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

10Be 和 14C 推断的放射性核素生产率的长期趋势之间的差异：可能的原因和影响

• 批准号: 162014675
• 负责人: Professorin Dr. Ingeborg Levin
• 金额: --
• 依托单位: Institut für Umweltphysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2013-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/162014675?language=en
• 关键词: Discrepancy; between; long; term; trends

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.

宇宙放射性核素的大气产生率取决于太阳活动和地磁场强度对宇宙射线的可变屏蔽效应。这些生产率变化的历史基本上可以从 14C 树木年轮/沉积物记录以及极地冰芯中存档的 10Be 推断出来。然而，虽然这两项重建工作在十年到百年的变化方面相当一致，但由于未知的原因，它们在千年时间尺度上系统性地偏离，特别是在全新世早期和冰期晚期。该项目旨在通过将全球碳循环模型与大气 10Be 循环模型相结合，并在空气/空气传输模块的支持下，查明这种明显不一致的主要原因。这项创新尝试包括将现有的碳循环箱模型扩展到气溶胶中的放射性核素的模拟，并得到新型 10Be 和 7Be 气溶胶数据以及专门的敏感性研究的支持。因此，应调查非生产相关变化对 14C 和 10Be 档案数据的各种影响，重点关注与碳和大气 10Be 循环相关的可能的长期变化。结果的最终评估旨在描绘现实场景，从而减少重建失配，从而提高对过去宇宙生成速率变化的理解。