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Atmospheric CO2 across the Plio-Pleistocene

Nuber, Sophie 2020. Atmospheric CO2 across the Plio-Pleistocene. PhD Thesis, Cardiff University.
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The study of climate parameters and their feedback mechanisms have becomeexceedingly important in light of anthropogenic CO2release and its initiation ofclimate change. In this thesis, I investigate the interaction between different climateparameters during Late Pleistocene climate cycles and the Mid-Pleistocene transition(MPT). I use ocean sediment core-derived foraminiferal shells and geochemicalanalyses to reconstruct surface water temperature, salinity, and atmospheric CO2from a new site U1476 in the Mozambique Channel. I show for the first time thata peak in glacial Indian Ocean surface salinity creates a particularly salty AgulhasLeakage during Late Pleistocene deglaciations. This may influence changes inglobal climate by altering the surface salinity budgets at deep water convection sites,potentially driving a more vigorous overturning circulation. Late Pleistocene climatetransitions established during the MPT “900kyr event”, when glacial ice volumesignificantly increased forming a 100kyr cycle. I demonstrate that ice sheets duringthe early MPT sustained glacial ice volume, despite increases in summer durationinsolation and temperature. The data combined with newpCO2reconstructionssuggest that the early de-coupling of ice sheet dynamics caused a disruption in theforcing of earth’s internal feedback mechanisms, leading to the global phenomenonof the “900kyr event”. ThepCO2data was reconstructed using multi-collectorinductively coupled plasma mass spectrometry (MC-ICPMS) boron isotope analysis.I present accuracy and precision data of boron isotope standard measurements conducted on a new Nu plasma II instrument. Best results were achieved afteradopting a PFA cyclonic spray chamber, 1011Ωresistors, and concentrated solutions.My additional laboratory test studies provide evidence that cleaning large samples,as used in boron isotope analyses, can be efficiently conducted without the necessityfor scaling reagents. My research concludes that Late Pleistocene Indian Oceancirculation and early Pleistocene ice sheet dynamics are important internal climatedrivers that have the potential for shaping Pleistocene climate when coupled withinsolation- or atmospheric CO2 change.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Earth and Environmental Sciences
Subjects: Q Science > QE Geology
Date of First Compliant Deposit: 18 August 2020
Date of Acceptance: 18 August 2020
Last Modified: 25 May 2021 01:29

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