Abstract
Abstract We investigated 4.84-m-long sediment record spanning over the Late Glacial and Holocene from Lake Donggi Cona to be able to reconstruct circulation pattern on the Tibetan Plateau (TP). Presently, Lake Donggi Cona is located at the boundaries of Westerlies and Asian monsoon circulations in the northeastern TP. However, the exact timing and stimulating mechanisms for climatic changes and monsoon shifts in this region are still debated. We used a 19-ka-long stable isotope record of sedimentary n -alkanes to address this discrepancy by providing insights into paleohydrological conditions. The δD of n C 23 is influenced by lake water evaporation; the δD values of sedimentary n C 29 are mainly controlled by moisture source and temperature changes. Long-chain n -alkanes dominate over the core whereas three mean clusters (i.e. microbial, aquatic and terrestrial) can be inferred. Multi-proxies suggest five major episodes in the history of Lake Donggi Cona. The Lake Donggi Cona record indicates that the Late Glacial (18.4–14.8 cal ka BP) was dominated by low productivity of mainly microbial and aquatic organisms. Relatively low δD values suggest low temperatures and moist conditions eventually caused by stronger Westerlies, winter monsoon and melt-water influence. Likely, the shift (∼17.9 cal ka BP) from microbial to enhanced aquatic input suggests either a change from deep to shallow water lake or a break in local stratification. Between 14.8 and 13.0 cal ka BP, variable climatic conditions prevailed. Although the Westerlies weekend, the increase in temperature enhanced the permafrost and snow melting (displayed by a high sedimentary accumulation rate). Higher δD values indicate increasingly arid conditions with higher temperatures which eventually lead to high evaporative conditions and lowest lake levels. Low vegetation cover and high erosion rates led to high sediment accumulation resulting in stratification followed by anoxia in the terminal lake. From 13.0 to 9.2 cal ka BP, lowered values of δD along with high contents of terrestrial organic matter marked the early-Holocene warming indicating a further strengthening of summer precipitation and higher lake levels. A cooling trend was observed in the mid-Holocene between 9.2 and 3.0 cal ka BP accompanied by higher moisture availability (displayed by lowered δD values) caused by reduced evaporative conditions due to a drop in temperature and recovering Westerlies. After 3.0 cal ka BP, a decrease in lake productivity and cold and semi-arid conditions prevailed suggesting lower lake levels and reduced moisture from recycled air masses and Westerlies. We propose that the summer monsoon was the predominant moisture source during the Bolling-Allerod warm complex and early-Holocene followed by Westerlies in mid-to-late Holocene period. Stable carbon isotope values ∼ - 32‰ indicate the absence of C 4 -type vegetation in the region contradicting with their presence in the Lake Qinghai record. The δD record from lake Donggi Cona highlights the importance of the interplay between Westerlies and summer monsoon circulation at this location, which is highly dynamic in northeastern plateau compared to the North Atlantic circulation and insolation changes. Consequently lake Donggi Cona might be an important anchor point for environmental reconstructions on the Tibetan Plateau.
Highlights
Lake level fluctuations and moisture evolution at the Tibetan Plateau (TP) are closely related with large scale environmental changes
Our records support the previously reconstructed hydroclimatic changes on northeastern TP with deuterium depletion starting at ca. 14e15 ka driven by a major change of moisture source at the glacial to the Holocene transition
We propose that the climatic conditions were cold and moist with higher lake levels between 19 and 14.8 cal ka BP due to enhanced moisture availability coming from ever stonger Westerlies, Winter air masses and melt-water from adjacent glaciated mountains
Summary
Lake level fluctuations and moisture evolution at the Tibetan Plateau (TP) are closely related with large scale environmental changes. The quest to understand past climatic changes and the interplay between the Asian monsoon and the Westerlies has been the focus for the last few decades, especially in the northern part of the TP (An et al, 2012a; Chen et al, 2008; Mischke et al, 2008; Morrill et al, 2003; Shen et al, 2005a, b; Wang et al, 2005; Zhao et al, 2007) It is still ambiguous whether the general climate history at the TP since the LGM is similar to those of areas influenced by Asian summer monsoon (An, 2000; Herzschuh et al, 2009; Morrill et al, 2003). The glaciers at the TP are currently experiencing significant melting due to anthropogenic climate warming (Qin and Xiao, 2009; Tian et al, 2006; Yao et al, 1996, 2013)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
