Findings from an in-Depth Annual Tree-Ring Radiocarbon Intercomparison

Wacker, Lukas; Scott, E. M.; Bayliss, Alex; Brown, David; Bard, Édouard; Bollhalder, Silvia; Friedrich, Michael; Capano, Manuela; Cherkinsky, Alexander; Chivall, David; Culleton, Brendan J.; Dee, Michael W.; Friedrich, Ronny; Hodgins, Gregory W. L.; Hogg, Alan G.; Kennett, Douglas J.; Knowles, Timothy; Kuitems, Margot; Lange, Todd; Miyake, Fusa; Nadeau, Marie Josee; Nakamura, Toshio; Naysmith, J. P.; Olsen, Jesper; Omori, Takayuki; Petchey, Fiona; Philippsen, Bente; Ramsey, Christopher Bronk; Prasad, Ganesh; Seiler, Martin; Southon, John; Staff, Richard A.; Tuna, Thibaut

doi:10.1017/rdc.2020.49

Cited by 24 publications

(25 citation statements)

References 15 publications

(15 reference statements)

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“…However, offsets could also result, in theory, from the location of the tree relative to the ITCZ and monsoons, growing season differences, polar latitudes, proximity to upwelling of 14 C-depleted ocean water, proximity to industrial centers, and high altitude. Regional offsets within a hemisphere can be difficult to corroborate, as they are of a scale similar to observed inter-laboratory variation (Wacker et al 2020 The ITCZ is an asymmetric area of low pressure around the thermal equator where the northeast and southeast trade winds converge. The ITCZ migrates on seasonal and longer timescales (Haug et al 2001;Schneider et al 2014).…”

Section: Intcal20 14 C Calibration Curve 729mentioning

confidence: 99%

The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP)

et al. 2020

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Radiocarbon (14C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international 14C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable 14C offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the 14C ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine 14C data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals.

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Section: Intcal20 14 C Calibration Curve 729mentioning

confidence: 99%

The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP)

et al. 2020

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“…The information gained from these studies informed the choice of both model on the offsets and the prior on the level of additional variation incorporated in IntCal20 construction (Heaton et al 2020a this issue). At the same time, more focal intercomparisons have refined estimation of the additional variation based solely on tree-rings (Wacker et al 2020 in this issue) and on much smaller subsets of laboratories.…”

Section: Developments In Data and The Calibration Curve Data And Undementioning

confidence: 99%

Recent Developments in Calibration for Archaeological and Environmental Samples

et al. 2020

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The curves recommended for calibrating radiocarbon (14C) dates into absolute dates have been updated. For calibrating atmospheric samples from the Northern Hemisphere, the new curve is called IntCal20. This is accompanied by associated curves SHCal20 for the Southern Hemisphere, and Marine20 for marine samples. In this “companion article” we discuss advances and developments that have led to improvements in the updated curves and highlight some issues of relevance for the general readership. In particular the dendrochronological based part of the curve has seen a significant increase in data, with single-year resolution for certain time ranges, extending back to 13,910 calBP. Beyond the tree rings, the new curve is based upon an updated combination of marine corals, speleothems, macrofossils, and varved sediments and now reaches back to 55,000 calBP. Alongside these data advances, we have developed a new, bespoke statistical curve construction methodology to allow better incorporation of the diverse constituent records and produce a more robust curve with uncertainties. Combined, these data and methodological advances offer the potential for significant new insight into our past. We discuss some implications for the user, such as the dating of the Santorini eruption and also some consequences of the new curve for Paleolithic archaeology.

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“…In order to certify our high-precision in wood dating, we successfully participated in the International Intercomparison on wood dating organized by ETH (Zurich) in 2017–2018. Indeed, two wood blanks and three wooden sequences, dated to different periods, were annually dated and the results were compared with those of other laboratories (Wacker et al 2018).…”

Section: Methodsmentioning

confidence: 99%

Onset of the Younger Dryas Recorded with ¹⁴C at Annual Resolution in French Subfossil Trees

Capano

Miramont²,

Shindo³

et al. 2019

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Subfossil trees with their annual rings constitute the most accurate and precise archive to calibrate the radiocarbon (14C) method. The Holocene part of the IntCal curve is based on tree-ring chronologies, absolutely dated by dendrochronological matching. For the Northern Hemisphere, the absolute curve starts at 12,325 cal BP. For the early part of the Younger Dryas (YD) climatic event (≈ 12,850–11,650 cal BP), there are only a few floating dendrochronological sequences, mainly from Switzerland and France. We present new 14C results from subfossil trees (Pinus sylvestris L.) collected from the Barbiers site (southeast French Alps). The dendrochronological series covers 416 years, corresponding to the onset of the YD period. In order to date our sequence, we matched it with the 14C record based on kauri trees from New Zealand. The Barbiers data were first averaged at the same decadal resolution as the kauri record. Statistical comparison of the different averaging options and matching techniques enables dating the Barbiers sequence to 13,008–12,594 ±10 cal BP, which thus includes the boundary between the Allerød and YD events. The new Barbiers record allows to calculate the 14C inter-hemispheric gradient (14C-IHG) during the period overlapping the kauri sequence. For the optimal dating option, the mean 14C-IHG is 37 yr with a standard deviation (SD) of 21 yr based on 43 decadal estimations (−6‰ with SD of 2‰). The 14C-IHG record exhibits minimal values, down to zero, between 12,960–12,840 cal BP. Excluding these minima leads to an average 14C-IHG of 45 yr with a SD of 14 yr based on 33 decadal values, in agreement with observations for the last two millennia. The Barbiers record suggests a 14C-IHG increase between the end of the Allerød period (IHG of 37 yr with SD of 14 yr) and the early part of the YD (IHG of 48 yr with SD of 14 yr), which is compatible with previously reported drop of deep-water convection in the North-Atlantic and the associated increase in wind-driven upwelling in the Southern Ocean.

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Findings from an in-Depth Annual Tree-Ring Radiocarbon Intercomparison

Cited by 24 publications

References 15 publications

The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP)

The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP)

Recent Developments in Calibration for Archaeological and Environmental Samples

Onset of the Younger Dryas Recorded with ¹⁴C at Annual Resolution in French Subfossil Trees

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Findings from an in-Depth Annual Tree-Ring Radiocarbon Intercomparison

Cited by 24 publications

References 15 publications

The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP)

The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP)

Recent Developments in Calibration for Archaeological and Environmental Samples

Onset of the Younger Dryas Recorded with 14C at Annual Resolution in French Subfossil Trees

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Onset of the Younger Dryas Recorded with ¹⁴C at Annual Resolution in French Subfossil Trees