Triggering Mechanisms and Carbon Sequestration Timescales of Late Paleocene-Early Eocene Carbon Cycle Perturbations
Creators: name: Piedrahita Velez, Victor
Publisher: name: The Australian National University
Year: 2023

description: The representative concentration pathway (RCP) 8.5 of the the intergovernmental panel on climate change (IPCC) indicates that if anthropogenic carbon emissions follow dramatic increasing trends, in the next ~200-300 years mean global temperatures can be ~5-10oC higher than today. This temperature increase may generate climate conditions similar to those of the late Paleocene-early Eocene (~58-52 Ma), which recorded the highest temperatures in the last ~60 Ma. Late Paleocene-early Eocene climates were characterized by a series of light carbon injections that produced major global warming/ocean acidification events called hyperthermals, and other smaller carbon cycle perturbations. Although late Paleocene-early Eocene geological records offer a possibility to identify global warming impacts under the worst anthropogenic-driven climatic scenario, important aspects related to the triggers and environmental responses of late Paleocene-early Eocene carbon cycle perturbations remain elusive. Here, two major scientific problems of late Paleocene-early Eocene carbon cycle perturbations are addressed. Initially, new chemical datasets are presented to clarify the origins of the largest Paleocene-Eocene carbon cycle perturbation, the Paleocene-Eocene Thermal Maximum (PETM). Early Eocene carbon cycle perturbations have been interpreted to be orbitally forced events; however, the influence of orbital controls on PETM triggering remains controversial. New probabilistic-based approaches are used to indicate that the PETM was at least partially triggered by an orbitally controlled mechanism, which contrasts with previous studies that restricted PETM triggering to volcanic activity. Secondly, probabilistic-based age models and statistical assessments are presented to refine poorly studied carbon sequestration timescales following Paleocene-Eocene light carbon injections. New temporal constraints reveal that carbon sequestration following Paleocene-Eocene light carbon injections was accelerated in proportion to the size of the initial perturbation. Optimized carbon removal was partially related to accelerated chemical weathering. This process also ended ocean acidification induced by Paleocene-Eocene carbon cycle perturbations, and reestablished predominant calcium carbonate sedimentation in the oceans. However, chemical weathering was not the only optimized carbon sequestration mechanism following Paleocene-Eocene light carbon injections. Temperature variations associated with Paleocene-Eocene carbon cycle perturbations exerted controls on oxygen levels. Reduced oxygen levels associated with higher temperatures may have accelerated export production and oceanic biological pump, which also promoted enhanced carbon removal. The findings presented in this thesis represent significant advances for our knowledge of origins and carbon cycle feedbacks associated with global warming events; furthermore, this thesis emphasizes that probabilistic-based approaches and statistical assessments can provide a better understanding of paleoclimate records.