Constraining the timing, forcing, and climate impacts of volcanic eruptions during the Common Era and beyond

Gabriel, Imogen Anne (2024). Constraining the timing, forcing, and climate impacts of volcanic eruptions during the Common Era and beyond. (Dissertation, University of Bern, Faculty of Science)

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Volcanic eruptions can have climatic and societal impacts which, for major eruptions, may persist for several years after the event. Consequently, they are considered a key natural forcer in the climate system and reconstructions of volcanic forcing are an important input into climate models used for future climate forecasting and policy decision making. Generating a robust record of past global volcanic eruptions is therefore essential, with the polar ice-core records a key archive in this process. However, eruption records are incomplete across the last 2000 years. This thesis presents a multi-proxy toolkit comprising of cryptotephra, sulfur isotopes, and novel glaciochemical tracers, which, when applied to ice-core records from Greenland and Antarctica, allowed the timing and forcing of volcanic eruptions during the Common Era to be constrained. Using this toolkit, smaller and prolonged volcanic events, currently absent from existing forcing reconstructions, were identified and attributed to their sources. In addition, existing mismatches were resolved within the Antarctic records, enabling a revision of volcanic stratospheric sulfur injection estimates during the 17th century. Having constrained eruption parameters (timing, quantity of sulfur injected, provenance, and altitude of injection), a network of paleo-proxy records were employed to explore the climate impacts associated with selected events. This revealed the pronounced northern hemisphere climate impacts following northern hemisphere extratropical eruptions. Alongside ice core derived eruption parameters and petrological estimates, paleo-proxy records were also used to generate eruption emission scenarios for selected Icelandic events, thereby assisting in reconciling existing offsets with model outputs. Ultimately, through the adoption of this multi-proxy toolkit and an interdisciplinary approach, this thesis has constrained the eruption parameters for several volcanic events and explored their climate impacts. This has contributed to improving existing global records of past volcanic eruptions and forcing reconstructions during the Common Era.

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