[S-VC34] Volcanoes in the Sea

[SVC34-P11] Sulfur dioxide flux from Nishinoshima volcano, Japan, in 2021–2022

*Masaaki Morita¹, Toshiya Mori², Takayuki Kaneko¹ (1.Earthquake Research Institute, The University of Tokyo, 2.Graduate School of Science, The University of Tokyo)

Keywords:Sulfur dioxide flux, Volcanic gas, Satellite observations, TROPOMI, Nishinoshima

At Nishinoshima volcano, Izu–Ogasawara arc, a series of eruptive activities (Episode 4) lasted from December 2019 to August 2020. Since then, no eruptions have been confirmed for about a year, but on August 14, 2021, the emission of volcanic ash was confirmed by satellite observations. After that, no eruptions were documented again. However, ash emissions were confirmed from the end of September to the middle of October 2022. Intermittent ash emissions were confirmed until January 2023. In this study, we monitored sulfur dioxide (SO₂) flux to clarify the eruptive sequence of this activity. The data were obtained from Tropospheric Monitoring Instrument (TROPOMI) onboard Sentinel-5 Precursor, and the SO₂ flux was estimated based on the daily spatial distribution of SO₂ column amount and meteorological field data. The results since August 2021 showed daily mean values of 100–1,000 t d^–1 when no eruptions were confirmed, and the values were frequently below the detection limit (100 t d^–1). Daily mean values above 3,000 t d-1 were often observed on August 14, 2021, and in September–October 2022, when eruptions were confirmed. Especially in early October, when ash emissions were particularly active, the daily values exceeded 10,000 t d^–1. The eruption peaked in early October 2022 and was smaller in scale than the 2019–2020 eruption. The eruptive activity is considered to have abruptly ceased in mid-October. We will discuss the mechanism of these eruptions by comparing the SO₂ flux to the data from other satellites and geophysical observations.