Warm Permafrost Research Articles

Advances in operational permafrost monitoring on Svalbard and in Norway

The cryosphere web portal maintained by the Norwegian Meteorological Institute (MET Norway), https://cryo.met.no, provides access to the latest operational data and the current state of sea ice, snow, and permafrost in Norway, the Arctic, and the Antarctic. We present the latest addition to this portal: the operational permafrost monitoring at MET Norway and methods for visualising real-time permafrost temperature data. The latest permafrost temperatures are compared to the climatology generated from the station’s data record, including median, confidence intervals, extremes, and trends. There are additional operational weather stations with extended measurement programs at these locations. The collocated monitoring offers daily updated data for studying and monitoring the current state, trends, and the effects of, e.g. extreme climate events on permafrost temperatures. Ground temperature rates obtained from the long-term records in the warmer permafrost found in Norway are typically 0.1 ∘C–0.2 ∘C per decade. In contrast, in the colder permafrost of the High Arctic on Svalbard, a warming of up to 0.7 ∘C per decade is apparent. The operational monitoring provides information faster than ever before, potentially assisting in the early detection of, e.g. record high active layer thickness and pronounced permafrost temperature increases. It may also become an important cornerstone of early warning systems for natural hazards associated with permafrost warming and degradation. Currently, data are submitted manually to the international Global Terrestrial Network for Permafrost and are scheduled for integration with World Meteorological Organisation (WMO) operational services through the WMO Global Cryosphere Watch.

Permafrost changes in the northwestern Da Xing'anling Mountains, Northeast China, in the past decade

Abstract. Under a pronounced climate warming, permafrost has been degrading in most areas globally, but it is still unclear in the northwestern part of the Da Xing'anling Mountains, Northeast China. According to a 10-year observation of permafrost and active-layer temperatures, the multi-year average of mean annual ground temperatures at 20 m was −2.83, −0.94, −0.80, −0.70, −0.60, and −0.49 ∘C, respectively, at boreholes Gen'he4 (GH4), Mangui3 (MG3), Mangui1 (MG1), Mangui2 (MG2), Gen'he5 (GH5), and Yituli'he2 (YTLH2), with the depths of the permafrost table varying from 1.1 to 7.0 m. Ground cooling at shallow depths has been detected, resulting in declining thaw depths in Yituli'he during 2009–2020, possibly due to relatively stable mean positive air temperature and declining snow cover and a dwindling local population. In most study areas (e.g., Mangui and Gen'he), permafrost warming is particularly pronounced at larger depths (even at 80 m). These results can provide important information for regional development and engineering design and maintenance and also provide a long-term ground temperature dataset for the validation of models relevant to the thermal dynamics of permafrost in the Da Xing'anling Mountains. All of the datasets are published through the National Tibetan Plateau Data Center (TPDC), and the link is https://doi.org/10.11888/Geocry.tpdc.271752 (Chang, 2021).

Active Layer and Permafrost Investigations Using Geophysical and Geocryological Methods—A Case Study of the Khanovey Area, Near Vorkuta, in the NE European Russian Arctic

Permafrost in the NE European Russian Arctic is suffering from some of the highest degradation rates in the world. The rising mean annual air temperature causes warming permafrost, the increase in the active layer thickness (ALT), and the reduction of the permafrost extent. These phenomena represent a serious risk for infrastructures and human activities. ALT characterization is important to estimate the degree of permafrost degradation. We used a multidisciplinary approach to investigate the ALT distribution in the Khanovey railway station area (close to Vorkuta, Arctic Russia), where thaw subsidence leads to railroad vertical deformations up to 2.5 cm/year. Geocryological surveys, including vegetation analysis and underground temperature measurements, together with the faster and less invasive electrical resistivity tomography (ERT) geophysical method, were used to investigate the frozen/unfrozen ground settings between the railroad and the Vorkuta River. Borehole stratigraphy and landscape microzonation indicated a massive prevalence of clay and silty clay sediments at shallow depths in this area. The complex refractive index method (CRIM) was used to integrate and quantitatively validate the results. The data analysis showed landscape heterogeneity and maximum ALT and permafrost thickness values of about 7 and 50 m, respectively. The active layer was characterized by resistivity values ranging from about 30 to 100 Ωm, whereas the underlying permafrost resistivity exceeded 200 Ωm, up to a maximum of about 10 kΩm. In the active layer, there was a coexistence of frozen and unfrozen unconsolidated sediments, where the ice content estimated using the CRIM ranged from about 0.3 – 0.4 to 0.9. Moreover, the transition zone between the active layer base and the permafrost table, whose resistivity values ranged from 100 to 200 Ωm for this kind of sediments, showed ice contents ranging from 0.9 to 1.0. Taliks were present in some depressions of the study area, characterized by minimum resistivity values lower than 10 Ωm. This thermokarst activity was more active close to the railroad because of the absence of insulating vegetation. This study contributes to better understanding of the spatial variability of cryological conditions, and the result is helpful in addressing engineering solutions for the stability of the railway.

