Thaw hazards in high-latitude and glaciated regions are becoming increasingly frequent because of global climate warming and human activities, posing significant threats to infrastructure stability and environmental sustainability. However, despite these risks, comprehensive investigations of thaw-hazard susceptibility in permafrost regions remain limited. Here, this gap is addressed by a systematic and long-term investigation of thaw hazards in China's Qinghai Province as a representative permafrost area. A detailed inventory of 534 thawhazard sites was developed based on remote sensing, field verification, and surveys by a UAV, providing critical data for susceptibility analysis. Eleven environmental factors influencing thaw hazards were identified and analyzed using information gain and Shapley additive explanation. By using the random forest model, a susceptibility map was generated, categorizing the study area into five susceptibility classes: very low, low, moderate, high, and very high. The key influencing factors include precipitation, permafrost type, temperature change rate, and human activity. The results reveal that 17.5 % of the permafrost region within the study area is classified as high to very high susceptibility, concentrated primarily near critical infrastructure such as the Qinghai-Tibet Railway, potentially posing significant risks to its structural stability. The random forest model shows robust predictive capability, achieving an accuracy of 0.906 and an area under the receiver operating characteristic curve of 0.965. These findings underscore the critical role of advanced modeling in understanding the spatial distribution and drivers of thaw hazards, offering actionable insights for hazard mitigation and infrastructure protection in permafrost regions under a changing climate.

Permafrost degradation on the Tibetan Plateau (TP) has triggered widespread retrogressive thaw slumps (RTSs), affecting hydrology, carbon sequestration and infrastructure stability. To date, there is still a lack of long-term monitoring of RTSs across the TP, the thaw dynamics and comprehensive driving factors remain unclear. Here, using time-series Landsat imagery and change detection algorithm, we identified RTSs on permafrost regions of the TP from 1986 to 2020. Existing RTSs inventories and high-resolution historical imagery were employed to verify the identified results, the temporal validation of RTSs disturbance pixels demonstrated a high accuracy. In the study area, a total of 3537 RTSs were identified, covering a total area of 5997 ha, representing a 26-fold increase since 1986, and 69.2 % of RTSs formed since 2010. Most RTSs are located on gentle slope (4-12 degrees) at elevations between 4500 m and 5300 m, with a tendency to form in alpine grassland and alpine meadow. Annual variations in RTSs area exhibited a significant positive correlation with minimum air temperature, mean land surface temperature, and annual thawing index, while it showing a significant negative correlation with the decrease in downward shortwave radiation. Spatially, RTSs were more common in areas with higher soil water content and shallower active layer. Landsat imagery captured the vast majority of RTSs on the TP and revealed interannual disturbance details, but the 30 m resolution remains inadequate for delineating the refined boundaries of some micro-scale (< 0.18 ha) RTSs. Detected RTSs disturbances on the TP will aid in hazard management and carbon feedback assessments, and our findings provide novel insights into the impacts of climate change and permafrost environments on RTSs formation.

Cycas panzhihuaensis inhabits regions where summer temperatures can exceed 40 degrees C, and these extreme conditions may intensify with ongoing global warming. However, how this species adapts to such thermal extremes is not well understood. To investigate the responses of C. panzhihuaensis to heat stress, some physiological characteristics along with lipid and fatty acid profiles were analyzed. The results show that heat stress induced soil water loss but did not cause leaf water loss and visible symptoms of leaf damage. However, photoinhibition was induced and heat dissipation was inhibited under the stress. In the recovered plants, both heat dissipation and maximum photochemical efficiency exhibited significant increases compared to the stressed plants but did not return to the control level. Most lipid categories including phospholipids and saccharolipids accumulated significantly following both the stress and subsequent recovery. However, the content of total neutral glycerolipids maintained unchanged after various treatments. The ratio of phosphatidylcholine/phosphatidylethanolamine decreased significantly and the ratios of both digalactosyldiacylglycerol/monogalactosyldiacylglycerol and triacylglycerol/diacylglycerol increased significantly in the stressed plants. Compared to the control plants, the relative content of polyunsaturated fatty acids significantly increased, while that of both saturated and monounsaturated fatty acids significantly declined in both stressed and recovered plants. Under stress conditions, the unsaturation levels of total neutral glycerolipids and their constituent components significantly increased, whereas those of phosphatidylglycerol and total saccharolipids exhibited a marked decrease. In conclusion, C. panzhihuaensis can tolerate extremely high temperatures to some extent which might be associated with the adjustments in lipid composition and unsaturation levels.

