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Ground surface temperature (GST), measured at approximately 5 cm in depth is a key parameter controlling subsurface biophysical processes at the land-atmosphere boundary. This work presents a valuable dataset of GST observations at various spatial scales in the Headwater Area of the Yellow River (HAYR). The HAYR is a representative area of high plateau permafrost on northeastern Qinghai-Tibet Plateau (QTP). GST was measured every three hours using 72 iButton temperature loggers (DS1922L) at 39 sites from 2019 to 2020. At each site, GST was recorded in two plots at distances from 2 to 16 m under similar and different landcover conditions (steppe, meadow, swamp meadow, and bare ground). These sensors proved their reliability in harsh environments as only 165 measurements were biased from a total of 210,816. A high significant correlation (> 0.96, p < 0.001) was observed between plots, with a mean absolute error (MAE) of 0.2 to 1.2 °C. The daily intra-plot differences in GST were mainly < 2 °C for sites with similar landcover in both plots and > 2 °C when bare ground was compared to vegetation. From autumn to spring, the differences can increase to 4-5 °C for up to 15 days. The values of the frost number (FN) were quite similar between the plots with differences < 0.05 for most of the sites. This dataset complements the sparse observations of GST on the QTP and helps to identify the permafrost distribution and degradation at high resolution and to validate and calibrate the regional permafrost models. The datasets are openly available in the National Tibetan Plateau/Third Pole Environment Data Center (https://dx.doi.org/10.11888/Cryos.tpdc.272945, Șerban and Jin, 2022). [ABSTRACT FROM AUTHOR]

The thermal state of permafrost in the present and future is fundamental to the ecosystem evolution, hydrological process, carbon release, and infrastructure integrity in cold regions. From 2011, we began to establish permafrost monitoring network along the China-Russia crude oil pipelines (CRCOPs) route at the eastern flank of the northern Da Xing'anling Mountains in Northeast China. Based on meteorological data near the southern limit of latitudinal permafrost (SLLP), ground temperature data in 20 boreholes with the depths of 10-60.6 m, soil volumetric liquid water contents and 2-D electrical resistivity tomography (ERT) data, we compiled an integrated dataset of the ground thermal state along the CRCOPs route. Study results demonstrate that permafrost in the vicinity of SLLP has experienced marked warming (2011-2020) to climate change, manifested as the rising permafrost temperatures depth. Local thermal disturbances triggered by the construction and operation of CRCOPs have resulted in significant permafrost warming and subsequent thawing on the right-of-way (ROW) of the pipeline. This permafrost thaw will persist, but it can be alleviated by adopting mitigative measures, such as insulation layer and thermosyphons. The in29 situ observational dataset is of great value for assessing the variability of permafrost under the linear disturbances of the CRCOPs and related environmental effects, for understanding hydro-thermal-mechanical interactions between the buried pipelines and permafrost foundation soils, and for evaluating the operational and structural integrity of the pipeline systems in the future. The dataset is available at the National Tibetan Plateau/Third Pole Environment Data Center (http://doi.org/10.11888/Cryos.tpdc.272357; Li, 2022). [ABSTRACT FROM AUTHOR]

Under a pronounced climate warming, permafrost has been degrading in most areas, but it is still unclear in the northwestern part of the Da Xing'anling Mountains, Northeast China. According to a ten-year observation of permafrost and active-layer temperatures, the multi-year average of mean annual ground temperatures at 20 m was -2.83, -0.94, -0.80, -0.70, -0.60 and -0.49, respectively, at Boreholes GH4, MG3, MG1, MG2, GH5 and YTLH2, with the depths of permafrost table varying from 1.1 to 7.0 m. Ground cooling at shallow depths has been detected, resulting in declining thaw depths in Yituli'he during 2009-2020, possibly due to relatively stable mean positive air temperature and declining snow cover and dwindling local population. In most study areas (e.g., Mangui and Genhe), permafrost warming is particularly pronounced at larger depths (even at 80 m). These results can provide important information for regional development and engineering design and maintenance. [ABSTRACT FROM AUTHOR]

Monitoring of the thermal state of permafrost is important in environmental science and engineering applications. However, such data are generally unavailable mainly due to the lack of ground observations and the uncertainty of traditional physical models. This study produces novel permafrost datasets for the Northern Hemisphere (NH), including predictions of the mean annual ground temperature (MAGT) at the zero annual amplitude depth and active layer thickness (ALT) with a 1- km resolution for the period of 2000–2016, as well as estimates of the probability of permafrost occurrence and permafrost zonation based on hydrothermal conditions. These datasets integrate unprecedentedly large amounts of field data (1,002 boreholes for MAGT and 452 sites for ALT) and multisource geospatial data, especially remote sensing data, using statistical learning modelling with an ensemble strategy. Thus, these data are more accurate than those of previous circumpolar maps (bias=0.02±0.16 °C, RMSE=1.32±0.13 °C for MAGT; bias=2.71±16.46 cm, RMSE=86.93±19.61 cm for ALT). The datasets suggest that the areal extent of permafrost (MAGT≤0 °C) in the NH, excluding glaciers and lakes, is approximately 15.03 (13.84–19.29) ×106 km², and the areal extent of permafrost regions (permafrost probability>0) is approximately 20.14×106 km². The areal fractions of humid, semiarid/subhumid, and arid permafrost regions are 51.84%, 44.83%, and 3.33%, respectively. The areal fractions of cold (≤-3.0 °C), cool (-3.0 °C to -1.5 °C), and warm (>-1.5 °C) permafrost regions are 37.93%, 14.35%, and 47.72%, respectively. These new datasets based on the most comprehensive field data to date contribute to an updated understanding of the thermal state and zonation of permafrost in the NH. They are potentially useful for various fields, such as in climatology, hydrology, ecology, agriculture, public health, and engineering planning. As a baseline, these datasets are also of great importance for evaluating future changes in MAGT, ALT, permafrost extent, and other spatial features of permafrost in the NH. All of the datasets are published through the National Tibetan Plateau Data Center (TPDC), and the link is https://data.tpdc.ac.cn/en/data/5093d9ff-a5fc-4f10-a53f-c01e7b781368 or https://doi.org/10.11888/Geocry.tpdc.271190 (Ran et al., 2021b). [ABSTRACT FROM AUTHOR]