Bard Edouard

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Marine20-the marine radiocarbon age calibration curve (0-55,000 cal BP)

(Cambridge University Press, 2020-08-12) Heaton, Timothy J. ; Köhler, Peter ; Butzin, Martin ; Bard, Edouard ; Reimer, Ron W. ; Austin, William E. N. ; Bronk Ramsey, Christopher ; Grootes, Pieter M. ; Hughen, Konrad A. ; Kromer, Bernd ; Reimer, Paula J. ; Adkins, Jess F. ; Burke, Andrea ; Cook, Mea S. ; Olsen, Jesper ; Skinner, Luke C.

The concentration of radiocarbon (14C) differs between ocean and atmosphere. Radiocarbon determinations from samples which obtained their 14C in the marine environment therefore need a marine-specific calibration curve and cannot be calibrated directly against the atmospheric-based IntCal20 curve. This paper presents Marine20, an update to the internationally agreed marine radiocarbon age calibration curve that provides a non-polar global-average marine record of radiocarbon from 0–55 cal kBP and serves as a baseline for regional oceanic variation. Marine20 is intended for calibration of marine radiocarbon samples from non-polar regions; it is not suitable for calibration in polar regions where variability in sea ice extent, ocean upwelling and air-sea gas exchange may have caused larger changes to concentrations of marine radiocarbon. The Marine20 curve is based upon 500 simulations with an ocean/atmosphere/biosphere box-model of the global carbon cycle that has been forced by posterior realizations of our Northern Hemispheric atmospheric IntCal20 14C curve and reconstructed changes in CO2 obtained from ice core data. These forcings enable us to incorporate carbon cycle dynamics and temporal changes in the atmospheric 14C level. The box-model simulations of the global-average marine radiocarbon reservoir age are similar to those of a more complex three-dimensional ocean general circulation model. However, simplicity and speed of the box model allow us to use a Monte Carlo approach to rigorously propagate the uncertainty in both the historic concentration of atmospheric 14C and other key parameters of the carbon cycle through to our final Marine20 calibration curve. This robust propagation of uncertainty is fundamental to providing reliable precision for the radiocarbon age calibration of marine based samples. We make a first step towards deconvolving the contributions of different processes to the total uncertainty; discuss the main differences of Marine20 from the previous age calibration curve Marine13; and identify the limitations of our approach together with key areas for further work. The updated values for ΔR, the regional marine radiocarbon reservoir age corrections required to calibrate against Marine20, can be found at the data base http://calib.org/marine/.
Comment on "Radiocarbon calibration curve spanning 0 to 50,000 years BP based on paired 230Th/234U/238U and 14C dates on pristine corals" by R.G. Fairbanks et al. (Quaternary Science Reviews 24 (2005) 1781-1796), and "Extending the radiocarbon calibration beyond 26,000 years before present using fossil corals" by T.-C. Chiu et al. (Quaternary Science Reviews 24 (2005) 1797-1808).

( 2006-02) Reimer, Paula J. ; Baillie, Mike G. L. ; Bard, Edouard ; Beck, J. Warren ; Blackwell, Paul G. ; Buck, Caitlin E. ; Burr, George S. ; Edwards, R. Lawrence ; Friedrich, Michael ; Guilderson, Thomas P. ; Hogg, Alan G. ; Hughen, Konrad A. ; Kromer, Bernd ; McCormac, Gerry ; Manning, Sturt ; Reimer, Ron W. ; Southon, John R. ; Stuiver, Minze ; van der Plicht, Johannes ; Weyhenmeyer, Constanze E.

