Description
- Abstract:
- Tropical ocean upwelling zones like the eastern equatorial Pacific (EEP) Ocean regulate global climate by absorbing heat and carbon dioxide from the atmosphere. The influx of colder and nutrient-rich subsurface water upwelled to the EEP supports among the highest surface primary productivity of photosynthetic marine organisms in the global oceans, which in turn fuels globally important fisheries. EEP surface water originates in the northern and southern high latitudes, and water mass properties like temperature and nutrient content are transmitted through oceanic tunneling to tropical upwelling zones. Given the region’s potential to counteract anthropogenic warming and carbon dioxide emissions, it is critical to understand how high latitude controls on EEP temperature and productivity have evolved from the equilibrated warmer climates of the Late Miocene and Pliocene to the colder world of Pleistocene glaciations to anticipate the future consequences of anthropogenic warming. In this dissertation I assess the evolution of east-west temperature and productivity gradients across the EEP surface and subsurface from the Late Miocene to present. I reconstruct paleo-temperature, productivity, and nutrient content of surface, subsurface, and deep ocean waters using proxies archived in marine sediment cores, including organic biomarkers, X-ray fluorescence elemental composition, and planktic and benthic foraminiferal shell stable isotopic signatures. The first two chapters reconstruct surface features of EEP climate evolution over the last three and a half million years. I find that despite the modern tight coupling between surface temperature and productivity characteristic of EEP climate variability today, warmer waters that upwelled in the Pliocene EEP were able to support higher biological productivity than modern, suggesting an unexpected decoupling between temperature and productivity. The final two chapters investigate subsurface and deep ocean water mass evolution to capture the influences of high latitude changes transmitted through oceanic tunneling to the EEP thermocline and nutricline. I find that delivery of temperature and nutrients led to significant surface cooling and decreasing productivity over the last several million years. The unifying theme of this dissertation is that physical and biogeochemical properties of high latitude source waters shaped EEP climate since the Late Miocene.
- Notes:
- Thesis (Ph. D.)--Brown University, 2024
Citation
Kimble, Kristin Mary,
"High Latitude Influences on Eastern Equatorial Pacific Climate Evolution Since the Pliocene"
(2024).
Earth, Environmental and Planetary Sciences Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://repository.library.brown.edu/studio/item/bdr:2vczrc5j/
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Earth, Environmental and Planetary Sciences Theses and Dissertations
Theses and Dissertations for the Earth, Environmental and Planetary Sciences department....