Variations in Solar Activity Across the Spörer Minimum Based on Radiocarbon in Danish Oak

• Published in: Geophysical research letters 2019-08, Vol.46 (15), p.8617-8623
• Main Authors: Fogtmann‐Schulz, A., Kudsk, S. G. K., Trant, P. L. K., Baittinger, C., Karoff, C., Olsen, J., Knudsen, M. F.
• Format: Article
• Language: English
• Subjects: Beryllium 10; Carbon 14; Dendrochronology; grand solar minimum; Maunder Minimum; Minima; New records; radiocarbon; Radiocarbon dating; Solar activity; Solar minimum; solar variability; Spörer Minimum; tree rings; Variability
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2019GL083537

Several aspects concerning the origin and nature of grand solar minima remain unclear, and more high‐resolution 10Be and 14C records are needed to improve our understanding of these phenomena. Here, we report 137 new high‐precision, annually resolved radiocarbon concentrations based on oak from the Danish dendrochronology. The new record covers a period (CE 1432–1578) that encompasses most of the penultimate grand solar minima known as the Spörer Minimum. A detailed comparison between the Spörer and Maunder (CE 1640–1720) minima shows that the Spörer Minimum is associated with enhanced Δ14C variability in a band centered around the 11‐year Schwabe cycle from CE 1450 to 1479 and between CE 1545 and 1578, whereas little 11‐year variability is observed from CE 1479 to 1539. In contrast, we only observe enhanced 11‐year variability after the end of the Maunder Minimum at CE 1722–1744, which could indicate that the nature and origin of the two minima were different. Key Points This study presents the first European high‐precision annual radiocarbon record across the Spörer Minimum Band‐pass filtering shows periods of enhanced and dampened variability of the Schwabe cycle The new record confirms a flat, longer peak compared to the narrower and distinctly different peak associated with the Maunder Minimum