Modeling the Transport and Deposition of <sup>10</sup>Be Produced by the Strongest Solar Proton Event During the Holocene
Tobias Spiegl, Shigeo Yoden, Ulrike Langematz, Tatsuhiko Sato, Rattana Chhin, S. Noda, Fusa Miyake, K. Kusano, K. Schaar, Markus Kunze
Abstract
Abstract Prominent excursions in the number of cosmogenic nuclides (e.g., 10 Be) around 774 CE/775 document the most severe solar proton event (SPE) throughout the Holocene. Its manifestation in ice cores is valuable for geochronology, but also for solar‐terrestrial physics and climate modeling. Using the ECHAM/MESSy Atmospheric Chemistry (EMAC) climate model in combination with the Warning System for Aviation Exposure to SEP (WASAVIES), we investigate the transport, mixing, and deposition of the cosmogenic nuclide 10 Be produced by the 774 CE/775 SPE. By comparing the model results to the reconstructed 10 Be time series from four ice core records, we study the atmospheric pathways of 10 Be from its stratospheric source to its sink at Earth's surface. The reconstructed post‐SPE evolution of the 10 Be surface fluxes at the ice core sites is well captured by the model. The downward transport of the 10 Be atoms is controlled by the Brewer‐Dobson circulation in the stratosphere and cross‐tropopause transport via tropopause folds or large‐scale sinking. Clear hemispheric differences in the transport and deposition processes are identified. In both polar regions the 10 Be surface fluxes peak in summertime, with a larger influence of wet deposition on the seasonal 10 Be surface flux in Greenland than in Antarctica. Differences in the peak 10 Be surface flux following the 774 CE/775 SPE at the drilling sites are explained by specific meteorological conditions depending on the geographic locations of the sites.