A recently published radiocarbon calibration curve extending to 50,000 cal BP (Fairbanks et al. 2005) is purportedly superior to that generated by the IntCal working group beyond the end of the tree-ring data at 12,400 cal BP (Reimer et al. 2004). This claim is based, in part, on different diagenetic screening criteria and pretreatment for coral samples (Fairbanks et al. 2005; Chiu et al. 2005) which do not stand up under careful scrutiny. Also at issue is the conversion of the coral-based calibration curve to an atmospheric curve where large inter-annual variability in the sea-surface age reservoir age has been observed in the southwest Pacific where one of two sets of corals used were sampled. In addition we comment on the seemingly ad hoc statistical methods utilized by Fairbanks et al. (2005) to construct their curve. We recognize the value of the Fairbanks et al. (2005) coral radiocarbon data set, but reassert the need for multiple, independently derived data to provide confirmation and validation to all radiocarbon calibration data. This is especially important before 26,000 cal BP when lower sea-levels of the last glacial maximum exposed most coral samples to alteration by fresh water.
A response to community questions on the marine20 radiocarbon age calibration curve: marine reservior ages and the calibration of 14 C samples from the oceans

(Cambridge University Press, 2022-11-02) Heaton, Timothy J. ; Bard, Edouard ; Bronk Ramsey, Christopher ; Butzin, Martin ; Hatté, Christine ; Hughen, Konrad A. ; Köhler, Peter ; Reimer, Paula J.

Radiocarbon (14C) concentrations in the oceans are different from those in the atmosphere. Understanding these ocean-atmospheric 14C differences is important both to estimate the calendar ages of samples which obtained their 14C in the marine environment, and to investigate the carbon cycle. The Marine20 radiocarbon age calibration curve is created to address these dual aims by providing a global-scale surface ocean record of radiocarbon from 55,000–0 cal yr BP that accounts for the smoothed response of the ocean to variations in atmospheric 14C production rates and factors out the effect of known changes in global-scale palaeoclimatic variables. The curve also serves as a baseline to study regional oceanic 14C variation. Marine20 offers substantial improvements over the previous Marine13 curve. In response to community questions, we provide a short intuitive guide, intended for the lay-reader, on the construction and use of the Marine20 calibration curve. We describe the choices behind the making of Marine20, as well as the similarities and differences compared with the earlier Marine calibration curves. We also describe how to use the Marine20 curve for calibration and how to estimate ΔR—the localized variation in the oceanic 14C levels due to regional factors which are not incorporated in the global-scale Marine20 curve. To aid understanding, illustrative worked examples are provided.
Timing of meltwater pulse 1a and climate responses to meltwater injections

(American Geophysical Union, 2006-12-09) Stanford, Jennifer D. ; Rohling, Eelco J. ; Hunter, Sally E. ; Roberts, Andrew P. ; Rasmussen, Sune O. ; Bard, Edouard ; McManus, Jerry F. ; Fairbanks, Richard G.

The temporal relationship between meltwater pulse 1a (mwp-1a) and the climate history of the last deglaciation remains a subject of debate. By combining the Greenland Ice Core Project δ 18O ice core record on the new Greenland ice core chronology 2005 timescale with the U/Th-dated Barbados coral record, we conclusively derive that mwp-1a did not coincide with the sharp Bølling warming but instead with the abrupt cooling of the Older Dryas. To evaluate whether there is a relationship between meltwater injections, North Atlantic Deep Water (NADW) formation, and climate change, we present a high-resolution record of NADW flow intensity from Eirik Drift through the last deglaciation. It indicates only a relatively minor 200-year weakening of NADW flow, coincident with mwp-1a. Our compilation of records also indicates that during Heinrich event 1 and the Younger Dryas there were no discernible sea level rises, and yet these periods were characterized by intense NADW slowdowns/shutdowns. Clearly, deepwater formation and climate are not simply controlled by the magnitude or rate of meltwater addition. Instead, our results emphasize that the location of meltwater pulses may be more important, with NADW formation being particularly sensitive to surface freshening in the Arctic/Nordic Seas.
Hydrology in the Sea of Marmara during the last 23 ka : implications for timing of Black Sea connections and sapropel deposition

(American Geophysical Union, 2010-02-06) Vidal, L. ; Menot, Guillemette ; Joly, C. ; Bruneton, H. ; Rostek, F. ; Cagatay, M. Namik ; Major, Candace O. ; Bard, Edouard

