With the global climate change, glaciers on the Qinghai-Tibet Plateau (QTP) and its adjacent mountainous regions are retreating rapidly, leading to an increase in active rock glaciers (ARGs) in front of glaciers. As crucial components of water resources in alpine regions and indicators of permafrost boundaries, ARGs reflect climatic and environmental changes on the QTP and its adjacent mountainous regions. However, the extensive scale of rock glacier development poses a challenge to field investigations and sampling, and manual visual interpretation requires substantial effort. Consequently, research on rock glacier cataloging and distribution characteristics across the entire area is scarce. This study statistically analyzed the geometric characteristics of ARGs using high- resolution GF-2 satellite images. It examined their spatial distribution and relationship with local factors. The findings reveal that 34,717 ARGs, covering an area of approximately 6873.54 km2, with an average area of 0.19 +/- 0.24 km2, a maximum of 0.0012 km2, and a minimum of 4.6086 km2, were identified primarily in north-facing areas at elevations of 4300-5300 m and slopes of 9 degrees-25 degrees, predominantly in the Karakoram Mountains and the Himalayas. Notably, the largest concentration of ARGs was found on north-facing shady slopes, constituting about 42 % of the total amount, due to less solar radiation and lower near-surface temperatures favorable for interstitial ice preservation. This research enriches the foundational data on ARG distribution across the QTP and its adjacent mountainous regions, offering significant insights into the response mechanisms of rock glacier evolution to environmental changes and their environmental and engineering impacts.

Permafrost degradation varies spatially; however, the underlying mechanism remains partially unclear. In this study, we predicted permafrost variation under the influence of climate change to investigate the sensitivity of permafrost degradation to geological and climatic conditions. The results revealed that geological strata can strongly impact the permafrost degradation process. Mainly due to the greater thermal conductivity of sandy gravel in the Arctic, the complete thaw of permafrost will be greatly delayed by more than 160 years compared with that on the Qinghai-Tibet Plateau (QTP). Climatic conditions, such as snow depth, can also greatly affect the degradation process of permafrost: The thaw of permafrost will be delayed by more than 140 years when the snow depth decreases from 0.7 to 0.1 m. Peat soil thickness at ground surface can also affect permafrost degradation. The permafrost temperature increases as peat soil thickens when the thickness is less than 1.0 m, whereas there is a critical peat soil thickness (approximately 0.2 and 0.5 m on the QTP and in the Arctic, respectively) under which permafrost will thaw at the fastest rate. The findings highlight the influence of geology and climate over permafrost degradation.

Over the past decades, the cryosphere has changed significantly in High Mountain Asia (HMA), leading to multiple natural hazards such as rock-ice avalanches, glacier collapse, debris flows, landslides, and glacial lake outburst floods (GLOFs). Monitoring cryosphere change and evaluating its hydrological effects are essential for studying climate change, the hydrological cycle, water resource management, and natural disaster mitigation and prevention. However, knowledge gaps, data uncertainties, and other substantial challenges limit comprehensive research in climate-cryosphere-hydrology-hazard systems. To address this, we provide an up-to-date, comprehensive, multidisciplinary review of remote sensing techniques in cryosphere studies, demonstrating primary methodologies for delineating glaciers and measuring geodetic glacier mass balance change, glacier thickness, glacier motion or ice velocity, snow extent and water equivalent, frozen ground or frozen soil, lake ice, and glacier-related hazards. The principal results and data achievements are summarized, including URL links for available products and related data platforms. We then describe the main challenges for cryosphere monitoring using satellite-based datasets. Among these challenges, the most significant limitations in accurate data inversion from remotely sensed data are attributed to the high uncertainties and inconsistent estimations due to rough terrain, the various techniques employed, data variability across the same regions (e.g., glacier mass balance change, snow depth retrieval, and the active layer thickness of frozen ground), and poor-quality optical images due to cloudy weather. The paucity of ground observations and validations with few long-term, continuous datasets also limits the utilization of satellite-based cryosphere studies and large-scale hydrological models. Lastly, we address potential breakthroughs in future studies, i.e., (1) outlining debris-covered glacier margins explicitly involving glacier areas in rough mountain shadows, (2) developing highly accurate snow depth retrieval methods by establishing a microwave emission model of snowpack in mountainous regions, (3) advancing techniques for subsurface complex freeze-thaw process observations from space, (4) filling knowledge gaps on scattering mechanisms varying with surface features (e.g., lake ice thickness and varying snow features on lake ice), and (5) improving and cross-verifying the data retrieval accuracy by combining different remote sensing techniques and physical models using machine learning methods and assimilation of multiple high-temporal-resolution datasets from multiple platforms. This comprehensive, multidisciplinary review highlights cryospheric studies incorporating spaceborne observations and hydrological models from diversified techniques/methodologies (e.g., multi-spectral optical data with thermal bands, SAR, InSAR, passive microwave, and altimetry), providing a valuable reference for what scientists have achieved in cryosphere change research and its hydrological effects on the Third Pole.

