Eruption plume height and its impact on volcanic forcing: towards more realistic forcing reconstructions and scenarios for future climate projections
Friday, 23 March 2018: 11:30
Salon Vilaflor (Hotel Botanico)
Thomas Jacques Aubry, University of British Columbia, Earth, Ocean and Atmospheric Sciences, Vancouver, BC, Canada, Mark Jellinek, Univ British Columbia, Vancouver, BC, Canada, Anja Schmidt, University of Cambridge, Cambridge, United Kingdom and Matthew Toohey, GEOMAR, Kiel, Germany
Abstract:
Easy Volcanic Aerosol (EVA) generates idealized volcanic aerosol forcing from the mass of SO
2 injected into the stratosphere by a volcanic eruption. Whereas prognostic aerosol models are computationally expensive, the simplicity of EVA facilitates sensitivity analysis to assess the climate response to aspects of stratospheric volcanic aerosols forcing. However, some of the simplifying assumptions on which EVA is built neglect key processes that affect the magnitude of volcanic aerosol forcing. First, the forcing generated is independent of the height of injection of the SO
2 into the atmosphere, which may impact the longevity of sulfate aerosols in the atmosphere, in particular for upper tropospheric/lower stratospheric eruptions. Secondly, aerosol effective radius is defined as a simple function of the total mass of aerosol, which neglects potential sensitivity of aerosol growth to physical or chemical variations in the stratosphere. We propose to explore strategies to implement more realistic parameterizations for these two aspects in EVA while conserving its flexibility. Parameterizations will be based on satellite and ground-based observations of the forcing associated with the moderate magnitude eruptions of the 21st century and the Mount Pinatubo 1991 eruption, as well as prognostic aerosol model simulations.
In this work, we will use observations, aerosol model results and extensions to the EVA forcing generator to address the following research questions:
i) How would the potential impacts of climate change on volcanic plume dynamics affect future volcanic forcing? Projected changes in atmospheric conditions would lead to a decrease of the plume height of tropical eruptions relative to the tropopause height (Aubry et al, 2016). We quantify how such decrease translates in terms of volcanic forcing.
ii) What may future stratospheric volcanic aerosol forcing be like? We use resampling techniques, satellite data (since 1979) and ice cores (past 2500 years) records of volcanic sulfur injections into the stratosphere to design scenarios for future stratospheric volcanic aerosol forcing. These scenarios can be implemented in Earth system models for use in future climate projection simulations.
