@article{9a81c3011eec49039f615d5a4c0cb737,
title = "Solar Activity of the Past 100 Years Inferred From 10Be in Ice Cores—Implications for Long-Term Solar Activity Reconstructions",
abstract = "Differences between 10Be records from Greenland and Antarctica over the last 100 years have led to different conclusions about past changes in solar activity. The reasons for this disagreement remain unresolved. We analyze a seasonally resolved 10Be record from a firn core (North Greenland Eemian Ice Drilling [NEEM] ice core project) in Northwestern Greenland for 1887–2002. By comparing the NEEM data to 10Be data from the NGRIP and Dye3 ice cores, we find that the Dye3 data after 1958 are significantly lower. These low values lead to a normalization problem in solar reconstructions when connecting 10Be variations to modern observations. Excluding these data strongly reduces the differences between solar reconstructions over the last 2,000 years based on Greenland and Antarctic 10Be data. Furthermore, 10Be records from polar regions and group sunspot numbers do not support a substantial increase in solar activity for the 1937–1950 period as proposed by previous extensions of the neutron monitor data.",
keywords = "Dye3, NEEM, ice core, neutron monitor data, seasonally resolved Be, solar reconstructions",
author = "Minjie Zheng and Florian Adolphi and Jesper Sjolte and Ala Aldahan and G{\"o}ran Possnert and Mousong Wu and Peng Chen and Raimund Muscheler",
note = "Funding Information: Minjie Zheng is supported by the China Scholarship Council (CSC) under grant CSC no. 201606710087 (grant to Minjie Zheng) and the Royal Physiographic Society of Lund (2016, 2017, and 2018, grants to Minjie Zheng). This work was partially supported by the Swedish Research Council (Dnr: 2013–8421, grant to Raimund Muscheler). Florian Adolphi is supported by a grant of the Swedish Research Council (Dnr: 2016–00218). Jesper Sjolte is supported by the strategic research program of ModEling the Regional and Global Earth system (MERGE) hosted by the Faculty of Science at Lund University. Ala Aldahan acknowledges the UAEU through the UPAR funding. Mousong Wu is supported by the National Key Research and Development Program of China (2016YFA0600204), the National Natural Science Foundation of China (41901266), and the Natural Science Foundation of Jiangsu Province (BK20190317). The authors thank the many persons involved in logistics, drilling, and ice‐core processing and analysis. NEEM is directed and organized by the Center of Ice and Climate at the Niels Bohr Institute and US NSF, Office of Polar Programs. It is supported by funding agencies and institutions in Belgium (FNRS‐CFB and FWO), Canada (NRCan/GSC), China (CAS), Denmark (FIST), France (IPEV, CNRS/INSU, CEA and ANR), Germany (AWI), Iceland (RannIs), Japan (NIPR), South Korea (KOPRI), The Netherlands (NWO/ALW), Sweden (VR), Switzerland (SNF), the United Kingdom (NERC), and the USA (US NSF, Office of Polar Programs) and the EU Seventh Framework programs Past4Future and Water under the Ice. Funding Information: Minjie Zheng is supported by the China Scholarship Council (CSC) under grant CSC no. 201606710087 (grant to Minjie Zheng) and the Royal Physiographic Society of Lund (2016, 2017, and 2018, grants to Minjie Zheng). This work was partially supported by the Swedish Research Council (Dnr: 2013?8421, grant to Raimund Muscheler). Florian Adolphi is supported by a grant of the Swedish Research Council (Dnr: 2016?00218). Jesper Sjolte is supported by the strategic research program of ModEling the Regional and Global Earth system (MERGE) hosted by the Faculty of Science at Lund University. Ala Aldahan acknowledges the UAEU through the UPAR funding. Mousong Wu is supported by the National Key Research and Development Program of China (2016YFA0600204), the National Natural Science Foundation of China (41901266), and the Natural Science Foundation of Jiangsu Province (BK20190317). The authors thank the many persons involved in logistics, drilling, and ice-core processing and analysis. NEEM is directed and organized by the Center of Ice and Climate at the Niels Bohr Institute and US NSF, Office of Polar Programs. It is supported by funding agencies and institutions in Belgium (FNRS-CFB and FWO), Canada (NRCan/GSC), China (CAS), Denmark (FIST), France (IPEV, CNRS/INSU, CEA and ANR), Germany (AWI), Iceland (RannIs), Japan (NIPR), South Korea (KOPRI), The Netherlands (NWO/ALW), Sweden (VR), Switzerland (SNF), the United Kingdom (NERC), and the USA (US NSF, Office of Polar Programs) and the EU Seventh Framework programs Past4Future and Water under the Ice. Publisher Copyright: {\textcopyright} 2021. The Authors.",
year = "2021",
month = feb,
day = "28",
doi = "10.1029/2020GL090896",
language = "English",
volume = "48",
journal = "Geophysical Research Letters",
issn = "0094-8276",
publisher = "American Geophysical Union",
number = "4",
}