Long-term drying trends since the mid-Holocene in the Qaidam Basin

Abstract

This study was conducted to improve our understanding of climate changes and landscape evolution in the transitional area between the westerly-dominated regions and monsoonal regions, with the aim of contributing to solving the increasing debate over the “westerlies model” or “monsoon model” in the northeastern Tibetan Plateau. This research mainly focuses on glycerol dialkyl glycerol tetraethers (GDGTs) in a well-dated sediment core that covers the last ∼ 14.1 ka from Hurleg Lake in the Qaidam Basin, combined with grain size and organic element characteristics, to explore the climate and landscape evolution under the influence of potential forcing. Based on the variations in core sedimentary facies and careful calibrations selection, this study reveals that Hurleg Lake experienced a warm–dry climate in the last deglaciation (14.1–11.2 cal ka BP), a cold–wet climate in the early Holocene (11.2–9.3 cal ka BP), a warm–wet climate in the mid-Holocene (9.3–3.5 cal ka BP), and a cool–dry climate in the late Holocene (after 3.5 cal ka BP). Our study suggests that the moisture evolution in the Hurleg Lake area was controlled by the Asian summer monsoon (ASM) and exhibits a typical “monsoon model”, and the modern climate is drier than that in the mid-Holocene. The weakening of ASM since the mid-Holocene has caused the ASM boundary to retreat southeastward to the modern one. Therefore, long-term declines in temperature and precipitation may lead to vegetation deterioration, glacier advancement, and aeolian activity exacerbation, which in turn influence regional ecological landscape.