Publication Date
2024
Document Type
Dissertation/Thesis
First Advisor
Stansell, Nathan D.
Degree Name
Ph.D. (Doctor of Philosophy)
Legacy Department
Department of Earth, Atmosphere, and Environment (EAE)
Abstract
In light of the rising global temperatures, there is an increasing need to understand the potential shifts in hydroclimate. Past climate reconstructions offer a glimpse into the possible temperature-moisture dynamics by providing quantitative constraints for hydroclimate variability under different temperature conditions, which can ultimately aid in decreasing the uncertainty in future climate projections. The research presented in this dissertation focuses on utilizing various proxies to reconstruct past hydroclimate conditions, particularly in the Baltic region, with a specific emphasis on Estonia. The second and third chapter aim to improve the understanding of sedimentary plant wax hydrogen isotope (δ2H) data by first investigating the relationship between local climate conditions, plant source water, leaf water, and plant lipids for individual plant species in modern catchment systems in two lake catchments. Second, this modern relationship is applied to sedimentary archives, where δ2H values obtained from n-alkanes are combined with carbonate-based oxygen stable isotope (δ18O) data to derive deuterium (d-) excess at Lake Nuudsaku. The δ2H values from different n-alkanes are used to reconstruct the magnitude of hydroclimate, while the d-excess provides a comprehensive view of past airmass movements. Third, a ground penetrating radar (GPR) survey and sedimentological analyses were conducted on Lake Pangodi in southern Estonia to identify periods of lake-level high- and low-stands. These data were then used to guide the interpretation of sedimentary δ18O data from the same lake basin to identify environmental factors shaping the isotope curve.
This research highlights the importance of using a multi-proxy approach to reconstruct past environmental responses to temperature and moisture changes, by increasing the spatiotemporal resolution of the paleo-hydrological history. A key outcome of the first chapter is the application of a Péclet modified Craig-Gordon leaf water model to characterize the δ2H values of the biosynthetic source water pool throughout plant growth season. This model allows for a detailed analysis of hydroclimatic signals from precipitation δ2H values, which are modified by environmental and plant physiological conditions that ultimately affect biosynthetic isotope fractionation associated with n alkane production by each studied plant species. The results from the second study demonstrate past shifts in relative humidity (RH), temperature, and moisture sources, with higher RH values and increased warm season precipitation during the middle Holocene compared to the late Holocene. In the third study, a lake-level reconstruction shows distinct variations in water levels, suggesting changes in effective moisture balance in response to climate fluctuations. The last study offers a glance into Holocene-spanning environmental and anthropogenic influences on the lake basin.
Recommended Citation
Eensalu, Mariliis, "Tracing Past Climate Signals Through Multi-Proxy Analysis: Insights from Sedimentary Plant Wax Hydrogen Isotope Data and Long-Term Hydroclimate Records in Estonia" (2024). Graduate Research Theses & Dissertations. 7957.
https://huskiecommons.lib.niu.edu/allgraduate-thesesdissertations/7957
Extent
275 pages
Language
en
Publisher
Northern Illinois University
Rights Statement
In Copyright
Rights Statement 2
NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.
Media Type
Text
