Depletion of H2O2 in a Greenland ice core: implications for oxidation of volcanic SO2

Abstract

MAJOR volcanic eruptions inject large quantities of sulphur compounds into the atmosphere1. A principal component is sulphur dioxide; subsequent oxidation of SO2 in the atmosphere to sulphuric acid aerosol may lead to climate perturbations2. Here we present evidence to suggest that SO2 oxidation may occur at high latitudes by reaction with H2O2. Variations in sulphate and H2O2 concentrations in four sections of a Greenland ice core (corresponding to four volcanic events) show that high sulphate concentrations, from volcanic fallout, are accompanied by depletion of H2O2. This suggests that some of the volcanic sulphur was still in the form of SO2 when it reached Greenland, and was then oxidized by H2O2 in Greenland precipitation. As SO2 oxidation in the stratosphere is very slow, volcanic events that inject SO2 into the stratosphere could produce large depletions of distant H2O2 reservoirs when the material is later reinjected into the troposphere.