Sediments deposited under lacustrine and marine conditions in the Sea of Marmara hold a Late Quaternary record for water exchange between the Black Sea and the Mediterranean Sea. Here we report a multiproxy data set based on oxygen and strontium isotope results obtained from carbonate shells, major and trace elements, and specific organic biomarker measurements, as well as a micropaleontological study from a 14C-dated sediment core retrieved from the Sea of Marmara. Pronounced changes occurred in δ18O and 87Sr/86Sr values at the fresh and marine water transition, providing additional information in relation to micropaleontological data. Organic biomarker concentrations documented the marine origin of the sapropelic layer while changes in n-alkane concentrations clearly indicated an enhanced contribution for organic matter of terrestrial origin before and after the event. When compared with the Black Sea record, the results suggest that the Black Sea was outflowing to the Sea of Marmara from the Last Glacial Maximum until the warmer Bølling-Allerød. The first marine incursion in the Sea of Marmara occurred at 14.7 cal ka B.P. However, salinification of the basin was gradual, indicating that Black Sea freshwaters were still contributing to the Marmara seawater budget. After the Younger Dryas (which is associated with a high input of organic matter of terrestrial origin) both basins were disconnected, resulting in a salinity increase in the Sea of Marmara. The deposition of organic-rich sapropel that followed was mainly related to enhanced primary productivity characterized by a reorganization of the phytoplankton population.
An interlaboratory study of TEX86 and BIT analysis using high-performance liquid chromatography–mass spectrometry

(American Geophysical Union, 2009-03-20) Schouten, Stefan ; Hopmans, Ellen C. ; van der Meer, Jaap ; Mets, Anchelique ; Bard, Edouard ; Bianchi, Thomas S. ; Diefendorf, Aaron ; Escala, Marina ; Freeman, Katharine H. ; Furukawa, Yoshihiro ; Huguet, Carme ; Ingalls, Anitra ; Menot, Guillemette ; Nederbragt, Alexandra J. ; Oba, Masahiro ; Pearson, Ann ; Pearson, Emma J. ; Rosell-Mele, Antoni ; Schaeffer, Philippe ; Shah, Sunita R. ; Shanahan, Timothy M. ; Smith, Richard W. ; Smittenberg, Rienk ; Talbot, Helen M. ; Uchida, Masao ; Van Mooy, Benjamin A. S. ; Yamamoto, Masanobu ; Zhang, Zhaohui ; Sinninghe Damste, Jaap S.

Recently, two new proxies based on the distribution of glycerol dialkyl glycerol tetraethers (GDGTs) were proposed, i.e., the TEX86 proxy for sea surface temperature reconstructions and the BIT index for reconstructing soil organic matter input to the ocean. In this study, fifteen laboratories participated in a round robin study of two sediment extracts with a range of TEX86 and BIT values to test the analytical reproducibility and repeatability in analyzing these proxies. For TEX86 the repeatability, indicating intra-laboratory variation, was 0.028 and 0.017 for the two sediment extracts or ±1–2°C when translated to temperature. The reproducibility, indicating among-laboratory variation, of TEX86 measurements was substantially higher, i.e., 0.050 and 0.067 or ±3–4°C when translated to temperature. The latter values are higher than those obtained in round robin studies of Mg/Ca and U37 k′ paleothermometers, suggesting the need to primarily improve compatibility between labs. The repeatability of BIT measurements for the sediment with substantial amounts of soil organic matter input was relatively small, 0.029, but reproducibility was large, 0.410. This large variance could not be attributed to specific equipment used or a particular data treatment. We suggest that this may be caused by the large difference in the molecular weight in the GDGTs used in the BIT index, i.e., crenarchaeol versus the branched GDGTs. Potentially, this difference gives rise to variable responses in the different mass spectrometers used. Calibration using authentic standards is needed to establish compatibility between labs performing BIT measurements.
An interlaboratory study of TEX86 and BIT analysis of sediments, extracts, and standard mixtures

