AEON

Climate ModellingAEON

Overview

Volcanic activity and solar variability are the most important natural climate forcings and were the dominant drivers of climate variability in the pre-industrial era. Nowadays, they still play an important but poorly quantified role in the atmosphere and climate behaviour (e.g. IPCC, 2021). Part of the solar variability is manifested through the abrupt emission of solar energetic particles, which affect the atmosphere and can also be hazardous for modern technology. The sporadic nature of both the volcanic eruptions and the solar particle events, and the absence of very strong events already for several decades also makes their potential appearance in the near future more likely. The potential for extremely powerful events can be estimated from the ice core data. However, interpretation of this data is currently complicated because of the incomplete understanding of atmospheric transport and deposition from the atmosphere to ice sheets and potential effects of volcanic aerosols on the transport of cosmogenic nuclides such as Beryllium-10 (10Be) and Chlorine-36 (36Cl). Further progress in this area can only be achieved in a synergistic way by combining the expertise in both the modelling of atmospheric effects of such events and interpretation  of the radionuclides  measurements in ice cores.

Introduction

Volcanic eruptions and extreme solar proton events (SPEs) contribute significantly to variability in the chemical composition and dynamics of the stratosphere, which in turn can affect vertical coupling between the stratosphere and troposphere. Our knowledge of past solar and volcanic events is based on the interpretation of ice core records of the cosmogenic nuclides 10Be and 36Cl, and sulphate, respectively. The 10Be signal is a proxy for past solar activity but it is also affected by stratospheric volcanic eruptions. The 36Cl/10Be ratio is used for reconstructions of SPE energy spectra, however out of these solar events, the ratio differs significantly from theoretical atmospheric production models probably because of different modes of transport, deposition, and post-deposition effects on 10Be and 36Cl. The 36Cl/10Be ratio must therefore be studied/modelled individually for each volcanic or solar event and for a given site. Our project aims at improving our understanding of the 36Cl/10Be as a proxy for past extreme SPEs as well as to characterise the effects of stratospheric volcanic eruptions and SPEs on the atmospheric composition and dynamics.

Figure 1. What links solar and volcanic eruptions? Click to enlarge.

The main planned activities of the project are to:

  • Characterise and clarify the effects of the stratosphere, the downward transport and tropospheric circulation of strong volcanic and solar particle events of the past;
  • Model the production, transport, and deposition of 10Be, 36Cl, and sulphate aerosols;
  • Analyse the modelled 10Be, 36Cl, and sulphate deposition with respect to ice core measurements;
  • Clarify the role of volcanic aerosols in modulation of the 10Be transport;
  • Produce new 10Be and 36Cl ice core data around known SPEs or candidates for SPEs, as well as perform new ones to search for new SPEs between 0 CE and 1000 CE.

These activities will be performed within two main interrelated work packages (WP). In WP1, the aerosol-chemistry-climate model SOCOLv4 will be improved and used to characterise the atmospheric effects of volcanic events and their impact on the deposition of 10Be, 36Cl, and sulphate. SPEs and GCR will be better described in the model, by using the revised spectra from the recent publications and from WP2. In WP2, new 10Be and 36Cl data will be produced from the Talos Dome ice core (Antarctica) at the time of several known SPEs and new SPEs will be looked for between 0 CE and 1000 CE. Based on the modelling efforts of WP1 and new ice core data obtained in WP2, energy spectra of SPEs will be revisited. Similarly to volcanic events, the atmospheric effects of several SPEs will be modelled and analysed.

 Model

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Figure 2.

References

References
For further information please contact: Dr. T. Sukhodolov