A large frozen debris avalanche entraining warming permafrost ground—the June 2021 Assapaat landslide, West Greenland

A large landslide (frozen debris avalanche) occurred at Assapaat on the south coast of the Nuussuaq Peninsula in Central West Greenland on June 13, 2021, at 04:04 local time. We present a compilation of available data from field observations, photos, remote sensing, and seismic monitoring to describe the event. Analysis of these data in combination with an analysis of pre- and post-failure digital elevation models results in the first description of this type of landslide. The frozen debris avalanche initiated as a 6.9 * 106 m3 failure of permafrozen talus slope and underlying colluvium and till at 600–880 m elevation. It entrained a large volume of permafrozen colluvium along its 2.4 km path in two subsequent entrainment phases accumulating a total volume between 18.3 * 106 and 25.9 * 106 m3. About 3.9 * 106 m3 is estimated to have entered the Vaigat strait; however, no tsunami was reported, or is evident in the field. This is probably because the second stage of entrainment along with a flattening of slope angle reduced the mobility of the frozen debris avalanche. We hypothesise that the initial talus slope failure is dynamically conditioned by warming of the ice matrix that binds the permafrozen talus slope. When the slope ice temperature rises to a critical level, its shear resistance is reduced, resulting in an unstable talus slope prone to failure. Likewise, we attribute the large-scale entrainment to increasing slope temperature and take the frozen debris avalanche as a strong sign that the permafrost in this region is increasingly at a critical state. Global warming is enhanced in the Arctic and frequent landslide events in the past decade in Western Greenland let us hypothesise that continued warming will lead to an increase in the frequency and magnitude of these types of landslides. Essential data for critical arctic slopes such as precipitation, snowmelt, and ground and surface temperature are still missing to further test this hypothesis. It is thus strongly required that research funds are made available to better predict the change of landslide threat in the Arctic.

Hanging glacier avalanche (Raunthigad–Rishiganga) and debris flow disaster on 7 February 2021, Uttarakhand, India: a preliminary assessment

A catastrophic debris flow in the Rishiganga and Dhauliganga rivers in Uttarakhand, India, on 7 February 2021 left a trail of disaster. Around 100–150 people lost their lives according to Uttarakhand Chief Secretary statement given to ANI news portal, two hydropower projects were badly damaged and a bridge across the Rishiganga River was washed off in the event. Study shows that the debris flow is caused due to detachment of 0.59 km2 right lobe of a hanging glacier and resultant ice-rock avalanche. This right lobe of the glacier was located over a mountain slope having an average slope of 35° at 4700–5555 m a.s.l. and travelled 12.4 km before hitting the infrastructure projects. Role of precipitation, snow cover, land surface temperature, and permafrost processes were investigated for identifying causes of the event. Since 2012, monsoon precipitation and mean annual land surface temperature (LST) showed significant increasing trend. Snow cover during monsoon months showed increasing trend and September, October and November experienced decreasing trend at glacier elevations. Mean annual LST increased from − 0.3 °C in 2012 to a peak of 0.4 °C in 2016. Central lobe of the glacier advanced during this period and eventually fell off in 2016 suggesting that the LST warming forced reduction of frictional drag at the interface facilitating it advancement and eventual dislodgement. Permafrost modelling suggests warm permafrost below 50 m and conditions favourable for intense frost cracking up to 10–15 m. At ~ 40 m depth, the delayed response of 2012–2016 warming produced peak positive temperature conditions by December and probably facilitated the formation of thin film of water at the deeper layers acting as a lubricant for glacier sliding. It is also suggested that the increase in summer precipitation might have forced thickening of the accumulation area and thereby increasing the shear stress for sliding of the glacier. It is proposed that the recent change in the weather conditions in the region is primarily responsible for this event through geological, glaciological, and permafrost processes. Flood modelling study suggests a flood volume of ~ 10 MCM generating 24.5 m flow depth at the bridge site with 12.7 m/s flow velocity. The event highlighted the need for improved monitoring of the cryosphere areas of the Himalaya to capture the early warning signs for better preparedness.

