Rapid Permafrost Research Articles

Permafrost and Structural Controls on Holocene Bedrock Landslide Occurrence Around Eyjafjörður, North‐Central Iceland

AbstractRapid, transient, landscape‐scale changes associated with deglaciation can condition slopes for failure and trigger bedrock landslides. However, the mechanisms leading to paleo rock slope failures following the last glacial period are challenging to infer because observations of how both landsliding and potential driving factors were distributed in space and time are limited. Here, we map and analyze the spatiotemporal pattern of 676 post‐glacial bedrock landslides around Eyjafjörður in north‐central Iceland using 2‐m resolution digital elevation data generated from optical stereo satellite imagery. Frequency‐ratio analysis demonstrates that after controlling for slope, landslides are most overrepresented within 2.6 km horizontal distances from surface projections of major Tertiary bedrock structures and at land surface elevations within 300 m of a modeled lower limit to permafrost. Surface roughness analysis of landslide deposits indicates that peak landslide frequency of at least 0.2 landslides yr−1 in the 5,579 km2 study area lagged deglaciation by several thousand years. This timing aligns well with that of rapid permafrost degradation from the Younger Dryas (12.9–11.7 cal ky BP) through the Holocene Thermal Maximum (∼10–7 cal ky BP). Landslide frequency has averaged about 0.014 landslides yr−1 since the Holocene Thermal Maximum when the climate has generally been cooler and permafrost has been more extensive. However, present day warming is likely to reduce permafrost extent and increase the potential for bedrock landslides in north‐central Iceland, as has already been observed for several recent shallower landslides in regolith.

Biogeographic patterns shape the bacterial community beyond permafrost gradients

Abstract Global warming has led to extensive permafrost degradation, particularly in thermally vulnerable permafrost in the marginal or transitional zones of altitudinal or latitudinal permafrost. However, comprehensive knowledge about microbial communities in response to rapid permafrost degradation at large (or interregional) scales remains elusive. In this meta-analysis, existing published data were utilized to identify the distributive and co-occurrence patterns of the microbiome in two interregional locations: the Qilian Mountains on the northeastern Qinghai–Tibet Plateau (NE-QTP) and the Xing’anling Mountains in Northeast China (NE-China). Both areas are situated in the marginal zone of large permafrost units. The results reveal that the rapidly degrading permafrost did not overshadow the regional biogeographic pattern of the microbial community. Instead, the results show some distinctive biogeographic patterns, as characterized by different groups of characteristic bacterial lineages in each of the two regions. Soil pH has emerged as a crucial controlling factor on the basis of the available environmental data. Network-based analyses suggest a generally high level of natural connectivity for bacterial networks on the NE-QTP; however, it collapses more drastically than that in NE-China if the environmental perturbations exceed the tipping point. These findings indicate that the biogeographic patterns of the bacterial community structure are not significantly altered by permafrost degradation. This research provides valuable insights into the development of more effective management methods for microbiomes in rapidly degrading permafrost.

Insights into permafrost aggradation and thawing: A case study of Zonag Lake on the Qinghai–Tibet Plateau using SAR interferometry

AbstractLakes on the Qinghai–Tibet Plateau (QTP) are important indicators of climate change. The water level and area of Zonag Lake have increased sharply since 2000, and the west lake bottom area was exposed after an outburst of flood in September 2011. The drained basin was exposed to the cold environment, causing rapid permafrost forming. In this paper, time‐series synthetic aperture radar interferometry (InSAR) was utilized to monitor the surface deformation of the drained basin using Sentinel‐1A images within a 4‐year period (2017–2020). This research focused on characterizing the spatial and temporal dynamics of ground deformation and exploring changes in the permafrost base around the drained basin based on the deformation information. The experimental results revealed spatially variable ground deformation, with long‐term deformation rates ranging from −78.3 mm/year to 72.8 mm/year and seasonal amplitudes of 0–14 mm. Subsidence was prominent in the lakeshore, the thermokarst region and the slope drainage area, indicative of the thawing of ice‐rich permafrost. Conversely, uplift was concentrated in the exposed unconsolidated sediment region, with a maximum displacement of 110 mm over the nearly 4‐year observation period, suggesting ground ice aggradation. The uplift information was used to estimate the change in the permafrost base in the drained basin, yielding a maximum value of 4 m. The estimated permafrost base change closely aligned with simulated results, with an error of 0.28 m. This study demonstrates the capability of InSAR in monitoring permafrost stability and improving the understanding of the dynamic permafrost formation process.

