Constraining the timing and climate forcing of the Long Island (Papua New Guinea) and Tarumae (Japan) eruptions and other 17th century volcanic eruptions

The 17 th century was a period when several major (VEI > 5) tropical and extratropical volcanic eruptions occurred. Amongst these is the VEI 6 eruption of Long Island (Papua New Guinea), which is suggested to have occurred between 1665 and 1668 CE based on historical accounts, radiocarbon dating constraints, and an ice-core record from South Pole. Accepting such an attribution on the basis of this ice-core chronology would imply a hitherto undiagnosed dating error of up to 6 years during the 17 th century within all ice-core records from Antarctica. Here we constrain the timing of the Long Island eruption through tephrochronology and high-resolution glaciochemical measurements from an array of records from Antarctica and Greenland. We identify cryptotephra glass shards in association with the Greenland 1667 CE sulfate peak and geochemically attribute them to the historic Japanese Tarumae (Shikotsu) eruption. This attribution shows that the ice-core records are not misaligned during this period and refines the timing of the Long Island eruption to two candidate dates: 1654 ±1 CE and 1662 ±1 CE. Both candidate dates are within previous best age estimates based on radiocarbon dating (1651 and 1671 CE, 95.4 % probability). However, here we tentatively use 1662 ±1 CE as the timing of the Long Island eruption, as previous radiocarbon constraints suggest a 68.2 % probability of occurrence between 1655 and 1665 CE. With a higher confidence in the dating, we revised volcanic stratospheric sulfur injection (VSSI) estimates across the 17 th century. Using these alongside paleo-proxy records, we explored the Northern Hemisphere climate response to the Long Island and Tarumae eruptions and found them to be more limited compared to other major (VEI >5) eruptions during this century. Ultimately, this study has highlighted the accuracy of ice core chronologies, having wider implications for volcanic forcing reconstructions and detection and attribution studies of natural climate variability. • Cryptotephra from 1667 CE Tarumae (Ta-b, Japan) eruption identified in two Greenland ice cores • 1662 ±1 CE likely date of Long Island eruption with 1654 ±1 CE an alternative candidate, owing to previous best age estimates • Revised volcanic stratospheric sulfur injection estimates across the 17 th century • Limited Northern Hemisphere climate response of Long Island and Tarumae compared to other VEI ≥5 17 th century eruptions