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Due to the continuous degradation (gradual thawing) of permafrost, supra-permafrost water has become an important component of runoff that occurs in cold regions. However, current research has only focused on the amount of water provided by permafrost, and little has been reported regarding the source and formation mechanisms of supra-permafrost water. Due to the difficulty of observation and sampling in cold regions and insufficient data accumulation, model simulations face various difficulties in regard to solving problems related to hydrological processes. Considering the advantages of stable isotope tracer methods in hydrology, the source of supra-permafrost water in Qilian Mountain was analyzed based on 1,840 samples, and the source of supra-permafrost water was determined by end-member mixing analysis (EMMA). Negative line-conditioned excess (lc-excess), lower slope, and particularly the negative intercept of the evaporation line (EL) indicates strong evaporation effects on supra-permafrost water. Remarkably, the evolutionary process, influencing factors, and relationship with other water bodies all indicate that supra-permafrost water is replenished by precipitation, ground ice meltwater, and snow meltwater. The results indicated that from May to October, the contributions of precipitation to the supra-permafrost water were 79%, 83%, 90%, 84%, 87%, and 83%, respectively. Snow meltwater contributed 11%, 13%, 10%, 16%, 11%, and 9%, respectively. Permafrost degradation impacts the water cycle and can increase the minimum monthly runoff and increase groundwater storage. To mitigate the effects of this change, monitoring and early warning systems are essential for detecting signs of permafrost degradation in a timely manner so that appropriate measures can be taken. This may involve the use of remote-sensing technologies, sensor networks, and other methods for real-time monitoring. Establishing mechanisms for sharing information with the relevant departments is crucial. The research results provide scientific and technological support and aid in decision-making to mitigate the negative effects of continuous permafrost degradation in a changing environment., Competing Interests: Declaration of competing interest I wish to submit an original research manuscript for publication in Journal of Environmental Management, entitled " The effect of freeze-thaw action on the dynamic change of supra-permafrost water source：A stable isotope perspective ". The paper was coauthored by Juan Gui, Zongxing Li, Jian Xue, Fa Du and Qiao Cui. We believe that our study makes a significant contribution to the literature because it provides newly available data and interpretations from a region that has scantily been studied by the methods of this research. I hereby certify that this paper consists of original, unpublished work which is not under consideration for publication elsewhere. The original manuscript and figures will be transferred, following the instruction by the Editorial Committee when the paper is accepted. This manuscript has not been published or presented elsewhere in part or in entirety and is not under consideration by another journal. We have read and understood your journal's policies, and we believe that neither the manuscript nor the study violates any of these. There are no conflicts of interest to declare. There are no conflicts of interest to declare., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The Qilian Mountains, located on the northeastern edge of the Qinghai–Tibet Plateau, are characterized by unique high-altitude and cold-climate terrain, where permafrost and seasonally frozen ground are extensively distributed. In recent years, with global warming and increasing precipitation on the Qinghai–Tibet Plateau, permafrost degradation has become severe, further exacerbating the fragility of the ecological environment. Therefore, timely research on surface deformation and the freeze–thaw patterns of alpine permafrost in the Qilian Mountains is imperative. This study employs Sentinel-1A SAR data and the SBAS-InSAR technique to monitor surface deformation in the alpine permafrost regions of the Qilian Mountains from 2017 to 2023. A method for spatiotemporal interpolation of ascending and descending orbit results is proposed to calculate two-dimensional surface deformation fields further. Moreover, by constructing a dynamic periodic deformation model, the study more accurately summarizes the regular changes in permafrost freeze–thaw and the trends in seasonal deformation amplitudes. The results indicate that the surface deformation time series in both vertical and east–west directions obtained using this method show significant improvements in accuracy over the initial data, allowing for a more precise reflection of the dynamic processes of surface deformation in the study area. Subsidence is predominant in permafrost areas, while uplift mainly occurs in seasonally frozen ground areas near lakes and streams. The average vertical deformation rate is 1.56 mm/a, with seasonal amplitudes reaching 35 mm. Topographical (elevation; slope gradient; aspect) and climatic factors (temperature; soil moisture; precipitation) play key roles in deformation patterns. The deformation of permafrost follows five distinct phases: summer thawing; warm-season stability; frost heave; winter cooling; and spring thawing. This study enhances our understanding of permafrost deformation characteristics in high-latitude and high-altitude regions, providing a reference for preventing geological disasters in the Qinghai–Tibet Plateau area and offering theoretical guidance for regional ecological environmental protection and infrastructure safety. [ABSTRACT FROM AUTHOR]

