatest influence on the spatial distribution of wetland soil total N content. The study unravels the spatial pattern of soil total N content in frozen zones of Northeast China and reflects the direct and indirect effects of environmental factors on total N content. This provides a basis for the management and protection of wetland ecosystems.

Toward long-term monitoring of regional permafrost thaw with satellite interferometric synthetic aperture radar

Abstract. Active-layer thickness (ALT) is estimated for a study area in northern Alaska's continuous-permafrost zone using satellite data from Sentinel-1 (radar) and ICESat-2 (lidar) for the period 2017 to 2022. Synthetic aperture radar (SAR) interferograms were generated using the Short Baseline Subset (SBAS) approach. Displacement time series over the thaw season (June–September) are fit well with a linear model (root mean square error (RMSE) scatter is less than 7 mm) and show maximum seasonal subsidence of 20–60 mm. ICESat-2 products were used to validate the interferometric synthetic aperture radar (InSAR) displacement time series. ALT was estimated from measured subsidence using a widely used model exploiting the volume difference between ice and water, reaching a maximum depth in our study area of 1.5 m. Estimated ALT is in good agreement with in situ and other remotely sensed data but is sensitive to assumed thaw season onset, indicating the need for reliable surface temperature data. Our results suggest the feasibility of long-term permafrost monitoring with satellite InSAR. However, the C-band (∼55 mm center wavelength) Sentinel radar is sensitive to vegetation cover and, in our studies, was not successful for similar monitoring in the heavily treed discontinuous-permafrost zone of central Alaska.

Effects of Wildfires on Soil Organic Carbon in Boreal Permafrost Regions: A Review

ABSTRACTWildfire strongly influences permafrost environment and soil organic carbon (SOC) pool. In this study, we reviewed the effects of fire severity, time after a fire, and frequency on SOC in boreal permafrost regions. This review highlighted several key points: the effect of wildfires on SOC increased with an increase of fire severity, and the amount of vegetation returned and surface organic matter replenished was less in a short term, which resulted in a significantly lower SOC content compared to that of before the fire. Within a short period after fire, the SOC in near‐surface permafrost and the active layer decreased significantly due to the loss of above ground biomass, permafrost thaw, and increased microbial decomposition; as the years pass after a fire, the SOC gradually accumulates due to the contributions of litter layer accumulation and rooting systems from different stages of succession. The increase in fire frequency accelerated permafrost thawing and the formation of thermokarst, resulting in the rapid release of a large amount of soil carbon and reduced SOC storage. Therefore, the study on the effects of wildfires on SOC in the boreal permafrost region is of great significance to understanding and quantifying the carbon balance of the ecosystem.

High biological N fixation potential dominated by heterotrophic diazotrophs in alpine permafrost rivers on the Qinghai‒Tibet Plateau

Biological nitrogen (N) fixation is a pivotal N source in N-deficient ecosystems. The Qinghai‒Tibet Plateau (QTP) region, which is assumed to be N limited and suboxic, is an ideal habitat for diazotrophs. However, the diazotrophic communities and associated N fixation rates in these high-altitude alpine permafrost QTP rivers remain largely unknown. Herein, we examined diazotrophic communities in the sediment and biofilm of QTP rivers via the nitrogenase (nifH) gene sequencing and assessed their N fixing activities via a 15N isotope incubation assay. Strikingly, anaerobic heterotrophic diazotrophs, such as sulfate- and iron-reducing bacteria, had emerged as dominant N fixers. Remarkably, the nifH gene abundance and N fixation rates increased with altitude, and the average nifH gene abundance (2.57 ± 2.60 × 108 copies g−1) and N fixation rate (2.29 ± 3.36 nmol N g−1d−1) surpassed that documented in most aquatic environments (nifH gene abundance: 1.31 × 105 ∼ 2.57 × 108 copies g−1, nitrogen fixation rates: 2.34 × 10−4 ∼ 4.11 nmol N g−1d−1). Such distinctive heterotrophic diazotrophic communities and high N fixation potential in QTP rivers were associated with low-nitrogen, abundant organic carbon and unique C:N:P stoichiometries. Additionally, the significant presence of psychrophilic bacteria within the diazotrophic communities, along with the enhanced stability and complexity of the diazotrophic networks at higher altitudes, clearly demonstrate the adaptability of diazotrophic communities to extreme cold and high-altitude conditions in QTP rivers. We further determined that altitude, coupled with organic carbon and phosphorus, was the predominant driver shaping diazotrophic communities and their N-fixing activities. Overall, our study reveals high N fixation potential in N-deficient QTP rivers, which provides novel insights into nitrogen dynamics in alpine permafrost rivers.

