02 Dec 2021

02 Dec 2021

Review status: this preprint is currently under review for the journal CP.

The 852/3 CE Mount Churchill eruption: examining the potential climatic and societal impacts and the timing of the Medieval Climate Anomaly in the North Atlantic Region

Helen Mackay1, Gill Plunkett2, Britta Jensen3, Thomas Aubry4, Christophe Corona5,6, Woon Mi Kim7,8, Matthew Toohey9, Michael Sigl7,8, Markus Stoffel6,10,11, Kevin Anchukaitis12, Christoph Raible7,8, Matthew Bolton3, Joesph Manning13, Timothy Newfield14,15, Nicola Di Cosmo16, Francis Ludlow17, Conor Kostick17, Zhen Yang17, Lisa Coyle McClung2, Matthew Amesbury18, Alistair Monteath3, Paul Hughes19, Pete Langdon19, Dan Charman18, Robert Booth20, Kimberley Davies21, Antony Blundell22, and Graeme Swindles23 Helen Mackay et al.
  • 1Department of Geography, Durham University, Durham, DH1 3LE, UK
  • 2Archaeology & Palaeoecology, School of Natural and Built Environment, Queen’s University Belfast, Belfast, BT7 1NN, UK
  • 3Earth and Atmospheric Sciences, Faculty of Science, University of Alberta, Edmonton, Alberta, T6G 2E3, Canada
  • 4Department of Geography, University of Cambridge, UK; Sidney Sussex College, Cambridge, CB2 3HU, UK
  • 5Université Clermont-Auvergne, Geolab UMR 6042 CNRS, France
  • 6Institute for Environmental Sciences, University of Geneva, CH-1205 Geneva, Switzerland
  • 7Climate and Environmental Physics, Physics Institute, University of Bern, Bern, CH-3012, Switzerland
  • 8Oeschger Centre for Climate Change Research, University of Bern, Bern, CH-3012, Switzerland
  • 9Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, S7N 5E2, Canada
  • 10Department of Earth Sciences, University of Geneva, CH-1205 Geneva, Switzerland
  • 11Department F.-A. Forel for Environmental and Aquatic Sciences, University of Geneva, CH-1205 Geneva, Switzerland
  • 12School of Geography, Development, and Environment and Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ 85721 USA
  • 13Department of History, Yale University, New Haven, 06520, USA
  • 14Department of History, Georgetown University, Washington, 20057, USA (TN)
  • 15Department of Biology, Georgetown University, Washington, 20057, USA (TN)
  • 16Institute for Advanced Study, Princeton, New Jersey, 08540, USA
  • 17Department of History, and Trinity Centre for Environmental Humanities, Trinity College Dublin, Dublin, D02 PN40, Ireland
  • 18Geography, College of Life and Environmental Sciences, University of Exeter, EX4 4ST, UK
  • 19School of Geography and Environmental Science, University of Southampton, SO17 1BJ, UK
  • 20Earth and Environmental Science Department, Lehigh University, Pennsylvania, 18015, USA
  • 21Institute for Modelling Socio-Environmental Transitions, Bournemouth University, Bournemouth, BH12 5BB, UK
  • 22School of Geography, University of Leeds, Leeds, LS2 9JT, UK
  • 23Geography, School of Natural and Built Environment, Queen’s University Belfast, Belfast, BT7 1NN, UK

Abstract. The 852/3 CE eruption of Mount Churchill, Alaska, was one of the largest first millennium volcanic events, with a magnitude of 6.7 (VEI 6) and a tephra volume of 39.4–61.9 km3 (95 % confidence). The spatial extent of the ash fallout from this event is considerable and the cryptotephra (White River Ash east; WRAe) extends as far as Finland and Poland. Proximal ecosystem and societal disturbances have been linked with this eruption; however, wider eruption impacts on climate and society are unknown. Greenland ice-core records show that the eruption occurred in winter 852/3 ± 1 CE and that the eruption is associated with a relatively moderate sulfate aerosol loading, but large abundances of volcanic ash and chlorine. Here we assess the potential broader impact of this eruption using palaeoenvironmental reconstructions, historical records and climate model simulations. We also use the fortuitous timing of the 852/3 CE Churchill eruption and its extensively widespread tephra deposition of the White River Ash (east) (WRAe) to examine the climatic expression of the warm Medieval Climate Anomaly period (MCA; ca. 950–1250 CE) from precisely linked peatlands in the North Atlantic region.

The reconstructed climate forcing potential of 852/3 CE Churchill eruption is moderate compared with the eruption magnitude, but tree-ring-inferred temperatures report a significant atmospheric cooling of 0.8 °C in summer 853 CE. Modelled climate scenarios also show a cooling in 853 CE, although the average magnitude of cooling is smaller (0.3 °C). The simulated spatial patterns of cooling are generally similar to those generated using the tree-ring-inferred temperature reconstructions. Tree-ring inferred cooling begins prior to the date of the eruption suggesting that natural internal climate variability may have increased the climate system’s susceptibility to further cooling. The magnitude of the reconstructed cooling could also suggest that the climate forcing potential of this eruption may be underestimated, thereby highlighting the need for greater insight into, and consideration of, the role of halogens and volcanic ash when estimating eruption climate forcing potential.

Precise comparisons of palaeoenvironmental records from peatlands across North America and Europe, facilitated by the presence of the WRAe isochron, reveal no consistent MCA signal. These findings contribute to the growing body of evidence that characterizes the MCA hydroclimate as time-transgressive and heterogeneous, rather than a well-defined climatic period. The presence of the WRAe isochron also demonstrates that no long-term (multidecadal) climatic or societal impacts from the 852/3 CE Churchill eruption were identified beyond areas proximal to the eruption. Historical evidence in Europe for subsistence crises demonstrate a degree of temporal correspondence on interannual timescales, but similar events were reported outside of the eruption period and were common in the 9th century. The 852/3 CE Churchill eruption exemplifies the difficulties of identifying and confirming volcanic impacts for a single eruption, even when it is precisely dated.

Helen Mackay et al.

Status: open (until 17 Feb 2022)

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  • RC1: 'Comment on cp-2021-170', Mukund Palat Rao, 20 Jan 2022 reply

Helen Mackay et al.

Helen Mackay et al.


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Short summary
We assess the climatic and societal impact of the 852/3 CE Alaska Mount Churchill eruption using environmental reconstructions, historical records and climate simulations. The eruption is associated with significant northern hemisphere summer cooling, despite having only a moderate sulfate-based climate forcing potential; however, evidence of a widespread societal reponse is lacking. We discuss the difficulties of confirming volcanic impacts of a single eruption, even when it is precisely dated.