AEON (ANR - PRCI)

Volcanic eruptions and extreme solar events (or Solar Proton Events (SPE)) contribute significantly to the variability of the chemical composition and dynamics of the stratosphere, which in turn can affect the vertical coupling between the stratosphere and the troposphere. Our knowledge of past solar and volcanic events is based on the interpretation of records in ice cores, cosmogenic nuclides of beryllium-10 (¹⁰Be) and chlorine-36 (³⁶Cl), and sulphate, respectively.

The ¹⁰Be is an indicator of past solar activity, but is greatly affected by stratospheric volcanic eruptions. The report ³⁶Cl/¹⁰Be is used to reconstruct the energy spectra of SPEs, but outside these solar events, the ratio differs significantly from the predictions of theoretical production models, probably because of the transport, deposition and post-deposition effects of the ¹⁰Be and ³⁶Cl, different. The ratio ³⁶Cl/¹⁰Be must therefore be studied/modelled individually for each volcanic or solar event and for a given study site. The AEON project is based on a data-model approach, using high-precision measurements of cosmogenic nuclides and the SOCOLv4 aerosol-climate model. The objectives are 1- to obtain new data on ¹⁰Be and ³⁶Cl from the Talos Dome ice core (Antarctica) around known SPEs and to search for new SPEs between 0 and 1000CE 2- improve our understanding of isotope ratios ³⁶Cl/¹⁰Be to determine the energy spectrum of SPEs and thus improve reconstructions of past solar activity 3- clarify the role of volcanic aerosols in the transport and deposition of ¹⁰Be 4- to characterise the effects of past volcanic eruptions and SPEs on the stratosphere, stratosphere/troposphere exchanges and tropospheric dynamics.