Southon John R.

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  • Article
    The Keck Carbon Cycle AMS Laboratory, University of California, Irvine : status report
    (Dept. of Geosciences, University of Arizona, 2010-08) Beverly, Robert K. ; Beaumont, Will ; Tauz, Denis ; Ormsby, Kaelyn M. ; von Reden, Karl F. ; Santos, Guaciara M. ; Southon, John R.
    We present a status report of the accelerator mass spectrometry (AMS) facility at the University of California, Irvine, USA. Recent spectrometer upgrades and repairs are discussed. Modifications to preparation laboratory procedures designed to improve sample throughput efficiency while maintaining precision of 2–3‰ for 1-mg samples (Santos et al. 2007c) are presented.
  • Article
    Cs feed tests and emittance measurements on a modified MC-SNICS ion source for radiocarbon AMS
    (Dept. of Geosciences, University of Arizona, 2007-11) Southon, John R. ; Santos, Guaciara M. ; Han, Baoxi
    We report on 2 recent developments in an ongoing program of characterizing and improving the National Electrostatics Corp. (NEC) MC-SNICS ion source at University of California (UC) Irvine’s Keck AMS laboratory. First, we have investigated the possibility of modifying a large-body (134-sample) MC-SNICS to incorporate the UC Irvine Cs oven and vacuum-insulated Cs feed tube, which provide better confinement of Cs than the standard NEC setup. In our 40-sample source, the feed tube enters the source housing directly below the ionizer assembly. This area cannot be accessed for machining on the 134-sample source, but we have successfully tested a modified geometry where the delivery tube enters the body via the source end flange. Second, we recently installed a second beam profile monitor in the injection line of our spectrometer to allow us to make online emittance measurements. At full output (150 μA of C– at 55 keV), the emittance of our source at 8 kV sputtering voltage is approximately 40π mm mrad.
  • Article
    Limited contribution of ancient methane to surface waters of the U.S. Beaufort Sea shelf
    (American Association for the Advancement of Science, 2018-01-17) Sparrow, Katy J. ; Kessler, John D. ; Southon, John R. ; Garcia-Tigreros, Fenix ; Schreiner, Kathryn M. ; Ruppel, Carolyn D. ; Miller, John B. ; Lehman, Scott J. ; Xu, Xiaomei
    In response to warming climate, methane can be released to Arctic Ocean sediment and waters from thawing subsea permafrost and decomposing methane hydrates. However, it is unknown whether methane derived from this sediment storehouse of frozen ancient carbon reaches the atmosphere. We quantified the fraction of methane derived from ancient sources in shelf waters of the U.S. Beaufort Sea, a region that has both permafrost and methane hydrates and is experiencing significant warming. Although the radiocarbon-methane analyses indicate that ancient carbon is being mobilized and emitted as methane into shelf bottom waters, surprisingly, we find that methane in surface waters is principally derived from modern-aged carbon. We report that at and beyond approximately the 30-m isobath, ancient sources that dominate in deep waters contribute, at most, 10 ± 3% of the surface water methane. These results suggest that even if there is a heightened liberation of ancient carbon–sourced methane as climate change proceeds, oceanic oxidation and dispersion processes can strongly limit its emission to the atmosphere.
  • Preprint
    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.
  • Article
    Low reservoir ages for the surface ocean from mid-Holocene Florida corals
    (American Geophysical Union, 2008-05-13) Druffel, Ellen R. M. ; Robinson, Laura F. ; Griffin, Sheila ; Halley, Robert B. ; Southon, John R. ; Adkins, Jess F.
    The 14C reservoir age of the surface ocean was determined for two Holocene periods (4908–4955 and 3008–3066 calendar (cal) B.P.) using U/Th-dated corals from Biscayne National Park, Florida, United States. We found that the average reservoir ages for these two time periods (294 ± 33 and 291 ± 27 years, respectively) were lower than the average value between A.D. 1600 and 1900 (390 ± 60 years) from corals. It appears that the surface ocean was closer to isotopic equilibrium with CO2 in the atmosphere during these two time periods than it was during recent times. Seasonal δ 18O measurements from the younger coral are similar to modern values, suggesting that mixing with open ocean waters was indeed occurring during this coral's lifetime. Likely explanations for the lower reservoir age include increased stratification of the surface ocean or increased Δ14C values of subsurface waters that mix into the surface. Our results imply that a more correct reservoir age correction for radiocarbon measurements of marine samples in this location from the time periods ∼3040 and ∼4930 cal years B.P. is ∼292 ± 30 years, less than the canonical value of 404 ± 20 years.
