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. 2022 Apr 29;1(2):pgac048. doi: 10.1093/pnasnexus/pgac048

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© The Author(s) 2022. Published by Oxford University Press on behalf of the National Academy of Sciences.

This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs licence (https://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reproduction and distribution of the work, in any medium, provided the original work is not altered or transformed in any way, and that the work is properly cited. For commercial re-use, please contact journals.permissions@oup.com

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Fig. 1. — Ice-core synchronization (blue vertical lines) using layer counts between bipolar volcanic aerosol records from Greenland (A) and Antarctica (B) and calendar dated tree-ring counts between climatic markers (C), anchored at 1628 BCE (7). V1 to V7 were assigned to aid navigation across key events discussed in the text. (A) Northern Hemisphere; GISP 2—Greenland Ice-Sheet Project (31); GRIP—Greenland Ice-Core Project (32), EGRIP (East) (33), and NGRIP (North) (27): (B) Southern Hemisphere; WDC—West Antarctic Ice-Sheet Divide ice core (34, 35), EDML—EPICA Dronning Maud Land ice core (36): EDML was volcanically synchronized to the annual-layer counted chronology (WD2014) of WDC. A shift of +1 year (i.e. toward younger ages) is necessary at 1628 BCE to anchor WD2014 with the tree-ring chronology (7), whereas +14 years (MB19) were used to align the Greenland GICC05 chronology with the tree-ring chronology. Previous tephra associations (25,27, 37–39) and tephra recovered in this study are shown relative to the new synchronization. GISP2, NGRIP, and GRIP were resampled for tephra and sulfate across V5, GISP2, and NGRIP across V2.