Synergy Between Radionuclide and Infrasound Observations and Atmospheric Transport Modelling Simulations: Case of Bogoslof

Abstract

To demonstrate a synergy between radionuclide (RN) and infrasound observations and Atmospheric Transport Modelling (ATM), the volcanic activity of Bogoslof in Alaska, USA, is used as an example. The study period covers 3 months of intense eruptive activity, from 19 December 2016 to 8 March 2017. During that period, the International Monitoring System (IMS) infrasound station located in Alaska, USA, recorded signals from three eruptive sequences. The second sequence was reported in the International Data Centre (IDC) Reviewed Event Bulletin (REB) with 3 infrasound stations: in Alaska, USA, in Kamchatka, Russian Federation and in Hawaii, USA. As reported by The Alaska Volcano Observatory (AVO), during each of these events ash plumes reaching the altitude of more than 10 km were observed for several consecutive days. These observations were used to identify the length of each eruptive episode. To demonstrate the influence of volcanic ash on the berillium-7 (Be-7) activity concentration values measured by two IMS RN stations in Alaska, the ATM was used. To monitor the arrival time of a volcanic ash plume at the IMS stations, a series of 14 days forward simulations released daily from Bogoslof during each of these events, was generated. Comparison of Be-7 daily surface values with the seasonal median for the period of 9 years (2009–2017), revealed that an influx of volcanic ash up to the tropopause (1.5–12 km) tends to locally increase surface Be-7 concentrations in area under the influence of subsiding ash plume. It is also demonstrated that with the arrival of volcanic ash at the surface level, the enrichment in radioactive particulates like uranium, thorium, and potassium was observed.