Permafrost Type Research Articles

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.

Assessment of a tiling energy budget approach in a land surface model, ORCHIDEE-MICT (r8205)

Abstract. The surface energy budget plays a critical role in terrestrial hydrological and biogeochemical cycles. Nevertheless, its highly spatial heterogeneity across different vegetation types is still missing in the ORCHIDEE-MICT (ORganizing Carbon and Hydrology in Dynamic EcosystEms–aMeliorated Interactions between Carbon and Temperature) land surface model. In this study, we describe the representation of a tiling energy budget in ORCHIDEE-MICT and assess its short-term and long-term impacts on energy, hydrology, and carbon processes. With the specific values of surface properties for each vegetation type, the new version presents warmer surface and soil temperatures (∼ 0.5 °C, +3 %), wetter soil moisture (∼ 10 kg m−2, +2 %), and increased soil organic carbon storage (∼ 170 Pg C, +9 %) across the Northern Hemisphere. Despite reproducing the absolute values and spatial gradients of surface and soil temperatures from satellite and in situ observations, the considerable uncertainties in simulated soil organic carbon and hydrological processes prevent an obvious improvement in the temperature bias existing in the original ORCHIDEE-MICT model. However, the separation of sub-grid energy budgets in the new version improves permafrost simulation greatly by accounting for the presence of discontinuous permafrost types (∼ 3×106 km2), which will facilitate various permafrost-related studies in the future.

Lake changes and their driving factors in circum-arctic permafrost regions from 1990 to 2022

The rapid increase in temperatures and escalating human activities have led to a reduction or even disappearance of the thickness of the permafrost layer around the Arctic. Meanwhile, the degradation of permafrost has impacted the ecosystems within the circum-Arctic permafrost regions, also triggering a series of geological environmental changes. Consequently, research in the circum-Arctic permafrost regions is crucial not only for understanding the impact of climate change on the cryosphere but also for predicting and managing future environmental changes in the area. In this study, we extracted the number of lakes and their areas within certain areas of the circum-Arctic permafrost region from 1990 to 2022, and further investigated the factors driving lake changes. Analysis revealed a stabilization of lake areas in continuous permafrost regions, expansion in discontinuous and sporadic permafrost, and reduction in isolated permafrost, indicating the significant impact of global warming on the degradation of discontinuous and sporadic permafrost, while continuous permafrost remains less affected. Lake area dynamics across various permafrost types were influenced by distinct factors: in discontinuous permafrost, lake expansions correlated positively with snowfall, rainfall, snowmelt, and evapotranspiration; in sporadic permafrost, area reductions were tied to temperature increases, despite positive correlations with snowmelt and evapotranspiration; and in isolated permafrost, lake contractions were negatively associated with air temperature. Furthermore, permafrost degradation notably influenced lake area changes, especially in sporadic and isolated permafrost, where an inverse relationship between lake area and temperature was observed.

Geographical and genetic features of soil formation and diversity of the permafrost soils of Central Yakutia

