| Summary: | M.S. The full text PDF of this thesis is embargoed at author's request until 2021-06-10. With projections of increased global precipitation and temperature, regional precipitation dynamics need to be better constrained. Precipitation isotopes, δ2H and δ18O, provide information about how precipitation amount, moisture sources, evaporation and moisture transport change through time throughout the world. The combination of both δ2H and δ18O in observational and paleoclimate records provides detailed insight into, and potentially quantification of moisture recycling and precipitation seasonality on daily to millennial time scales. Two applications of a dual isotope approach in the Laurentian Great Lakes region and in the Disko Bugt region in western Greenland are presented. The modern Great Lakes study includes the results of a three year, 2015-2018, event-based precipitation record of δ2H and δ18O. On western Greenland, a Holocene (8 ka-present) lake water δ18O record at ~400 yr resolution reconstructed using chironomid head capsule δ18O is compared to a lake water δ2H record inferred from aquatic leaf wax δ2H. The modern Great Lakes study uses the combination of δ2H and δ18O, deuterium-excess, to reconstruct changes in moisture recycling to understand atmospheric and land interactions during lake effect precipitation events. The potential of reconstructing paleo-deuterium-excess using a dual isotope approach because an annual average deuterium-excess signal preserves the lake effect precipitation signal at sites downwind of the Great Lakes is highlighted. In the Arctic, the chironomid δ18O and aquatic leaf wax δ2H records reflect summer and winter precipitation changes respectively, and suggest an overall increase in precipitation throughout the year likely linked to a warmer and stronger West Greenland Current. This dual approach of reconstructing precipitation δ18O and δ2H captures changes in precipitation in both winter and summer from the same aquatic setting, eliminating complexities of residence times and basin characteristics in other lake systems. These studies illustrate that applying a dual isotope approach to regions throughout the world, at fine and coarse sampling resolution in both modern and paleo time scales, is a promising method to use to understand regional precipitation response to global warming.
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