Extreme climate after massive eruption of Alaska's Okmok volcano in 43 BCE and effects on the late Roman Republic and Ptolemaic Kingdom

• Published in: Proceedings of the National Academy of Sciences
• Main Authors: McConnell, Joseph R., Sigl, Michael, Plunkett, Gill, Burke, Andrea, Kim, Woon Mi, Raible, Christoph C., Wilson, Andrew I., Manning, Joseph G., Ludlow, Francis, Chellman, Nathan J., Innes, Helen M., Yang, Zhen, Larsen, Jessica F., Schaefer, Janet R., Kipfstuhl, Sepp, Mojtabavi, Seyedhamidreza, Wilhelms, Frank, Opel, Thomas, Meyer, Hanno, Steffensen, Jørgen Peder
• Other Authors: European Commission, University of St Andrews. School of Earth & Environmental Sciences, University of St Andrews. St Andrews Isotope Geochemistry
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2020
• Subjects: Ice core; Volcano; Okmok; Rome; Climate forcing; GE Environmental Sciences; DAS; SDG 13 - Climate Action; GE; Arctic; Shackleton; ice core; Alaska
• Online Access: http://hdl.handle.net/10023/21184; https://doi.org/10.1073/pnas.2002722117

Funding: National Science Foundation grants 1925417, 1023672, and 0909541 to J.R.M., and 1824770 to J.G.M. and F.M.L. funded this research, as well as support to A.I.W. and J.R.M. from the John Fell Oxford University Press (OUP) Research Fund and All Souls College, Oxford. Clare Hall, Cambridge provided additional support to J.R.M. through the Sir Nicholas Shackleton fellowship. F.M.L. also acknowledges support from an Irish Research Council Laureate Award (CLICAB project, IRCLA/2017/303). Swiss National Science Foundation grant 18001 funded C.C.R. and W.M.K. European Research Council grant 820047 under the European Union’s Horizon 2020 research and innovation programme supported M.S. A.B. was supported by Marie Curie Career Integration Grant CIG14-631752. The assassination of Julius Caesar in 44 BCE triggered a power struggle that ultimately ended the Roman Republic and, eventually, the Ptolemaic Kingdom, leading to the rise of the Roman Empire. Climate proxies and written documents indicate that this struggle occurred during a period of unusually inclement weather, famine, and disease in the Mediterranean region; historians have previously speculated that a large volcanic eruption of unknown origin was the most likely cause. Here we show using well-dated volcanic fallout records in six Arctic ice cores that one of the largest volcanic eruptions of the past 2,500 y occurred in early 43 BCE, with distinct geochemistry of tephra deposited during the event identifying the Okmok volcano in Alaska as the source. Climate proxy records show that 43 and 42 BCE were among the coldest years of recent millennia in the Northern Hemisphere at the start of one of the coldest decades. Earth system modeling suggests that radiative forcing from this massive, high-latitude eruption led to pronounced changes in hydroclimate, including seasonal temperatures in specific Mediterranean regions as much as 7 °C below normal during the 2 y period following the eruption and unusually wet conditions. While it is difficult to establish ...