The aim of the study. The aim of this article was to identify the geographical and genetic features of soil formation in the cryolithozone of Central Yakutia and to assess the diversity of all types of permafrost soils of this territory. Location and time of the study. Soil-geographical and soil-genetic studies were carried out near the Middle Lena, on the territory of Central Yakutia within various geomorphological tiers of the Central Yakut Plain at different times, starting from the 1990s. Methodology. In carrying out these works, widely used methods of soil research were used, such as comparative geographical, profile genetic and comparative analytical in combination with well-known and commonly used analytical methods. At the same time, all the main results of soil studies conducted on this territory by our predecessor permafrost soil scientists were taken into account in a comparative aspect. Main results. According to the obtained results, it is necessary to state that this region of the cryolithozone is characterized by extremely peculiar landscape and climatic conditions of soil formation, the formation of the cryogenic soils occurring in a cryoarid climate, mainly on loose alluvial deposits of various ages, under forest and meadow-steppe vegetation and continuous permafrost. In the studied territory, the cryogenic soil-forming processes are crucial for the development of properties, composition and regimes of these permafrost soils, causing their high diversity and diversity of the soil cover of Central Yakutia. The systematic list of permafrost soils of the studied territory includes 17 types and 21 subtypes of soils and is forecasted to expand as the study of the soil cover of this unique region of the cryolithozone deepens. At the same time, the diversity of soils there is formed by the six types of zonal and azonal forest, five types of meadow-steppe and five intrazonal types of the permafrost soils. A broader concept of "permafrost soils" is proposed, in contrast to that interpreted in the current classification of soils of Russia and WRB, the essence of which is that regardless of the depth of seasonal thawing, all soils underlain by the permafrost are called permafrost soils. In these soils, the interlocking of seasonally and permanently frozen layers is observed in winter. These soils may differ in pronounced cryomorphic features (cryozems, fawn) or not have them (podburs, podzols, chernozems), being characterized by a permafrost type of temperature regime. Conclusion. In the cryolithozone environment of Central Yakutia, elementary soil-forming processes occur under cryogenesis conditions, which in the general hierarchy of soil-forming factors is considered at the subfactorial level; minor variations of the soil-forming factors can change the directions and rates of the soil-forming processes and, ultimately, lead to a high degree of diversity and contrast in the soil cover of the studied territory.

Soil temperature regimes on the southern border of the zone of frozen bogs in Western Siberia

Numto Nature Park (Western Siberia) is one of the southernmost locations of frozen peatlands. In 2019–2022, soil temperatures were measured there using an automatic monitoring system. The measurements were carried out for Murshik Hemic Cryic Histosol on flat palsa peatlands and frost mounds. The temperature for Folic Albic Podzol was measured for reference. The average annual temperature of the soil surface was found to be positive in all study areas: + 0.8 °C on the frost mound; +1.3 °C on the flat palsa peatlands; and + 4.5 °C in Folic Albic Podzol. The low temperature on the frost mound is due to the low snow cover, so the soil surface cools down to the minimum in winter. As for flat palsa peatlands, peat remains frozen all year round, starting from a depth of 0.5 m. On the frost mound, at the same time, the depth of seasonal thawing is 2 m. In winter, the frost penetration on the mound doesn't reach the permafrost table, revealing its probable degradation in case of further climate warming. According to the soil thermal regime classification, the soil on the frost mound falls into the category of long-term seasonally frozen soils, while high palsa peatlands nearby Nadym Town belong to the permafrost type. Data from the nearby meteorological station show a trend of rising air temperature and rainfall. An analysis of the soil temperature regime and the course of exogenous processes demonstrate that Murshik Hemic Cryic Histosol on high palsa peatlands is unstable. Permafrost persists there due to the low thickness of the snow cover on the peaks, which facilitates winter cooling. If the snow-cover height increases, permafrost is likely to melt there.

Effects of complex environment on soil thermal regime alteration under crushed-rock embankment structures in the permafrost region on the Roof of the World

The thermal stability of permafrost under complex environment (climate scenarios, permafrost types and regional air temperatures) directly affects the long-term service performance of highway or railway. This study uses a large amount of valuable soil temperature monitoring and simulation data to examine the stability of typical crushed-rock embankments (CREs) along Qinghai-Tibet Railway, which is located in the permafrost region on the Roof of the World. Firstly, a novel numerical model for CREs considering a complex heat transfer environment is established and verified. Then, alteration characteristics of recent-term thermal regime of permafrost across time and space under three CREs are revealed based on a decade of field monitoring data. Finally, long-term thermal regime of permafrost under three CREs under complex environment is analyzed by numerical simulation. Results include: 1) Soil temperature near the ground surface under the three CREs shows a decreasing trend, whereas the overall temperature around the deep permafrost increases over time under a recent climate warming. 2) The warming rate of permafrost under CREs rises with the acceleration of climate scenarios and regional air temperature and the decrease of regional ground temperatures. 3) U-shaped crushed-rock embankment is the most suitable CRE for managing complex environment, especially when the mean annual ground temperature is 0 ∼ − 1 °C or climate scenarios are RCP 2.6 and RCP 4.5. 4) Transition from low-temperature permafrost to warm permafrost is a warning signal of permafrost degradation under climate warming. 5) With an increase of permafrost degradation rate (the thawing and warming rates of permafrost), embankment stability becomes worse. These findings will not only serve as a scientific basis for the embankment damage prevention of the Qinghai-Tibet Railway, but also provide important technical supports for the successful building of infrastructure in permafrost regions under complex environment.

