Description
- Abstract:
- Earth’s high-latitude regions experienced warm, wet, and deglaciated conditions during the Miocene Climatic Optimum, which ended with cooling, aridification, and ice sheet expansion during the Middle Miocene Climate Transition and Late Miocene cooling interval. In this dissertation, I present new biomarker temperature proxy records from deep ocean sediment cores at high-latitude sites to quantitatively constrain the magnitude and timing of peak Miocene warmth and subsequent cooling that accompanied these environmental transformations. In addition, I present other geochemical records from the same cores to interpret the response of high-latitude systems, such as ice sheet behavior, terrestrial hydrology, and marine productivity, to temperature forcing during the global warmth of the Miocene. In Chapter 2, I present an orbitally-resolved surface temperature record from ODP Site 884 in the subpolar North Pacific which spans the entire MCO and MMCT. I demonstrate the synchrony of temperature changes between the northern and southern high-latitude regions surrounding the MCO as well as the persistently asymmetrical nature of warmth between the North Atlantic and North Pacific basins throughout the Miocene. In Chapter 3, I use X-ray fluorescence scanning of cores from Site 884 constrained with geochemical measurements to quantify sediment composition at high resolution. Combining biogenic sediment fluxes with other proxies for surface productivity, I explore the controls on productivity in the subpolar North Pacific during the Early and Middle Miocene. In Chapter 4, I present ocean temperature reconstructions using multiple biomarker proxies from ODP Site 1165 in the polar Southern Ocean which span most of the Miocene. By comparing these temperatures with evidence of East Antarctic Ice Sheet behavior, I constrain interactions between the ocean and ice sheet, finding a strong response of the marine ice margin to ocean temperature forcing but a more complex, threshold response of terrestrial ice volume. In Chapter 5, I reconstruct precipitation isotopes in East Antarctica over the Miocene as recorded by plant waxes preserved at Site 1165. I find a strong, though complex, relationship between temperatures in the polar Southern Ocean and terrestrial hydrology in East Antarctica, which defies straightforward application of modern-like Antarctic temperature-precipitation isotope relationships to the Miocene.
- Notes:
- Thesis (Ph. D.)--Brown University, 2026
Citation
Nirenberg, Jared Ethan,
"High-Latitude Climate, Ice Sheet, and Oceanographic Evolution During the Miocene"
(2026).
Earth, Environmental and Planetary Sciences Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://repository.library.brown.edu/studio/item/bdr:shkf9pbr/
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Earth, Environmental and Planetary Sciences Theses and Dissertations
Theses and Dissertations for the Earth, Environmental and Planetary Sciences department....