Permafrost degradation has been widely reported on the Tibetan Plateau (TP). However, directly observed evidence of permafrost thawing processes and degradation rates are very limited, although it is expected to be prevalent near the periphery of a permafrost area. Here, we report permafrost changes and disappearance in the Qilian Mountains (northeastern TP) based on three boreholes instrumented along a 100 m transect during 2014–2021. Our results show that permafrost has significantly degraded in the study area: the mean downward thawing rate from the permafrost table was about 0.16 m per year while the mean upward thawing rate from the permafrost base was about 0.23 m per year. We estimate the mean lateral degradation rate of permafrost in this area was ∼4.14 m per year. More dramatically, the 1.5 m thick permafrost layer at one of the boreholes thawed completely between April of 2018 and December of 2019. Our results indicate that changes in climatic condition may have played only a limited role in controlling the active layer thickness in the vicinity of the altitudinal limit of permafrost; moisture content and soil conditions play key roles in site-specific permafrost thawing. This study provides new quantitative insights for understanding changes near the altitudinal limit of permafrost, and we suggest that land surface models or Earth system model studies of the lateral heat exchanges should be implemented in order to better represent permafrost thawing processes.

The increase in temperatures and changing precipitation patterns resulting from climate change are accelerating the occurrence and development of landslides in cold regions, especially in permafrost environments. Although the boundary regions between permafrost and seasonally frozen ground are very sensitive to climate warming, slope failures and their kinematics remain barely characterized or understood in these regions. Here, we apply multisource remote sensing and field investigation to study the activity and kinematics of two adjacent landslides (hereafter referred to as "twin landslides") along the Datong River in the Qilian Mountains of the Qinghai-Tibet Plateau. After failure, there is no obvious change in the area corresponding to the twin landslides. Based on InSAR measurements derived from ALOS PALSAR-1 and -2, we observe significant downslope movements of up to 15 mm/day within the twin landslides and up to 5 mm/day in their surrounding slopes. We show that the downslope movements exhibit distinct seasonality; during the late thaw and early freeze season, a mean velocity of about 4 mm/day is observed, while during the late freeze and early thaw season the downslope velocity is nearly inactive. The pronounced seasonality of downslope movements during both pre- and post-failure stages suggest that the occurrence and development of the twin landslide are strongly influenced by freeze–thaw processes. Based on meteorological data, we infer that the occurrence of twin landslides are related to extensive precipitation and warm winters. Based on risk assessment, InSAR measurements, and field investigation, we infer that new slope failure or collapse may occur in the near future, which will probably block the Datong River and cause catastrophic disasters. Our study provides new insight into the failure mechanisms of slopes at the boundaries of permafrost and seasonally frozen ground. [ABSTRACT FROM AUTHOR]

As a sensitive indicator of climate change, frozen ground (including permafrost and seasonally frozen ground (SFG)) has changed obviously due to climate warming during the past few decades. Simulated permafrost area in the Qilian Mountains has decreased about 2.63 × 104 km2 from 1960s to 2000s, with an average decreased rate of −6.1%/decade. Simulated unchanged permafrost (which did not degrade to SFG) mainly distributed in the high altitude parts of Qilian Mountains, and decreased permafrost mainly distributed at the edge of permafrost. The spatial distribution of the SFG freeze state in the Qilian Mountains can be explained primarily by altitude and longitude, not by latitude. From September 1, 1961 to August 31, 2015, the SFG freeze state has changed obviously in the Qilian Mountains, which was affected mainly by air temperature, air freezing index and air thawing index, less by precipitation. The first date of freezing was delayed by about 12 ± 2 days with a rate of 0.21 ± 0.04 days/year, whereas the last date advanced obviously by about 13 ± 3 days with a rate of 0.24 ± 0.06 days/year. Accordingly, the duration and actual number of freeze days experienced a significant decrease by 24 ± 3 and 34 ± 3 days with rates of 0.45 ± 0.06 and 0.62 ± 0.06 days/year, respectively. The maximum seasonally frozen depth decreased by 25 ± 5 cm with a rate of 0.46 ± 0.09 cm/year. [ABSTRACT FROM AUTHOR]