Thaw slump development and other rapid permafrost disturbances in Hollendardalen Valley, Svalbard

From 2019 to 2022, for the first time in Svalbard, the rapid development of a thaw slump was observed in Hollendardalen Valley (Nordenskiöld Land, West Spitsbergen), affecting an area of 6300 m2. Fast-paced thermokarst and thermo-erosion processes exposed massive ground ice, as well as thick ground ice veins within frozen silt strata. In the riverbed – in a non-carbonate, non-karstifying geological setting – thaw funnels appeared, swallowing part of the river flow, presumably via a local fault zone connecting to deep aquifers. The exposed ground ice has extremely low mineralization, dominated by Na+ and SO42− ions. The properties and morphology of the ice veins point to segregation origins. The broad middle reaches of the Hollendardalen Valley exhibit thermokarst depressions and lakes, tabular terrace remnants and traces of past thaw slumping. Such morphology represents a thermo-erosional plain, formed through the interplay of fluvial erosion and a series of fast-paced thermo-erosion and thermokarst events. The very presence of massive ground ice in places where its appearance was previously unexpected indicates the possibility of detecting further ground ice of various thicknesses in Svalbard. Thus, ongoing and future permafrost warming will likely accelerate rapid permafrost thaw in Svalbard, reshaping the surface morphology and subsurface hydrology.

Abrupt increase in Arctic-Subarctic wildfires caused by future permafrost thaw

Unabated 21st-century climate change will accelerate Arctic-Subarctic permafrost thaw which can intensify microbial degradation of carbon-rich soils, methane emissions, and global warming. The impact of permafrost thaw on future Arctic-Subarctic wildfires and the associated release of greenhouse gases and aerosols is less well understood. Here we present a comprehensive analysis of the effect of future permafrost thaw on land surface processes in the Arctic-Subarctic region using the CESM2 large ensemble forced by the SSP3-7.0 greenhouse gas emission scenario. Analyzing 50 greenhouse warming simulations, which capture the coupling between permafrost, hydrology, and atmosphere, we find that projected rapid permafrost thaw leads to massive soil drying, surface warming, and reduction of relative humidity over the Arctic-Subarctic region. These combined processes lead to nonlinear late-21st-century regime shifts in the coupled soil-hydrology system and rapid intensification of wildfires in western Siberia and Canada.

Profound loss of microbial necromass carbon in permafrost thaw-subsidence in the central Tibetan Plateau

Climate warming is causing rapid permafrost degradation, including thaw-induced subsidence, potentially resulting in heightened carbon release. Nevertheless, our understanding of the levels and variations of carbon components in permafrost, particularly during the degradation process, remains limited. The uncertainties arising from this process lead to inaccurate assessments of the climate effects during permafrost degradation. With vast expanses of permafrost in the Tibetan Plateau, there is limited research available on SOC components, particularly in the central Tibetan Plateau. Given remarkable variations in hydrothermal conditions across different areas of the Tibetan Plateau, the existing limited studies make it challenging to assess the overall SOC components in the permafrost across the Tibetan Plateau and simulate their future changes. In this study, we examined the properties of soil organic carbon (SOC) and microbial necromass carbon (MicrobialNC) in a representative permafrost thaw-subsidence area at the southern edge of continuous permafrost in the central Tibetan Plateau. The results indicate that prior to the thaw-subsidence, the permafrost had a SOC content of 72.68 ± 18.53 mg g−1, with MicrobialNC accounting for 49.6%. The thaw-subsidence of permafrost led to a 56.4% reduction in SOC, with MicrobialNC accounting for 70.0% of the lost SOC. MicrobialNC constitutes the primary component of permafrost SOC, and it is the main component that is lost during thaw-subsidence formation. Changes in MicrobialNC are primarily correlated with factors pH, plant input, and microbial properties. The present study holds crucial implications for both the ecological and biogeochemical processes associated with carbon release from permafrost, and it furnishes essential data necessary for modeling the global response of permafrost to climate warming. Based on this study and previous research, permafrost thawing in the Tibetan Plateau causes substantial loss of SOC. However, there's remarkable heterogeneity in SOC component changes across different regions, warranting further in-depth investigation.