Permafrost Degradation Impacts on the Trans-Alaska Pipeline

The Trans-Alaska Pipeline System transports warm crude oil over 800 miles through a 4-ft-diameter pipeline (i.e., the “mainline”) from Prudhoe Bay on Alaska's North Slope to the Valdez Marine Terminal on the Gulf of Alaska. TAPS traverses three major mountain ranges, several active faults, and continuous and discontinuous permafrost terrain. Permafrost is generally defined as ground that remains at or below 32°F for at least two consecutive years. Permafrost with temperatures between 32°F and 30°F is generally referred to as “warm permafrost,” while permafrost with temperatures below 30°F is referred to as “cold permafrost.”

Compressive strength of cemented soil in pre-bored grouted planted piles under negative temperature environment

As a new type of pile, if the pre-bored grouted planted nodular (PGPN) pile can be successfully applied to the permafrost engineering, it will have significant economic and ecological values. However, the law of strength development of cemented soil of PGPN pile under warm permafrost environment is still unclear. In this study, the strength characteristics of cemented soil were examined through unconfined compressive strength test, and factors such as the curing time at negative temperature, the types of cementitious materials, and the dosages of cement and early strength agent (ESA) were considered. The experimental results indicate thatthe cemented soil with sulpho aluminate cement (SAC) and Ordinary Portland cement (OPC) + ESA as cementitious materials show high strength and stable performance. In addition, the Reasonable dosages of the cement and ESA were suggested, respectively.

Increasing impacts of extreme winter warming events on permafrost

Winter warming events (WWE) are abrupt and short-lasting (hours-to-days) events of extraordinarily warm weather occurring during wintertime, sometimes accompanied by rainfall (rain on snow events; ROS). Through direct heat transfer and changes in the snowpack properties, these events cause changes in the below-ground thermal regime that, in turn, controls a suite of ecosystem processes ranging from microbial activity to permafrost and vegetation dynamics. In addition, the overall impacts of WWE on ground temperatures may also depend on the timing of the events and the preceding snowpack characteristics. The frequency and intensity of these events in the Arctic, including the Swedish subarctic, has increased remarkably during the recent decades and is expected to increase even further during the 21st Century. In addition, snow depth (not necessarily snow duration) is projected to increase in many parts of the Arctic. In 2005, a manipulation experiment was set up on a lowland permafrost mire in the Swedish subarctic, to simulate projected future increases in winter precipitation. In this study, we analyse this 15-year record of ground temperature, AL thickness, and meteorological variables, to evaluate the influence of different types and timings of WWE on permafrost under different snowpack conditions. We found that all WWE types were strongly linked to permafrost warming in both the ambient and the manipulated plots during the winter months, but that significantly warmer summer ground temperatures and, consequently, thicker active layer (AL) were only linked to ROS events in manipulated plots. Additional long-term AL thickness data from nearby permafrost sites indicate an increasingly stronger influence of WWE over time since the mid-1990s, to the detriment of the influence of summer air temperatures.