Response of active layer thickening to wildfire in the pan-Arctic region: Permafrost type and vegetation type influences

Northern high-latitude permafrost holds the largest soil carbon pool in the world. Understanding the responses of permafrost to wildfire is crucial for improving our ability to predict permafrost degradation and further carbon emissions. Recently, studies have demonstrated that wildfires in the pan-Arctic region induced the thickening of the active layer based on site or fire event observations. However, how this induced thickening is influenced by vegetation and permafrost types remains not fully understood due to the lack of wall-to-wall analysis. Therefore, this study employed remotely sensed fire data and modelled active layer thickness (ALT) to identify the fire-induced ALT change (ΔALT) for the pan-Arctic region, and the contributions of vegetation and permafrost were quantified using the random forest (RF) model. Our results showed that the average ΔALT and the sensitivity of ΔALT to burn severity both increased with decreasing ground ice content in permafrost. The largest values were detected in thick permafrost with low ground ice content. Regarding vegetation, the average and sensitivity of ΔALT in tundra were highest, followed by those in forest and shrub. When the individual environmental factors were all taken into account, the results showed that the contribution of vegetation types was much higher than that of permafrost types (20.2 % vs. 3.5 %). Our findings highlighted the importance of environmental factors in regulating the responses of permafrost to fire.

Research on the Characteristics of Thermosyphon Embankment Damage and Permafrost Distribution Based on Ground-Penetrating Radar: A Case Study of the Qinghai–Tibet Highway

In order to research the special embankment (thermosyphon embankment) damages and the distribution of permafrost under the Qinghai–Tibet Highway (QTH) embankment. The section K2952–K2953, which is a typical representative of the QTH, was chosen for the detection and research of the permafrost and embankment damages in order to determine the sources of the damages. In this study, the performance characteristics of the embankment, the active layer, and the permafrost table found in ground-penetrating radar (GPR) images were researched, combined with multi-source. According to the research findings, the construction of the embankment in this section has stabilized the effect on the permafrost table. Under the embankment of the unemployed thermosyphon section, the permafrost distribution has good structural integrity and continuity, with the permafrost table at a depth of around 5 m. The continuity of the permafrost distribution under the embankment in the thermosyphon section was poor, and there was localized degradation, with the permafrost table being approximately 6 m deep. The main cause of the irregular settlement and other damage in this section is the presence of a loose area at the base of the embankment. Although the thermosyphon on both sides of the embankment also plays a role in lifting the permafrost table, it is not ideal for managing the damage to high embankments where the type of permafrost under the embankment is high-temperature permafrost with a high ice content and where the sunny–shady slope effect is obvious. The research results described in this article can therefore provide a crucial foundation for the detection of highway damage and permafrost under embankments in permafrost regions in the future.

The start of frozen dates over northern permafrost regions with the changing climate.

