Volcanic drivers of the stratospheric sulfur cycle in GFDL ESM4

Abstract:

Sulfur plays an important role in the stratosphere for its chemical processes and radiative impact, as sulfate aerosols provide surface for ozone-depleting chemistry, scatter shortwave radiation, and absorb longwave radiation. The major source and driver of variability in the stratospheric sulfur budget are volcanic eruptions, which inject sulfur dioxide and sulfate aerosols into the stratosphere causing perturbations to the Earth’s global radiative balance that are detectable in observational temperature records. While the impact of major volcanic eruptions on the stratosphere has garnered increasing interest in recent years, modeling efforts to fully account for the chemistry and climate effects of direct volcanic sulfur injections into the stratosphere remain limited. An interactive representation of the stratospheric sulfur cycle in global climate models driven by explicit volcanic emissions of aerosol precursors captures the interactions between the sulfur cycle and climate change and variability. In the GFDL Earth System Model (ESM4.2), we replace the previously prescribed distributions of aerosol optical properties with a newly implemented capability to simulate stratospheric sulfur aerosols prognostically, driven by volcanic emissions as well as non-volcanic sources. Simulating the 1991 Mount Pinatubo volcanic eruption as a perturbation and benchmark event for model evaluation, we share some of the insights learned from this experiment and discuss its comparisons against observations as well as ESM4.1 with prescribed volcanic aerosol forcing. The new model capabilities and simulation provide a fresh look into volcanic drivers that play key roles in the stratospheric sulfur cycle and the first step for understanding the impacts of stratospheric aerosols on chemistry and climate using the GFDL model.