Modeling the 1783–1784 Laki Eruption in Iceland: 1. Aerosol Evolution and Global Stratospheric Circulation Impacts

The 1783–1784 CE Laki flood lava eruption began on 8 June 1783. Over the course of 8 months, the eruption released approximately 122 Tg of sulfur dioxide gas into the upper troposphere and lower stratosphere above Iceland. Previous studies that have examined the impact of the Laki eruption on sulfate aerosol and climate have either used an aerosol model coupled off-line to a general circulation model (GCM) or used a GCM with incomplete aerosol microphysics. Here, we study the impact on stratospheric aerosol evolution and stratospheric and tropospheric circulation using a fully coupled GCM with complete aerosol microphysics, the Community Earth System Model version 1, with the Whole Atmosphere Chemistry Climate Model high-top atmosphere component. Simulations indicate that the Laki aerosols had peak average effective radii of approximately 0.4 μm in Northern Hemisphere (NH) middle and high latitudes, with peak average effective radii of 0.25 μm in NH tropics and 0.2 μm in the Southern Hemisphere. We find that the Laki aerosols are transported globally and have significant impacts on the circulation in both hemispheres, strengthening the Southern Hemisphere polar vortex and shifting the tropospheric NH subtropical jet equatorward.