The global cryosphere is retreating under ongoing climate change. The Third Pole (TP) of the Earth, which serves as a critical water source for two billion people, is also experiencing this decline. However, the interplay between rising temperatures and increasing precipitation in the TP results in complex cryospheric responses, introducing uncertainties in the future budget of TP cryospheric water (including glacier and snow water equivalents and frozen soil moisture). Using a calibrated model that integrated multiple cryospheric-hydrological components and processes, we projected the TP cryospheric water budgets under both low and high climatic forcing scenarios for the period 2021-2100 and assessed the relative impact of temperature and precipitation. Results showed (1) that despite both scenarios involving simultaneous warming and wetting, under low climatic forcing, the total cryospheric budget exhibited positive dynamics (0.017 mm yr-1 with an average of 1.77 mm), primarily driven by increased precipitation. Glacier mass loss gradually declined with the rate of retreat slowing, accompanied by negligible declines in the budget of snow water equivalent and frozen soil moisture. (2) By contrast, high climatic forcing led to negative dynamics in the total cryospheric budget (-0.056 mm yr-1 with an average of -1.08 mm) dominated by warming, with accelerated decreases in the budget of all cryospheric components. These variations were most pronounced in higher-altitude regions, indicating elevation-dependent cryospheric budget dynamics. Overall, our findings present alternative futures for the TP cryosphere, and highlight novel evidence that optimistic cryospheric outcomes may be possible under specific climate scenarios.

The acclimation capacity of Betula pendula and Betula pubescens was studied over 4 years in common gardens in central Italy (43 degrees N) and southern (61 degrees N) and northern Finland (67 degrees N), representing drastically different photoperiod and climate in temperate, boreal and subarctic vegetation zones. Two study sites that differed in soil fertility were established at each location, giving a total of six common gardens. The birch material was micropropagated from naturally regenerated stands of B. pendula and B. pubescens from Susa Valley and Rochemolle Valley in northern Italy, Punkaharju in southern Finland and Kittil & auml; in northern Finland. The plants were measured for height growth, stem diameter, leaf chlorophyll content, leaf herbivory and pathogen damage. The effects of soil fertility on the common garden results were also analyzed. The results showed high acclimation capacity of B. pendula and B. pubescens after a long-range transfer from southern to northern Europe, despite the major shift in climate and photoperiod. First-year growth on average was best in boreal southern Finland for all origins. Betula pendula grew more than B. pubescens in Italy and southern Finland, while B. pubescens grew more in northern Finland and better tolerated the northward transfer. The height growth of origins showed a clear latitude gradient from slowly growing northern to fast growing southern origins in the nursery and laboratory, but not in the field. Soil fertility explained a significant part of variation among locations not only for growth variables, but also for leaf chlorophyll content and leaf herbivory and pathogen damage. Leaf herbivore and pathogen damage was greatest in southern Finland. Our results demonstrate good survival of birch from northern Italy in Finnish conditions and support the possibility of long-range south-to-north transfer of Betula species to provide resistant planting material in boreal forests for the rapidly changing climate.

Permafrost underpins engineering in cold regions but is highly sensitive to climate change. The mechanisms linking climate warming, precipitation changes, and permafrost degradation to infrastructure stability remain poorly understood on the Qinghai-Xizang Plateau (QXP). Here, we present a multi-factor framework to quantify climate impacts on permafrost engineering stability. Our findings reveal a 26.7% decline in permafrost engineering stability from 2015 to 2100, with areas of extremely poor stability expanding by 0.3 x 104 km2 per decade (SSP2-4.5) and 0.6 x 104 km2 per decade (SSP5-8.5). Meanwhile, regions with relatively better stability shrink by 2.0 x 104 km2 and 2.9 x 104 km2 per decade, respectively. These changes driven primarily by a warming and wetting climate pattern. Moreover, engineering stability is maintained in northwestern and interior regions, whereas warmer, ice-saturated areas in the central plateau and southern Qilian Mountains degrade rapidly. Notably, cold permafrost is warming faster than warm permafrost, increasing its vulnerability. These insights provide a critical basis for guiding the future design, construction, and maintenance of permafrost infrastructure, enabling the development of adaptive engineering strategies that account for projected climate change impacts.

Thermokarst landslide (TL) activity in the Qinghai-Tibet Plateau (QTP) is intensifying due to climate warminginduced permafrost degradation. However, the mechanisms driving landslide formation and evolution remain poorly understood. This study investigates the spatial distribution, annual frequency, and monthly dynamics of TLs along the Qinghai-Tibet engineering corridor (QTEC), in conjunction with in-situ temperature and rainfall observations, to elucidate the interplay between warming, permafrost degradation, and landslide activity. Through the analysis of high-resolution satellite imagery and field surveys, we identified 1298 landslides along the QTEC between 2016 and 2022, with an additional 386 landslides recorded in a typical landslide-prone subarea. In 2016, 621 new active-layer detachments (ALDs) were identified, 1.3 times the total historical record. This surge aligned with unprecedented mean annual and August temperatures. The ALDs emerged primarily between late August and early September, coinciding with maximum thaw depth. From 2016 to 2022, 97.8 % of these ALDs evolved into retrogressive thaw slumps (RTSs), identified as active landslides. Landslides typically occur in alpine meadows at moderate altitudes and on gentle northward slopes. The thick ice layer near the permafrost table serves as the material basis for ALD occurrence. Abnormally high temperature significantly increased the active layer thickness (ALT), resulting in melting of the ice layer and formation of a thawed interlayer, which was the direct causing factor for ALD. By altering the local material, micro-topography, and thermal conditions, ALD activity significantly increases RTS susceptibility. Understanding the mechanisms of ALD formation and evolution into RTS provides a theoretical foundation for infrastructure development and disaster mitigation in extreme environments.

