New insights into past atmospheric circulation dynamics
Sammanfattning: Climate change associated with shifts in atmospheric circulation patterns has a great influence on ecosystems and societies. To predict future climate change it is important to obtain a detailed understanding of how climate behaved in the past, with special focus on the regional-scale and short-term expressions of changes in atmospheric circulation dynamics. This scientific goal can be pursued by using stable isotope records from terrestrial sequences and/or by comparing several proxy reconstructions that cover broad geographical regions. As such, isotope records have the ability to provide useful information on past changes in precipitation patterns and atmospheric physical characteristics, whereas the examination of multiple reconstructions distributed over a large area give information on the spatio-temporal variability and the direction of physical changes associated with climatic changes.The results presented in this thesis comprise i) the first Holocene stable isotope record from Gotland, which sheds light on past climate variability associated with the Siberian High over the Baltic Sea region, and ii) a comparison of pollenstratigraphic records from densely 14C dated terrestrial sequences, which provides insight into the spatial and temporal succession of vegetation shifts at the onset of the Younger Dryas cold event over northern Europe.The findings shown in these studies stress the value of using isotope records to assess past regional atmospheric circulation patterns and show the efficacy of examining well-dated networks of climate reconstructions to better understand spatio-temporal propagations of past atmospheric perturbations.
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