Global climate warming is accelerating permafrost degradation. The large amounts of soil organic matter in permafrost-affected soils are prone to increased microbial decomposition in a warming climate. Along with permafrost degradation, changes to the soil microbiome play a crucial role in enhancing our understanding and in predicting the feedback of permafrost carbon. In this article, we review the current state of knowledge of carbon-cycling microbial ecology in permafrost regions. Microbiomes in degrading permafrost exhibit variations across spatial and temporal scales. Among the short-term, rapid degradation scenarios, thermokarst lakes have distinct biogeochemical conditions promoting emission of greenhouse gases. Additionally, extreme climatic events can trigger drastic changes in microbial consortia and activity. Notably, environmental conditions appear to exert a dominant influence on microbial assembly in permafrost ecosystems. Furthermore, as the global climate is closely connected to various permafrost regions, it will be crucial to extend our understanding beyond local scales, for example by conducting comparative and integrative studies between Arctic permafrost and alpine permafrost on the Qinghai-Tibet Plateau at global and continental scales. These comparative studies will enhance our understanding of microbial functioning in degrading permafrost ecosystems and help inform effective strategies for managing and mitigating the impacts of climate change on permafrost regions.

The amount of rainfall varies unevenly in different regions of the Qinghai-Tibet Plateau, with some regions becoming wetter and others drier. Precipitation has an important impact on the process of surface energy balance and the energy-water transfer within soils. To clarify the thermal-moisture dynamics and thermal stability of the active layer in permafrost regions under wet/dry conditions, the verified water-vapour-heat coupling model was used. Changes in the surface energy balance, energy-water transfer within the soil, and thickness of the active layer were quantitatively analyzed. The results demonstrate that rainfall changes significantly affect the Bowen ratio, which in turn affects surface energy exchange. Under wet/dry conditions, there is a positive correlation between rainfall and liquid water flux under the hydraulic gradient; water vapour migration is the main form under the temperature gradient, which indicates that the influence of water vapour migration on thermalmoisture dynamics of the active layer cannot be neglected. Concurrently, regardless of wet or dry conditions, disturbance of the heat transport by conduction caused by rainfall is stronger than that of convection by liquid water. In addition, when rainfall decreases by 1.5 times (212 mm) and increases by 1.5 times (477 mm), the thickness of the active layer increases by 0.12 m and decreases by 0.21 m, respectively. The results show that dry conditions are not conducive to the preservation of frozen soil; however, wet conditions are conducive to the preservation of frozen soil, although there is a threshold value. When this threshold value is exceeded, rainfall is unfavourable for the development of frozen soil.

Global climate warming is accelerating permafrost degradation. The large amounts of soil organic matter in permafrost-affected soils are prone to increased microbial decomposition in a warming climate. Along with permafrost degradation, changes to the soil microbiome play a crucial role in enhancing our understanding and in predicting the feedback of permafrost carbon. In this article, we review the current state of knowledge of carbon-cycling microbial ecology in permafrost regions. Microbiomes in degrading permafrost exhibit variations across spatial and temporal scales. Among the short-term, rapid degradation scenarios, thermokarst lakes have distinct biogeochemical conditions promoting emission of greenhouse gases. Additionally, extreme climatic events can trigger drastic changes in microbial consortia and activity. Notably, environmental conditions appear to exert a dominant influence on microbial assembly in permafrost ecosystems. Furthermore, as the global climate is closely connected to various permafrost regions, it will be crucial to extend our understanding beyond local scales, for example by conducting comparative and integrative studies between Arctic permafrost and alpine permafrost on the Qinghai-Tibet Plateau at global and continental scales. These comparative studies will enhance our understanding of microbial functioning in degrading permafrost ecosystems and help inform effective strategies for managing and mitigating the impacts of climate change on permafrost regions.

As an important indicator of permafrost degradation, surface deformation is often used to monitor the thawing and freezing process in the permafrost active layer. However, due to the large area of the continuous permafrost of the Qinghai-Tibet Plateau (QTP) and the large amount of data processed by conventional time-series InSAR, previous studies have mostly focused on local area investigations, and regional characteristics of surface deformation of the continuous permafrost area on the QTP are still unclear. In this paper, we characterized surface deformation in space and time over the main continuous permafrost area on the QTP, by analyzing 11 ascending and 8 descending orbits of Sentinel-1 SAR data acquired between 2018 and 2021 with the time-series InSAR processing system LiCSAR. The reliability of the InSAR deformation results was verified by a combination of leveling measurement data, the intercomparison of overlapping area results, and field verification. The results show that the permafrost regions of the central QTP exhibited the most significant linear subsidence trend. The subsidence trend of permafrost on the QTP was mainly related to the thermal stability of permafrost, and the regions with larger subsidence rates were concentrated in sub-stable, transitional and unstable permafrost areas. We also found that, according to analysis of time-series displacement, the beginning and ending times of permafrost thawing were highly spatially heterogeneous, with the time of maximum thawing depth varying between mid-October and mid-November, which was probably attributed to the active layer thickness (ALT), water content in the active layer, and vegetation cover in these regions. This study is of great significance for understanding the changing trend of permafrost on the QTP under the background of climate change. In addition, this study also demonstrates that combination of Sentinel-1 SAR images with the LiCSAR system has significant potential for detecting permafrost deformation with high accuracy and high efficiency at regional and global scales.