Topological acoustic sensing of ground stiffness: Presenting a potential means of sensing warming permafrost in a forest

The exploitation of sound as a remote sensing platform for environmental monitoring is a novel avenue for detecting changes in subsurface temperatures and properties in permafrost. We present a workflow for using the geometric phase of ground-supported acoustic waves (i.e., seismic waves) due to scattering by trees in a forest as a means of detecting global changes in permafrost stiffness. We work with a simulated environment composed of discrete masses and springs as a testbed for the vibrational response of a forest. For two different spatial distributions of trees, the geometric phase of ground-supported acoustic waves is numerically calculated using MATLAB to show how changes in ground stiffness, due e.g., to changes in subsurface temperature, affect changes in the phase. For acoustic waves with frequencies near the resonant frequencies of the trees the phase is shown to vary more drastically with ground stiffness. This topological acoustic workflow may present a new approach to characterizing changes in permafrost and provide early warning of thawing permafrost, which is vital to maintaining infrastructure and access to natural resources.

A poromechanics-based constitutive model for warm frozen soil

This study presents a poromechanics-based constitutive model for warm frozen soil. In the model, the effect of pressure melting on unfrozen water content is taken into account. Through the method of poromechanics, the model can consider the interaction between soil particles, ice crystals and unfrozen water. Both the unfrozen water pressure and ice pressure during loading process can also be predicted by this model. Compared with the cryogenic triaxial tests on warm frozen silt and silty clay, it is demonstrated that the constitutive model can simulate the mechanical behaviors especially for strain softening and volumetric dilatancy behaviors of warm frozen soil in triaxial tests. In addition, the constitutive model reflects that the unfrozen water pressure in warm frozen soil is mainly caused by skeleton deformation and pressure melting, among which the pressure melting also has a great influence on unfrozen water pressure. In general, this study proposed here provides a potential basis for analyzing the deformation mechanism of warm frozen soil in warm permafrost regions

Influence of permafrost and hydrogeology on seasonal and spatial variations in water chemistry of an alpine river in the northeastern Qinghai-Tibet Plateau, China

Known as the third pole of the world, the Qinghai-Tibet Plateau has been experiencing rapid permafrost warming and thawing over the last few decades. However, the impact of permafrost distribution and hydrogeology on river hydrochemistry in alpine areas remains unclear. This study conducted four sampling campaigns to reveal the temporal and spatial variations in and factors driving river hydrochemistry in the upper reaches of the Heihe River, the northeastern Qinghai-Tibet Plateau. We found that the concentrations of major ions and total dissolved solids (TDS) in river water showed substantial seasonal variations; the concentrations were generally lower during the initial thawing and thawed periods than during the initial freezing period. However, solute fluxes during the thawed period were much higher than those during the frozen period. The concentrations of major ions and TDS gradually decreased to a minimum from the permafrost meander (PM) section to the seasonal frost meander (SFM) section and then increased the seasonal frost canyon section. Using the revised forward model, we found that river solutes were contributed by carbonate weathering (mean 38.9%) > sulfide oxidation (22.9%) > evaporite dissolution (20.2%) > atmospheric precipitation (8.7%) > silicate weathering (5.0%) > glacial meltwater (4.3%). The higher TDS, Na+, Cl−, Ca2+, Mg2+, and SO42− concentrations in the PM section reflected the influence of freeze-out fractionation. The concentrations of major ions and TDS were lowest in the SFM section, indicating that the riparian porous aquifer was essential in regulating river hydrochemistry, thus reducing its spatiotemporal variations in the alpine area. In the mountain glacier–hillslope–riparian porous aquifer–river system, the river was mainly recharged by groundwater with insufficient water–rock interactions due to the rapid flow owing to the high elevation difference and high permeability of the riparian quaternary porous aquifers. Our findings provide insights into the construction of hydrogeochemical models in alpine areas and are practically important for the scientific management of water resources in the Qinghai-Tibet Plateau.

Field investigation on moisture, heat and deformation behaviors and their coupling effects of expressway in warm permafrost regions

Expressways construction in warm permafrost regions is faced with serious permafrost degradation, and expressways stability is closely related to its thermal-hydro-mechanical state. However, the behaviors of moisture, heat and deformation of expressway in warm permafrost regions are not completely clear. In this study, the experimental embankment for the proposed Qinghai-Tibet Expressway built on site is taken as the research object, and the behaviors of moisture, heat and deformation and their coupling effects are studied, and the expressway stability in warm permafrost regions is further discussed. The experimental results show that the permafrost degradation beneath expressway is more serious than that beneath ordinary highway. The moisture distribution is affected by temperature distribution and capillary effect, showing high moisture content in the top and bottom of the embankment and low moisture content in the middle. The expressway presents deformation difference due to the differential degradation of underlying permafrost, and the deformation difference increases with time. The embankment settlement is slow before reaching a new thawing depth, but it develops rapidly after reaching a new thawing depth. Frost heaving occurs in cold season and can counteract the creep of warm permafrost, leaving the embankment in a stable deformation state.

