C03_06

On Proposed New Single-Year Radiocarbon Production Events and the Limits of Event Detectability

Scifo A¹, Abi Nassif T¹, Zhang Q², Sharma U², Bayliss A⁴, Marshall P⁴, Pope B^2,3, Dee M¹

¹Centre For Isotope Research (CIO), University of Groningen, Groningen, the Netherlands, ²School of Mathematics and Physics, The University of Queensland, St Lucia, Australia, ³Centre for Astrophysics, University of Southern Queensland, Toowoomba, Australia, ⁴Historic England, London, United Kingdom

Over the last decade, the field of radiocarbon analysis has been revolutionised by the discovery of single-year production anomalies, sometimes called Miyake events, as they are both indicators of extreme space weather phenomena, and useful as anchors for exact-year dating. Brehm et al. (2021) proposed two new candidate events in the years 1052 and 1279 CE. Their data showed annual ∆¹⁴C increases over these years of 5.9‰ and 6.5‰, respectively. We have also recently analysed dendrochronologically dated samples spanning these two periods of time, from Furness Abbey and Apethorpe Church, England. Our results, although statistically consistent (at 2σ) with those presented by Brehm et al. (2021), show much less obvious increases of around 4.5‰ and 3‰, respectively. Furthermore, we have also modelled our new datasets, as well as those of Brehm et al. (2021), in ticktack, the first open-source Python package that connects box models of the carbon cycle with modern Bayesian inference tools (Zhang et al., forthcoming). The radiocarbon production rates we obtain pose questions about the actuality of cosmic ray events at these times, and the limits of detectability of such phenomena more generally.

Brehm et al. (2021). Eleven-year solar cycles over the last millennium revealed by radiocarbon in tree rings. Nature Geoscience 14: 10–15.

Zhang et al. (forthcoming). Bayesian inference of radiocarbon production from tree-ring data.