(John Wiley & Sons, 2013-12-20) Schouten, Stefan ; Hopmans, Ellen C. ; Rosell-Mele, Antoni ; Pearson, Ann ; Adam, Pierre ; Bauersachs, Thorsten ; Bard, Edouard ; Bernasconi, Stefano M. ; Bianchi, Thomas S. ; Brocks, Jochen J. ; Carlson, Laura Truxal ; Castaneda, Isla S. ; Derenne, Sylvie ; Selver, Ayca Dogrul ; Dutta, Koushik ; Eglinton, Timothy I. ; Fosse, Celine ; Galy, Valier ; Grice, Kliti ; Hinrichs, Kai-Uwe ; Huang, Yongsong ; Huguet, Arnaud ; Huguet, Carme ; Hurley, Sarah ; Ingalls, Anitra ; Jia, Guodong ; Keely, Brendan ; Knappy, Chris ; Kondo, Miyuki ; Krishnan, Srinath ; Lincoln, Sara ; Lipp, Julius S. ; Mangelsdorf, Kai ; Martínez-Garcia, Alfredo ; Menot, Guillemette ; Mets, Anchelique ; Mollenhauer, Gesine ; Ohkouchi, Naohiko ; Ossebaar, Jort ; Pagani, Mark ; Pancost, Richard D. ; Pearson, Emma J. ; Peterse, Francien ; Reichart, Gert-Jan ; Schaeffer, Philippe ; Schmitt, Gaby ; Schwark, Lorenz ; Shah, Sunita R. ; Smith, Richard W. ; Smittenberg, Rienk H. ; Summons, Roger E. ; Takano, Yoshinori ; Talbot, Helen M. ; Taylor, Kyle W. R. ; Tarozo, Rafael ; Uchida, Masao ; van Dongen, Bart E. ; Van Mooy, Benjamin A. S. ; Wang, Jinxiang ; Warren, Courtney ; Weijers, Johan W. H. ; Werne, Josef P. ; Woltering, Martijn ; Xie, Shucheng ; Yamamoto, Masanobu ; Yang, Huan ; Zhang, Chuanlun L. ; Zhang, Yige ; Zhao, Meixun ; Sinninghe Damste, Jaap S.

Two commonly used proxies based on the distribution of glycerol dialkyl glycerol tetraethers (GDGTs) are the TEX86 (TetraEther indeX of 86 carbon atoms) paleothermometer for sea surface temperature reconstructions and the BIT (Branched Isoprenoid Tetraether) index for reconstructing soil organic matter input to the ocean. An initial round-robin study of two sediment extracts, in which 15 laboratories participated, showed relatively consistent TEX86 values (reproducibility ±3–4°C when translated to temperature) but a large spread in BIT measurements (reproducibility ±0.41 on a scale of 0–1). Here we report results of a second round-robin study with 35 laboratories in which three sediments, one sediment extract, and two mixtures of pure, isolated GDGTs were analyzed. The results for TEX86 and BIT index showed improvement compared to the previous round-robin study. The reproducibility, indicating interlaboratory variation, of TEX86 values ranged from 1.3 to 3.0°C when translated to temperature. These results are similar to those of other temperature proxies used in paleoceanography. Comparison of the results obtained from one of the three sediments showed that TEX86 and BIT indices are not significantly affected by interlaboratory differences in sediment extraction techniques. BIT values of the sediments and extracts were at the extremes of the index with values close to 0 or 1, and showed good reproducibility (ranging from 0.013 to 0.042). However, the measured BIT values for the two GDGT mixtures, with known molar ratios of crenarchaeol and branched GDGTs, had intermediate BIT values and showed poor reproducibility and a large overestimation of the “true” (i.e., molar-based) BIT index. The latter is likely due to, among other factors, the higher mass spectrometric response of branched GDGTs compared to crenarchaeol, which also varies among mass spectrometers. Correction for this different mass spectrometric response showed a considerable improvement in the reproducibility of BIT index measurements among laboratories, as well as a substantially improved estimation of molar-based BIT values. This suggests that standard mixtures should be used in order to obtain consistent, and molar-based, BIT values.
Marine04 marine radiocarbon age calibration, 0-26 cal kyr BP