The degradation of near-surface permafrost under ongoing climate change on the Qinghai-Tibet Plateau (QTP) is of growing concern due to its impacts on geomorphological and ecological processes, as well as human activities. There is an increased need for an in-depth understanding of the evolution of permafrost temperature (Ttop) and active-layer thickness (ALT) at a fine scale on the QTP under climate change. This study evaluated the permafrost thermal development over the QTP for the period 1980-2100 at a 1 km(2) scale using a physically analytical model accounting for both climatic and local environmental factors based on multi-source data. The model results were validated against thermal borehole measurements and baseline maps. The modeled current (2001-2018) permafrost area (Ttop <= 0 degrees C) covers 1.42 x 106 km(2) (ca. 56.1% of the QTP land area), 10.1% of which thawed over the historical period 1981-2000. To assess how the ground thermal regime could develop in the future, we utilized the multi-model ensemble mean of downscaled outputs from eight climate models under three Shared Socio-economic Pathways (i.e., SSP126, 245, and 585) in CMIP6 to force the permafrost model. Model results suggest that the current (2001-2018) permafrost extent is likely to dramatically contract in the future period (2021-2100), as indicated by consistent Ttop warming and ALT increasing due to climate changing. About 26.9%, 59.9%, 80.1% of the current permafrost is likely to disappear by the end of the 21st century under SSP126, SSP245, and SSP585 scenarios, respectively. The simulation results may further provide new opportunities to assess the future impacts of climate warming on environments and engineering development over the QTP.

In the past several decades, the trend of rainfall have been significantly increasing in the Qinghai-Tibet Plateau, which inevitably leads to a change in the surface energy balance processes and thermal-moisture status of the permafrost active layers. However, the influence of mechanisms and associated effects of increasing rainfall on active layers are still poorly understood. Therefore, in this study, a validated coupled numerical water-vapor-heat model was applied for simulating the surface energy components, liquid and vapor water migration, and energy transfer within the permafrost active layer under the action of increasing rainfall in the case of an especially wet year. The obtained results demonstrate that the surface heat flux decreases with the increase in rainfall, and the dominant form of energy exchange between the ground and atmosphere becomes the latent heat flux, which is beneficial for the preservation of permafrost. The increasing rainfall will also cause the migration of liquid and vapor water, and the migration of liquid will be more significant. The liquid and vapor water migration caused by the increasing rainfall is also accompanied by energy transfer. With the increase in rainfall, the decrease in total soil heat flux directly leads to a cooling effect on the soil, and then the upper limit of the frozen soil rises, which alleviates the degradation of permafrost. These results provide further insights into engineering structures, regional ecological climate change, hydrology, and environmental issues in permafrost regions.

Global warming has led to extensive permafrost degradation, particularly in thermally vulnerablepermafrost in the marginal or transitional zones of altitudinal or latitudinal permafrost. However,comprehensive knowledge about microbial communities in response to rapid permafrostdegradation at large (or interregional) scales remains elusive. In this meta-analysis, existingpublished data were utilized to identify the distributive and co-occurrence patterns of themicrobiome in two interregional locations: the Qilian Mountains on the northeasternQinghai-Tibet Plateau(NE-QTP) and the Xing'anling Mountainsin Northeast China(NE-China).Both areas are situated in the marginal zone of large permafrost units. The results reveal that therapidly degrading permafrost did not overshadow the regional biogeographic pattern of themicrobial community. Instead, the results show some distinctive biogeographic patterns, ascharacterized by different groups of characteristic bacterial lineages in each of the two regions. SoilpH has emerged as a crucial controlling factor on the basis of the available environmental data.Network-basedanalysessuggestagenerallyhighlevelofnaturalconnectivityforbacterialnetworkson the NE-QTP; however, it collapses more drastically than that in NE-China if the environmentalperturbations exceed the tipping point. These findings indicate that the biogeographic patterns ofthe bacterial community structure are not significantly altered by permafrost degradation. Thisresearch provides valuable insights into the development of more effective management methodsfor microbiomes in rapidly degrading permafrost.