Extreme precipitation stable isotopic compositions reveal unexpected summer monsoon incursions in the Qilian Mountains

Liangju Zhao; Xiying Dong; Xiaohong Liu; Ninglian Wang; Christopher J Eastoe; Na Wei; Cong Xie; Hang Liu; Chuntan Han; Ting Hua; Lixin Wang

doi:10.1016/j.scitotenv.2023.165743

Extreme precipitation stable isotopic compositions reveal unexpected summer monsoon incursions in the Qilian Mountains

Sci Total Environ. 2023 Nov 20:900:165743. doi: 10.1016/j.scitotenv.2023.165743. Epub 2023 Jul 24.

Authors

Liangju Zhao¹, Xiying Dong², Xiaohong Liu³, Ninglian Wang², Christopher J Eastoe⁴, Na Wei⁵, Cong Xie², Hang Liu², Chuntan Han⁶, Ting Hua², Lixin Wang⁷

Affiliations

¹ Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, College of Urban and Environmental Sciences, Northwest University, Xi'an 710127, China. Electronic address: zhlj@nwu.edu.cn.
² Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, College of Urban and Environmental Sciences, Northwest University, Xi'an 710127, China.
³ School of Geography and Tourism, Shaanxi Normal University, Xi'an 710119, China.
⁴ Department of Geosciences (retired), University of Arizona, Tucson, AZ 85721, USA.
⁵ Climate Centre of Shaanxi Province, Xi'an 710049, China.
⁶ Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
⁷ Department of Earth Sciences, Indiana University-Purdue University Indianapolis (IUPUI), Indianapolis, IN 46202, USA.

PMID: 37495157
DOI: 10.1016/j.scitotenv.2023.165743

Abstract

Isotope composition and moisture sources of precipitation are important for understanding water cycles and reconstructing paleoclimate. Based on 15-years' precipitation stable Isotope composition (δ¹⁸O and δ²H) from four stations of the Qilian Mountains, we found unique δ¹⁸O and δ²H features associated with the incursion of the summer monsoon over the Qilian Mountains, northwestern China. In 12 of the 15 years, similar seasonal variations of δ¹⁸O and δ²H confirmed a dominant source of moisture from Westerly circulation, and higher intercepts of the local meteoric water line (LMWL) indicated strong recycling of continental moisture. However, in August 2016 and 2018, extremely low slopes and intercepts of the LMWL, and more negative δ¹⁸O and δ²H revealed substantial contributions of the Asian summer monsoon to precipitation of the Qilian Mountains, with extremely heavy precipitation in August 2016. The column moisture flux, land-sea thermal contrast, correlations of precipitation δ¹⁸O with East Asian Summer Monsoon Index and Westerlies Index, HYSPLIT modeling results and precipitation δ¹⁸O along backward trajectories confirmed incursions of the summer monsoon in August 2016 and 2018. Our redefining of the boundary of the summer monsoon region confirmed the summer monsoon incursion zone can extend to the west of longitude 96°E and north of latitude 40°N in strong monsoon years, corresponding to boundaries of monsoon incursions in the mid-Holocene. Temperature correlated with precipitation δ¹⁸O at monthly and shorter time scales, but not for whole seasons or at yearly scale, revealing that summer monsoon incursions are therefore more likely than changing temperature to explain the multi-year cycles in the Qilian Mountains ice archives. Continent-scale shifts in atmospheric circulation strongly influence water resources in the Qilian mountains, and may change in frequency as climate warms. This study therefore has important implications for understanding water resources in the Qilian mountains in the past and into the future.

Keywords: Atmospheric circulation; Moisture origin; Monsoons; Qilian Mountains; Stable isotopes; Westerly circulation.