The North Atlantic Ocean: A force for change at Earth’s Greenhouse-Icehouse Transition
Earth’s landmark greenhouse-icehouse transition at the Eocene Oligocene Transition (EOT) is arguably one of the most important climatic events in geological history. The dominant global geochemical signature of this dramatic shift in Earth’s climate (approximately 33.7 million years ago), a 1.2 - 1....
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| Format: | Thesis |
| Language: | English |
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2019
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| Online Access: | https://orca.cardiff.ac.uk/id/eprint/131206/ https://orca.cardiff.ac.uk/id/eprint/131206/1/2020thomassparkesaphd.pdf https://orca.cardiff.ac.uk/id/eprint/131206/2/thomassparkesa.pdf |
| Summary: | Earth’s landmark greenhouse-icehouse transition at the Eocene Oligocene Transition (EOT) is arguably one of the most important climatic events in geological history. The dominant global geochemical signature of this dramatic shift in Earth’s climate (approximately 33.7 million years ago), a 1.2 - 1.5%o increase in the stable oxygen isotope ratio (18O) of benthic foraminifera, represents a significant period of global cooling that occurred contemporaneously with the initiation of widespread Antarctic glaciation. The EOT represents the first establishment of a widespread, continental-scale, somewhat stable ice sheet on Antarctica and yet significant debate remains as to the forcing mechanism responsible for this substantial perturbation marking the end of the Eocene greenhouse world. Initiation of the step-wise shift in 18O occurred during an interval of low eccentricity and low-amplitude change in obliquity; an orbital configuration considered the ultimate trigger for glaciation at the EOT and the pacemaker for subsequent ice sheet growth. However, some other forcing mechanism(s) must have been important in conditioning the climate leading up to the EOT as these orbital configurations are found at other points in geological history where such large-scale changes in climate are absent. The overall aim of this thesis is to explore the evolution of temperature, ice volume and ocean circulation, the interactions between these key climatic parameters and the relative importance of different forcing and feedback mechanisms across the EOT. This thesis will place particular emphasis on paleoceanographic changes that occurred in the Atlantic Ocean region across this interval and their subsequent impacts. To this end, multiple records of foraminiferal stable isotopes and trace elements, and fish teeth neodymium isotopes are presented from sediment cores largely within the Atlantic Ocean or subject to its influence at the EOT. Findings of this thesis suggest a fascinating link between deep water formation in the North ... |
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