CHANGES IN SOLAR ACTIVITY DURING THE WOLF MINIMUM—NEW INSIGHTS FROM A HIGH-RESOLUTION 14C RECORD BASED ON DANISH OAK. Issue 1 (4th February 2021)

• Record Type: Journal Article
• Authors: Fogtmann-Schulz, Alexandra; Baittinger, Claudia; Karoff, Christoffer; Olsen, Jesper; Knudsen, Mads F
• Is Part Of: Radiocarbon. Volume 63:Issue 1(2021)
• Page Start: 91
• Page End: 104
• Publication Date: 2021-02-04
• Subjects: AMS dating, -- carbon, -- dating, -- radiocarbon, -- radiocarbon AMS dating; Radiocarbon dating -- Periodicals; 930.1028505
• DOI: 10.1017/RDC.2020.126
• Languages: English
• ISSNs: 0033-8222

Abstract

ABSTRACT: We present a new biennial record of radiocarbon ( 14 C) measured in Danish oak. The new record covers the years 1251–1378 CE, thereby spanning the Grand Solar Minimum known as the Wolf Minimum. Two oak samples from every other year were measured at the AMS facility at Aarhus University (Denmark), resulting in an average precision of 1.4‰ for the record. Spectral analysis of the new record revealed two peaks at 27 and 9.1 years, which could indicate the Hale cycle was lengthened and the Schwabe cycle shortened during the Wolf Minimum, but it is also possible that the amplitude of the Schwabe cycle was too small to be accurately identified with the acquired precision of this record. The record was bandpass filtered to investigate the variability of the amplitude in different bands, which showed a dampening of the amplitude during the second half of the Wolf Minimum in bands centered on the Schwabe and the Hale cycle, respectively. A reconstruction of the solar modulation function, Φ, also showed a periodicity of ca. 9 years, and indicated that the Wolf Minimum was preceeded by one cycle of decreased solar activity.