  • Article
    A preliminary determination of the absolute 14C/12C ratio of OX-I
    (Dept. of Geosciences, University of Arizona, 2007-11) Roberts, Mark L. ; Southon, John R.
    A preliminary determination of the absolute 14C/12C ratio of the oxalic acid I standard (NBS SRM 4990B) has been made. Using an accelerator mass spectrometry (AMS) system, a known number of radiocarbon ions were implanted in a thin copper foil. The foil was then combusted with the addition of 14C-free carrier material. This resulting gas (which had a known 14C/12C ratio) was graphitized and compared to OX-I material. This comparison yielded an absolute 14C/12C ratio of OX-I. The absolute 14C/12C ratio of OX-I, coupled with knowledge of the specific activity of OX-1, provides an alternative determination of the 14C half-life.
  • Article
    Blank assessment for ultra-small radiocarbon samples : chemical extraction and separation versus AMS
    (Dept. of Geosciences, University of Arizona, 2010-08) Santos, Guaciara M. ; Southon, John R. ; Drenzek, Nicholas J. ; Ziolkowski, Lori A. ; Druffel, Ellen R. M. ; Xu, Xiaomei ; Zhang, Dachun ; Trumbore, Susan E. ; Eglinton, Timothy I. ; Hughen, Konrad A.
    The Keck Carbon Cycle AMS facility at the University of California, Irvine (KCCAMS/UCI) has developed protocols for analyzing radiocarbon in samples as small as ~0.001 mg of carbon (C). Mass-balance background corrections for modern and 14C-dead carbon contamination (MC and DC, respectively) can be assessed by measuring 14C-free and modern standards, respectively, using the same sample processing techniques that are applied to unknown samples. This approach can be validated by measuring secondary standards of similar size and 14C composition to the unknown samples. Ordinary sample processing (such as ABA or leaching pretreatment, combustion/graphitization, and handling) introduces MC contamination of ~0.6 ± 0.3 μg C, while DC is ~0.3 ± 0.15 μg C. Today, the laboratory routinely analyzes graphite samples as small as 0.015 mg C for external submissions and ≅0.001 mg C for internal research activities with a precision of ~1% for ~0.010 mg C. However, when analyzing ultra-small samples isolated by a series of complex chemical and chromatographic methods (such as individual compounds), integrated procedural blanks may be far larger and more variable than those associated with combustion/graphitization alone. In some instances, the mass ratio of these blanks to the compounds of interest may be so high that the reported 14C results are meaningless. Thus, the abundance and variability of both MC and DC contamination encountered during ultra-small sample analysis must be carefully and thoroughly evaluated. Four case studies are presented to illustrate how extraction chemistry blanks are determined.
  • Article
    Cariaco Basin calibration update; revisions to calendar and 14C chronologies for core PL07-58PC
    (Dept. of Geosciences, University of Arizona, 2004) Hughen, Konrad A. ; Southon, John R. ; Bertrand, Chanda J. H. ; Frantz, Brian ; Zermeno, Paula
    This paper describes the methods used to develop the Cariaco Basin PL07-58PC marine radiocarbon calibration data set. Background measurements are provided for the period when Cariaco samples were run, as well as revisions leading to the most recent version of the floating varve chronology. The floating Cariaco chronology has been anchored to an updated and expanded Preboreal pine tree-ring data set, with better estimates of uncertainty in the wiggle-match. Pending any further changes to the dendrochronology, these results represent the final Cariaco 58PC calibration data set.
