Response of lake-catchment processes to Holocene climate variability: Evidences from the NE Tibetan Plateau

Investigating the so-called Third Pole Environment (TPE) became a major concern during the last decades since it was recognized that the high-altitude region of the Tibetan Plateau(TP) is a key area for the understanding of cause-effect mechanisms driven by climate change and geodynamic processes. Studies on the hydro-climatic evolution during the Late Quaternary were mainly carried out by single lake records or alternatively by individual terrestrial sites. Integrated source-to sink studies considering lake-catchment interactions were extremely seldom utilized. We investigated such relationships in the Kuhai Basin on the north-eastern Tibetan Plateau and analysed sedimentary processes based on 30 onshore sections and three sediment cores from different locations and water depth in the lake basin. Grain size variations, ostracod assemblages, geochemical proxies and absolute dating (luminescence, radiocarbon, Pb-210/Cs-137) were applied as key indicators that reveal interacting sediment fluxes under different hydro-climatic settings during the Younger Dryas interval and the Holocene. Our results indicate that wind-induced transportation processes and allocation of respective aeolian sands in the catchment are attributed to distinct phases of reduced effective moisture availability during summer time. Those phases corresponded to weak summer monsoon influence during the Younger Dryas interval, the Early Holocene (11.6-7.5 ka), dry-cold interlude (DCI: ca. 4.5-3.0 ka), Dark Ages Cold Period (DACP: ca. 1.8-1.1 ka) and the Little Ice Age (LIA: ca. 0.6-0.1 ka). Contemporaneous low lake levels during these periods corresponded with respective aeolian sand flux and variable composition of mixed sediments (fluvial and aeolian) in lake deposits. Different flux rates at the core sites could be assigned to local conditions in respect to inflow behaviour of individual drainage systems and nearshore morphology. Aeolian deposits in the catchment were not always preserved and underwent re -mobilisation during succeeding episodes and/or erosion during phases of high water availability. Wetter climatic conditions during the Mid -Holocene (ca. 7.5-5.1 ka), Roman Warm Period (RWP: ca. 2.8-1.5 ka) and Medieval Climate Anomaly (MCA: ca. 0.9-0.6 ka) revealed significant lake level rise due to enhanced river discharge, well documented by highest suspended flux rates, disappearance of ostracod communities at core sites and very low sand input. Climate shifts during the Holocene were linked to variations in effective moisture supply under the influence of the Asian summer monsoon (ASM) and the interplay with the mid-latitude westerlies (MLW). Cold-dry phases were likely a response to North Atlantic climatic anomalies transmitted by the MLW across the TP. (C) 2018 Elsevier Ltd. All rights reserved.