The soil freeze-thaw cycle in the permafrost regions has a significant impact on regional surface energy and water balance. Although increasing efforts have been made to understand the responses of spring thawing to climate change, the mechanisms controlling the global interannual variability of the start date of permafrost frozen (SOF) remain unclear. Using long-term SOF from the combinations of multiple satellite microwave sensors between 1979 and 2020, and analytical techniques, including partial correlation, ridge regression, path analysis, and machine learning, we explored the responses of SOF to multiple climate change factors, including warming (surface and air temperature), start date of permafrost thawing (SOT), soil properties (soil temperature and volume of water), and the snow depth water equivalent (SDWE). Overall, climate warming exhibited the maximum control on SOF, but SOT in spring was also an important driver of SOF variability; among the 65.9% significant SOT and SOF correlations, 79.3% were positive, indicating an overall earlier thawing would contribute to an earlier frozen in winter. The machine learning analysis also suggested that apart from warming, SOT ranked as the second most important determinant of SOF. Therefore, we identified the mechanism responsible for the SOT-SOF relationship using the SEM analysis, which revealed that soil temperature change exhibited the maximum effect on this relationship, irrespective of the permafrost type. Finally, we analyzed the temporal changes in these responses using the moving window approach and found increased effect of soil warming on SOF. In conclusion, these results provide important insights into understanding and predicting SOF variations with future climate change.

Spatial distribution of permafrost degradation and its impact on vegetation phenology from 2000 to 2020

As global temperatures rise, permafrost is degraded. Permafrost degradation alters vegetation phenology and community composition, thereby affecting local and regional ecosystems. The Xing'an Mountains, located on the southern edge of the Eurasian permafrost region, are very sensitive to the impact of permafrost degradation on ecosystems. Climate change has direct effects on permafrost and vegetation growth, and analysis of the indirect effects of permafrost degradation on vegetation phenology based on the normalized difference vegetation index (NDVI) can explain the internal impact mechanisms of ecosystem components. Based on the temperature at the top of permafrost (TTOP) model, which was used to simulate the spatial distribution of permafrost areas in the Xing'an Mountains from 2000 to 2020, the areas of the three permafrost types showed a decreasing trend. The mean annual surface temperature (MAST) increased significantly at a rate of 0.008 °C year−1 from 2000 to 2020, and the southern boundary of the permafrost region moved north by 0.1–1 degrees. The average NDVI value of the permafrost region increased significantly in 8.34 % of the region. The significant correlations between NDVI and permafrost degradation, temperature and precipitation in the permafrost degradation region were 92.06 % (80.19 % positive, 11.87 % negative), 50.37 % (42.72 % positive, 7.65 % negative), and 81.59 % (36.25 % positive, 45.34 % negative), and were mainly distributed along the southern boundary of the permafrost region. A significance test of phenology in the Xing'an Mountains showed that the end of the growing season (EOS) and the length of the growing season (GLS) were significantly delayed and prolonged in the southern sparse island permafrost region. Sensitivity analysis showed that permafrost degradation was the main factor that affected the start of the growing season (SOS) and GLS. When the effects of temperature, precipitation, and sunshine duration were excluded, the regions with a significant positive correlation between permafrost degradation and SOS (20.96 %) and GLS (28.55 %) were located in both continuous and discontinuous permafrost regions. The regions with a significant negative correlation between permafrost degradation and SOS (21.11 %) and GLS (8.98 %) were mainly distributed on the southern edge of the island permafrost region. In summary, the NDVI changed significantly in the southern boundary of the permafrost region, and this change was mainly attributed to permafrost degradation.

Spatial distribution and influencing factors of humus layer thickness of forest land in permafrost region of Northeast China

Humus has significant impacts on soil water dynamics, nutrient storage and plant growth. Studies have demonstrated that the humus layer is related to climate, soil properties, topography and other environmental factors. However, the thickness of the humus layer (HLT) and its spatial distributions are less investigated. Especially in boreal mountain forests underlain with permafrost, the environmental influences on HLT remain unclear. In a high-latitude watershed of boreal mountain forest in Northeast China, this study explores the effects of the environmental factors on HLT, and its relationships with permafrost types. The HLT distribution across the watershed is extracted using the geographically weighted regression kriging (GWRK) model. The elevation, slope, aspect, mean annual ground surface temperature and mean annual soil water content are determined to be statistically significant influencers factors of HLT. The elevation is the most important variable for HLT in this cold land, with an indirect effect on HLT through impacting ground surface temperature and soil water content. Topography casts more significant impact than ground surface temperature and soil water content. HLT ranges from 1.1 to 26.7 cm across three permafrost classes in the study area, decreasing with the discontinuity of permafrost types (continuous permafrost > sporadic permafrost > isolated patches). The findings suggest that the humus development is closely related to the permafrost type in northern high latitudes, and the permafrost degradation can lead to humus layer thinning under climate warming.

