Dataset Information

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 radiation. To improve understanding of the return frequency and intensity of past cosmic events, which is particularly important for assessing the potential threat of space weather on our society, further annually resolved ¹⁴C measurements are needed.

SUBMITTER: Buntgen U

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

REPOSITORIES: biostudies-literature

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

Büntgen Ulf U Wacker Lukas L Galván J Diego JD Arnold Stephanie S Arseneault Dominique D Baillie Michael M Beer Jürg J Bernabei Mauro M Bleicher Niels N Boswijk Gretel G Bräuning Achim A Carrer Marco M Ljungqvist Fredrik Charpentier FC Cherubini Paolo P Christl Marcus M Christie Duncan A DA Clark Peter W PW Cook Edward R ER D'Arrigo Rosanne R Davi Nicole N Eggertsson Ólafur Ó Esper Jan J Fowler Anthony M AM Gedalof Ze'ev Z Gennaretti Fabio F Grießinger Jussi J Grissino-Mayer Henri H Grudd Håkan H Gunnarson Björn E BE Hantemirov Rashit R Herzig Franz F Hessl Amy A Heussner Karl-Uwe KU Jull A J Timothy AJT Kukarskih Vladimir V Kirdyanov Alexander A Kolář Tomáš T Krusic Paul J PJ Kyncl Tomáš T Lara Antonio A LeQuesne Carlos C Linderholm Hans W HW Loader Neil J NJ Luckman Brian B Miyake Fusa F Myglan Vladimir S VS Nicolussi Kurt K Oppenheimer Clive C Palmer Jonathan J Panyushkina Irina I Pederson Neil N Rybníček Michal M Schweingruber Fritz H FH Seim Andrea A Sigl Michael M Churakova Sidorova Olga O Speer James H JH Synal Hans-Arno HA Tegel Willy W Treydte Kerstin K Villalba Ricardo R Wiles Greg G Wilson Rob R Winship Lawrence J LJ Wunder Jan J Yang Bao B Young Giles H F GHF

Nature communications 20180906 1

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 <sup>14</sup>C content in 484 individual tree rings formed in the periods 770-780 and 990-1000 CE. Distinct <sup>14</sup>C excursions starting in the boreal summer of 774 and the boreal spring of 993 ensure the preci ...[more]

PMID: 30190505

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Project description:Climate predictions for the Mediterranean Basin include increased temperatures, decreased precipitation, and increased frequency of extreme climatic events (ECE). These conditions are associated with decreased tree growth and increased vulnerability to pests and diseases. The anatomy of tree rings responds to these environmental conditions. Quantitatively, the width of a tree ring is largely determined by the rate and duration of cell division by the vascular cambium. In the Mediterranean climate, this division may occur throughout almost the entire year. Alternatively, cell division may cease during relatively cool and dry winters, only to resume in the same calendar year with milder temperatures and increased availability of water. Under particularly adverse conditions, no xylem may be produced in parts of the stem, resulting in a missing ring (MR). A dendrochronological network of Pinus halepensis was used to determine the relationship of MR to ECE. The network consisted of 113 sites, 1,509 trees, 2,593 cores, and 225,428 tree rings throughout the distribution range of the species. A total of 4,150 MR were identified. Binomial logistic regression analysis determined that MR frequency increased with increased cambial age. Spatial analysis indicated that the geographic areas of south-eastern Spain and northern Algeria contained the greatest frequency of MR. Dendroclimatic regression analysis indicated a non-linear relationship of MR to total monthly precipitation and mean temperature. MR are strongly associated with the combination of monthly mean temperature from previous October till current February and total precipitation from previous September till current May. They are likely to occur with total precipitation lower than 50 mm and temperatures higher than 5°C. This conclusion is global and can be applied to every site across the distribution area. Rather than simply being a complication for dendrochronology, MR formation is a fundamental response of trees to adverse environmental conditions. The demonstrated relationship of MR formation to ECE across this dendrochronological network in the Mediterranean basin shows the potential of MR analysis to reconstruct the history of past climatic extremes and to predict future forest dynamics in a changing climate.

Dataset Information

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

Publications

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

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