Response of lake-catchment processes to Holocene climate variability: Evidences from the NE Tibetan Plateau
Response of lake-catchment processes to Holocene climate variability: Evidences from the NE Tibetan Plateau
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DOI：
10.1016/j.quascirev.2018.10.017
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发表时间：
2018-12
影响因子：
4
通讯作者：
D. Yan;B. Wünnemann;Yongzhan Zhang;H. Long;G. Stauch;Qianli Sun;Guangchao Cao
中科院分区：
文献类型：
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作者：
D. Yan;B. Wünnemann;Yongzhan Zhang;H. Long;G. Stauch;Qianli Sun;Guangchao Cao
自认识到青藏高原高海拔地区是理解气候变化和地球动力学过程驱动的因果机制的关键区域以来，对所谓的第三极环境(TPE)的研究在过去几十年中成为一个主要关注的问题。晚第四纪水文气候演化的研究主要是通过单个湖泊记录进行的，也有个别陆地站点进行的。考虑湖泊-集水区相互作用的综合源-汇研究极少被利用。我们在青藏高原东北部的库海盆地研究了这种关系，并根据湖盆不同位置和不同水深的30个陆上剖面和3个沉积岩芯分析了沉积过程。应用粒度变化、介形类组合、地球化学指标和绝对定年(发光、放射性碳、~(210)Pb/~(137)Cs)作为关键指标，揭示了年轻仙女果期和全新世不同水文气候环境下相互作用的沉积物通量。我们的结果表明，风沙在流域内的输送过程和分配是由于夏季有效水分有效性降低的不同阶段所致。这些阶段对应于新仙女木期、全新世早期(11.6-7.5ka)、干冷期(DCI：约4.5-3.0ka)、暗期冷期(DACP：约1.8ka-1.1ka)和小冰期(LIA：约0.6ka-0.1ka)的弱夏季风影响。这些时期的同期低水位与各自的风沙通量和湖泊沉积中不同组成的混合沉积物(河流和风沙)相对应。根据个别排水系统的流入行为和近岸地貌，可以根据当地情况分配不同的核心地点的通量。流域中的风沙沉积并不总是被保存下来，在随后的事件和/或高可用水阶段的侵蚀中经历了重新动员。在中全新世(约7.5-5.1ka)、罗马暖期(RWP：约2.8-1.5ka)和中世纪气候异常(MCA：约0.9-0.6ka)期间较潮湿的气候条件表明，由于河流流量增加，湖泊水位显著上升，表现为最高的悬浮通量、核心地点介形虫群落的消失和极低的沙粒输入。全新世期间的气候变化与亚洲夏季风(ASM)以及与中纬度西风(MLW)相互作用下有效水汽供应的变化有关。冷-干阶段可能是对跨TP的MLW传播的北大西洋气候异常的响应。
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,210Pb/137Cs) 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.