Evaluating Permafrost Degradation in the Tuotuo River Basin by MT-InSAR and LSTM Methods.

Permafrost degradation can significantly affect vegetation, infrastructure, and sustainable development on the Qinghai-Tibet Plateau (QTP). The permafrost on the QTP faces a risk of widespread degradation due to climate change and ecosystem disturbances; thus, monitoring its changes is critical. In this study, we conducted a permafrost surface deformation prediction over the Tuotuo River tributary watershed in the southwestern part of the QTP using the Long Short-Term Memory model (LSTM). The LSTM model was applied to the deformation information derived from a time series of Multi-Temporal Interferometry Synthetic Aperture Radar (MT-InSAR). First, we designed a quadtree segmentation-based Small BAseline Subset (SBAS) to monitor the seasonal permafrost deformation from March 2017 to April 2022. Then, the types of frozen soil were classified using the spatio-temporal deformation information and the temperature at the top of the permafrost. Finally, the time-series deformation trends of different types of permafrost were predicted using the LSTM model. The results showed that the deformation rates in the Tuotuo River Basin ranged between -80 to 60 mm/yr. Permafrost, seasonally frozen ground, and potentially degraded permafrost covered 7572.23, 900.87, and 921.70 km2, respectively. The LSTM model achieved high precision for frozen soil deformation prediction at the point scale, with a root mean square error of 4.457 mm and mean absolute error of 3.421 mm. The results demonstrated that deformation monitoring and prediction using MT-InSAR technology integrated with the LSTM model can be used to accurately identify types of permafrost over a large region and quantitatively evaluate its degradation trends.

The Status and Influencing Factors of Surface Water Dynamics on the Qinghai-Tibet Plateau During 2000–2020

The Qinghai–Tibet Plateau is rich in water resources with numerous lakes, rivers, and glaciers, and, as a source of many rivers in Central Asia, it is known as the Asian Water Tower. Under global climate change, it is critical to understand the current influencing factors on surface water area in this region. Although there are numerous studies on surface water mapping, they are still limited by temporal/spatial resolution and record length. Moreover, the complicated topographic condition makes it challenging to map the surface water accurately. Here, we proposed an automatic two-step annual surface water classification framework using long time-series Landsat images and topographic information based on the Google Earth Engine (GEE) platform. The results showed that the producer accuracy (PA) and user accuracy (UA) of the surface water map in the Qinghai–Tibet Plateau in 2020 were 99% and 90%, respectively, and the Kappa coefficient reached 0.87. Our dataset showed high consistency with high-resolution images, indicating that the proposed large-scale water mapping method has great application potential. Furthermore, a new annual surface water area dataset on the Qinghai–Tibet Plateau from 2000 to 2020 was generated, and its relationship with climate, vegetation, permafrost, and glacier factors was explored. We found that the mean surface water area was about 59 481 km2, and there was a significant increasing trend (=322 km2/year, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$p &lt; 0.01$ </tex-math></inline-formula> ) during 2000–2020 in the plateau. Greening, warming, and wetting climate conditions contributed to the increase of surface water area. Active layer thickness and permafrost types may be the most related to the decrease of surface water area. This study provides important information for ecological assessment and protection of the plateau and promotes the implementation of sustainable development goals related to surface water resources.