(Dept. of Geosciences, University of Arizona, 2004) Hughen, Konrad A. ; Baillie, Mike G. L. ; Bard, Edouard ; Beck, J. Warren ; Bertrand, Chanda J. H. ; Blackwell, Paul G. ; Buck, Caitlin E. ; Burr, George S. ; Cutler, Kirsten B. ; Damon, Paul E. ; Edwards, R. Lawrence ; Fairbanks, Richard G. ; Friedrich, Michael ; Guilderson, Thomas P. ; Kromer, Bernd ; McCormac, Gerry ; Manning, Sturt ; Bronk Ramsey, Christopher ; Reimer, Paula J. ; Reimer, Ron W. ; Remmele, Sabine ; Southon, John R. ; Stuiver, Minze ; Talamo, Sahra ; Taylor, F. W. ; van der Plicht, Johannes ; Weyhenmeyer, Constanze E.

New radiocarbon calibration curves, IntCal04 and Marine04, have been constructed and internationally ratified to replace the terrestrial and marine components of IntCal98. The new calibration data sets extend an additional 2000 yr, from 0–26 cal kyr BP (Before Present, 0 cal BP = AD 1950), and provide much higher resolution, greater precision, and more detailed structure than IntCal98. For the Marine04 curve, dendrochronologically-dated tree-ring samples, converted with a box diffusion model to marine mixed-layer ages, cover the period from 0–10.5 cal kyr BP. Beyond 10.5 cal kyr BP, high-resolution marine data become available from foraminifera in varved sediments and U/Th-dated corals. The marine records are corrected with site-specific 14C reservoir age information to provide a single global marine mixed-layer calibration from 10.5–26.0 cal kyr BP. A substantial enhancement relative to IntCal98 is the introduction of a random walk model, which takes into account the uncertainty in both the calendar age and the 14C age to calculate the underlying calibration curve (Buck and Blackwell, this issue). The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed here. The tree-ring data sets, sources of uncertainty, and regional offsets are presented in detail in a companion paper by Reimer et al. (this issue).
IntCal04 terrestrial radiocarbon age calibration, 0-26 cal kyr BP

(Dept. of Geosciences, University of Arizona, 2004) Reimer, Paula J. ; Baillie, Mike G. L. ; Bard, Edouard ; Bayliss, Alex ; Beck, J. Warren ; Bertrand, Chanda J. H. ; Blackwell, Paul G. ; Buck, Caitlin E. ; Burr, George S. ; Cutler, Kirsten B. ; Damon, Paul E. ; Edwards, R. Lawrence ; Fairbanks, Richard G. ; Friedrich, Michael ; Guilderson, Thomas P. ; Hogg, Alan G. ; Hughen, Konrad A. ; Kromer, Bernd ; McCormac, Gerry ; Manning, Sturt ; Bronk Ramsey, Christopher ; Reimer, Ron W. ; Remmele, Sabine ; Southon, John R. ; Stuiver, Minze ; Talamo, Sahra ; Taylor, F. W. ; van der Plicht, Johannes ; Weyhenmeyer, Constanze E.

