Abstract
Hydroclimate evolution history and changes in the Tibetan Plateau play significant roles in depicting paleoclimate and evaluating climatic conditions in the coming future. However, the interaction of the westerlies and the Asian monsoon complicates our understanding of the mechanism of climate variation over the Tibetan Plateau. In this study, we assessed the paleoclimate of Hurleg Lake, which was previously located in the convergence area of the East Asian monsoon and westerly wind. We first reconstructed the climatic conditions based on fined-grained authigenic carbonate δ18O (δ18Ocarb), plant-derived proxies of C/N, and n-alkane-derived δ13C31. In the Hurleg Lake, δ18Ocarb was controlled by δ18O changes of the lake water and evaporation. The climate evolution since ∼16.1 cal kyr BP can be classified into three stages. The Lateglacial (16.1–11.0 cal kyr BP) was characterized by a warm-wet climate in the beginning, followed by a cold-dry climate since 12.0 cal kyr BP. Typical warm and cold phases occurred during 14.8–12.0 cal kyr BP and 12.0–11.1 cal kyr BP, which may correspond to the Bølling/Allerød (B/A) and Younger Dryas periods, respectively. The early to mid-Holocene was generally characterized by a warm-wet climate; however, notable cold-dry intervals occurred at ∼8.3 cal kyr BP. The Late Holocene (after 4.8 cal kyr BP) displayed a significantly cold-wet climate. Finally, we examined the possible mechanisms responsible for the climate variability in the study area. The results showed that the long-term warm trend in the Lateglacial and colder trend after early Holocene was controlled by insolation. The Asian summer monsoon and the westerlies played a significant role in determining moisture sources during the Lateglacial. The East Asian monsoon contributed greatly to the moisture variation from the early to mid-Holocene, whereas the westerly winds dominated during the late Holocene. Combined, our findings highlight the complex changes in hydroclimate conditions since the last glacial in the Tibetan Plateau and provide crucial implications for comprehending the hydroclimate pattern in the transition zone of westerlies and Asian monsoon.
Highlights
Since the 21st century, global environmental problems, such as sea level rise, extreme climate events, and ecological environmental damage, have increased in frequency and intensity in response to global warming (Klanderud, 2005; IPCC, 2014)
A total of 12 samples were collected at intervals of ∼50 cm for the analysis of the X-ray diffraction (XRD) results to determine the mineral types
Based on multiple geochemical proxies, including inorganic (δ18Ocarb), and organic indicators (C/N, δ13C31), we reconstructed paleoclimatic evolution history in the Hurleg Lake area, northeastern Tibetan Plateau since ∼16.1 cal kyr BP: 1) 16.1–11.1 cal kyr BP: a generally warm-wet climate occurred during 16.1–12.0 cal kyr BP, which was interrupted by a cold-dry phase at 12.0–11.1 cal kyr BP
Summary
Since the 21st century, global environmental problems, such as sea level rise, extreme climate events, and ecological environmental damage, have increased in frequency and intensity in response to global warming (Klanderud, 2005; IPCC, 2014). These climate events have adversely impacted human and social development and attracted the attention of researchers across the world (Haug et al, 2003; Mondoni et al, 2012). Thousands of lakes are distributed across the TP, where paleoclimate information is well preserved These include the hydroclimate and temperature records derived from lakes Naleng, Nam Co., Qinghai, Hurleg, Qionghai, etc. Analyses of past climate changes have advanced our understanding of the dynamic driving factors of hydroclimate and temperature, which are closely related to the monsoon and insolation, respectively, and are influenced by regional and global climate changes (Peterse et al, 2004, 2011; Dykoski et al, 2005; Wang et al, 2005, 2008; Zhao et al, 2011)
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