Permafrost degradation related to global warming has been widespread in the Tibetan Plateau (TP), manifesting prominently as variations in the soil thermal regime, an essential characteristic of permafrost. Altered soil thermal conditions can influence the energy and water balance between the atmosphere and land, leading to the release of stored carbon dioxide and methane. In this study, reanalysis and observed soil temperature data were combined to analyse the long-term changes in the thermal regime of the uppermost soil layer at six sites in the central TP. MERRA2 and ERA5-Land had the highest quality in matching the observed data at each site. The mean annual soil temperature ranged from -0.11 degrees C to 4.75 degrees C (averaging 1.73 degrees C) and warms at 0.059 degrees C a(-1). The mean annual first dates of freezing and thawing and the mean duration of freezing were 123.23 +/- 10.85 d, 285.67 +/- 10.34 d, and 161.44 +/- 20.54 d, respectively, indicating lagged, advanced, and shortened trends with 0.54 +/- 0.49 d a(-1), 0.50 +/- 1.06 d a(-1), and 1.05 +/- 1.16 d a(-1), respectively. The mean annual freezing and thawing N-factors were 0.53 +/- 0.13 and 2.43 +/- 2.09, respectively. The maximum and minimum monthly average soil temperatures were 11.81 +/- 2.17 degrees C in July and-9.54 +/- 3.24 degrees C in January, respectively. Partial correlation analysis was used to quantify the influences of factors (including surface air temperature, snow depth, rainfall, normalised difference vegetation index [NDVI], shortwave radiation, and soil moisture) on soil temperature implicated surface air temperature as the most significant influencing factor in the increased soil temperature. Rainfall and NDVI were implicated as being likely to suppress the soil temperature warming. This study provides detailed information about the thermal regime of the uppermost soil in the central TP and facilitates validation of the land surface model.

Study region: Nelson Churchill River Basin (NCRB), Canada, and USA.Study Focus: Soil temperature and moisture are essential variables that fluctuate based on soil depth, controlling several sub-surface hydrologic processes. The Hydrological Predictions for the Environment (HYPE) model's soil profile depth can vary up to four meters, discretized into three soil layers. Here, we further discretized the HYPE subsurface domain to accommodate up to seven soil layers to improve the representation of subsurface thermodynamics and water transfer more accurately. Soil moisture data from different locations across NCRB are collected from 2013 to 2017 for model calibration. We use multi-objective optimization (MOO) to account for streamflow and soil moisture variability and improve the model fidelity at a continental scale.New hydrological insights: Our study demonstrates that MOO significantly improves soil moisture simulation from the median Kling Gupta Efficiency (KGE) of 0.21-0.66 without deteriorating the streamflow performance. Streamflow and soil moisture simulation performance improvements are statistically insignificant between the original three-layer and seven-layer discretization of HYPE. However, the finer discretization model shows improved simulation in sub-surface components such as the evapotranspiration when verified against reanalysis products, indicating a 12 % underestimation of evapotranspiration from the three-layer HYPE model. The improvement of the discretized HYPE model and simulating the soil temperature at finer vertical resolution makes it a prospective model for permafrost identification and climate change analysis.

Permafrost degradation related to global warming has been widespread in the Tibetan Plateau (TP), manifesting prominently as variations in the soil thermal regime, an essential characteristic of permafrost. Altered soil thermal conditions can influence the energy and water balance between the atmosphere and land, leading to the release of stored carbon dioxide and methane. In this study, reanalysis and observed soil temperature data were combined to analyse the long-term changes in the thermal regime of the uppermost soil layer at six sites in the central TP. MERRA2 and ERA5-Land had the highest quality in matching the observed data at each site. The mean annual soil temperature ranged from -0.11 degrees C to 4.75 degrees C (averaging 1.73 degrees C) and warms at 0.059 degrees C a(-1). The mean annual first dates of freezing and thawing and the mean duration of freezing were 123.23 +/- 10.85 d, 285.67 +/- 10.34 d, and 161.44 +/- 20.54 d, respectively, indicating lagged, advanced, and shortened trends with 0.54 +/- 0.49 d a(-1), 0.50 +/- 1.06 d a(-1), and 1.05 +/- 1.16 d a(-1), respectively. The mean annual freezing and thawing N-factors were 0.53 +/- 0.13 and 2.43 +/- 2.09, respectively. The maximum and minimum monthly average soil temperatures were 11.81 +/- 2.17 degrees C in July and-9.54 +/- 3.24 degrees C in January, respectively. Partial correlation analysis was used to quantify the influences of factors (including surface air temperature, snow depth, rainfall, normalised difference vegetation index [NDVI], shortwave radiation, and soil moisture) on soil temperature implicated surface air temperature as the most significant influencing factor in the increased soil temperature. Rainfall and NDVI were implicated as being likely to suppress the soil temperature warming. This study provides detailed information about the thermal regime of the uppermost soil in the central TP and facilitates validation of the land surface model.

