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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. [ABSTRACT FROM AUTHOR]

Understanding the long‐term spatiotemporal evolution of irrigated cropland is essential for water resource management, but this knowledge remains elusive in most water‐stressed arid areas. In this study, we introduced an integrated framework for long‐term and field‐scale mapping of annual irrigated cropland in arid and semiarid regions. This framework combines the k‐means algorithm with a semiautomatically trained random forest classifier for initial classification and employs the Bayesian Updating of Land Cover algorithm for subsequent postprocessing. Taking the Heihe River basin in northwestern China as the experimental area, we generated 30‐m annual irrigated cropland maps spanning from 1990 to 2020 based on Landsat imagery and the Google Earth Engine. Comprehensive validation confirmed the reliability of this approach, with the overall accuracy of the annual maps ranging from 83% to 88.3% (mean: 86.6%). Our data set provides an unprecedentedly long‐term and fine‐scale perspective for understanding the continuous spatial and temporal dynamics of irrigated cropland in the Heihe River basin, surpassing previous studies in Central Asia and northwestern China. Notably, a rapid expansion of irrigated areas is occurring in the basin, especially in the water‐stressed midstream and downstream areas. This finding points to potential ecological risks in the foreseeable future due to water resource constraints. Key Points: A semiautomatic framework was developed to map irrigated cropland in arid and semiarid areasThe overall accuracy of the annual irrigated cropland maps in the Heihe River basin ranged from 83% to 88.3%The area of irrigated cropland in the Heihe River basin increased by 76% over the past 31 years [ABSTRACT FROM AUTHOR]

Permafrost impacts the subsurface hydrology and determines the transport of buried biochemical substances. Current evaluations of permafrost mostly focus on the overlying active layer. However, the basic but missing information of permafrost thickness constrains the quantification of trends and effects of permafrost degradation on subsurface hydrological processes. Our study quantified the long-term variations in permafrost thickness on the Tibetan Plateau (TP) between 1851 and 2100 based on layered soil temperatures calculated from eight earth system models (ESMs) of Coupled Model Intercomparison Project (the sixth phase) and validated by field observations and previous permafrost pattern from remote sensing. The calculated permafrost distribution based on ESMs was validated by the pattern derived from the MODIS datasets and field survey. Our results show that permafrost thicker than 10 m covers approximately 0.97 million km 2 of the total area of the TP, which represents an areal extent of over 36.49% of the whole TP. The mean permafrost thickness of the TP was 43.20 m between 1851 and 2014, and it would decrease at an average rate of 9.42, 14.99, 18.78, and 20.75 cm per year under scenarios SSP126, SSP245, SSP370, and SSP585 from 2015 to 2100, respectively. The permafrost thickness will decrease by over 50 cm per year in Qiangtang Basin under SSP585. Our study provides new insights for spatiotemporal changes in permafrost thickness and a basic dataset combined results of remote sensing, field measurements for further exploring relevant hydrological, geomorphic processes and biogeochemical cycles in the plateau cryospheric environment. [ABSTRACT FROM AUTHOR]