Assessment of thermal stability and application of engineering solutions to preserve the degrading road embankment near Hudson Bay Coast, Canada

There are 14 northern communities in Nunavik, the Arctic region of Quebec province, Canada. Transportation infrastructure plays a vital role in the social and economic development of these localities. The thawing of permafrost compromises the stability of northern transportation infrastructure. Harsh Arctic climate conditions limit the installation of effective monitoring systems to assess infrastructure stability. In Akulivik, the access road connects the Akulivik airport and the village of Akulivik. There is no monitoring to observe the thermal condition of the permafrost foundation of the access road, hindering the capacity to perform preventive maintenance activities, especially in the context of observed climate warming in Nunavik. This paper describes a project aiming at the assessment of the stability of the access road using a new approach and proposes adaptation solutions to stabilize the road, based on design tools recently developed. Particular attention was paid to the foundation soil under the side slope where relatively rapid permafrost degradation was occurring due to accumulated snow. The results indicate a positive thermal gradient of 0.29 °C/m under the side slope and a near-zero thermal gradient under the centerline. Projected climate warming was also considered to further investigate the thermal condition, providing a safety margin for the design of promising adaptation solutions. These results assist government agencies in evaluating the thermal conditions of underlying permafrost and deploying potential adaptation solutions in Akulivik.

Model test on cooling performance of a new method for mitigating permafrost thaw around buried oil pipeline

Buried pipelines have been widely used to transport petroleum-based products over long distances in permafrost regions. Field observations reveal that they are endangered by rapid permafrost thawing and resulting massive soil movements, despite adopting some measures to protect pipeline foundation permafrost. A new mitigation technique is proposed to slow down the permafrost thawing ulteriorly. With this technique, a seasonal air-cooled embankment (SACE), mainly composed of a crushed rock layer, supports the pipeline and transfers the heat from the pipeline to ambient air in the cold seasons. A scale model test with the controlled air and oil temperatures was carried out to evaluate the proposed measure. The temperature and volumetric unfrozen water content of the permafrost subgrade beneath both the SACE and the direct-buried pipeline, as well as ground surface displacements, were measured during the whole testing process. A comparison of the hydrothermal process of the subgrade permafrost under the SACE and the direct-buried warm pipeline indicates that the proposed measure can substantially mitigate the rapid thawing of permafrost by controlling the geothermal regimes of the pipeline.

Hydrological responses to permafrost degradation on Tibetan Plateau under changing climate

The Tibetan Plateau (TP) has undergone significant warming and humidification in recent years, resulting in rapid permafrost degradation and spatiotemporal variations in hydrological processes, such as subsurface water transport, hydrothermal conversion, and runoff generation. Understanding the mechanisms of hydrological processes in permafrost areas under changing climate is crucial for accurately evaluating hydrological responses on the TP. This study comprehensively discusses the permafrost hydrological processes of the TP under changing climate. Topics include climate conditions and permafrost states, subsurface water transport under freeze–thaw conditions, development of thermokarst lakes and hydrothermal processes, and runoff response during permafrost degradation. This study offers a comprehensive understanding of permafrost changes and their hydrological responses, contributing significantly to water security and sustainable development on the TP.