A new calibration curve for the conversion of radiocarbon ages to calibrated (cal) ages has been constructed and internationally ratified to replace IntCal98, which extended from 0–24 cal kyr BP (Before Present, 0 cal BP = AD 1950). The new calibration data set for terrestrial samples extends from 0–26 cal kyr BP, but with much higher resolution beyond 11.4 cal kyr BP than IntCal98. Dendrochronologically-dated tree-ring samples cover the period from 0–12.4 cal kyr BP. Beyond the end of the tree rings, data from marine records (corals and foraminifera) are converted to the atmospheric equivalent with a site-specific marine reservoir correction to provide terrestrial calibration from 12.4–26.0 cal kyr BP. A substantial enhancement relative to IntCal98 is the introduction of a coherent statistical approach based on a random walk model, which takes into account the uncertainty in both the calendar age and the 14C age to calculate the underlying calibration curve (Buck and Blackwell, this issue). The tree-ring data sets, sources of uncertainty, and regional offsets are discussed here. The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed in brief, but details are presented in Hughen et al. (this issue a). We do not make a recommendation for calibration beyond 26 cal kyr BP at this time; however, potential calibration data sets are compared in another paper (van der Plicht et al., this issue).
NotCal04; comparison/ calibration 14C records 26-50 cal kyr BP

(Dept. of Geosciences, University of Arizona, 2004) van der Plicht, Johannes ; Beck, J. Warren ; Bard, Edouard ; Baillie, Mike G. L. ; Blackwell, Paul G. ; Buck, Caitlin E. ; Friedrich, Michael ; Guilderson, Thomas P. ; Hughen, Konrad A. ; Kromer, Bernd ; McCormac, F. G. ; Bronk Ramsey, Christopher ; Reimer, Paul J. ; Reimer, Ron W. ; Remmele, Sabine ; Richards, D. A. ; Southon, John R. ; Stuiver, Minze ; Weyhenmeyer, Constanze E.

The radiocarbon calibration curve IntCal04 extends back to 26 cal kyr BP. While several high-resolution records exist beyond this limit, these data sets exhibit discrepancies of up to several millennia. As a result, no calibration curve for the time range 26–50 cal kyr BP can be recommended as yet, but in this paper the IntCal04 working group compares the available data sets and offers a discussion of the information that they hold.
Marine radiocarbon calibration in polar regions: a simple approximate approach using Marine20. Radiocarbon

(Cambridge University Press, 2023-08-08) Heaton, Timothy J. ; Butzin, Martin ; Bard, Edouard ; Bronk Ramsey, Christopher ; Hughen, Konrad A. ; Kohler, Peter ; Reimer, Paula J.

The Marine20 radiocarbon (14C) age calibration curve, and all earlier marine 14C calibration curves from the IntCal group, must be used extremely cautiously for the calibration of marine 14C samples from polar regions (outside ∼ 40ºS–40ºN) during glacial periods. Calibrating polar 14C marine samples from glacial periods against any Marine calibration curve (Marine20 or any earlier product) using an estimate of , the regional 14C depletion adjustment, that has been obtained from samples in the recent (non-glacial) past is likely to lead to bias and overconfidence in the calibrated age. We propose an approach to calibration that aims to address this by accounting for the possibility of additional, localized, glacial 14C depletion in polar oceans. We suggest, for a specific polar location, bounds on the value of during a glacial period. The lower bound may be based on 14C samples from the recent non-glacial (Holocene) past and corresponds to a low-depletion glacial scenario. The upper bound, , representing a high-depletion scenario is found by increasing according to the latitude of the 14C sample to be calibrated. The suggested increases to obtain are based upon simulations of the Hamburg Large Scale Geostrophic Ocean General Circulation Model (LSG OGCM). Calibrating against the Marine20 curve using the upper and lower bounds provide estimates of calibrated ages for glacial 14C samples in high- and low-depletion scenarios which should bracket the true calendar age of the sample. In some circumstances, users may be able to determine which depletion scenario is more appropriate using independent paleoclimatic or proxy evidence.
Development of the IntCal database

(Cambridge University Press, 2023-07-28) Bronk Ramsey, Christopher ; Adolphi, Florian ; Austin, William ; Bard, Edouard ; Bayliss, Alex ; Blaauw, Maarten ; Cheng, Hai ; Edwards, R. Lawrence ; Friedrich, Michael ; Heaton, Timothy

