Stansell, Nathan D.
M.S. (Master of Science)
Department of Earth, Atmosphere and Environment
A high-resolution Holocene record of groundwater isotopic composition from eastern Europe enhances the current understanding of ocean atmosphere interactions and moisture transport dynamics. In the modern system, it has been established that the amount of regional winter precipitation is driven by the strength and direction of the sea level atmospheric pressure gradient over the Atlantic Ocean. This is defined by the North Atlantic Oscillation (NAO) index, that shows a positive correlation with precipitation amount during the cold season. This study aims to discover the link between atmospheric dynamics and the ratio of warm season to cold season precipitation through the δ180 analysis of endogenic calcite from a sediment core from Lake Tõugjärv. The δ180 of its lake water suggests that it is directly connected to groundwater and not influenced by evaporation. δ180calcite is therefore interpreted as the mass balance of mixed isotopically light summer and heavy winter precipitation. To test the hypothesis that δ180calcite variability is driven by winter precipitation quantity changes, it is compared to weather station precipitation data to confirm that climate variability is the dominant driver of its variability. To ensure that δ180calcite is influenced by precipitation rather than diagenesis, Core lithology has been analyzed chemically, using loss on Ignition and X-ray fluorescence, Mineralogically using X-ray diffraction, and visually using a scanning electron microscope. The results suggest that winter conditions were wetter during the early and late Holocene, and relatively drier during the middle Holocene.
Boes, Maxwell Gordon, "Evaluating Holocene Precipitation Variability in the Baltic Region Using Oxygen Isotopes of Lacustrine Carbonate from Estonia" (2022). Graduate Research Theses & Dissertations. 6874.
Northern Illinois University
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