Simulation of Climatic Response to Supervolcano Eruption using MRI-CGCM3

Eruptions of large volcanoes inject sulfur dioxide (SO₂) gases into the stratosphere, which leads to increases of sulfate aerosol loading, and decrease of solar radiation that reaches the ground surface. In order to evaluate the capability of the climate model to reproduce the “volcanic winter”, we investigated the climatic response to the super-volcano eruption using our global climate model MRI-CGCM3. The model consists of an atmospheric general circulation model MRI-AGCM3, an ocean general circulation model MRI.COM, and a global aerosol model MASINGAR mk-2. These model components are interactively connected using a coupler library called Simple coupler (SCUP). The sulfate aerosol by volcanic eruption is produced via chemical reactions of SO₂ and transported in the aerosol model. In this study, we carried out a virtual super-eruption experiment of Mt. Toba in Indonesia, which is considered to have erupted about 74000 years B.P. Sulfur dioxide injection by the virtual super-eruption is assumed to be 6 Gt SO₂ which corresponds to 300 times that of the Mt. Pinatubo eruption in 1991, following Robock et al. (2009). The simulated results showed that the radiative cooling by the volcanic sulfate by 6 Gt SO₂ eruptions of Mt. Toba lasted about 9 - 10 years, but the recovery of surface air temperature was delayed mainly due to cooled ocean. The snow cover over land was increased because of the cooling, which leads to the increase of ground surface albedo. However, the ground surface was not exhaustively covered by the snow, due to the weakened precipitation after eruption. The globally averaged decrease in downward shortwave radiation reached its maximum of about 170 W m^-2 in the second year after the eruption. However, the globally averaged decrease in surface air temperature was continued until the seventh year after the eruption, and reached its maximum of about 15 K.