The IntCal family of radiocarbon (14C) calibration curves is based on research spanning more than three decades. The IntCal group have collated the 14C and calendar age data (mostly derived from primary publications with other types of data and meta-data) and, since 2010, made them available for other sorts of analysis through an open-access database. This has ensured transparency in terms of the data used in the construction of the ratified calibration curves. As the IntCal database expands, work is underway to facilitate best practice for new data submissions, make more of the associated metadata available in a structured form, and help those wishing to process the data with programming languages such as R, Python, and MATLAB. The data and metadata are complex because of the range of different types of archives. A restructured interface, based on the “IntChron” open-access data model, includes tools which allow the data to be plotted and compared without the need for export. The intention is to include complementary information which can be used alongside the main 14C series to provide new insights into the global carbon cycle, as well as facilitating access to the data for other research applications. Overall, this work aims to streamline the generation of new calibration curves.
The Intcal20 Northern Hemisphere radiocarbon age calibration curve (0-55 cal kBP)

(Cambridge University Press, 2020-08-12) Reimer, Paula J. ; Austin, William E. N. ; Bard, Edouard ; Bayliss, Alex ; Blackwell, Paul G. ; Bronk Ramsey, Christopher ; Butzin, Martin ; Cheng, Hai ; Edwards, R. Lawrence ; Friedrich, Michael ; Grootes, Pieter M. ; Guilderson, Thomas P. ; Hajdas, Irka ; Heaton, Timothy J. ; Hogg, Alan G. ; Hughen, Konrad A. ; Kromer, Bernd ; Manning, Sturt W. ; Muscheler, Raimund ; Palmer, Jonathan G. ; Pearson, Charlotte ; van der Plicht, Johannes ; Reimer, Ron W. ; Richards, David A. ; Scott, E. Marian ; Southon, John R. ; Turney, Christian S. M. ; Wacker, Lukas ; Adolphi, Florian ; Büntgen, Ulf ; Capano, Manuela ; Fahrni, Simon M. ; Fogtmann-Schulz, Alexandra ; Friedrich, Ronny ; Köhler, Peter ; Kudsk, Sabrina ; Miyake, Fusa ; Olsen, Jesper ; Reinig, Frederick ; Sakamoto, Minoru ; Sookdeo, Adam ; Talamo, Sahra

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.
IntCal09 and Marine09 radiocarbon age calibration curves, 0–50,000 years cal BP

(Dept. of Geosciences, University of Arizona, 2009-12) Reimer, Paula J. ; Bard, Edouard ; Bayliss, Alex ; Beck, J. Warren ; Blackwell, Paul G. ; Bronk Ramsey, Christopher ; Buck, Caitlin E. ; Cheng, Hai ; Edwards, R. Lawrence ; Friedrich, Michael ; Grootes, Pieter M. ; Guilderson, Thomas P. ; Haflidason, Haflidi ; Hajdas, Irka ; Hatte, Christine ; Heaton, Timothy J. ; Hoffmann, Dirk L. ; Hogg, Alan G. ; Hughen, Konrad A. ; Kaiser, K. Felix ; Kromer, Bernd ; Manning, Sturt W. ; Niu, Mu ; Reimer, Ron W. ; Richards, David A. ; Scott, E. Marian ; Southon, John R. ; Staff, Richard A. ; Turney, Christian S. M. ; van der Plicht, Johannes

The IntCal04 and Marine04 radiocarbon calibration curves have been updated from 12 cal kBP (cal kBP is here defined as thousands of calibrated years before AD 1950), and extended to 50 cal kBP, utilizing newly available data sets that meet the IntCal Working Group criteria for pristine corals and other carbonates and for quantification of uncertainty in both the 14C and calendar timescales as established in 2002. No change was made to the curves from 0–12 cal kBP. The curves were constructed using a Markov chain Monte Carlo (MCMC) implementation of the random walk model used for IntCal04 and Marine04. The new curves were ratified at the 20th International Radiocarbon Conference in June 2009 and are available in the Supplemental Material at www.radiocarbon.org.

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