Climate-changing volcanic eruptions from magma source to ice core archives: a sulfur isotope perspective

Explosive volcanic eruptions loft prodigious quantities of ash, gas and aerosol into the Earth's atmosphere and can have severe impacts on human health, the environment and the global economy. A detailed record of past volcanic events is critical for improving societal resilience to future eruptions, and of all the surface archives available to Earth Scientists it is the polar ice cores

which preserve the finest time-resolved record of past volcanic events. The key challenge with the ice core record of volcanism is that most analytical techniques fail to provide detailed information about the eruptive style (plume height) and source location (parameters that are essential for evaluating climate impacts). One new and promising tool for

fingerprinting plume height and source location is sulfur isotope analysis of ice core sulfate deposits (Figure 1). These analyses can be used to confirm whether the sulfate was formed in the stratosphere (e.g. Baroni et al., 2007) and provide information on the spatial separation between stratospheric and tropospheric aerosol clouds (which is strongly linked to source location, Burke et

al. 2019). However, though the technique has immense potential there is only a qualitative understanding of the atmospheric chemical processes that generate these unique isotope signals because no previous studies have carefully assessed plume isotope evolution from the eruptive source to the ice sheet deposition (Gautier et al., 2018).

This project will focus on carefully calibrating and validating these methods for well-known contemporary eruptions, and will compare and contrast the sulfur isotope signatures of two of the largest eruptions in recent history: the 1875 Askja (Öskjuvatn Caldera) eruption (Iceland), and the cataclysmic 1815 Plinian eruption of Tambora (Indonesia). These events will provide a fascinating

contrast; both caused prolonged Earth surface cooling and had significant global impacts (Sigl et al. 2015), but their magma composition, eruption style and location is fundamentally different. The Askja eruption had significant regional impacts, while the Tambora eruption caused prolonged Earth surface cooling and had global impacts (Sigl et al. 2015).