Recent climate warming has accelerated permafrost thaw and dynamics of thermokarst lakes (TLs) on the Tibetan Plateau (TP). Yet, owing to the lack of long-term monitoring of TLs, our understanding of lake evolution processes and their driving factors remains uncertain. Here, using the global surface water product and timeseries Landsat imagery, we identified 58,538 TLs (0.01-3 km2) and determined the primary occurrence year of lake changes from 1990 to 2022. Our results indicated that TLs on the TP are primarily located in the central inland region, over 82 % of lakes experienced area expansion, and only 15 % in the northwest show decrease in area. Annual number of lake expansion peaked in 2016, whereas lake shrinkage was most common in 2019. The calculated lake area errors, field investigations, and validation of lake disturbance time demonstrated high accuracy and consistency. We applied the optimal machine learning regression model to distinguish the different drivers for lake expansion and shrinkage. The topographic and climatic factors are primary drivers for lake expansion, while differences in evaporation trend and soil temperature trend might contribute to lake shrinkage. This study highlights the vulnerability of permafrost on the TP to climate change, which can contribute to carbon sequestration estimation and infrastructure maintenance.

Aerosols over the Tibetan Plateau (TP) strongly influence regional climate and hydrological cycles. Here we investigate the size-resolved microphysical and optical properties of aerosols in an urban area of the northern TP using a tandem system of a differential mobility analyzer, a condensation particle counter, and a single particle soot photometer. Under the 2021 summer conditions, the average particle number size distribution follows a lognormal pattern, peaking at similar to 70 nm. Refractory black carbon (rBC) aerosols constitute 17.7% of the total particle population in the 100-750 nm mobility diameter (D-mob) range, with their proportion rising to over 50% for D-mob > 500 nm. Most rBC particles are externally mixed, while only 12.2% are thickly coated with non-refractory materials. Externally mixed rBC particles show strong non-sphericity, with a dynamic shape factor increasing from 1.8 at 115 nm to 2.8 at 750 nm, consistent with aggregate structures. In contrast, thickly coated rBC particles are nearly spherical, with coating thickness increasing with size. The total rBC mass estimated from size-resolved measurements closely matches bulk rBC mass directly measured. rBC-free particles exhibit slight non-sphericity, with shape factor positively correlated with refractive index, likely due to dust contributions. Bulk scattering coefficients derived from size-resolved data match those estimated under the well-mixed spherical assumption. However, the later scheme-lacking observational constraints on morphology and mixing state-overestimates absorption by over a factor of three, thereby underestimating the single-scattering albedo. These results provide key constraints for improving aerosol radiative forcing estimates and advancing understanding of aerosol-climate interactions over the TP.

The Three-Rivers Headwater Region (TRHR) is located on the Tibetan Plateau, within a transitional zone between seasonally frozen ground and continuous permafrost. Over 70 % of the region is predominantly covered by alpine grasslands, a vulnerable ecosystem increasingly threatened by ongoing permafrost degradation. This study utilized satellite data to analyze permafrost degradation by measuring active layer thickness (ALT) and the soil non-frozen period (NFP), and to investigate their impacts on alpine grassland growth. Results showed significant permafrost degradation from 2000 to 2020, with ALT thickening at a rate of 7.79 cm/decade (p < 0.05) and NFP lengthening by 1.1 days/yr (p < 0.05). Simultaneously, grassland vegetation exhibited a significant greening trend (0.0014 yr(-1), p < 0.01). Using the partial least squares (PLS) regression method, the study evaluated the relationships between grassland dynamics and permafrost degradation, while jointly accounting for climate variables (temperature, precipitation, and sunshine duration). ALT thickening was the dominant explanatory variable for grassland growth in 11.09 % of the region, and it was positively correlated in relatively cold western and alpine areas, but negatively correlated in the relatively warm eastern and central regions. NFP extension was the dominant explanatory variable for grassland growth in 10.38 % of the region, although its positive correlation weakened as climate conditions transitioned from relatively cold-dry to relatively warm-wet. Although permafrost degradation was positively correlated with grassland greening in relatively cold regions, the diminishing benefit of NFP extension and the adverse effects of ALT thickening may increasingly undermine grassland stability in relatively warm regions under further climate warming.

