Modeling Atmospheric Transport of Cosmogenic Radionuclide 10Be Using GEOS‐Chem 14.1.1 and ECHAM6.3‐HAM2.3: Implications for Solar and Geomagnetic Reconstructions.

A prerequisite to applying 10Be in natural archives for solar and geomagnetic reconstructions is to know how 10Be deposition reflects atmospheric production changes. However, this relationship remains debated. To address this, we use two state‐of‐the‐art global models GEOS‐Chem and ECHAM6.3‐HAM2.3 with the latest beryllium production model. During solar modulation, both models suggest that 10Be deposition reacts proportionally to global production changes, with minor latitudinal deposition biases (<5%). During geomagnetic modulation, however, 10Be deposition changes are enhanced by ∼15% in the tropics and attenuated by 20%–35% in subtropical and polar regions compared to global production changes. Such changes are also hemispherically asymmetric, attributed to asymmetric production between hemispheres. For the solar proton event in 774/5 CE, 10Be shows a 15% higher deposition increase in polar regions than in tropics. This study highlights the importance of atmospheric mixing when comparing 10Be from different locations or to independent geomagnetic field records. Plain Language Summary: The cosmogenic radionuclide beryllium‐10 (10Be) deposition in natural archives can be used to reconstruct solar and geomagnetic changes in the past. Understanding how 10Be deposition reflects atmospheric production rate changes is crucial for these applications. However, this relationship remains debated. To address this issue, we use two state‐of‐the‐art global models, GEOS‐Chem 14.1.1 and ECHAM6.3‐HAM2.3, along with the latest beryllium production model (CRAC: Be). When responding to solar modulation, both models indicate that 10Be deposition corresponds proportionally to global production rate changes, with a minor latitudinal bias. However, during geomagnetic modulation, 10Be deposition changes significantly compared to global production rate changes. 10Be deposition also shows varying hemispheric responses to geomagnetic modulation, attributed to the asymmetric production between hemispheres. For the extreme solar proton event in 774/5 CE, 10Be shows a higher deposition flux increase in the polar regions compared to the tropics. These findings underscore the need to account for atmospheric mixing on 10Be deposition from different locations, especially for the changes due to the geomagnetic field variations. Key Points: We used two state‐of‐the‐art global models incorporating the latest beryllium production rates to study the sources of 10Be deposition10Be deposition shows strong regional bias compared to the global signal in response to geomagnetic modulation but not to solar modulation10Be deposition shows varying hemispheric responses to geomagnetic modulation, attributed to the asymmetric production between hemispheres [ABSTRACT FROM AUTHOR]