  • Preprint
    Temporal deconvolution of vascular plant-derived fatty acids exported from terrestrial watersheds
    ( 2018-09) Vonk, Jorien E. ; Drenzek, Nicholas J. ; Hughen, Konrad A. ; Stanley, Rachel H. R. ; McIntyre, Cameron P. ; Montlucon, Daniel B. ; Giosan, Liviu ; Southon, John R. ; Santos, Guaciara M. ; Druffel, Ellen R. M. ; Andersson, August A. ; Sköld, Martin ; Eglinton, Timothy I.
    Relatively little is known about the amount of time that lapses between the photosynthetic fixation of carbon by vascular land plants and its incorporation into the marine sedimentary record, yet the dynamics of terrestrial carbon sequestration have important implications for the carbon cycle. Vascular plant carbon may encounter multiple potential intermediate storage pools and transport trajectories, and the age of vascular plant carbon accumulating in marine sediments will reflect these different predepositional histories. Here, we examine down-core 14C profiles of higher plant leaf waxderived fatty acids isolated from high fidelity sedimentary sequences spanning the socalled “bomb-spike”, and encompassing a ca. 60-degree latitudinal gradient from tropical (Cariaco Basin), temperate (Saanich Inlet), and polar (Mackenzie Delta) watersheds to constrain integrated vascular plant carbon storage/transport times (“residence times”). Using a modeling framework, we find that, in addition to a "young" (conditionally defined as < 50 y) carbon pool, an old pool of compounds comprises 49 to 78 % of the fractional contribution of organic carbon (OC) and exhibits variable ages reflective of the environmental setting. For the Mackenzie Delta sediments, we find a mean age of the old pool of 28 ky (±9.4, standard deviation), indicating extensive pre-aging in permafrost soils, whereas the old pools in Saanich Inlet and Cariaco Basin sediments are younger, 7.9 (±5.0) and 2.4 (±0.50) to 3.2 (±0.54) ky, respectively, indicating less protracted storage in terrestrial reservoirs. The "young" pool showed clear annual contributions for Saanich Inlet and Mackenzie Delta sediments (comprising 24% and 16% of this pool, respectively), likely reflecting episodic transport of OC from steep hillside slopes surrounding Saanich Inlet and annual spring flood deposition in the Mackenzie Delta, respectively. Contributions of 5-10 year old OC to the Cariaco Basin show a short delay of OC inflow, potentially related to transport time to the offshore basin. Modeling results also indicate that the Mackenzie Delta has an influx of young but decadal material (20-30 years of age), pointing to the presence of an intermediate reservoir. Overall, these results show that a significant fraction of vascular plant C undergoes pre-aging in terrestrial reservoirs prior to accumulation in deltaic and marine sediments. The age distribution, reflecting both storage and transport times, likely depends on landscape-specific factors such as local topography, hydrographic characteristics, and mean annual temperature of the catchment, all of which affect the degree of soil buildup and preservation. We show that catchment-specific carbon residence times across landscapes can vary by an order of magnitude, with important implications both for carbon cycle studies and for the interpretation of molecular terrestrial paleoclimate records preserved in sedimentary sequences.
  • Article
    Punctuated shutdown of Atlantic Meridional Overturning Circulation during Greenland Stadial 1
    (Nature Publishing Group, 2016-05-19) Hogg, Alan G. ; Southon, John R. ; Turney, Christian S. M. ; Palmer, Jonathan G. ; Bronk Ramsey, Christopher ; Fenwick, Pavla ; Boswijk, Gretel ; Friedrich, Michael ; Helle, Gerhard ; Hughen, Konrad A. ; Jones, Richard ; Kromer, Bernd ; Noronha, Alexandra ; Reynard, Linda ; Staff, Richard ; Wacker, Lukas
    The Greenland Stadial 1 (GS-1; ~12.9 to 11.65 kyr cal BP) was a period of North Atlantic cooling, thought to have been initiated by North America fresh water runoff that caused a sustained reduction of North Atlantic Meridional Overturning Circulation (AMOC), resulting in an antiphase temperature response between the hemispheres (the ‘bipolar seesaw’). Here we exploit sub-fossil New Zealand kauri trees to report the first securely dated, decadally-resolved atmospheric radiocarbon (14C) record spanning GS-1. By precisely aligning Southern and Northern Hemisphere tree-ring 14C records with marine 14C sequences we document two relatively short periods of AMOC collapse during the stadial, at ~12,920-12,640 cal BP and 12,050-11,900 cal BP. In addition, our data show that the interhemispheric atmospheric 14C offset was close to zero prior to GS-1, before reaching ‘near-modern’ values at ~12,660 cal BP, consistent with synchronous recovery of overturning in both hemispheres and increased Southern Ocean ventilation. Hence, sustained North Atlantic cooling across GS-1 was not driven by a prolonged AMOC reduction but probably due to an equatorward migration of the Polar Front, reducing the advection of southwesterly air masses to high latitudes. Our findings suggest opposing hemispheric temperature trends were driven by atmospheric teleconnections, rather than AMOC changes.
