The 39 ka Campanian Ignimbrite (CI) super-eruption was the largest volcanic eruption of the past 200 ka in Europe. Tephra deposits indicate two distinct plume forming phases, Plinian and co-ignimbrite, characteristic of many caldera-forming eruptions. Previous numerical studies have characterized the eruption as a single-phase event, potentially leading to inaccurate assessment of eruption dynamics. To reconstruct the volume, intensity, and duration of the tephra dispersal, we applied a computational inversion method that explicitly accounts for the Plinian and co-ignimbrite phases and for gravitational spreading of the umbrella cloud. To verify the consistency of our results, we performed an additional single-phase inversion using an independent thickness dataset. Our better-fitting two-phase model suggests a higher mass eruption rate than previous studies, and estimates that 3/4 of the total fallout volume is co-ignimbrite in origin. Gravitational spreading of the umbrella cloud dominates tephra transport only within the first hundred kilometres due to strong stratospheric winds in our best-fit wind model. Finally, tephra fallout impacts would have interrupted the westward migration of modern hominid groups in Europe, possibly supporting the hypothesis of prolonged Neanderthal survival in South-Western Europe during the Middle to Upper Palaeolithic transition.

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Abstract. Traditionally, tephra transport and dispersal models have evolved decoupled (offline) from numerical weather prediction models. There is a concern that inconsistencies and shortcomings associated with this coupling strategy might lead to errors in the ash cloud forecast. Despite this concern and the significant progress in improving the accuracy of tephra dispersal models in the aftermath of the 2010 Eyjafjallajökull and 2011 Cordón Caulle eruptions, to date, no operational online dispersal model is available to forecast volcanic ash. Here, we describe and evaluate NMMB-MONARCH-ASH, a new online multi-scale meteorological and transport model that attempts to pioneer the forecast of volcanic aerosols at operational level. The model forecasts volcanic ash cloud trajectories, concentration of ash at relevant flight levels, and the expected deposit thickness for both regional and global configurations. Its online coupling approach improves the current state-of-the-art tephra dispersal models, especially in situations where meteorological conditions are changing rapidly in time, two-way feedbacks are significant, or distal ash cloud dispersal simulations are required. This work presents the model application for the first phases of the 2011 Cordón Caulle and 2001 Mount Etna eruptions. The computational efficiency of NMMB-MONARCH-ASH and its application results compare favorably with other long-range tephra dispersal models, supporting its operational implementation.

Ash emitted during explosive volcanic eruptions may disperse over vast areas of the globe posing a threat to human health and infrastructures and causing significant disruption to air traffic. In Antarctica, at least five volcanoes have reported historic activity. However, no attention has been paid to the potential socio-economic and environmental consequences of an ash-forming eruption occurring at high southern latitudes. This work shows how ash from Antarctic volcanoes may pose a higher threat than previously believed. As a case study, we evaluate the potential impacts of ash for a given eruption scenario from Deception Island, one of the most active volcanoes in Antarctica. Numerical simulations using the novel MMB-MONARCH-ASH model demonstrate that volcanic ash emitted from Antarctic volcanoes could potentially encircle the globe, leading to significant consequences for global aviation safety. Results obtained recall the need for performing proper hazard assessment on Antarctic volcanoes, and are crucial for understanding the patterns of ash distribution at high southern latitudes with strong implications for tephrostratigraphy, which is pivotal to synchronize palaeoclimatic records.