Spatial variations and controlling factors of ground ice isotopes in permafrost areas of the central Qinghai-Tibet Plateau

Weihua Wang; Tonghua Wu; Yaning Chen; Ren Li; Changwei Xie; Yongping Qiao; Xiaofan Zhu; Junming Hao; Jie Ni

doi:10.1016/j.scitotenv.2019.06.196

Spatial variations and controlling factors of ground ice isotopes in permafrost areas of the central Qinghai-Tibet Plateau

Sci Total Environ. 2019 Oct 20:688:542-554. doi: 10.1016/j.scitotenv.2019.06.196. Epub 2019 Jun 14.

Authors

Weihua Wang¹, Tonghua Wu², Yaning Chen¹, Ren Li³, Changwei Xie³, Yongping Qiao³, Xiaofan Zhu³, Junming Hao⁴, Jie Ni⁴

Affiliations

¹ State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China.
² Cryosphere Research Station on the Qinghai-Tibet Plateau, State Key Laboratory of Cryosphere Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China. Electronic address: thuawu@lzb.ac.cn.
³ Cryosphere Research Station on the Qinghai-Tibet Plateau, State Key Laboratory of Cryosphere Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
⁴ Cryosphere Research Station on the Qinghai-Tibet Plateau, State Key Laboratory of Cryosphere Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; University of Chinese Academy of Sciences, Beijing 100049, China.

PMID: 31254820
DOI: 10.1016/j.scitotenv.2019.06.196

Abstract

Ground ice is a distinctive feature of permafrost, and its thawing under climate change can alter the regional hydrological and biogeochemical cycles. Spatial variations and determinants of ground ice isotopes are critical to understand subsurface water cycling during freeze-thaw process in the context of climate change, while they are not well known in permafrost region due to lack of field investigation. We examined spatial distributions and controlling factors of ground ice isotopes using data of 8 soil profiles surveyed in permafrost areas of the Qinghai-Tibet Plateau (QTP). The stable isotope values (δ²H and δ¹⁸O) of subsurface water on the QTP were higher than those in Arctic tundra ecosystem and East Siberian permafrost region. Isotopic values of water components differed each other, and varied significantly among the sampling sites. The spatial distribution of isotopes was complex. Isotopes generally decreased with depth within the soil profile, implying a general isotope depth gradient across different permafrost-affected areas. Water source, evaporative and freeze-out fractionation, and cryoturbation affect soil water isotopes. Correlation analyses showed that δ²H and δ¹⁸O in soil water positively related to air temperature and soil temperature, while negatively related to soil moisture, depth, active layer thickness, vegetation coverage, elevation, and precipitation. Elevation and soil depth mainly controlled spatial distributions of ground ice isotopes. The results could provide a new insight into soil moisture movement and cycling during freeze-thaw process in the permafrost region of the QTP, which is helpful to understand subsurface water cycle mechanism in the context of permafrost degradation.

Keywords: Environmental factor; Ground ice; Permafrost; Qinghai-Tibet Plateau; Spatial variation; Stable isotope.