Characterizing Batagay megaslump topography dynamics and matter fluxes at high spatial resolution using a multidisciplinary approach of permafrost field observations, remote sensing and 3D geological modeling

Retrogressive thaw slumps (RTS) are an important landform of rapid permafrost degradation in regions with very high ground ice contents. RTS mobilize significant amounts of sediment, meltwater and organic carbon and impact downstream hydrological systems by directly affecting topography and water quality. The term megaslump has previously been coined for RTS exceeding 20 ha in size. The Batagay megaslump in the Yana highlands of NE Siberia with an area of 87.6 ha (in 2023, including the bowl-shaped part and the erosional outlet) has been identified as the largest megaslump on Earth. We use very high resolution remote sensing from satellite data and drones, geological structure modeling, and field data to assess how much and what material is thawed and mobilized in the Batagay megaslump. The total volume of permafrost thaw and material loss from the Batagay RTS amounts to about 1 million m3 per year. The material is by one third composed of thawed sediments and by two thirds of melted ground ice. About 4000 to 5000 tons of previously permafrost-locked organic carbon is released every year. Organic carbon content has been measured as Total Organic Carbon (TOC) of sediments and as Dissolved Organic Carbon (DOC) of ground ice. From its formation in the 1970s until 2023, the Batagay RTS – due to thermal denudation and headwalls retreat – mobilized a total volume of about 34.7 million m3 of which 23.4 million m3 were melted ground ice and 11.3 million m3 were thawed deposits including a total of about 169,500 t organic carbon. With these rates of sediment and carbon mobilization, the Batagay megaslump is not only a prominent local feature of rapid permafrost thaw, but offers excellent conditions to study rates and mechanisms of rapid permafrost degradations and to calculate the stock and release of, e.g., organic matter.

Thermo-mechanical stability analysis of thermosyphons for pipeline soil and their optimal layout in permafrost regions

In permafrost regions, warm-oil buried pipelines release vast amounts of heat energy to surrounding soils and lead to rapid permafrost degradation. Settlement disasters induced by permafrost degradation significantly increase the probability of pipeline failure. The two-phase closed thermosyphon (TPCT) can cool soil, inhibiting permafrost degradation, but its deployment is still at the experimental stages along the China–Russia Crude Oil Pipeline (CRCOP). Therefore, it is important to determine an optimal layout for TPCTs that can achieve both effective cooling and cost control. In this study, a strategy for a nonlinear thermo-mechanical coupled model is proposed through Python–Abaqus secondary development. Based on it, the thermal and mechanical effects of TPCTs under different spacings, as well as their optimal layout, are numerically investigated. Closer TPCT spacing leads to a lower degradation rate of frozen soil and a lower peak TPCT heat flux. In addition, the peak pipeline von Mises stress in the transition zone increases for greater TPCT axial distances over time. When the TPCT axial distance is ≤8 m, the minimum pipeline principal strains remain below the critical compression strain over 50 years. Finally, a backpropagation neural network is constructed to predict the maximum pipeline compressive strain, and most prediction results fall within the 95% confidence interval.

Effects of thaw slump on soil bacterial communities on the Qinghai-Tibet Plateau

The rapid permafrost degradation caused by climate warming can lead to thermokarst development, which in turn greatly alter soil parameters and impact the soil bacterial communities. However, the effects of thermokarst development on soil bacterial communities largely remain unclear. Here we selected a typical thaw slump in the Qinghai-Tibet Plateau. We classified three microfeatures in the thaw slump areas, i.e., control, slumping and exposed and collected surface 30 cm soils at a depth interval of 10 cm using a soil auger. The results showed that thaw slump decreased soil carbon and nitrogen contents especially for the topsoil (0–10 cm). Thaw slump increased the relative abundance of Gemmatimonadaceae, but decreased the relative abundance of Micrococcaceae. The richness indices including OTU numbers, Ace, Chao 1 and Simpson indices were the largest in the exposed area and lowest in the slumped area, and these trends were opposite to the Shannon index. Correlation analysis revealed that the relative abundance of Micrococcaceae was negatively correlated with moisture, Anaerolineaceae was positively correlated with organic carbon content. The Nitrospira, RB41 and Gemmatimonadaceae were negatively associated with total nitrogen, but Anaerolineaceae and JG30-KF-CM45 were positivity correlated with total nitrogen. C/N ratio was positively correlated with RB41 but negatively correlated with JG30-KF-CM45. We concluded that soil organic carbon, total nitrogen and C/N ratio were the most important factors shaping the bacterial community structure among the three microfeatures. The bacterial community diversity was the highest in the exposed area and lowest in the slumping area. The bacterial structure community was related with total nitrogen, soil organic carbon contents and C/N ratios. Overall, our findings showed thaw slump can decrease soil organic carbon and nitrogen content for the surface soils in the alpine meadow and further change the soil bacterial communities.

