Master Thesis Defense by Dennis Erdogan Bilginer
Title: Climatic Impact of Volcanic Eruptions during the last 3,800 Years as Reflected in Ice-Core Water Isotopes
Abstract:
Volcanic eruptions serve as critical natural drivers of short-term climate variability, with impacts on polar climates that are spatially complex and regionally distinct. This study examines isotopic responses to major volcanic events during the Late Holocene by synthesizing δ¹⁸O anomalies from multiple Greenland and Antarctic ice cores. Volcanic signals are isolated from background climatic variability by aligning these records with a comprehensive eruption chronology. Results show that 79% of eruptions, with a VSSI ≥ 15, coincide with negative δ¹⁸O anomalies in Greenland, averaging −0.29‰, corresponding to an estimated cooling of about −0.61 °C. Northern Hemisphere extratropical eruptions generate the most pronounced and spatially coherent cooling signals, while tropical eruptions produce broader but more variable isotopic responses. Antarctic ice cores display weaker and less consistent isotopic anomalies, likely due to complex regional climate dynamics and internal variability. Cross-validation with tree-ring temperature reconstructions confirms the observed magnitude and duration of Northern Hemisphere post-eruption cooling. Findings highlight the reliability of Greenland δ¹⁸O as a proxy for hemispheric volcanic climate forcing and emphasize the influence of eruption latitude, stratospheric aerosol lifetime, and seasonality on the climate response. Challenges in Antarctic data interpretation and eruption attribution remain, underscoring the value of integrated multi-proxy approaches and coupled model comparisons to improve understanding of volcanic impacts on polar climate.