Date of Award

5-11-2025

Date Published

June 2025

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Earth & Environmental Sciences

Advisor(s)

Tripti Bhattacharya

Keywords

Hydroclimate;Leaf Wax Isotopes;Organic Biogeochemistry;Pleistocene;Pliocene;Southern Africa

Abstract

In the recent decade, a number of extreme weather events have highlighted the vulnerability and unpreparedness of communities in Southern Africa (SA) to anthropogenic climate-change related weather events. Such occurrences are only expected to increase in frequency, however projections of the future mean state of hydroclimate in SA are uncertain; there is broad agreement of earth system models that Africa as a whole will become hotter and drier by 2100, however, projected changes to regional hydroclimate are ambiguous. Insights from past intervals of warm climates, like the Pliocene, or intervals of rapid climate change, like the Mid-Pleistocene Transition, can reveal mechanisms of future change and help benchmark models. In this work, I conduct a comprehensive examination of Southern African hydroclimate dynamics using a combination of organic biogeochemistry, statistical methods, and modeling approaches. I use leaf wax hydrogen and carbon isotopes to reconstruct precipitation and vegetation changes in Southern Africa. I employ a variety of statistical methods to identify long term and short term (sub-million-year) modes of variability in those records, and I utilize climate models, like the isotope-enabled Community Atmosphere Model and the Hadley Center Climate Model to evaluate the climate dynamics driving these precipitation and vegetation changes. Finally, I analyze a set of Community Earth System Model simulations to evaluate the influence of model resolution on the model’s ability to simulate Southern African hydroclimate. The work presented herein (1) contributes to our understanding of the processes driving long and short term changes in Southern African hydroclimate, (2) emphasizes the similarities of past mechanisms to those observed in the modern, and prompts us to consider whether the relatively short-lived drought events we see in the modern have the potential to become longer-lived features of the future climatology, and (3) revisits the debate for increased model resolution versus improved model parametrization.

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Open Access

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