A change in soil temperature (ST) is a significant indicator of climate change, so understanding the variations in ST is required for studying the changes of the Qinghai-Tibet Plateau (QTP) permafrost. We investigated the performance of three reanalysis ST products at three soil depths (0-10 cm, 10-40 cm, and 40-100 cm) on the permafrost regions of the QTP: the European Centre for Medium-Range Weather Forecasts interim reanalysis (ERA-Interim), the second version of the National Centers for Environmental Prediction Climate Forecast System (CFSv2), and the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). Our results indicate that all three reanalysis ST products underestimate observations with negative mean bias error values at all three soil layers. The MERRA-2 product performed best in the first and second soil layers, and the ERA-Interim product performed best in the third soil layer. The spatiotemporal changes of annual and seasonal STs on the QTP from 1980 to 2017 were investigated using Sen's slope estimator and the Mann-Kendall test. There was an increasing trend of ST in the deeper soil layer, which was less than that of the shallow soil layers in the spring and summer as well as annually. In contrast, the first-layer ST warming rate was significantly lower than that of the deeper soil layers in the autumn and winter. The significantly (P < 0.01) increasing trend of the annual ST indicates that the QTP has experienced climate warming during the past 38 years, which is one of the factors promoting permafrost degradation of the QTP.

Permafrost serves as a natural cold reservoir for viral communities. However, little is known about the viromes in deep permafrost soil, as most studies of permafrost were restricted to shallow areas. Here, permafrost soil samples of up to 100 m in depth were collected from two sites in the Tuotuo River permafrost area on the Tibetan Plateau. We investigated the viral composition in these permafrost soil samples and analyzed the relationship of viral composition and diversity along with depths. Our study revealed that greater permafrost thickness corresponds to higher diversity within the viral community. Bacteriophages were found to be the dominant viral communities, with kill the winner dynamics observed within the Siphoviridae and Myoviridae. The abundance and diversity of viral communities may follow a potential pattern along soil layers and depths, influenced by pH, trace elements, and permafrost thickness. Notably, strong correlations were discovered between the content of inorganic elements, including B, Mg, Cr, Bi, Ti, Na, Ni, and Cu, and the viral composition. Moreover, we discovered highly conserved sequences of giant viruses at depth of 10, 20, and 50 m in permafrost, which play a crucial role in evolutionary processes. These findings provide valuable insights into the viral community patterns from shallow to 100 -m -depth in high -elevation permafrost, offering crucial data support for the formulation of strategies for permafrost thaw caused by climate change and anthropogenic activities.

The response of microbial communities to the predicted rising temperatures in alpine regions might be an important part of the ability of these ecosystems to deal with climate change. Soil microbial communities might be significantly affected by elevated temperatures, which influence the functioning of soils within high-alpine ecosystems. To evaluate the potential of the permafrost microbiome to adapt to short-term moderate and extreme warming, we set up an incubation experiment with permafrost and active soil layers from northern and southern slopes of a high-alpine mountain ridge on Muot da Barba Peider in the Swiss Alps. Soils were acclimated to increasing temperatures (4-40 degrees C) for 26 days before being exposed to a heat shock treatment of 40 degrees C for 4 days. Alpha-diversity in all soils increased slightly under gradual warming, from 4 to 25 degrees C, but then dropped considerably at 40 degrees C. Similarly, heat shock induced strong changes in microbial community structures and functioning in the active layer of soils from both northern and southern slope aspects. In contrast, permafrost soils showed only minor changes in their microbial community structures and no changes in their functioning, except regarding specific respiration activity. Shifts in microbial community structures with increasing temperature were significantly more pronounced for bacteria than for fungi, regardless of the soil origin, suggesting higher resistance of high-alpine fungi to short-term warming. Firmicutes, mainly represented by Tumebacillus and Alicyclobacillaceae OTUs, increased strongly at 40 degrees C in active layer soils, reaching almost 50% of the total abundance. In contrast, Saccharibacteria decreased significantly with increasing temperature across all soil samples. Overall, our study highlights the divergent responses of fungal and bacterial communities to increased temperature. Fungi were highly resistant to increased temperatures compared to bacteria, and permafrost communities showed surprisingly low response to rising temperature. The unique responses were related to both site aspect and soil origin indicating that distinct differences within high-alpine soils may be driven by substrate limitation and legacy effects of soil temperatures at the field site.