Continentality determines warming or cooling impact of heavy rainfall events on permafrost

Permafrost thaw can cause an intensification of climate change through the release of carbon as greenhouse gases. While the effect of air temperature on permafrost thaw is well quantified, the effect of rainfall is highly variable and not well understood. Here, we provide a literature review of studies reporting on effects of rainfall on ground temperatures in permafrost environments and use a numerical model to explore the underlying physical mechanisms under different climatic conditions. Both the evaluated body of literature and the model simulations indicate that continental climates are likely to show a warming of the subsoil and hence increased end of season active layer thickness, while maritime climates tend to respond with a slight cooling effect. This suggests that dry regions with warm summers are prone to more rapid permafrost degradation under increased occurrences of heavy rainfall events in the future, which can potentially accelerate the permafrost carbon feedback.

How resilient are waterways of the Asian Himalayas? Finding adaptive measures for future sustainability

AbstractThe high‐mountain system, a storehouse of major waterways that support important ecosystem services to about 1.5 billion people in the Himalaya, is facing unprecedented challenges due to climate change during the 21st century. Intensified floods, accelerating glacial retreat, rapid permafrost degradation, and prolonged droughts are altering the natural hydrological balances and generating unpredictable spatial and temporal distributions of water availability. Anthropogenic activities are adding further pressure onto Himalayan waterways. The fundamental question of waterway management in this region is therefore how this hydro‐meteorological transformation, caused by climate change and anthropogenic perturbations, can be tackled to find avenues for sustainability. This requires a framework that can diagnose threats at a range of spatial and temporal scales and provide recommendations for strong adaptive measures for sustainable future waterways. This focus paper assesses the current literature base to bring together our understanding of how recent climatic changes have threatened waterways in the Asian Himalayas, how society has been responding to rapidly changing waterway conditions, and what adaptive options are available for the region. The study finds that Himalayan waterways are crucial in protecting nature and society. The implementation of integrated waterways management measures, the rapid advancement of waterway infrastructure technologies, and the improved governance of waterways are more critical than ever.This article is categorized under: Engineering Water > Sustainable Engineering of Water

Impacts of National Highway G214 on Vegetation in the Source Area of Yellow and Yangtze Rivers on the Southern Qinghai Plateau, West China

Engineering corridors on the Qinghai–Tibet Plateau have substantially modified the regional ecosystem functions and environment, resulting in changes in the alpine ecosystem. In addition, the building and operation of these engineering corridors have led to rapid permafrost degradation, which in turn has impacted local vegetation along these corridors. This study investigated vegetation changes and their driving factors by the methods of coefficient of variation, correlation analysis, and GeoDetector in a 30 km wide buffer zone at each side along the National Highway G214 (G214) at the northern and southern flanks of the Bayan Har Mountains in part of the source area of the Yellow and Yangtze rivers on the southern Qinghai Plateau, West China. The following results were obtained: (1) The Normalized Difference Vegetation Index in Growing Season (NDVIgs) rose slightly in 2010–2019, with an average annual change rate of 0.006/a. Patterns of NDVIgs along the G214 exhibited “low at the northern flank and high at the southern flank of the Bayan Har Mountains”. (2) Spatially, average NDVIgs increased from the first buffer zone at the distance of 0–10 km from the highway centerline to the second buffer zone at 20–30 km perpendicularly away from the G214. Furthermore, the first buffer zone had the lowest coefficient of variation, possibly due to a low vegetation recovery as a result of the greatest influence of the G214 on NDVIgs at 0–10 km. (3) Furthermore, annual precipitation (AP) was the dominant factor for significantly (p < 0.01) and positively influencing the variations in NDVIgs (R = 0.75, p < 0.01). Additionally, NDVIgs was more strongly influenced by the two combined factors than any single one, with the highest q-value (0.74) for the interactive influences of AP and annual average air temperature (AAAT) and followed by that of the AP and mean annual ground temperature (MAGT) at the depth of zero annual amplitude (15 m). Evidently, the construction and operation of the G214 have directly and indirectly affected vegetation through changing environmental variables, with significant impacts on NDVIgs extended at least 20 km outwards from the highway. This study helps better understand the environmental impacts along the engineering corridors in elevational permafrost regions at mid and low latitudes and their management.

