The origin of tree-ring reconstructed summer cooling in Northern Europe during the 18th century eruption of Laki

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Julie Edwards, Kevin Anchukaitis, Björn Gunnarson, Charlotte Pearson, Kristina Seftigen, Georg von Arx, Hans Linderholm


Basaltic fissure eruptions, which are characteristic of Icelandic volcanism, are extremely hazardous due to the large quantities of gases and aerosols they release into the atmosphere. The 1783 --1784 CE Laki eruption was one of the most significant high-latitude eruptions in the last millennium and had substantial environmental and climatic impacts. Contemporary observations recorded the presence of a sulfuric haze over Iceland and Europe, which caused famine from vegetation damage and resulted in a high occurrence of respiratory illnesses and related mortality. Historical records in northern Europe show that the summer of 1783 was anomalously warm, but regional tree-ring maximum latewood density (MXD) data from that year are low and lead to erroneously colder reconstructed summer temperatures. Here we measure wood anatomical characteristics of Scots pine (Pinus sylvestris) from Jämtland, Sweden in order to identify the cause of this discrepancy. We show that the presence of intra-annual density fluctuations in the majority of 1783 growth rings, a sudden reduction in lumen and cell wall area, and the measurement resolution of traditional x-ray densitometry lead to the observed reduced annual MXD value. Multiple independent lines of evidence suggest these anatomical anomalies were most likely the result of direct acidic damage to trees in Northern Europe. The common relationship between summer temperature and MXD can be disrupted by acidic haze damage to trees. Our study also demonstrates that quantitative wood anatomy offers a high resolution approach to identifying anomalous years and extreme events in the tree-ring record.



Physical Sciences and Mathematics



Published: 2021-11-09 08:40

Last Updated: 2021-11-09 16:40


CC BY Attribution 4.0 International

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