Tree ring evidence of rapid development of drunken forest induced by permafrost warming.

Black spruce trees growing on warming permafrost lean in all directions due to soil movement, forming a “drunken” forest. Two hypothetical drivers of drunken forest development are (i) loosening of the soil foundation induced by permafrost degradation in warm summers and (ii) mound rising induced by freezing soil in winter. However, no evidence has previously clarified whether recent tree leaning is related to climate warming or is part of a natural hummock formation process. Here, we provide evidence that tree leaning and soil hummock formation have accelerated due to climate warming. We find that trees’ leaning events synchronize with the development of soil hummocks as recorded in tree rings with lignin‐rich cells. Tree leaning is caused by mound rising in winter due to refreezing of soil following deep thaws in summer, rather than by loosening of the soil foundation in summer. Hummock formation shifted from periodic events before 1960 to continuous mound rising in the warmer succeeding 50 years. Although soil change is generally a slow process, recent permafrost warming has induced rapid hummock formation, which threatens the stability of drunken forests and organic carbon in soil hummocks based on shallow permafrost table.

Effects of thermosyphons on the thermal regime and stability of cast‐in‐place piles in permafrost regions on the Qinghai‐Tibet Plateau

AbstractThe thermal effects of cast‐in‐place piles on the surrounding permafrost frequently induce deformation or failure of piles in permafrost regions. Because piles are directly inserted into the permafrost layer, the thermal disturbance of the piles is more straightforward than that of road embankments to the permafrost. Thermosyphons have proven to be effective in stabilizing the embankments of highways and railways in permafrost regions. However, the effects of thermosyphons on the thermal regime and stability of the cast‐in‐place piles remain unclear. The foundation soils of most piles in permafrost regions along the Qinghai‐Tibet Power Transmission Line were cooled by thermosyphons, and the results of a 7‐year‐period monitoring of ground temperature and deformation of a pile are presented in this paper. The results showed that the extent of thawed permafrost during the installation of the pile extended more than 5 m away from the pile. Thermosyphons shortened the refreezing time by more than 2 months. Thermosyphons cooled the surrounding permafrost to temperatures below the ambient ground temperature at the end of the cold seasons, and the temperature difference lasted until the end of the warm seasons owing to cold reserves formed in the cold season. The thermosyphons mitigated the thermal effects of the concrete pile owing to their higher thermal conductivity. Thermosyphons also significantly decreased the rate of active layer thickening around the pile compared to that observed in a natural field under a warming climate. Generally, thermosyphons stabilized the piles during the observation period by cooling the permafrost around the pile and producing a greater adfreeze force to counteract the frost heave force and subsequently support the tower. Additional thermosyphons or insulation measures may be necessary to ensure the long‐term stability of piles, considering a faster degradation of the ambient permafrost than expected. The results may provide insights into the design and maintenance of cast‐in‐place piles in warm permafrost regions.

Strength of hard foundation rocks in the Southern Yakutian permafrost region (city of Neryungri)

This paper discusses the results of a statistical analysis of data from geotechnical surveys conducted in the mid-1970s in the city of Neryungri, southern Yakutia, located on sporadic, warm permafrost. The analysis included 162 laboratory determinations of uniaxial compressive strength of sandstone specimens. The test specimens were taken from core obtained boreholes. The study of the probabilistic distributions of sandstone strength values in the total sample population and in the formal groups divided into the rock strength categories has shown the following. In an unfavorable (artificially water-saturated) and favorable (frozen or air-dry) natural state, the Jurassic sandstone in the vast majority of cases is, according to the, a reliable and stable rock foundation for engineering structures. The range of average values for the rock varieties: sandstone of low strength and moderate strength together with sandstone of high strength in water-saturated and natural condition is 8.83–92.81 and 30.91–127.00 MPa. Comparison with the average dry strength values reported by Russian and foreign authors has shown that the Neryungri sandstone differs little in strength from sandstones southern Yakutia permafrost region (87.26 MPa), but also the territory of the former RSFSR, now Russia (84.53 MPa). On a regional scale, the proximity of a common measure of average strength and common territorial belonging, one of the sides of the natural essence of sandstone appears as a representative of the class of sedimentary rocks of the Eurasian continent.