Applicability analysis of thermosyphon for thermally stabilizing pipeline foundation permafrost and its layout optimization

Rapid permafrost thawing triggered by heat release from the buried warm-oil pipeline would result in the instability of the pipeline, posing a potential risk of an oil spill in permafrost regions. Therefore, how to precisely control the ground temperature to mitigate pipeline foundation permafrost from thawing is of significant importance. Thermosyphon is a widely-accepted and extensively-used countermeasure against permafrost thawing in permafrost engineering. This paper presents 3-year (2015–2018) monitored data of ground temperature and geophysical survey results conducted by electrical resistivity tomography in April 2018, to investigate the thermal stabilizing effect of thermosyphons installed nearby the China-Russia crude oil pipeline (CRCOP) and the influencing factors. Furthermore, numerical simulation tests were conducted to evaluate their long-term cooling applicability and to optimize their layout parameters. Field observations show that the thermosyphons can cool down and even freeze the thawed soil layers around the CRCOP, prohibiting the infiltration of water into the thawing front to some extent and effectively mitigating the rapid thawing of permafrost beneath the pipeline. The performance of the thermosyphons is greatly influenced by the method and time of thermosyphon installation, as well as layout parameters including the number and longitudinal spacing. Two pairs of thermosyphons with a shorter spacing are unable to control the thawing of the underlying permafrost due to the non-anticipated higher oil temperature, the thermal erosion of water ponding, and climate warming. The simulated results indicate that thermosyphons perform well in the first 5 years after installation. Thermosyphon lowers the mean annual temperature of soils surrounding it by about 2 and 1.4 times when the evaporator section length is increased by 50% and the longitudinal spacing is decreased by 0.5 m, respectively. The application of thermosyphons has proven its strength for thermally stabilizing the pipeline foundation permafrost along the CRCOP.

An Assessment of the Possibility of Restoration and Protection of Territories Disturbed by Thermokarst in Central Yakutia, Eastern Siberia

Rapid permafrost degradation is observed in northern regions as a result of climate change and expanding economic development. Associated increases in active layer depth lead to thermokarst development, resulting in irregular surface topography. In Central Yakutia, significant areas of the land surface have been deteriorated by thermokarst; however, no mitigation or land rehabilitation efforts are undertaken. This paper presents the results of numerical modeling of the thermal response of permafrost to changes in the active layer hydrothermal regime using field data from the village of Amga, Republic of Sakha (Yakutia), and mathematical analysis. The results suggest that restoring a thick ice-enriched layer will require increasing the pre-winter soil moisture contents in order to increase the effective heat capacity of the active layer. Snow removal or compaction during the winter is recommended to maximize permafrost cooling. The thickness of the restored transition layer varies from 0.3 to 1.3 m depending on soil moisture contents in the active layer. The modeling results demonstrate that damaged lands can be restored through a set of measures to lower the subsurface temperatures. A combination of the insulating layer (forest vegetation) and the high heat capacity layer (transition layer) in the atmosphere–ground system would be more effective in providing stable geocryological conditions.

Assessment of permafrost disturbances caused by two parallel buried warm-oil pipelines: A case study at a high-latitude wetland site in Northeast China