River discharge has changed significantly in high-latitude permafrost regions due to climate warming, but these changes are still unclear in high-mountain permafrost regions. Long-term discharge data of 8 inland river catchments in the Qilian Mountains were analysed, and increased winter (minimum monthly) discharge, decreased recession coefficient and decreased ratio of maximum monthly to minimum monthly discharge (Q max /Q min) was detected commonly. This implies that the degradation of mountain permafrost under the warming climate has significantly changed the river discharge of high mountain catchments. Permafrost degradation may influence the relationship between summer precipitation and the following cold-season discharge by promoting liquid water infiltration, increasing the groundwater storage capacity and supporting deep flow paths. However, the role of summer precipitation on cold-season discharge may be affected by different glacier runoff rates (the percentage of glacier runoff contribution to the total annual flow). Under permafrost degradation, summer precipitation will strongly influence the following cold-season discharge in catchments with a low glacier runoff rate (less than 10%) but not the discharge in catchments with a high glacier runoff rate (more than 40%). The results of this study may provide important information for local water resource management and future permafrost hydrological simulation. [ABSTRACT FROM AUTHOR]

The permafrost in the Qilian Mountains (QLMs), the northeastern margin of the Qinghai–Tibet Plateau, changed dramatically in the context of climate warming and increasing anthropogenic activities, which poses significant influences on the stability of the ecosystem, water resources, and greenhouse gas cycles. Yet, the characteristics of the frozen ground in the QLMs are largely unclear regarding the spatial distribution of active layer thickness (ALT), the maximum frozen soil depth (MFSD), and the temperature at the top of the permafrost or the bottom of the MFSD (TTOP). In this study, we simulated the dynamics of the ALT, TTOP, and MFSD in the QLMs in 2004–2019 in the Google Earth Engine (GEE) platform. The widely-adopted Stefan Equation and TTOP model were modified to integrate with the moderate-resolution imaging spectroradiometer (MODIS) land surface temperature (LST) in GEE. The N-factors, the ratio of near-surface air to ground surface freezing and thawing indices, were assigned to the freezing and thawing indices derived with MODIS LST in considerations of the fractional vegetation cover derived from MODIS normalized difference vegetation index (NDVI). The results showed that the GEE platform and remote sensing imagery stored in Google cloud could be quickly and effectively applied to obtain the spatial and temporal variation of permafrost distribution. The area with TTOP < 0 °C is 8.4 × 104 km2 (excluding glaciers and lakes) and accounts for 46.6% of the whole QLMs, the regional mean ALT is 2.43 ± 0.44 m, while the regional mean MFSD is 2.54 ± 0.45 m. The TTOP and ALT increase with the decrease of elevation from the sources of the sub-watersheds to middle and lower reaches. There is a strong correlation between TTOP and elevation (slope = −1.76 °C km−1, p < 0.001). During 2004–2019, the area of permafrost decreased by 20% at an average rate of 0.074 × 104 km2·yr−1. The regional mean MFSD decreased by 0.1 m at a rate of 0.63 cm·yr−1, while the regional mean ALT showed an exception of a decreasing trend from 2.61 ± 0.45 m during 2004–2005 to 2.49 ± 0.4 m during 2011–2015. Permafrost loss in the QLMs in 2004–2019 was accelerated in comparison with that in the past several decades. Compared with published permafrost maps, this study shows better calculation results of frozen ground in the QLMs.

Abstract: To investigate the thermal characteristics and dynamics of permafrost as well as seasonally frozen ground over the upper reaches of the Heihe River Basin (URHR), an observation network with 14 boreholes was established during 2011–2014. The in situ measurements indicated mean annual air temperature that ranged from −5.2 to −2.3°C at the monitored elevation range of ∼3,600–4,150 m, and mean annual ground surface temperature that ranged from −1.3 to 1.7°C during 2013–2017. The mean annual ground temperature at 16‐ to 18‐m depth ranged from −1.71°C on the high (>4,000 m above sea level) north facing slope to about 0‐C around areas near the lower limit of permafrost. Active layer thickness at the monitored sites varied significantly with the range of 0.77–4.90 m during 2011–2017, and maximum frozen depth in seasonally frozen ground was about 5 m. Permafrost thickness was between ∼136 m and less than 10 m. Both permafrost and seasonally frozen ground were found to be subject to serious warming during the measured period in the URHR. This study provides new quantitative insights for permafrost and seasonally frozen ground in the URHR. [ABSTRACT FROM AUTHOR]

