Increased drought events in southwest China revealed by tree ring oxygen isotopes and potential role of Indian Ocean Dipole

Chenxi Xu; Wenling An; S-Y Simon Wang; Liang Yi; Junyi Ge; Takeshi Nakatsuka; Masaki Sano; Zhengtang Guo

doi:10.1016/j.scitotenv.2019.01.186

Increased drought events in southwest China revealed by tree ring oxygen isotopes and potential role of Indian Ocean Dipole

Sci Total Environ. 2019 Apr 15:661:645-653. doi: 10.1016/j.scitotenv.2019.01.186. Epub 2019 Jan 17.

Authors

Chenxi Xu¹, Wenling An², S-Y Simon Wang³, Liang Yi⁴, Junyi Ge⁵, Takeshi Nakatsuka⁶, Masaki Sano⁷, Zhengtang Guo⁸

Affiliations

¹ Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China. Electronic address: cxxu@mail.iggcas.ac.cn.
² Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China.
³ Department of Plants, Soils, and Climate, Utah State University, Logan, UT, USA.
⁴ State Key Laboratory of Marine Geology, Tongji University, Shanghai, China.
⁵ CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China; Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China.
⁶ Research Institute for Humanity and Nature, Motoyama, Kamigamo, Kita-ku, Kyoto, Japan.
⁷ Research Institute for Humanity and Nature, Motoyama, Kamigamo, Kita-ku, Kyoto, Japan; Faculty of Human Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa 359-1192, Japan.
⁸ Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China; University of Chinese Academy of Sciences, Beijing, China.

PMID: 30682614
DOI: 10.1016/j.scitotenv.2019.01.186

Abstract

The highlands in southwestern China experience pronounced fluctuations in the hydroclimate with profound impacts on agriculture and economics. To investigate the drought history of this region beyond instrumental records, a tree ring cellulose oxygen isotope (δ¹⁸O_c) chronology was developed for the period 1733-2013 using samples collected from six Larix trees in the low-latitude highlands (LLH) of southwestern China. The analysis revealed that δ¹⁸O_c is significantly correlated with the rainy season (May-October) precipitation and relative humidity, as well as drought severity. The δ¹⁸O_c chronology accounts for 46% of the observed variance in the rainy season precipitation and it was subsequently used to reconstruct precipitation. The reconstructed precipitation reveals an apparent drying trend since 1840, accompanied by increasingly frequent drought events since 1970. Interdecadal variability is also present, characterized with two distinct wet periods in 1740-1760 and 1800-1900 and two drier periods in 1760-1800 and 1900-2013. On the interannual timescale, the LLH precipitation was modulated collectively by the El Niño-Southern Oscillation (ENSO) and the Indian Ocean dipole (IOD). There appears to be an enhanced precipitation-IOD relationship since 1970 in response to the increase in positive-IOD events, implying an increasing likelihood of drought for the southwest China LLH.

Keywords: Indian Ocean Dipole; Precipitation; Southwest China; Tree ring oxygen isotope.