  • Preprint
    Marine-derived C-14 calibration and activity record for the past 50,000 years updated from the Cariaco Basin
    ( 2006-03-01) Hughen, Konrad A. ; Southon, John R. ; Lehman, Scott J. ; Bertrand, Chanda J. H. ; Turnbull, J.
    An expanded Cariaco Basin 14C chronology is tied to 230Th-dated Hulu Cave speleothem records in order to provide detailed marine-based 14C calibration for the past 50,000 years. The revised, high resolution Cariaco 14C calibration record agrees well with data from 230Th-dated fossil corals back to 33 ka, with continued agreement despite increased scatter back to 50 ka, suggesting that the record provides accurate calibration back to the limits of radiocarbon dating. The calibration data document highly elevated Δ14C during the Glacial period. Carbon cycle box model simulations show that the majority of observed Δ14C change can be explained by increased 14C production. However, from 45 to 15 ka, Δ14C remains anomalously high, indicating that the distribution of radiocarbon between surface and deep ocean reservoirs was different than it is today. Additional observations of the magnitude, spatial extent and timing of deep ocean Δ14C shifts are critical for a complete understanding of observed Glacial Δ14C variability.
  • Article
    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).
  • Article
    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.
  • Article
    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.
  • Article
    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.
  • Preprint
    Decadally resolved lateglacial radiocarbon evidence from New Zealand kauri
    ( 2016-10) Hogg, Alan G. ; Southon, John R. ; Turney, Christian S. M. ; Palmer, Jonathan G. ; Bronk Ramsey, Christopher ; Fenwick, Pavla ; Boswijk, Gretel ; Büntgen, Ulf ; Friedrich, Michael ; Helle, Gerhard ; Hughen, Konrad A. ; Jones, Richard ; Kromer, Bernd ; Noronha, Alexandra ; Reinig, Frederick ; Reynard, Linda ; Staff, Richard ; Wacker, Lukas
    The Last Glacial-Interglacial Transition (LGIT; 15,000-11,000 cal BP) was characterized by complex spatiotemporal patterns of climate change, with numerous studies requiring accurate chronological control to decipher leads from lags in global paleoclimatic, -environmental and archaeological records. However, close scrutiny of the few available tree-ring chronologies and 14C-dated sequences composing the IntCal13 radiocarbon calibration curve, indicates significant weakness in 14C calibration across key periods of the LGIT. Here, we present a decadally-resolved atmospheric 14C record derived from New Zealand kauri spanning the Lateglacial from ~13,100 - 11,365 cal BP. Two floating kauri 14C time series, curve-matched to IntCal13, serve as a radiocarbon backbone through the Younger Dryas. The floating Northern Hemisphere (NH) 14C datasets derived from the YD-B and Central European Lateglacial Master tree-ring series are matched against the new kauri data, forming a robust NH 14C time series to ~14,200 cal BP. Our results show that IntCal13 is questionable from ~12,200 - 11,900 cal BP and the ~10,400 BP 14C plateau is approximately five decades too short. The new kauri record and re-positioned NH pine 14C series offer a refinement of the international 14C calibration curves IntCal13 and SHCal13, providing increased confidence in the correlation of global paleorecords.
  • Article
    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).
  • Article
    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.