The Tibetan Railway has introduced pressures on the fragile grassland ecosystems of the Tibetan Plateau. However, the impact of the railway on the carbon sequestration remains unclear, as existing studies primarily focus on in-situ vegetation observations. In this study, we extracted the start and end of the growing season (SOS, EOS) and maximum daily GPP (GPPmax) along the railway corridor from the satellite-derived Gross Primary Productivity (GPP) data, and quantified the extent and intensity of the railway's disturbance on these indicators. We further employed the Statistical Model of Integrated Phenology and Physiology (SMIPP) to translate these disturbances into annual cumulative GPP (GPPann). Results show that Tibetan Railway significantly influences grassland within 50-meters, causing earlier SOS (0.1086 d m-1), delayed EOS (0.0646 d m-1), and reduced GPPmax (0.0069 gC m-2 d-1 m-1) as the distance to the railway gets closer. The advanced SOS and delayed EOS contributed gains of 28.82 and 104.26 MgC y-1, but reduction in GPPmax accounted for a loss of 2952.79 MgC y-1. Railway-induced phenology-physiology trade-off causes GPPann loss of 2819.71 MgC y-1. This study reveals Tibetan Railway's impact on grassland carbon cycling, offering insights for grassland conservation and sustainable transportation infrastructure projects.

Vegetation greening across the Tibetan Plateau, a critical ecological response to climate warming and land-cover change, affects soil hydrothermal regimes, altering soil moisture (SM) and soil temperature (ST) dynamics. However, its effects on SM-ST coupling remain poorly understood. Using integrated field measurements from a vegetation-soil (V-S) network, reanalysis, and physics-based simulations, we quantify responses of SM, ST, and their coupling to vegetation changes across the Upper Brahmaputra (UB) basin, southern Tibetan Plateau. Results show that strong positive SM-ST correlations occur throughout 0-289 cm soil layers across the basin, consistent with the monsoon-driven co-occurrence of rainy and warm seasons. Spatially, SM-ST coupling strength exhibits pronounced spatial heterogeneity, demonstrating strongest coupling in central basin areas with weaker intensities in eastern and western regions. Overall, vegetation greening consistently induces soil warming and drying: as leaf area index (LAI) increases from 20 % to 180 % of its natural levels, SM (0-160 cm) declines by 15 % to 29 % due to enhanced evapotranspiration and root water uptake. Mean ST simultaneously increases by 1.4 +/- 0.9 degrees C. Crucially, sparsely vegetated regions sustain warming (1.4-2.1 degrees C), while densely vegetated areas transition from initial warming to gradual cooling. These findings advance our understanding of soil hydrothermal dynamics and their broader environmental impacts, improving climate model parameterizations and informing sustainable land management strategies in high-altitude ecosystems.

Study region: The Tibetan Plateau (TP), China, contains the world's largest permafrost area outside the Polar Regions. Study focus: This study investigates the precipitation-induced advective heat flux (E-Pre), which represents the energy transfer resulting from the temperature difference between rainfall and soil. Observational data from three permafrost monitoring sites (Qumalai, Xidatan, and Tanggula) were combined with simulations from the Community Land Model version 5.0 (CLM5.0) to quantify E-Pre precipitation infiltration depth, and the probability of infiltration reaching the frozen soil layer. The analysis further examines how precipitation amount, soil texture, soil moisture, and freeze-thaw state jointly control infiltration processes and influence the soil thermal regime. New hydrological insights for the region: Infiltration depth varies with initial soil moisture and precipitation duration, from shallow retention to deep percolation. E-Pre is generally negative, with maximum cooling of-84.14 W m(-2) at QML,-73.24 W m(-2) at XDT, and -56.63 W m(-2) at TGL, but becomes positive during prolonged summer rainfall, reaching 45.43 W m(-2) at QML. Diurnal soil temperature variations shift E-Pre from cooling by day to reduced cooling or warming at night. Across the TP, mean infiltration depth is similar to 5 cm, higher in southeastern Tibet, with a regional mean E-Pre of-0.08 W m(-2). Warming effects are concentrated in the southeastern and central TP, while cooling dominates the arid west and high-elevation north.

The source area of the Yangtze River (SAYR), part of the Tibetan Plateau, is an ecologically fragile alpine region sensitive to climate change. Current research has predominantly examined hydrological and ecological responses as isolated systems, failing to address the coupled mechanisms through which permafrost degradation mediates water-carbon interactions. In this study, we used a fully coupled eco-hydrological model that integrates permafrost processes, along with multi-source remote sensing data, experimental monitoring, and machine learning, to quantify the water retention and carbon sequestration capacity over the past 20 years. The region was categorized into three risk zones based on changes in soil moisture, net ecosystem productivity (NEP), and dissolved organic carbon (DOC) fluxes in streams. We evaluated eight factors, including precipitation, temperature, vegetation phenology and cover, and their contributions to changes of water retention and carbon sequestration using an interpretable machine learning approach. Results show that the central and eastern regions of the study area face the highest risk of declining water retention and carbon sequestration capacity. The changes of temperatures and precipitation have led to depletion of soil water and carbon reserves. This depletion raises concerns about the potential shift from a carbon sink to a carbon source considering land-to-river carbon loss. Our study provides critical insights into the water and carbon flux dynamics and offers valuable guidance for water resource and ecological management in alpine river systems.