Spatial variability and influential factors of active layer thickness and permafrost temperature change on the Qinghai-Tibet Plateau from 2012 to 2018

Due to the complex topography and localized climate, active layer thickening and permafrost warming varied distinctly in different regions on the Qinghai-Tibet Plateau (QTP). Based on the borehole-temperature data at 93 sites from 2012 to 2018, we analyzed the temporal and spatial characteristics of active layer thickness, permafrost temperature, and relevant climatic factors in 8 typical geomorphological units on the QTP. The active layer thickened at 86 sites and thinned at 7 sites. The permafrost warmed at 89 sites and cooled at 4 sites. The median values of the annual increase rate of active layer thickness were from 0.04 to 0.13 m/a for the monitored regions. The highest rate reached 0.46 m/a, indicating severe permafrost degradation in local areas. The mean annual soil temperatures at a 6-m depth generally increased faster for cold permafrost, and the active layer thickened more significantly in warm permafrost sites. Among these regions, Kekexili Mountains showed a lower increase rate of active layer thickness, and the temperature rise of permafrost in the Fenghuoshan Mountains was more significant. The temporal change of snow cover duration was closely related to the active layer thickness variation in the northern permafrost regions on the QTP (Kunlunshan Mountains and Chumaerhe High Plain). In contrast, the temporal variation of freezing index was the dominant factor in the southern regions (Wuli Basin, Tongtianhe Basin, and Tanggula Mountains). No linear correlation between the temporal variations of climatical factors and active layer thickness variation was found for the regions in the middle of QTP (Kekexili Mountains, Beiluhe Basin, and Fenghuoshan Mountains ). The comprehensive effects of freezing index and snow cover duration result in the different relationships between air temperature variation and permafrost change in different regions on the QTP. These findings are beneficial for understanding the relationship between climate change and permafrost evolution.

Thermal and deformational repairing effect of crushed rock revetment acting as reinforcement along Qinghai–Tibet railway in permafrost regions

Due to the particularity and complexity of permafrost subgrade, research on its long-term maintenance and reinforcement under climate warming and engineering activities is of great significance. To mitigate subgrade diseases caused by thermal disturbance during the engineering construction and operation in the initial stage, the crushed-rock revetment (CRR) was additionally paved with a thickness of 1.5 m and 1.0 m on some sunny and shady shoulders of the traditional embankments along the Qinghai–Tibet railway, respectively. The improving effects for thermal and deforming stability are evaluated based on observation data of ground temperatures and embankment deformations at two sites from 2002 to 2014. The results show that a larger uplifting magnitude in the artificial permafrost table (APT), greater ground temperature decreasing amplitudes and reduction ranges of settling rate appear under the shady embankment shoulder in warm permafrost region, and both sides in the cold permafrost region when reinforcing with CRR. However, in warm permafrost region, the laying of CRR on the sunny slope of subgrade may cause considerable thermal disturbance to the underlying permafrost foundation, combined with the resulting additional stress, induce the further expansion of differential settlement. Moreover, the thermal stability strengthening effect of the CRR is closely related to the variation of the APT thickness in the earlier stage, convection intensity inside the CRR, ‘cold energy reserve’ in the deeper permafrost, and amount of solar radiation received by the CRR. More effective reinforcements should be implemented to alleviate the potential threaten beneath sunny embankment slope in warm permafrost regions.