Allocation and transfer of photosynthetic 13C in the vegetation‐soil system and its response to permafrost degradation

AbstractThe Xing'an Mountains, located on the southern edge of the Eurasian permafrost zone, are sensitive to permafrost degradation. In particular, the impact of wetland degradation in permafrost regions on carbon sequestration capacity cannot be ignored. Therefore, there is an urgent need to understand the allocation and transfer of photosynthetic 13C in the wetland vegetation‐soil system and its response to permafrost degradation. Three regions with different types of permafrost were selected predominantly continuous and island permafrost (located in Mohe); sparse island permafrost (located in Heihe); and isolated patches of permafrost (located in Yichun). The effects of permafrost degradation on the allocation and transfer of photosynthetic 13C in trees, shrubs, herb vegetation, and mosses were investigated using isotope tracing techniques, redundancy analysis, and structural equation modeling. Mohe had the largest 13C excess and more transfer of shrubs and herbs to the underground carbon pool. The recoveries of photosynthate‐13C for Larix gemlini, Vaccinium uliginosum, and Sphagnum sp. were significantly different in different permafrost regions using Tukey's honestly significant difference (HSD) post hoc comparisons of means tests. The amount of Δphotosynthate‐13C transfer was larger in Mohe than in Heihe and Yichun. The allocation of photosynthetic 13C in the plant roots in the three permafrost regions was positively correlated with the total soil phosphorus content. The active layer thickness was an important factor affecting the transfer of Δphotosynthate‐13C. The allocation and transfer of photosynthetic 13C to the subsurface were larger in the predominantly continuous and island permafrost areas than in the sparse island and isolated patch permafrost regions. The allocation and transfer of photosynthetic 13C in the vegetation‐soil system were affected by the soils' physicochemical properties and the environmental changes after permafrost degradation.

Modelling Permafrost Characteristics and Its Relationship with Environmental Constraints in the Gaize Area, Qinghai-Tibet Plateau, China

The impact of environmental constraints on permafrost distribution and characteristics of the remote western Qinghai-Tibetan Plateau (QTP) were seldom reported. Using augmented Noah land surface model, this study aims to elaborate the permafrost characteristics and their relationship with key environmental constraints in the Gaize, a transitional area with mosaic distribution of permafrost and seasonally frozen ground in the western QTP. There were two soil parameter schemes, two thermal roughness schemes, and three vegetation parameter schemes with optimal minimum stomatal resistance established using MODIS NDVI, turbulent flux, and field survey data. Forcing data were extracted from the China Meteorological Forcing Dataset (CMFD) and downscaled to 5 km × 5 km resolution. Results show that the error of simulated mean annual ground temperatures (MAGT) were less than 1.0 °C for nine boreholes. The Kappa coefficiency between three types of permafrost and three types of vegetation is 0.654, which indicates the close relationship between the presence of certain vegetation types and the occurrence of certain permafrost types in the Gaize. Permafrost distribution and characteristics of the Gaize are jointly influenced by both altitude and vegetation. The relationship of permafrost with environmental constraints over the Gaize is significantly different from that of the West Kunlun, a western, predominantly permafrost-distributed area.

Response of terrestrial water storage and its change to climate change in the endorheic Tibetan Plateau

