Tree rings reveal globally coherent signature of cosmogenic radiocarbon events in 774 and 993 CE.

ABSTRACT: Though tree-ring chronologies are annually resolved, their dating has never been independently validated at the global scale. Moreover, it is unknown if atmospheric radiocarbon enrichment events of cosmogenic origin leave spatiotemporally consistent fingerprints. Here we measure the ¹⁴C content in 484 individual tree rings formed in the periods 770-780 and 990-1000 CE. Distinct ¹⁴C excursions starting in the boreal summer of 774 and the boreal spring of 993 ensure the precise dating of 44 tree-ring records from five continents. We also identify a meridional decline of 11-year mean atmospheric radiocarbon concentrations across both hemispheres. Corroborated by historical eye-witness accounts of red auroras, our results suggest a global exposure to strong solar proton r

SUBMITTER: Buntgen U 

PROVIDER: S-EPMC6127282 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature