Modeling the distribution of the volcanic aerosol cloud from the 1783-1784 Laki eruption

We conducted simulations of the atmospheric transformation and transport of the emissions of the 1783-1784 Laki basaltic flood lava eruption (64.10 degrees N, 17.15 degrees W) using the NASA Goddard Institute for Space Studies modelE climate model coupled to a sulfur cycle chemistry model. The model simulations successfully reproduced the aerosol clouds of the 1912 Katmai and 1991 Mount Pinatubo eruptions, giving us confidence in the Laki simulations. Simulations of the Laki eruption produce peak zonal mean sulfate ( SO4) concentrations of over 70 ppbv during August and into September 1783 in the upper troposphere and lower stratosphere at high latitudes. While the majority of the sulfate aerosol was removed during the fall and early winter, a significant aerosol perturbation remained into 1784. The peak SO2 gas loading was just over 37 megatons (Mt) in late June with the sulfate loading peaking in late August 1783 at 60 Mt over the average of 3 runs. This yielded a peak sulfate aerosol (75% H2SO4, 25% H2O) loading of over 80 Mt with the total aerosol produced during the entire eruption being about 165 Mt. The resulting sulfate deposition compares well with ice cores taken across Greenland. The top of atmosphere net radiative forcing peaks at -27 W/m(2) over the high latitudes during late summer 1783 and produces a global mean forcing of -4 W/m(2). The model results confirm that Northern Hemisphere high-latitude volcanic eruptions produce aerosols that remain mostly confined north of 30 degrees N latitude.