Speaker: ALex Archibald

The 1257 CE eruption of Mount Samalas (Indonesia) is the source of the largest stratospheric injection of volcanic gases in the Common Era. Sulfur dioxide emissions produced sulfate aerosols that cooled Earth’s climate with a range of impacts on society. The co-emission of halogenated species has also been speculated to have led to wide-scale ozone depletion. Here we present simulations from HadGEM3-ES, a fully-coupled atmosphere-ocean general circulation model with interactive atmospheric chemistry and a microphysical treatment of sulfate aerosol, which assess the chemical and climate impacts from the injection of sulfur and halogen species into the stratosphere as a result of the Samalas eruption. Whilst our model simulations support a climate response to the eruption of the order of 1°C, performing well against multiple reconstructions of surface temperature from tree ring records, we find little evidence to support significant (up to 20%) injections of halogens into the stratosphere. Including modest fractions of the halogen emissions reported from Samalas leads to significant impacts on the composition of the atmosphere and on surface temperature. As little as 20% of the halogen inventory from Samalas reaching the stratosphere results in catastrophic ozone depletion; extending the cooling response from the eruption. However, based on available constraints on surface temperature we can not rule out the possibility of very minor fractions (1%) of the halogen inventory reaching the stratosphere and suggest that further constraints are needed to fully resolve the issue. 

Wednesday April 29, 2020, 13:00

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