Hydroclimate and environmental changes associated with GS-20 and the Toba eruption in the Indo-Pacific region

Abstract

Despite being the largest volcanic eruption of the Quaternary period, the climatic and environmental impacts of the Toba eruption remain debated. Its potential connection to glacial stadial 20 (GS-20), a major episode of abrupt cooling, also remains unresolved. Here, we reconstruct changes in regional hydroclimate and vegetation-soil productivity between 68,000 and 79,500 years ago using speleothem oxygen and carbon isotopic ratios (δ¹⁸O and δ¹³C) from Central Vietnam and compare these data with regional and global speleothem records to evaluate the role of Toba eruption in driving climatic shifts associated with GS-20. The Central Vietnam records reveal a delayed onset of GS-20 hydroclimate response, which emerged only after the temperature- and/or volcanic-driven productivity decline associated with the Toba eruption. Comparisons with regional and global speleothem records corroborate widespread ecosystem productivity changes during the eruption period, and a delayed low-latitude hydroclimate response to GS-20 relative to mid-latitudes, which likely reflects prolonged disruptions to coupled ocean–atmosphere circulation triggered by the eruption. Utilizing a meridional transect of Indo-Pacific speleothem δ¹⁸O records, we demonstrate that regional Intertropical Convergence Zone (ITCZ) experienced prominent southward migration and overall weakened convection during the glacial stadials, which was accompanied by expansion in the peripheral of its seasonal extent and contraction in its core region. Our findings underscore the complex ocean-atmosphere interaction and non-linear responses of the ITCZ to volcanic and North Atlantic forcing, refining our insights into the climatic and environmental impact of volcanic eruptions as well as predictions of future volcanic impacts.