First comprehensive stable isotope dataset of diverse water units in a permafrost-dominated catchment on the Qinghai–Tibet Plateau

Abstract. Considered the Asian water tower, the Qinghai–Tibet Plateau (QTP) processes substantial permafrost, and its hydrological environments are spatially different and can be easily disturbed by changing permafrost and melting ground ice. Permafrost degradation compels melting permafrost to become an important source of surface runoff, changes the storage of groundwater, and greatly influences the hydrological processes in permafrost regions. However, the evidence linking permafrost degradation and hydrological processes on the QTP is lacking, which increases the uncertainties in the evaluation of the results of changing permafrost on the water resources. Stable isotopes offer valuable information on the connections between changing permafrost (ground ice) and water components. It is therefore particularly important to observe the changes in the stable isotopes of different waterbodies which can vary over hourly to annual timescales and truly capture the thawing signals and reflect the influence of permafrost (ground ice) on the regional hydrological processes. The Beiluhe Basin (BLH) in the hinterland of the QTP was selected; it integrates all the water components related to hydrological cycles well and is an ideal site to study the hydrological effect of permafrost change. This paper presents the temporal data of stable isotopes (δ18O, δD, and d-excess) in different waterbodies (precipitation, stream water, thermokarst lake, and groundwater) in the BLH produced between 2017 and 2022. Here, the first detailed stable isotope data of ground ice at 17 boreholes and 2 thaw slumps are presented. A detailed description of the sampling processes, sample pretreating processes, and isotopic data quality control is given. The data first described the full seasonal isotope amplitude in the precipitation, stream, and thermokarst lakes and delineated the depth isotopic variability in ground ice. In total, 554 precipitation samples, 2402 lake/pond samples, 675 stream water samples, 102 supra-permafrost water samples, and 19 sub-permafrost water samples were collected during 6 years of continuous sampling work. Importantly, 359 ground ice samples at different depths from 17 boreholes and 2 profiles were collected. This first dataset provides a new basis for understanding the hydrological effects of permafrost degradation on the QTP. It also provides support for the cryospheric study on the Northern Hemisphere. The dataset provided in this paper can be obtained at https://doi.org/10.5281/zenodo.10684110 (Yang, 2024).