Persisting volcanic ash particles impact stratospheric SO2 lifetime and aerosol optical properties

Abstract

Volcanic ash is often neglected in climate simulations because ash particles are assumed to have a short atmospheric lifetime, and to not participate in sulfur chemistry. After the Mt. Kelut eruption in 2014, stratospheric ash-rich aerosols were observed for months. Here we show that the persistence of super-micron ash is consistent with a density near 0.5 g cm⁻³, close to pumice. Ash-rich particles dominate the volcanic cloud optical properties for the first 60 days. We also find that the initial SO₂ lifetime is determined by SO₂ uptake on ash, rather than by reaction with OH as commonly assumed. About 43% more volcanic sulfur is removed from the stratosphere in 2 months with the SO₂ heterogeneous chemistry on ash particles than without. This research suggests the need for re-evaluation of factors controlling SO₂ lifetime in climate model simulations, and of the impact of volcanic ash on stratospheric chemistry and radiation.

Volcanic ash is often neglected in climate simulations as it is assumed to have a short atmospheric lifetime. Here, the authors show a persistent super-micron ash layer after the Mt. Kelut eruption in 2014 that impacts the stratospheric sulfur burden and chemistry for over the first months after the eruption.