Carbon dynamics in an alluvial fan in the eastern Canadian Arctic

Alluvial fans are common features of mountainous landscapes in circumpolar regions and are characterized by a suit of hillslope processes that drive sediment distribution. At present there is little known about the biogeochemistry of these systems. Thus, this study aimed to understand alluvial fan soil carbon (C) dynamics. Surface and permafrost soil was retrieved in the apex, mid-section, and foot of a fan on Bylot Island in the Canadian Arctic. Soil characteristics such as grain size distribution, ice content and major ions, electric conductivity, as well as total C and nitrogen (N) contents were determined. Moreover, soil organic carbon (SOC) pools were assessed using density fractionation in combination with acid hydrolysis. Despite the strong influence of hillslope processes on physical sediment characteristics, hillslope location had no effect on SOC and N stocks. However, fractionation analysis showed that hillslope processes facilitate the degradation of soil C prior to its burial and integration into permafrost soil, where over 90% of the SOC pool associated with the mineral-fraction is resistant to degradation. Hence, SOC pools at the foot of alluvial fans may be considered relatively stable.

Substantiation of the Monitoring Network of Talik Zones in Urbanized Permafrost Areas Based on GPR Profiling Data (Anadyr, Chukotka)

Modern climatic changes have an impact on the bearing capacity of permafrost soils at the base of the foundations of buildings and structures in the urbanized territories of the Arctic and Subarctic. The activation of cryogenic processes leads to the destruction of infrastructure and to social, economic, and environmental consequences for the population. Based on the results for the geothermy of frozen and thawing soil, and on the georadar profiling of the city of Anadyr, it was concluded that the main risks of permafrost degradation are associated with the spread of hydrogenic melting zones. Maps of the soil temperature in imaginary cross-sections with depths of 3, 5, and 10 m were compiled, along with maps of the capacity of thawing soils, the permafrost aquifer, and the dangerous spread zones for exogenous cryogenic processes. The total area of talik zones with a depth of 6 m or more in the urban area was 2.34 km2, or 67% of the built-up area. The system of permafrost monitoring in the territory of Anadyr was substantiated, and is based on monitoring the boundaries of talik zones. It consists of an automated network of observations of the ground temperature in 35 wells at the boundary and in the center of 20 zones of the dangerous development of exogenous cryogenic processes, as well as 12 control GPR profiles at the intersection of linear hydrogenic taliks.

Upland Yedoma taliks are an unpredicted source of atmospheric methane

Landscape drying associated with permafrost thaw is expected to enhance microbial methane oxidation in arctic soils. Here we show that ice-rich, Yedoma permafrost deposits, comprising a disproportionately large fraction of pan-arctic soil carbon, present an alternate trajectory. Field and laboratory observations indicate that talik (perennially thawed soils in permafrost) development in unsaturated Yedoma uplands leads to unexpectedly large methane emissions (35–78 mg m−2 d−1 summer, 150–180 mg m−2 d−1 winter). Upland Yedoma talik emissions were nearly three times higher annually than northern-wetland emissions on an areal basis. Approximately 70% emissions occurred in winter, when surface-soil freezing abated methanotrophy, enhancing methane escape from the talik. Remote sensing and numerical modeling indicate the potential for widespread upland talik formation across the pan-arctic Yedoma domain during the 21st and 22nd centuries. Contrary to current climate model predictions, these findings imply a positive and much larger permafrost-methane-climate feedback for upland Yedoma.