Taking Earth's volcanic pulse: understanding global volcanic hazards by unlocking the ice core archive

At the start of 2022, a little studied Pacific Island volcano, Hunga Tonga-Hunga Ha apai, erupted with an energy ~1000x greater than the atomic bomb dropped on Hiroshima. This eruption created waves that reverberated around the Earth and sent up a volcanic plume that reached ~55 km, half-way to space. Although this eruption was devastating for Tonga, mercifully, from a global perspective, it was short in duration and did not occur in a densely populated area or one of vital food production, transport, or energy transmission. Had it done so there would have been major impacts on climate and society.

Volcanologists study past volcanic events so that we can understand their return periods and impacts and help prepare society for the next 'big one'. Large eruptions loft enormous quantities of ash and gas into the atmosphere, these plumes undergo regional and global distribution and can travel thousands of kilometres from their source. In most surface environments the fine-grained volcanic fallout is rapidly washed away. Ice sheets are the exception to this, and by drilling into the ice and extracting core scientists can identify the sulfur-rich layers and ash deposited by these past eruptions. Although ice cores provide the undisputed best archive of past volcanism, interpreting this record is not straightforward and our current techniques tell us little about where the source volcano was located and what its climate impact might have been. Even in records that span the last 2500 years, we only know the location of 7 of the 25 largest volcanic eruptions.

This project will develop novel ice core chemical analyses to extract detailed information on the source, style, and environmental impacts of past volcanism. It will take advantage of two recent breakthroughs in ice core research. The first is high time resolution chemical analysis of volcanic sulfur which provide critical information about the height the volcanic plume reached in the atmosphere and the proximity of the eruptive source to the ice sheet. The second is ash particle chemistry which can help pinpoint the volcanic source and setting. During the first phase of this fellowship, we validated these techniques for well-known eruptions where we already have good information on the eruptive source, style and climatic impacts. We set up new protocols to analyse tiny fragments of ash (many of which are smaller in diameter than a human hair) and developed a computer model that can predict the sulfur chemistry for different eruption styles, allowing us to infer the source and climate impact directly from the ice core fingerprint.

In the final phase of this project, we will apply our new techniques to unravel the source and climate impacts of the greatest eruptions in the ice core archive. Many of these are mystery eruptions, where we know there was a massive sulfur emission, but we don't yet know the exact volcanic source. Understanding the source of these massive mystery eruptions is one of the outstanding challenges in volcanology and paleoclimate, and our techniques will undoubtedly provide fascinating insights into these exceptional events and stimulate new interactions between volcanologists, climatologists, and historians.

This project will provide critical new information about volcanism on Earth. To ensure maximum impact we will embed these findings in global volcanic hazard databases which will be used by scientists, governments, and industry (e.g., aviation and insurance) to quantify the magnitude, frequency and style of past eruptions and improve forecasts of future volcanic events. Our work will provide fundamental insights the climate impacts of past eruptions and will also help scientists and policy makers to target volcano monitoring in regions of the globe that are prone to large volcanic events. Ultimately, with this knowledge we will be better prepared for the next 'big one' and this will help limit the loss of life and reduce the economic losses.