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

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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).