Date of Award

Spring 8-1-2024

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Earth & Environmental Systems

First Advisor

Jeffery Stone

Second Advisor

Karlyn S. Westover

Third Advisor

Chad L. Yost

Abstract

Hydroclimate variability in the Midwest has increased over the past few decades, as as evidenced by increases in average precipitation and frequency of extreme hydroclimate events. Understanding natural climate variability in this region will help communities in the Midwest to better prepare and mitigate the risks associated with extreme hydroclimate variability in the future. Natural lakes in the Midwest are often effective archives of hydroclimate; many have been shown to respond directly to changes in climate both locally and regionally. We extracted a 4.5-meter sediment core, representing approximately 2050 years of sediment accumulation, from the deepest part of Marl Lake in Waushara County, Wisconsin. From this core, we identified fossil diatoms to document shifts in assemblages over time. Changes in the dominant diatom species of Marl Lake reflect important environmental changes such as lake-level fluctuations, nutrient concentration, and changes in lake stratification. The diatom data suggests that Marl Lake has undergone drastic hydrologic changes over the 2050-year record. Nutrient content has also been higher in the lake over the last ~700 years. The shallowest lake period occurred in the late 20th century and that dry period is evident in historical aerial imagery. While Marl Lake went through many changes, the hydrology of the lake did not clearly respond to known climate phenomena like the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). Our robust hydroclimate record will fill a gap in millennial-scale records from the midwestern United States (US), providing policymakers with additional critical information needed for future planning.

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