Session: Last Millennium & Past2K
Author: Chi-Ju Wu / email@example.com / Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany
Co-author: Ilya Usoskin, Space Climate Research Unit, University of Oulu, Finland;
Natalie Krivova, Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany;
Gennady Kovaltsov, Ioffe Physical-Technical Institute, 194021 St. Petersburg, Russia;
The Sun is the main external energy source to the Earth's system. The overall energy input and its spectral distribution are described by the total and spectral solar irradiance, respectively. The irradiance has only been measured directly for the last four decades, and thus models need to be used to reconstruct the past changes. Such models require an input proxy of solar magnetic activity. The directly observed sunspot number goes back to 1610 and covers the Maunder Minimum. To go further back in time one has to rely on indirect proxies, such as concentrations of cosmogenic isotopes 10Be or 14C in terrestrial archives. These isotopes are produced in the atmosphere by cosmic rays, whose flux is modulated by the solar magnetic field. Although the cosmogenic isotope series retrieved from the natural archives around the globe show a high degree of similarity due to their common origin, significant deviations over some periods of time can be observed due to, e.g., their differing geochemical paths in the atmosphere or local conditions. We will present the most recent total and spectral irradiance reconstruction based on a new method of consistent analysis of multi-isotope proxy series covering the last 9000 years. The record reveals the global and robust nature of solar variability in the past.