Reconstructing Holocene climatic and environmental change using molecular and isotopic proxies from lake sedimentary records
Greater understanding of Holocene climatic and environmental variability and processes, as well as about feedback and forcing mechanisms of the climate system is crucial for the assessment of both natural and anthropogenic future climate and environmental changes. Compared to prior epochs in earth’s...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | German English |
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2017
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| Online Access: | https://kups.ub.uni-koeln.de/7836/ https://kups.ub.uni-koeln.de/7836/1/DissertationThienemann.pdf |
| Summary: | Greater understanding of Holocene climatic and environmental variability and processes, as well as about feedback and forcing mechanisms of the climate system is crucial for the assessment of both natural and anthropogenic future climate and environmental changes. Compared to prior epochs in earth’s history, the climate of the Holocene is traditionally regarded as relatively stable. However, Holocene climate also showed significant fluctuations although perturbation were smaller in magnitude compared to Pleistocene. These fluctuations can be assessed by organic geochemical molecular and isotope analyses of lake sedimentary organic matter (OM) that have the potential to reveal a variety of information regarding physical, chemical and biological changes and processes of the lake, its environment, and the climate. Therefore, within the scope of this thesis, sedimentary archives from selected lakes from the Sub-Artic (Lake Torneträsk), the Mediterranean (Lake Dojran), and the African tropics (Lake Dendi) were analyzed using various analytical methods including the analysis of lipid biomarker and compound specific leaf wax stable isotopes, as well as palynological, microcharcoal, and inorganic sedimentological analyses. All three lakes are situated in key regions for the understanding of northern hemispheric Holocene climate variability and natural/anthropogenic forcing and feedback mechanisms: To constrain changes in atmospheric circulation patterns and their effects on the environment in the Fennoscandian sub-arctic, lipid biomarker, inorganic proxies, and compound specific δD analysis are applied to a Holocene sedimentary record from Lake Torneträsk (NW Sweden). Owing to its climate being influenced by both the North Atlantic and the polar frontal zone, northern Fennoscandia can be regarded as a key region to better understand the regional expression and potential threshold effects of insolation-forced migrations of atmospheric circulation systems. The results indicate a non-linear reorganization of the ... |
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