Palaeoclimatology of Central Asia and the northeastern Tibetan Plateau on basis of compound-specific isotope analysis of biomarkers.

本项目初始阶段的目的是通过主要应用有机地球化学指标，建立至少追溯到末次盛冰期的中亚干旱地区和青藏高原东北部的水文气候记录。在提出这一建议时，已在三个湖泊（中亚帕米尔湖卡拉库尔湖；东北-太平洋东吉湖；东北-太平洋哈拉湖）成功地取得了进展。陆相生物标志物氢同位素数据显示，两个研究区在晚冰期季风的增强是不同步的。北半球快速气候事件对中亚的影响似乎比东北-太平洋上两个研究湖泊的影响更强。来自同位素全球环流模式的综合数据表明，降水季节性变化是冰川晚期中亚卡拉库尔湖流域观测到的大尺度水文和生态变化的主要驱动因素。在项目的扩展阶段，我计划对已经处理的样品（烯酮，不饱和脂肪族化合物）中的其他水生化合物进行额外的dD测量。其目标是破译过去湖水同位素和盐度的变化，基于已经分析过的有机和无机代用物，这些变化还不清楚。进一步，我的目标是分析b)更多的样品，以提高哈拉湖沉积物岩心全新世剖面的时间分辨率；c)其他指示生物质燃烧的化合物（左旋葡萄糖糖）和温度（长链二醇）。这种多代理方法结合了几种温度敏感代理（烯烃、长链二醇）和火灾指标，旨在促进正在进行的讨论，即NE-TP上的社会文化行为，特别是高海拔地区的定居，是否受到全新世冷事件的影响。(部分)。此外，我建议对来自中亚卡拉库尔湖及其集水区的至少6个样本进行化合物特定放射性碳分析（CSRA），以更好地了解陆地有机化合物的命运以及它们在超干旱环境中运输到沉积物中的潜在滞后时间（B部分）。

The aim of the initial phase of this project was to establish hydroclimatic records from both arid Central Asia and the northeaster Tibetan Plateau (NE-TP) which reach back at least to the last glacial maximum, by applying mainly organic geochemical proxies. At the timing of this proposal this has been progressed successfully at three lakes (Lake Karakul, Pamir, Central Asia; Lake Donggi Cona, NE-TP; Lake Hala Hu, NE-TP). Hydrogen isotopic data of terrestrial biomarkers show an asynchronous intensification of monsoons during the late glacial in the two study areas. Impacts of Northern Hemispheric rapid climate events appear stronger in Central Asia compared to the two studied lakes on the NE-TP. Integration of data derived from isotope enabled global circulation models give evidence for changes in precipitation seasonality as a major driving factor behind the observed large scale hydrological and ecological changes in the catchment of central Asian Lake Karakul during the late glacial.Within the extension phase of the project, I´m planning to do a) additional dD measurements on additional compounds of aquatic origin in already processed samples (alkenones, unsaturated aliphatic compounds). The goal is to decipher past changes of lake water isotopes and salinities, which is yet unclear based on already analysed organic and inorganic proxies. Further I aim to analyse b) more samples to increase time-resolution in the Holocene section of the lake Hala Hu sediment core and c) additional compounds indicative for biomass burning (levoglucosan) and temperature (long-chain diols). This multiproxy approach combining several temperature sensitive proxies (alkenones, long-chain diols) and fire indicators aims to contribute to the ongoing discussion if socio-cultural behaviour on the NE-TP, specifically the settling of higher altitudes, was influenced by Holocene cold-events. (Part A). Further, I propose to conduct compound-specific-radiocarbon analysis (CSRA) of a minimum of 6 selected samples from central Asian Lake Karakul and its catchment to better understand the fate of terrestrial organic compounds and potential lag-times during their transport into the sediment in a hyperarid environment (Part B).