Seasonally frozen ground (SFG) is a significant component of the cryosphere, and its extent is gradually increasing due to climate change. The hydrological influence of SFG is complex and varies under different climatic and physiographic conditions. The summer rainfall dominant climate pattern in Qinghai Lake Basin (QLB) leads to a significantly different seasonal freeze-thaw process and groundwater flow compared to regions with winter snowfall dominated precipitation. The seasonal hydrological processes in QLB are not fully understood due to the lack of soil temperature and groundwater observation data. A coupled surface and subsurface thermal hydrology model was applied to simulate the freeze-thaw process of SFG and groundwater flow in the QLB. The results indicate that SFG begins to freeze in early November, reaches a maximum freezing depth of approximately 2 meters in late March, and thaws completely by June. This freeze-thaw process is primarily governed by the daily air temperature variations. During the early rainy season from April to June, the remaining SFG in deep soil hinders the majority of rainwater infiltration, resulting in a two-month delay in the peak of groundwater discharge compared to scenario with no SFG present. Colder conditions intensify this effect, delaying peak discharge by 3 months, whereas warmer conditions reduce the lag to 1 month. The ice saturation distribution along the hillslope is affected by topography, with a 10 cm deeper ice saturation distribution and 3 days delay of groundwater discharge in the steep case compared to the flat case. These findings highlight the importance of the freeze-thaw process of SFG on hydrological processes in regions dominated by summer rainfall, providing valuable insights into the hydro-ecological response. Enhanced understanding of these dynamics may improve water resource management strategies and support future research into climate-hydrology interactions in SFG-dominated landscapes.

Climate warming has caused increased air temperature as well as increased subsurface temperature. Many previous studies on subsurface warming simplified heat advection by neglecting the horizontal component of regional groundwater flow or even neglected heat advection accompanying groundwater flow. In this study, the simultaneous control of heat advection and conduction on subsurface warming is numerically investigated in a 2D hypothetical basin cross section. By calculating the increment of subsurface temperature, we find that heat advection could accelerate subsurface warming. In a given basin, subsurface warming in the recharge area with downward groundwater flow is more significant than that in the discharge area with upward groundwater flow. By using a 1D model with vertical groundwater flow only for comparison, we find that in any part of a basin, even if the horizontal flux is very small compared with the vertical flux, neglecting the horizontal flux would underestimate the propagation depth of climate warming. This implies that when the propagation depth of climate warming is a priori known variable, existing 1D models would overestimate downward groundwater flux or underestimate upward groundwater flux. Moreover, we find pumping would cause deeper propagation depths of climate warming by accelerating groundwater circulation, whereas basin-scale heterogeneity and anisotropy of hydraulic conductivity would cause shallower propagation depths of climate warming because of the relative dominance of horizontal flow. By demonstrating the importance of 2D groundwater flow on subsurface warming, the results provide new insight into understanding the regulation of temperature among the atmosphere, the hydrosphere and the lithosphere.

The abrupt warming events punctuating the Termination 1 (about 11.7-18 ka Before Present, BP) were marked by sharp rises in the concentration of atmospheric methane (CH4). The role of permafrost organic carbon (OC) in these rises is still debated, with studies based on top-down measurements of radiocarbon (14C) content of CH(4 )trapped in ice cores suggesting minimum contributions from old and strongly C-14-depleted permafrost OC. However, organic matter from permafrost can exhibit a continuum of C-14 ages (contemporaneous to >50 ky). Here, we investigate the large-scale permafrost remobilization at the Younger Dryas-Preboreal transition (ca. 11.6 ka BP) using the sedimentary record deposited at the Lena River paleo-outlet (Arctic Ocean) to reflect permafrost destabilization in this vast drainage basin. Terrestrial OC was isolated from sediments and characterized geochemically measuring delta C-13, Delta C-14, and lignin phenol molecular fossils. Results indicate massive remobilization of relatively young (about 2,600 years) permafrost OC from inland Siberia after abrupt warming triggered severe active layer deepening. Methane emissions from this young fraction of permafrost OC contributed to the deglacial CH4 rise. This study stresses that underestimating permafrost complexities may affect our comprehension of the deglacial permafrost OC-climate feedback and helps understand how modern permafrost systems may react to rapid warming events, including enhanced CH4 emissions that would amplify anthropogenic climate change.