Multiple studies demonstrate that narrow-linear strong disturbances triggered by pipeline engineering activities have resulted in rapid permafrost degradation. However, the extent, duration, and severity of permafrost disturbances induced by two parallel buried warm-oil pipelines remain unclear. Here, we examine the thermal disturbances of the China-Russia crude oil pipelines (CRCOPs I and II) on the surrounding permafrost. Ground temperature measurements on and off the right-of-way of the CRCOPs and an electrical resistivity tomography survey were conducted at a selected high-latitude wetland site in northeastern China. The observations showed that warm oil flow in pipelines dissipated heat to the surrounding soil, resulting in the thawing of underlying permafrost accompanied by the formation and development of thaw bulbs around the pipes. Currently, the thaw bulb of CRCOP-I was about four times as large as that of CRCOP-II, mainly due to the longer 7-year working duration of CRCOP-I. To quantify the permafrost disturbances around the pipeline, a conductive heat transfer model was established. A numerical simulation of the soil thermal regime around the pipeline suggested the initial growth of the thaw bulb was quite fast but gradually slowed with time, of which the shape was modified to ellipse from a semicircle. The existence of CRCOP-II would accelerate the warming of permafrost on the CRCOP-I right-of-way due to the small separation distance between them. We expect that the thaw bulbs of the two pipelines will expand larger than previously estimated due to the adverse effects of pipeline settlement and surface water flow, sparking a wider permafrost disturbance.

The Potential of UAV Imagery for the Detection of Rapid Permafrost Degradation: Assessing the Impacts on Critical Arctic Infrastructure

Ground subsidence and erosion processes caused by permafrost thaw pose a high risk to infrastructure in the Arctic. Climate warming is increasingly accelerating the thawing of permafrost, emphasizing the need for thorough monitoring to detect damages and hazards at an early stage. The use of unoccupied aerial vehicles (UAVs) allows a fast and uncomplicated analysis of sub-meter changes across larger areas compared to manual surveys in the field. In our study, we investigated the potential of photogrammetry products derived from imagery acquired with off-the-shelf UAVs in order to provide a low-cost assessment of the risks of permafrost degradation along critical infrastructure. We tested a minimal drone setup without ground control points to derive high-resolution 3D point clouds via structure from motion (SfM) at a site affected by thermal erosion along the Dalton Highway on the North Slope of Alaska. For the sub-meter change analysis, we used a multiscale point cloud comparison which we improved by applying (i) denoising filters and (ii) alignment procedures to correct for horizontal and vertical offsets. Our results show a successful reduction in outliers and a thorough correction of the horizontal and vertical point cloud offset by a factor of 6 and 10, respectively. In a defined point cloud subset of an erosion feature, we derive a median land surface displacement of −0.35 m from 2018 to 2019. Projecting the development of the erosion feature, we observe an expansion to NNE, following the ice-wedge polygon network. With a land surface displacement of −0.35 m and an alignment root mean square error of 0.99 m, we find our workflow is best suitable for detecting and quantifying rapid land surface changes. For a future improvement of the workflow, we recommend using alternate flight patterns and an enhancement of the point cloud comparison algorithm.

Rapid Permafrost Thaw Removes Nitrogen Limitation and Rises the Potential for N2O Emissions

Ice–rich Pleistocene permafrost deposits (Yedoma) store large amounts of nitrogen (N) and are susceptible to rapid thaw. In this study, we assess whether eroding Yedoma deposits are potential sources of N and gaseous carbon (C) losses. Therefore, we determined aerobic net ammonification and nitrification, as well as anaerobic production of nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) in laboratory incubations. Samples were collected from non-vegetated and revegetated slump floor (SF) and thaw mound (TM) soils of a retrogressive thaw slump in the Lena River Delta of Eastern Siberia. We found high nitrate concentrations (up to 110 µg N (g DW)−1) within the growing season, a faster transformation of organic N to nitrate, and high N2O production (up to 217 ng N2O-N (g DW)−1 day−1) in revegetated thaw mounds. The slump floor was low in nitrate and did not produce N2O under anaerobic conditions, but produced the most CO2 (up to 7 µg CO2-C (g DW)−1 day−1) and CH4 (up to 65 ng CH4-C (g DW)−1 day−1). Nitrate additions showed that denitrification was substrate limited in the slump floor. Nitrate limitation was rather caused by field conditions (moisture, pH) than by microbial functional limitation since nitrification rates were positive under laboratory conditions. Our results emphasize the relevance of considering landscape processes, geomorphology, and soil origin in order to identify hotspots of high N availability, as well as C and N losses. High N availability is likely to have an impact on carbon cycling, but to what extent needs further investigation.