Atmospheric CO₂ across the Plio-Pleistocene

The study of climate parameters and their feedback mechanisms have become exceedingly important in light of anthropogenic CO2 release and its initiation of climate change. In this thesis, I investigate the interaction between different climate parameters during Late Pleistocene climate cycles and the Mid-Pleistocene transition(MPT). I use ocean sediment core-derived foraminiferal shells and geochemical analyses to reconstruct surface water temperature, salinity, and atmospheric CO2 from a new site U1476 in the Mozambique Channel. I show for the first time that a peak in glacial Indian Ocean surface salinity creates a particularly salty Agulhas Leakage during Late Pleistocene deglaciations. This may influence changes in global climate by altering the surface salinity budgets at deep water convection sites, potentially driving a more vigorous overturning circulation. Late Pleistocene climate transitions established during the MPT “900kyr event”, when glacial ice volume significantly increased forming a 100kyr cycle. I demonstrate that ice sheets during the early MPT sustained glacial ice volume, despite increases in summer duration insolation and temperature. The data combined with new pCO2 reconstructions suggest that the early de-coupling of ice sheet dynamics caused a disruption in the forcing of earth’s internal feedback mechanisms, leading to the global phenomenon of the “900kyr event”. The pCO2 data was reconstructed using multi-collector inductively 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 after adopting a PFA cyclonic spray chamber, 1011Ω resistors, 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 necessity for scaling reagents. My research concludes that Late Pleistocene Indian Ocean circulation and early Pleistocene ice sheet dynamics are important internal climate drivers that have the potential for shaping Pleistocene climate when coupled with insolation - or atmospheric CO2 change.