Terrestrial water storage (TWS) and its change (TWSC) are extremely sensitive to climate change, and are good indicators of the response of the hydrological system to climate change in the Tibetan Plateau (TP). However, long-term variation in TWS and its components, as well as contributions of these component changes to TWSC, are still not well documented. In this study, we extended monthly TWS anomaly (TWSA) and TWSC from 1989 to 2019 using the random forest (RF) method, analyzed the long-term contribution rates of each component change to TWSC using a mass balance approach, and compared them with the rates estimated by the RF method. Our major findings are: (1) the warming and wetting trend in the entire analysis period (PA) and in the pre-mutation period (P1) was slowed down or even reversed in the post-mutation period (P2), which was caused mainly by the decrease in temperature and precipitation in the north-eastern Inner Basin (IB) and southern Qaidam Basin (QB); (2) the RF method is capable of estimating monthly TWSA and TWSC (0.872 ≤ R2 ≤ 0.957 in training data, 0.528 ≤ R2 ≤ 0.860 in test data). Variable selection has an important impact on the method, and TWSC can be used as an alternative when TWSA estimate is poor; (3) Significant annual TWSA increase (2.20 mm/a, P < 0.05) in the IB during PA comes from a higher increase during P2 (3.62 mm/a, P < 0.05) and a small variation during P1 (−0.65 m/a, P > 0.1). Spatially, the increase is attributed to the higher increase trends (> 4.50 mm/a, P < 0.05) in north-eastern IB during PA and P2, and slight decrease in western and southern IB during PA. The spatial and temporal heterogeneity was mainly caused by the differences in precipitation amount, glacier proportions, and permafrost types. (4) During PA, TWSC in the IB was mainly determined by lake water storage change (LWSC) with a contribution rate of 62 %, while in the QB it was mainly determined by soil water change (−43 %), and LWSC had a contribution rate of −27 %. LWSC impact on TWSC was more significant in the IB, especially in the southeastern sub-regions with regional water storage surplus (TWSC > 0). The overall increase in water storages and fluxes, and exchanges imply an intensified hydrologic cycle in the region.

Effects of Permafrost Degradation on Soil Carbon and Nitrogen Cycling in Permafrost Wetlands

Climate change is one of the greatest threats to high-latitude permafrost and leads to serious permafrost degradation. However, few attention has been paid to whether peat soil carbon or nitrogen is sensitive to permafrost degradation. This study has selected three typical sample areas (MoHe-continuous permafrost, TaHe-Island-shaped melting permafrost, Jagdaqi-Island-shaped melting permafrost) as research object to compare the response rate and degree of peat soil carbon and nitrogen under permafrost degradation. The results show that soil organic carbon and nitrogen contents are the highest in 0–10 cm soil and permafrost regions show obvious surface aggregation. The carbon content of different types of frozen soil decreases with the depth of soil layer, and the differences are significant (p &amp;lt; 0.01). The distribution pattern of total nitrogen content in each soil layer among different permafrost types is Mohe &amp;lt; Tahe &amp;lt; Jagedaqi. And when it is getting vertically deeper than the surface layer, there is no significant difference between the soil layers in soil profile. The study also focuses on the variations of carbon and nitrogen content in different soil layers of peatland in typical permafrost regions. The results show that soil carbon responds faster to the degradation of frozen soil than soil nitrogen. Moreover, the accumulation degree of soil carbon is also significantly higher than soil nitrogen. Under climate change and for better permafrost conservation, it is necessary to study how the peatland’s soil carbon and the nitrogen are influenced by the permafrost degradation in high latitude.

Seismic physics-based characterization of permafrost sites using surface waves

Abstract. The adverse effects of climate warming on the built environment in (sub-)arctic regions are unprecedented and accelerating. The planning and design of climate-resilient northern infrastructure, as well as predicting deterioration of permafrost from climate model simulations, require characterizing permafrost sites accurately and efficiently. Here, we propose a novel algorithm for the analysis of surface waves to quantitatively estimate the physical and mechanical properties of a permafrost site. We show the existence of two types of Rayleigh waves (R1 and R2; R1 travels faster than R2). The R2 wave velocity is highly sensitive to the physical properties (e.g., unfrozen water content, ice content, and porosity) of active and frozen permafrost layers, while it is less sensitive to their mechanical properties (e.g., shear modulus and bulk modulus). The R1 wave velocity, on the other hand, depends strongly on the soil type and mechanical properties of permafrost or soil layers. In situ surface wave measurements revealed the experimental dispersion relations of both types of Rayleigh waves from which relevant properties of a permafrost site can be derived by means of our proposed hybrid inverse and multiphase poromechanical approach. Our study demonstrates the potential of surface wave techniques coupled with our proposed data-processing algorithm to characterize a permafrost site more accurately. Our proposed technique can be used in early detection and warning systems to monitor infrastructure impacted by permafrost-related geohazards and to detect the presence of layers vulnerable to permafrost carbon feedback and emission of greenhouse gases into the atmosphere.