Observational data collection on permafrost and active layer freeze–thaw cycle is extremely limited in the upper reaches of the Heihe River (URHHR) in the Qilian Mountains of the north-eastern Qinghai-Tibet Plateau. It acts as a bottleneck, restricting the hydrological effects of the changes in the permafrost and active layer in the Heihe River Basin. Using soil temperature, moisture and air temperature data collected from the four active layer observation sites (AL1, AL3, AL4 and AL7) established in the alpine permafrost regions in the URHHR, from 2013 to 2014, the region's active layer freeze–thaw cycle and the soil hydrothermal dynamics were comparatively analysed. As the elevation increased from 3700 m a.s.l. to 4132 m a.s.l., the mean annual ground temperatures (MAGTs) of the active layer and the active layer thicknesses (ALTs) decreased, the onset date of soil freeze of the active layer occurred earlier and the soil freeze rate increased. However, the onset date of soil thaw and the thaw rate did not exhibit significant trends. Compared to the thaw process, the duration of the active layer freeze process was significantly shortened and its rate was significantly higher. The soil freeze from bottom to top did not occur earlier than that from top to bottom. Furthermore, as elevation increased, the proportion of the bottom-up freeze layer thickness increased. The soil moisture in the thaw layer continuously moved to the freeze front during the active layer's two-way freeze process, causing the thaw layer to be dewatered. The seasonal thaw process resulted in significant reduction of the soil water content in the thaw layer, accounting for the high ice content in the vicinity of the permafrost table. Controlled by elevation, the active layer's seasonal freeze–thaw cycle was also affected by local factors, such as vegetation, slope, water (marsh water and super-permafrost water), lithology and water (ice) content. This study provides quantitative data that identify, simulate and predict the hydrological effects of the changes in the permafrost and active layer of the Heihe River Basin. [ABSTRACT FROM AUTHOR]

Abstract: Permafrost is a physical geographic phenomenon that is sensitive to temperature, and climate change has a great effect on alpine permafrost distributions. Based on topographic and meteorological factors and a benchmark map of alpine permafrost distribution, this paper puts forward a GIS-based empirical permafrost model. This model uses a multi-criteria approach to derive the permafrost distribution in 5-year intervals in the Qilian Mountains over the past 30years. The simulation results show that: (1) the model can use multiple factors to simulate alpine permafrost, which can reduce dependence on field survey data. (2) The simulated distribution of alpine permafrost presents an overall degraded tendency, about 17.11% of which has decreased over the past 30years. (3) Based on the climate change tendency, simulated Qilian permafrost will continue to degrade about 0.51×104 km2 over the next 15years. [Copyright &y& Elsevier]

The ecological environment in alpine regions is fragile and sensitive to land-use and land-cover (LULC) change and climate warming. However, there are limited studies on the response of LULC and vegetation activity to climate change and human interference in mountainous permafrost regions. Based on in-situ meteorological and multi-source remote sensing data, we performed time trend and partial correlation analyses to investigate the spatial and temporal variation of LULC, landscape pattern, and vegetation growth under the impact of climate change and human activities in the source region of the Datong River from 2000 to 2019. Our results showed that the alpine desert area decreased significantly at a rate of −13.1 km2 yr−1 (p < 0.05), while the alpine meadow area increased at a rate of 8.3 km2 yr−1 (p < 0.1). Mining and road areas showed a significant increasing trend at a rate of 3.2 km2 yr−1 and 1.2 km2 yr−1, respectively. The increasing alpine meadow and mining areas were mainly derived from alpine deserts and alpine wetlands, respectively. The number of alpine wetland patches increased significantly along with a significant decrease in the landscape shape index of the rivers. Vegetation growth, as indicated by the enhanced vegetation index (EVI) was positively correlated with temperature but negatively correlated with precipitation and solar radiation in 59.6%, 52.3%, and 56.5% of the vegetated areas, respectively (p < 0.05). Temperature was the dominant climate factor controlling vegetation dynamics, and the recent warming hiatus resulted in a significant increase in EVI for alpine deserts, but no significant changes in EVI for alpine wetlands and alpine meadows. Increasing risk of negative impacts from human activities, including mineral exploration and grazing, on vegetation distribution and growth was observed. This study provides clear evidence of the upward invasion of alpine meadows into alpine desert areas under warm and humid climatic conditions. As climate warming intensifies, alpine meadow expansion may be impeded by extreme precipitation and permafrost thawing. • Alpine meadow moves to higher altitudes. • Mining area and grazing intensity increase significantly. • Alpine desert EVI increases significantly. • Alpine vegetation growth is limited by air temperature. [ABSTRACT FROM AUTHOR]

