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Volcanic sulfur emissions from magma source to ice core archive: the case of the 1783 Laki eruption

William Hutchison 1, Florian Brouillet1, Andrea Burke1, Patrick Sugden1, Eliza Harris2, Michael Sigl2, Margaret Hartley3, David Neave3, Zoltán Taracsák4 and EIMF5

  • Affiliations:  1School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK; 2Climate and Environmental Physics & Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland; 3Department of Earth and Environmental Sciences, University of Manchester, Oxford Road, M13 9PL, United Kingdom; 4Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, United Kingdom; 5Edinburgh Ion Microprobe Facility, School of GeoSciences, University of Edinburgh, James Hutton Road, EH9 3FE, United Kingdom 

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 228

  • Programme No: 3.17.15

  • Theme 3 > Session 17

Abstract

Large magnitude volcanic eruptions inject prodigious quantities of SO2 into the atmosphere which can have major impacts on climate and society. While it is well established that SO2 is oxidised to sulfate (H2SO4), a range of aqueous and gaseous oxidation pathways are known and there is debate as to which is dominant. Answering this question is difficult because of the challenges of sampling volcanic plumes, yet it is critical to understanding the fate and longevity of climate-impacting S species. Polar ice-cores capture high-time-resolution records of sulfate fallout from volcanic plumes and isotopic analysis of this sulfate can help determine the oxidation pathway. Despite this, no study has constrained S isotopes of erupted SO2 and compared these values to the corresponding ice-core sulfate horizon to understand and model atmospheric processing of SO2. Here, we examine ice-core and eruptive deposits of the 1783 Laki fissure eruption, the largest volcanic S emission of the Common Era. S isotopes of melt inclusions and matrix glass reveal characteristic degassing patterns and using mass balance we reconstruct δ34S of the initial SO2. Laki sulfate deposited in Greenland ice shows a large time evolution in δ34S (from -5 to +5 ‰) and a small but detectable change in Δ33S (~0.2 ‰). Using a plume box model (incorporating isotope fractionation) to compare data and models indicates a major role of the aqueous oxidation pathway catalysed by transition metals. This finding is consistent with recent photochemical models and emphasises the importance of including this pathway in volcanic emission scenarios.