Sulfur isotopes and tephra geochemistry in identifying the volcanic sources of mystery, climate forcing eruptions preserved in ice cores

Ice cores provide the best record of volcanic sulfate aerosol emissions in the pre-satellite era, which are used in model simulations to understand the past and future climate hazards of volcanic stratospheric injection. However, the vast majority of ice core recorded events used in climate models are not attributed to known eruptive sources. Therefore, it is necessary to make assumptions of source latitude, plume height, and stratospheric sulfur loading – all variables which impact the climate forcing of an eruption. This is even the case for relatively recent eruptions recorded in ice during the post-industrial era, where cold conditions were experienced by global societies, but no historical records of the culprit eruptions exist.

Using a multi-pronged approach that combines high time resolution sulfur isotope analysis of deposited aerosols and geochemical analysis of microscopic ash particles in polar ice cores, these eruption characteristics can be better constrained. We demonstrate how this multi-method approach has recently aided the investigations into several volcanic eruptions recorded in polar ice cores which are associated with periods of notable climate cooling in the Common Era, including the mysterious 1831 CE eruption. These efforts will improve the volcanic forcing used in model simulations of the climate over the last 2000 years.