Abstract: Based on a bench-mark distribution map of alpine permafrost, topographic factors and meteorological factors in every decade, the decadal distributions of alpine permafrost from 1960 to 2009 in the Qilian Mountains were simulated by using Logistic Regression Model (LM), and the overall accuracy of the simulation results was estimated to above 80%. Moreover, the changing conditions of alpine permafrost in the Qilian Mountains during each adjoining two decades, as well as over the past 50years, had also been analyzed. The research results show: (1) LM simulation in this research not only decreases the dependency on the field survey data, but achieves dynamic simulation of alpine permafrost distribution; (2) the simulated areas of alpine permafrost in 1960s, 1970s, 1980s, 1990s and 2000s are 10.7×104 km2, 9.8×104 km2, 10.0×104 km2, 8.5×104 km2 and 8.7×104 km2 respectively. Hence, the distribution of alpine permafrost presents an overall degraded tendency with two slight fluctuations. [Copyright &y& Elsevier]

The permafrost in the Qilian Mountains (QLMs), the northeastern margin of the Qinghai–Tibet Plateau, changed dramatically in the context of climate warming and increasing anthropogenic activities, which poses significant influences on the stability of the ecosystem, water resources, and greenhouse gas cycles. Yet, the characteristics of the frozen ground in the QLMs are largely unclear regarding the spatial distribution of active layer thickness (ALT), the maximum frozen soil depth (MFSD), and the temperature at the top of the permafrost or the bottom of the MFSD (TTOP). In this study, we simulated the dynamics of the ALT, TTOP, and MFSD in the QLMs in 2004–2019 in the Google Earth Engine (GEE) platform. The widely-adopted Stefan Equation and TTOP model were modified to integrate with the moderate-resolution imaging spectroradiometer (MODIS) land surface temperature (LST) in GEE. The N-factors, the ratio of near-surface air to ground surface freezing and thawing indices, were assigned to the freezing and thawing indices derived with MODIS LST in considerations of the fractional vegetation cover derived from MODIS normalized difference vegetation index (NDVI). The results showed that the GEE platform and remote sensing imagery stored in Google cloud could be quickly and effectively applied to obtain the spatial and temporal variation of permafrost distribution. The area with TTOP < 0 °C is 8.4 × 104 km2 (excluding glaciers and lakes) and accounts for 46.6% of the whole QLMs, the regional mean ALT is 2.43 ± 0.44 m, while the regional mean MFSD is 2.54 ± 0.45 m. The TTOP and ALT increase with the decrease of elevation from the sources of the sub-watersheds to middle and lower reaches. There is a strong correlation between TTOP and elevation (slope = −1.76 °C km−1, p < 0.001). During 2004–2019, the area of permafrost decreased by 20% at an average rate of 0.074 × 104 km2·yr−1. The regional mean MFSD decreased by 0.1 m at a rate of 0.63 cm·yr−1, while the regional mean ALT showed an exception of a decreasing trend from 2.61 ± 0.45 m during 2004–2005 to 2.49 ± 0.4 m during 2011–2015. Permafrost loss in the QLMs in 2004–2019 was accelerated in comparison with that in the past several decades. Compared with published permafrost maps, this study shows better calculation results of frozen ground in the QLMs. [ABSTRACT FROM AUTHOR]

Based on the results of remote sensing data interpretation, this paper aims to simulate and predict the mountain permafrost distribution changes affected by the mean decadal air temperature (MDAT), from the 1990s to the 2040s, in the Qilian Mountains. A bench-mark map is visually interpreted to acquire a mountain permafrost distribution from the 1990s, based on remote sensing images. Through comparison and estimation, a logistical regression model (LRM) is constructed using the bench-mark map, topographic and land coverage factors and MDAT data from the 1990s. MDAT data from the 2010s to the 2040s are predicted according to survey data from meteorological stations. Using the LRM, MDAT data and the factors, the probabilities (p) of decadal mountain permafrost distribution from the 1990s to the 2040s are simulated and predicted. According to the p value, the permafrost distribution statuses are classified as 'permafrost probable' (p > 0.7), 'permafrost possible' (0.7 ≥ p ≥ 0.3) and 'permafrost improbable' (p < 0.3). From the 1990s to the 2040s, the 'permafrost probable' type mainly degrades to that of 'permafrost possible', with the total area degenerating from 73.5 × 103 km2 to 66.5 × 103 km2. The 'permafrost possible' type mainly degrades to that of 'permafrost impossible', with a degradation area of 6.5 × 103 km2, which accounts for 21.3% of the total area. Meanwhile, the accuracy of the simulation results can reach about 90%, which was determined by the validation of the simulation results for the 1990s, 2000s and 2010s based on remote sensing data interpretation results. This research provides a way of understanding the mountain permafrost distribution changes affected by the rising air temperature rising over a long time, and can be used in studies of other mountains with similar topographic and climatic conditions. [ABSTRACT FROM AUTHOR]