14:30 〜 14:45
[SCG57-04] アイスコア硫酸の同位体分子計測による気候変動を引き起こした火山噴火記録の復元
★招待講演
キーワード：硫酸エアロゾル、火山噴火、同位体分子、質量非依存分別
Volcanoes influence climate through the generation of sulfate aerosols, however it is difficult to determine the climate impact of a specific historical eruption using proxy records. In the stratospheric eruptions, where volcanic sulfur dioxide (SO2) in a plume penetrates the stratosphere, the stratospheric sulfate aerosol (SSA) layer generated multiyear climate impacts by increasing the planet's albedo for more than a year. Sulfate records in ice cores provide a key record of volcanic activity. However, the concentration of sulfate in the ice core does not alone indicate the explosiveness of the event and, specifically, whether the plume reached the stratosphere. Thus, the history of volcanic activity and its connection to climate impact and/or other surface-environment effects are unknown.
Developments in isotopic techniques permit the detection of stratospheric eruptions in ice cores. The isotope ratios d33S, d34S, and d36S are mass-dependently related in the troposphere. Thus, the initial composition of SO2 emitted by a point volcanic source is mass-dependent (D33S = 0‰). In the stratosphere, sulfate obtains a mass-independent composition (D33S ≠ 0‰) as a result of photo-oxidation of SO2 by shortwave UV radiation that is unique to the stratosphere. Thus, the only cause of considerable D33S in a volcanic sulfate layer is the injection of sulfur gases into the stratosphere. In addition, the oxygen anomaly D17O reflects the oxidation of oxygen atoms from SO2 to sulfate in the atmosphere, which is another constraint on tropospheric/stratospheric volcanism.
In Gautier et al. (2018 Nature Comm.), a novel 2600-year history of stratospheric volcanic episodes based on these isotopic techniques was demonstrated using five ice cores from Dome C, Antarctica. To discover stratospheric volcanisms in different ice core sites and sulfate peaks, subsequent investigations also applied D33S measurements by the MC-ICP-MS method, which requires much smaller sample volumes. In the talk, I will provide an overview of these isotope approaches and their latest applications, as well as a discussion of the relationship between volcanism and the surface environment.
Developments in isotopic techniques permit the detection of stratospheric eruptions in ice cores. The isotope ratios d33S, d34S, and d36S are mass-dependently related in the troposphere. Thus, the initial composition of SO2 emitted by a point volcanic source is mass-dependent (D33S = 0‰). In the stratosphere, sulfate obtains a mass-independent composition (D33S ≠ 0‰) as a result of photo-oxidation of SO2 by shortwave UV radiation that is unique to the stratosphere. Thus, the only cause of considerable D33S in a volcanic sulfate layer is the injection of sulfur gases into the stratosphere. In addition, the oxygen anomaly D17O reflects the oxidation of oxygen atoms from SO2 to sulfate in the atmosphere, which is another constraint on tropospheric/stratospheric volcanism.
In Gautier et al. (2018 Nature Comm.), a novel 2600-year history of stratospheric volcanic episodes based on these isotopic techniques was demonstrated using five ice cores from Dome C, Antarctica. To discover stratospheric volcanisms in different ice core sites and sulfate peaks, subsequent investigations also applied D33S measurements by the MC-ICP-MS method, which requires much smaller sample volumes. In the talk, I will provide an overview of these isotope approaches and their latest applications, as well as a discussion of the relationship between volcanism and the surface environment.