How much does ice sheet sulfate deposition tell us about volcanic forcing?

Current reconstructions of volcanic forcing over the last 2000 years rely on scaling volcanic sulfate measured in ice cores to estimates of stratospheric sulfate burdens and optical properties using relationships derived from the 1991 eruption of Mt. Pinatubo. However, there are large uncertainties associated with these conversions and consequently a large uncertainty in the reconstructions. Here, we explore the relationship between ice sheet sulfate deposition and volcanic forcing in model simulations of the last millennium conducted using the UK Earth System Model with an interactive stratospheric aerosol scheme. Treating the model sulfate deposition timeseries as a measured ice-core record and using established conversions, we explore how many of the large-magnitude volcanic events simulated in the model are missed by looking at deposition alone, and how the volcanic forcing may be overpredicted or underpredicted compared to the model itself. These results will enable us to further explore uncertainty in these relationships, and aid in improving methods to calculate forcing for past eruptions.