The freeze-thaw erosion zone of the Tibetan Plateau (FTZTP) maintains an ecologically fragile system with enhanced thermal sensitivity under climate warming. Vegetation phenology in this cryosphere-dominated environment acts as a crucial biophysical indicator of climate variability, showing potentially amplified responses to environmental changes relative to other ecosystems. To investigate vegetation phenological characteristics and their climate responses, we derived key phenological parameters (the start, end and length of growing season-SOS, EOS, LOS) for the FTZTP from 2001 to 2021 using MODIS EVI data and analysed their spatiotemporal patterns and climatic drivers. Results indicated that the spatial distribution of phenology was highly heterogeneous, influenced by local climate, complex topography and diverse vegetation. SOS generally exhibited a delayed trend from east to west, while EOS was progressively later from the central plateau towards the southeast and southwest. Consequently, LOS shortened along both east-west and south-north gradients. Under sustained warming and wetting, the region experienced intensified freeze-thaw cycles, characterised by a delayed freeze-start, advanced thaw-end and shortened freeze-thaw duration. Both climate warming and freeze-thaw changes drove an overall significant advancement of SOS (-3.1 days/decade), delay of EOS (+2.2 days/decade) and extension of LOS (+5.3 days/decade) over the 21-year period. Notably, an abrupt phenological shift occurred around 2015. Prior to 2015, both SOS and EOS advanced, whereas afterward, SOS transitioned to a delaying trend and EOS exhibited a markedly stronger delay, leading to a pronounced extension of LOS. This regime shift was primarily attributed to changes in hydrothermal conditions controlled by climate warming and evolving freeze-thaw dynamics, with temperature being the dominant factor and precipitation exerting seasonally differential effects. Our findings elucidate the complex responses of alpine cryospheric ecosystems to climate change, revealing freeze-thaw processes as a key modulator of vegetation phenology.

Permafrost degradation under climate warming plays a crucial role in hydrological and ecological processes, including the regional water cycle and terrestrial carbon balance. The Tibetan Plateau (TP), which contains the largest expanse of high-altitude permafrost globally, remains understudied in terms of how permafrost degradation affects surface water resources and regional carbon dynamics. Using permafrost simulation models and quantitative analysis, we assess the spatiotemporal impacts of permafrost degradation on surface water resources and carbon dynamics. In the inner endorheic regions of the TP, ground ice meltwater contributed 12.6% of the total lake volume increase from 2000 to 2020, accelerating lake expansion and affecting nearby infrastructure and ecosystems. Cryospheric meltwater accounted for 4.6% of total runoff in the source areas of the Yangtze, Yellow, Lancang, Yarlung Zangbo, and Nujiang Rivers in 2002-2018. This cryospheric meltwater contribution is projected to peak in the 2030s-2040s, followed by a decline, with potentially profound implications for downstream water availability. From 2000 to 2020, carbon sequestration of alpine grassland in permafrost regions is 1.05-1.29 Tg C a-1 in 2000-2020. This estimate is underestimated by approximately 35.5% to 48.1% without considering the impact of permafrost degradation. Top-down thawing of permafrost from 2002 to 2050 is projected to release 129.39 +/- 21.02 Tg C a-1 of thawed soil organic carbon (SOC), with 20.82 +/- 3.06 Tg C a-1 decomposed annually. Additionally, permafrost collapse and thermokarst lake are estimated to reduce ecosystem carbon sinks by 0.41 (0.29-0.52) Tg C a-1 in 2020. (c) 2025 The Authors. Published by Elsevier B.V. and Science China Press. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Thawing permafrost alters climate not only through carbon emissions but also via energy-water feedback and atmospheric teleconnections. This review focuses on the Tibetan Plateau, where strong freeze-thaw cycles, intense radiation, and complex snow-vegetation interactions constitute non-carbon climate responses. We synthesize recent evidence that links freeze-thaw cycles, ground heat flux dynamics, and soil moisture hysteresis to latent heat feedback, monsoon modulation, and planetary wave anomalies. Across these pathways, both observational and simulation studies reveal consistent signals of feedback amplification and nonlinear threshold behavior. However, most Earth system models underrepresent these processes due to simplifications in freezethaw processes, snow-soil-vegetation coupling, and cross-seasonal memory effects. We conclude by identifying priority processes to better simulate multi-scale cryosphere-climate feedback, especially under continued climate warming in high-altitude regions.