Air-convection-reflective sheds: A mitigation technique that stopped degradation and promoted permafrost recovery under the Alaska Highway, south-western Yukon, Canada

This study tested the efficacy of air-convection-reflective sheds (ACRS) installed along the Alaska Highway in Yukon (Canada) as a mitigation technique to reduce heat absorption during the thawing season and to increase heat loss during the freezing season. Soil surface, air, and ground temperatures were recorded under the ACRS between 2008 and 2016, which were then compared with values from an unmitigated road embankment and from the natural ground near the road embankment. The design of the ACRS blocked incoming solar radiation, prevented snow accumulation, and promoted air convection through the stack effect, which resulted in a cooling efficiency of 358% compared to the reference site. The net heat loss resulted in a 6.3 °C cooling of the average soil surface temperature and caused the active layer thickness to decrease by nearly two meters, thus stopping permafrost warming and promoting permafrost recovery and its upward aggradation in the embankment. Implementations of the ACRS in specific vulnerable or degraded sections of roads and airstrips represents a viable solution to permafrost thaw and embankment failure.

New high-resolution estimates of the permafrost thermal state and hydrothermal conditions over the Northern Hemisphere

Abstract. Monitoring the thermal state of permafrost (TSP) is important in many environmental science and engineering applications. However, such data are generally unavailable, mainly due to the lack of ground observations and the uncertainty of traditional physical models. This study produces novel permafrost datasets for the Northern Hemisphere (NH), including predictions of the mean annual ground temperature (MAGT) at the depth of zero annual amplitude (DZAA) (approximately 3 to 25 m) and active layer thickness (ALT) with 1 km resolution for the period of 2000–2016, as well as estimates of the probability of permafrost occurrence and permafrost zonation based on hydrothermal conditions. These datasets integrate unprecedentedly large amounts of field data (1002 boreholes for MAGT and 452 sites for ALT) and multisource geospatial data, especially remote sensing data, using statistical learning modeling with an ensemble strategy. Thus, the resulting data are more accurate than those of previous circumpolar maps (bias = 0.02±0.16 ∘C and RMSE = 1.32±0.13 ∘C for MAGT; bias = 2.71±16.46 cm and RMSE = 86.93±19.61 cm for ALT). The datasets suggest that the areal extent of permafrost (MAGT ≤0 ∘C) in the NH, excluding glaciers and lakes, is approximately 14.77 (13.60–18.97) × 106 km2 and that the areal extent of permafrost regions (permafrost probability >0) is approximately 19.82×106 km2. The areal fractions of humid, semiarid/subhumid, and arid permafrost regions are 51.56 %, 45.07 %, and 3.37 %, respectively. The areal fractions of cold (≤-3.0 ∘C), cool (−3.0 ∘C to −1.5 ∘C), and warm (>-1.5 ∘C) permafrost regions are 37.80 %, 14.30 %, and 47.90 %, respectively. These new datasets based on the most comprehensive field data to date contribute to an updated understanding of the thermal state and zonation of permafrost in the NH. The datasets are potentially useful for various fields, such as climatology, hydrology, ecology, agriculture, public health, and engineering planning. All of the datasets are published through the National Tibetan Plateau Data Center (TPDC), and the link is https://doi.org/10.11888/Geocry.tpdc.271190 (Ran et al., 2021a).

Damage characteristics of the Qinghai-Tibet Highway in permafrost regions based on UAV imagery

ABSTRACT For the particular engineering-geological conditions and natural environment in permafrost regions, the highway has a high damage ratio during the operation. In warm and ice-rich permafrost regions, highway pavement and embankment have poor serviceability, which threatens driving the vehicle and safe operation. Traditional field surveys on highway damage cannot entirely, rapidly and precisely obtain the distress information along the whole road. In this paper, the Qinghai-Tibet Highway (QTH) pavement distress was investigated in 550-km-long permafrost regions based on the field surveys in 2014 and 2019 and the unmanned aerial vehicle (UAV) imagery. The type and damage ratio of distress were extracted by the remote sensing image classification method. The pavement roughness and embankment height were acquired by the spatial analysis of geographical information system. This paper provides a novel insight and efficient method for the distress investigation and exploration of distress formation in permafrost region, which can be applied in other similar engineering projects in the cold and inclement permafrost region. Furthermore, this paper also presents valuable and first-hand field data for evaluating highway serviceability and prevention of road damage during operation and maintenance stages.