High‐Resolution ¹⁰Be and ³⁶Cl Data From the Antarctic Dome Fuji Ice Core (∼100 Years Around 5480 BCE): An Unusual Grand Solar Minimum Occurrence?

Abstract

Cosmogenic nuclides are an excellent proxy of reconstructing the past solar activity. These nuclides are produced in the Earth's atmosphere by nuclear cascade initiated by galactic cosmic ray (GCR) particles, which mainly consist of protons and helium nuclei. As the GCR intensity on Earth is modulated by activity of the solar magnetic field, the past production rate of the cosmogenic nuclides reflects the solar activity at that time (e.g., Beer et al., 2012). To reconstruct the variations of past solar activity, researchers measure the cosmogenic nuclides stored in archived samples, such as 14 C in tree rings and 10 Be in polar ice cores (e.g.,

Modelling cosmic radiation events in the tree-ring radiocarbon record

“…[24]. For comparison, a decade-long rise in 5480 BCE, less than a century before the single-year rise in 5410 BCE, is ascribed by multiradionuclide evidence to an unusual grand solar minimum of very great depth and short duration [25,26]. No other sharp rises in 14 C so far detected have shown evidence of substructure in time.…”

“…Meanwhile, although the other events show sharp single-year rises, the event of 660 BCE has a prolonged rise over a couple of years, which could be due to a prolonged production or a succession of events [24]. For comparison, a decade-long rise in 5480 BCE, less than a century before the single-year rise in 5410 BCE, is ascribed by multiradionuclide evidence to an unusual grand solar minimum of very great depth and short duration [25,26]. No other sharp rises in Δ14C so far detected have shown evidence of substructure in time.…”

The Dome Fuji ice core DF2021 chronology (0–207 kyr BP)

“…For the last 60 kyr, we fully utilize the constraints on the ice age and gas age by matching the DF core data (volcanic signals, 10 Be and CH 4 ) with the volcanic signals and CH 4 of the layer-counted chronologies of high-accumulation ice cores (WD2014 of WDC and GICC05 of Greenland cores) as well as the tree ring 14 C. More specifically, the DF ice age intervals (the age difference between two volcanic layers) are constrained by WD2014 for 0e31.2 kyr BP (164 intervals) where WD2014 is determined by the layer counting (Sigl et al, 2016). Also, the DF ice age at 16 layers ( 10 Be peaks) for 0.13e7.4 kyr BP are constrained by tree-ring chronologies through 10 Bee 14 C matching (Horiuchi et al, 2008;Miyake et al, 2015Miyake et al, , 2019Kanzawa et al, 2021). For the gas age, we match the DF and WD CH 4 records and NGRIP d 18 O ice records at DansgaardeOeschger (DO) events or other transitions.…”

“…For the deep part of the DF2 core (~2500e3028 m), the chronology is based on the synchronization to the Antarctic Ice Cores Chronology 2012 (AICC2012) age scale (Bazin et al, 2013) using isotope matching (Dome Fuji Ice Core Project Members, 2017). For the late Holocene, some parts of the DF chronology can be modified by matching its 10 Be records to tree-ring 14 C records (Horiuchi et al, 2008;Miyake et al, 2015Miyake et al, , 2019Kanzawa et al, 2021). Problems in the existing DF chronologies and the potentials for significant improvements are summarized as the following three points.…”

“…In this paper, we construct precise and coherent ice and gas time scales of the DF core over the last 207 kyr (0e2150 m), by iterating between the Paleochrono probabilistic dating model (Parrenin et al, 2021) and the inverse Herron-Langway densification model (Buizert et al, 2021) with various types of constraints, including new dO 2 /N 2 ice age markers, CH 4 gas age markers, and d 15 N for firn properties, obtained by recent precise gas measurement on the DF core (Oyabu et al, 2020(Oyabu et al, , 2021, as well as published tie points between the 10 Be flux record in the second DF core and tree-ring 14 C record (Horiuchi et al, 2008;Miyake et al, 2015Miyake et al, , 2019Kanzawa et al, 2021). Also, a new volcanic matching of the DF to WDC, and indirectly to NGRIP core (Svensson et al, 2020) were made.…”