Type Classification and Engineering Stability Evaluation of Permafrost Wetlands on the Qinghai–Tibet Plateau

On the Qinghai–Tibet Plateau area, the permafrost and the wetlands are interdependent to form a symbiotic system, called permafrost wetlands (PWs). Due to the extremely complex hydrothermal conditions, the PWs greatly impact road stability. Thus, it is necessary to classify PWs in terms of engineering characteristics and evaluate their engineering stability. In this study, the typical diseases of subgrade in permafrost wetland areas are analyzed based on field investigation. Then, the permafrost type, waterlogged area ratio, and meadow development degree are used as the main indicators for classifying PWs by a three-level division method. Finally, a scheme for the engineering stability evaluation of PWs was established based on the fuzzy comprehensive theory and used for the pre-evaluation of the engineering stability for the proposed Qinghai 224 highway. The results indicate that the longitudinal cracks and uneven deformation are the main road diseases in this area, caused by the combined effect of permafrost, waterlogged areas, and meadow development. The PWs are divided into 15 types according to the engineering characteristics. Waterlogged area ratio and meadow development degree are proven to represent the development of underlying permafrost. The influencing factors include climatic environment, permafrost property, and wetland conditions, which have decreased influence on the engineering stability of PWs. The engineering stability of k230 + 100 and k255 + 400 is evaluated as basically stable and less stable, and the corresponding measures are adopted. At present, no significant damage occurred on the two road sections. The results suggest that the evaluation model in this article can be used to pre-evaluate the engineering stability of PWs.

Different responses of surface freeze and thaw phenology changes to warming among Arctic permafrost types

Arctic permafrost surface freeze–thaw (FT) changes related to warming could regulate the magnitude of global warming by altering the terrestrial carbon cycle and energy balances. This study investigated the sensitivity of surface FT changes to warming over Arctic permafrost regions by analyzing long-term changes in surface FT phenology from satellite remote sensing and meteorological variables from the climate data for the period from 1979 to 2017. Averaging over the entire Arctic permafrost regions, spring thawed date apparently advanced by −2.05 days decade−1, whereas autumn frozen date showed weak delaying trend of 0.83 days decade−1, implying the lengthening of the thawed season. Dividing the regions by permafrost types, advancing trends of thawed dates in continuous and high ice content permafrost areas (−2.57 and −2.70 days decade−1) were stronger than those over the discontinuous and low ice content permafrost areas (−1.61 and −1.73 days decade−1). The difference in changes in spring thawed dates between the regions is attributed to the difference in absolute magnitude of warming trends (e.g., 0.72 °C decade−1 for continuous vs. 0.44 °C decade−1 for discontinuous). However, the temperature sensitivity over discontinuous (low ice content) permafrost areas was 23% (10%) stronger than that over continuous (high ice content) permafrost areas for thawed date. In case of autumn, delaying trends of frozen dates were smaller over continuous and high ice content areas (0.69 and 0.74 days decade−1) than those over discontinuous and low ice content areas (1.01 and 0.88 days decade−1). This is mainly explained by the difference in temperature sensitivity (e.g., 1.57 days °C−1 for continuous vs. 2.18 days °C−1 for discontinuous) to warming between the regions rather than the difference in the absolute warming trends between the regions (e.g., 0.91 °C decade−1 for continuous vs. 0.51 °C decade−1 for discontinuous). The stronger temperature sensitivity of discontinuous and low ice content permafrost could be related to the lower demand of latent heat for the phase change of ground ice (or water). Overall, our results suggest that discontinuous and low ice content permafrost are more vulnerable to atmospheric warming. In addition to the magnitude of warming, the sensitivity to warming also needs to be considered when predicting permafrost FT changes.