Discrepancy between long-term trends of the 10Be- and 14C-inferred radionuclide production rate: Likely reasons and implications

• Applicant: Professorin Dr. Ingeborg Levin
• Subject Area: Atmospheric Science
• Term: from 2010 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 162014675

The atmospheric production rate of cosmogenic radionuclides depends on the variable shielding effects of cosmic rays by the solar activity and the geomagnetic field intensity. The history of these production rate changes can be basically inferred from 14C tree ring/sediment records as well as from 10Be archived in polar ice cores. However, while both reconstruction efforts agree fairly well in view of their decadal to centennial variability, they systematically deviate, for unknown reasons, on the millennia time scale, particularly in the early Holocene and late Glacial. The project aims at pinning down the main reasons for this apparent inconsistency by combining a global carbon cycle model with an atmospheric 10Be cycle model, supported by an air/firn transfer module. This innovative attempt comprises the extension of an existing carbon cycle box model to the simulation of aerosol-borne radionuclides, backed up by novel 10Be and 7Be aerosol data as well as dedicated sensitivity studies. Thereby, the various impacts of non-production related changes on the 14C and 10Be archive data shall be investigated, focussing on possible long term changes, related to the carbon and to the atmospheric 10Be cycles. Final evaluation of the results aims at depicting realistic scenarios, which allow to reduce the reconstruction mismatch, and thus, to improve the understanding of past cosmogenic production rate changes.

• DFG Programme: Research Grants
• Participating Person: Dr. Dietmar Wagenbach (†)