Linked to major volcanic eruptions around 536 and 540 CE, the onset of the Late Antique Little Ice Age has been described as the coldest period of the past two millennia. The exact timing and spatial extent of this exceptional cold phase are, however, still under debate because of the limited resolution and geographical distribution of the available proxy archives. Here, we use 106 wood anatomical thin sections from 23 forest sites and 20 tree species in both hemispheres to search for cell-level fingerprints of ephemeral summer cooling between 530 and 550 CE. After cross-dating and double-staining, we identified 89 Blue Rings (lack of cell wall lignification), nine Frost Rings (cell deformation and collapse), and 93 Light Rings (reduced cell wall thickening) in the Northern Hemisphere. Our network reveals evidence for the strongest temperature depression between mid-July and early-August 536 CE across North America and Eurasia, whereas more localised cold spells occurred in the summers of 532, 540-43, and 548 CE. The lack of anatomical signatures in the austral trees suggests limited incursion of stratospheric volcanic aerosol into the Southern Hemisphere extra-tropics, that any forcing was mitigated by atmosphere-ocean dynamical responses and/or concentrated outside the growing season, or a combination of factors. Our findings demonstrate the advantage of wood anatomical investigations over traditional dendrochronological measurements, provide a benchmark for Earth system models, support cross-disciplinary studies into the entanglements of climate and history, and question the relevance of global climate averages.

Archaeology and Palaeoecology School of Natural and Built Environment Queen's University Belfast Belfast BT7 1NN UK

Change Impacts and Risks in the Anthropocene Institute for Environmental Sciences University of Geneva Geneva 1205 Switzerland; Department of Earth Sciences University of Geneva Geneva 1205 Switzerland; Department F A Forel for Environmental and Aquatic Sciences University of Geneva Geneva 1205 Switzerland

CNR IBE Institute of BioEconomy National Research Council Trento 38121 Italy

Department of Biology Chemistry and Geography University of Quebec in Rimouski Rimouski Qc G5L 3A1 Canada

Department of Earth Sciences the College of Wooster Wooster OH 44691 USA

Department of Geography Johannes Gutenberg University Mainz 55099 Germany

Department of Geography University of Cambridge Cambridge CB2 3EN UK

Department of Geography University of Cambridge Cambridge CB2 3EN UK; Department of Physical Geography Bolin Centre for Climate Research Stockholm University Stockholm 10691 Sweden

Department of Geography University of Cambridge Cambridge CB2 3EN UK; Forest Biometrics Laboratory Faculty of Forestry Stefan cel Mare University of Suceava Suceava 720229 Romania

Department of Geography University of Cambridge Cambridge CB2 3EN UK; Swiss Federal Research Institute Brno 60300 Czech Republic; Department of Geography Faculty of Science Masaryk University Brno 61300 Czech Republic

Department of Geography University of Innsbruck Innsbruck 6020 Austria

Department of Geology State University of New York at Cortland Cortland NY 13045 USA

Department of History Stockholm University Stockholm 10691 Sweden; Bolin Centre for Climate Research Stockholm University Stockholm 10691 Sweden; Swedish Collegium for Advanced Study Uppsala 75238 Sweden

Department of Physical Geography Bolin Centre for Climate Research Stockholm University Stockholm 10691 Sweden

Global Change Research Centre Brno 60300 Czech Republic

Global Change Research Centre Brno 60300 Czech Republic; Department of Geography Johannes Gutenberg University Mainz 55099 Germany

Initiative for the Science of the Human Past Department of History Max Planck Harvard Research Center for the Archaeoscience of the Ancient Mediterranean Harvard University Cambridge MA 02138 USA

Institute of Ecology and Geography Siberian Federal University Krasnoyarsk 660041 Russia; Sukachev Institute of Forest SB RAS Krasnoyarsk 660036 Russia

Institute of Humanities Siberian Federal University Krasnoyarsk 660041 Russia

Institute of Plant and Animal Ecology Ural Branch Russian Academy of Sciences Yekaterinburg 620144 Russia; Ural Institute of Humanities Ural Federal University Yekaterinburg 620002 Russia

Key Laboratory of Desert and Desertification Northwest Institute of Eco Environment and Resources Chinese Academy of Sciences Lanzhou 730000 China

Key Laboratory of Desert and Desertification Northwest Institute of Eco Environment and Resources Chinese Academy of Sciences Lanzhou 730000 China; Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of Sciences Beijing 100101 China

Laboratorio de Dendrocronología y Cambio Global Universidad Austral de Chile Valdivia 509000 Chile

Laboratorio de Dendrocronología y Cambio Global Universidad Austral de Chile Valdivia 509000 Chile; Center for Climate and Resilience Research Punta Arenas 6200000 Chile

Laboratory of Tree Ring Research University of Arizona Tucson AZ 85721 USA

National Scientific and Technical Research Council Instituto Argentino de Nivología Glaciología y Ciencias Ambientales Mendoza CP 5500 Argentina

School of Environment The University of Auckland Auckland 1010 New Zealand

Swiss Federal Research Institute Birmensdorf 8903 Switzerland

Swiss Federal Research Institute Birmensdorf 8903 Switzerland; Institute of Ecology and Geography Siberian Federal University Krasnoyarsk 660041 Russia

The University of New South Wales Sydney NSW 2052 Australia

Tree Ring Laboratory Lamont Doherty Earth Observatory Columbia University Palisades NY 10964 USA

Tree Ring Laboratory Lamont Doherty Earth Observatory Columbia University Palisades NY 10964 USA; Department of Environmental Science William Paterson University Wayne NJ 07470 USA

Citace poskytuje Crossref.org

Highest Occurring Vascular Plants from Ladakh Provide Wood Anatomical Evidence for a Thermal Limitation of Cell Wall Lignification

Blue rings in trees and shrubs as indicators of early and late summer cooling events at the northern treeline

Reply to: Biogeographic implications of plant stature and microclimate in cold regions