Wacker Lukas

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  • Preprint
    Global-scale evidence for the refractory nature of riverine black carbon
    ( 2018-05) Coppola, Alysha I. ; Wiedemeier, Daniel B. ; Galy, Valier ; Haghipour, Negar ; Hanke, Ulrich ; Nascimento, Gabriela S. ; Usman, Muhammed ; Blattmann, Thomas M. ; Reisser, Moritz ; Freymond, Chantal V. ; Zhao, Meixun ; Voss, Britta M. ; Wacker, Lukas ; Schefuß, Enno ; Peucker-Ehrenbrink, Bernhard ; Abiven, Samuel ; Schmidt, Michael W. I. ; Eglinton, Timothy I.
    Wildfires and incomplete combustion of fossil fuel produce large amounts of black carbon. Black carbon production and transport are essential components of the carbon cycle. Constraining estimates of black carbon exported from land to ocean is critical, given ongoing changes in land use and climate, which affect fire occurrence and black carbon dynamics. Here, we present an inventory of the concentration and radiocarbon content (∆14C) of particulate black carbon for 18 rivers around the globe. We find that particulate black carbon accounts for about 15.8 ± 0.9% of river particulate organic carbon, and that fluxes of particulate black carbon co-vary with river-suspended sediment, indicating that particulate black carbon export is primarily controlled by erosion. River particulate black carbon is not exclusively from modern sources but is also aged in intermediate terrestrial carbon pools in several high-latitude rivers, with ages of up to 17,000 14C years. The flux-weighted 14C average age of particulate black carbon exported to oceans is 3,700 ± 400 14C years. We estimate that the annual global flux of particulate black carbon to the ocean is 0.017 to 0.037 Pg, accounting for 4 to 32% of the annually produced black carbon. When buried in marine sediments, particulate black carbon is sequestered to form a long-term sink for CO2.
  • Article
    Millennial soil retention of terrestrial organic matter deposited in the Bengal Fan
    (Nature Publishing Group, 2018-08-10) French, Katherine L. ; Hein, Christopher J. ; Haghipour, Negar ; Wacker, Lukas ; Kudrass, Hermann ; Eglinton, Timothy I. ; Galy, Valier
    The abundance of organic carbon (OC) in vegetation and soils (~2,600 PgC) compared to carbon in the atmosphere (~830 PgC) highlights the importance of terrestrial OC in global carbon budgets. The residence time of OC in continental reservoirs, which sets the rates of carbon exchange between land and atmosphere, represents a key uncertainty in global carbon cycle dynamics. Retention of terrestrial OC can also distort bulk OC- and biomarker-based paleorecords, yet continental storage timescales remain poorly quantified. Using “bomb” radiocarbon (14C) from thermonuclear weapons testing as a tracer, we model leaf-wax fatty acid and bulk OC 14C signatures in a river-proximal marine sediment core from the Bay of Bengal in order to constrain OC storage timescales within the Ganges-Brahmaputra (G-B) watershed. Our model shows that 79–83% of the leaf-waxes in this core were stored in continental reservoirs for an average of 1,000–1,200 calendar years, while the remainder was stored for an average of 15 years. This age structure distorts high-resolution organic paleorecords across geologically rapid events, highlighting that compound-specific proxy approaches must consider storage timescales. Furthermore, these results show that future environmental change could destabilize large stores of old - yet reactive - OC currently stored in tropical basins.
  • Preprint
    Differential mobilization of terrestrial carbon pools in Eurasian Arctic river basins
    ( 2013-07) Feng, Xiaojuan ; Vonk, Jorien E. ; van Dongen, Bart E. ; Gustafsson, Orjan ; Semiletov, Igor P. ; Dudarev, Oleg V. ; Wang, Zhiheng ; Montlucon, Daniel B. ; Wacker, Lukas ; Eglinton, Timothy I.
    Mobilization of Arctic permafrost carbon is expected to increase with warming-induced thawing. However, this effect is challenging to assess due to the diverse processes controlling the release of various organic carbon (OC) pools from heterogeneous Arctic landscapes. Here, by radiocarbon dating various terrestrial OC components in fluvially- and coastally-integrated estuarine sediments, we present a unique framework for deconvoluting the contrasting mobilization mechanisms of surface versus deep (permafrost) carbon pools across the climosequence of the Eurasian Arctic. Vascular-plant-derived lignin phenol 14C contents reveal significant inputs of young carbon from surface sources whose delivery is dominantly controlled by river runoff. In contrast, plant wax lipids predominantly trace ancient (permafrost) OC that is preferentially mobilized from discontinuous permafrost regions where hydrological conduits penetrate deeper into soils and thermokarst erosion occurs more frequently. As river runoff has significantly increased across the Eurasian Arctic in recent decades, we estimate from an isotopic mixing model that, in tandem with an increased transfer of young surface carbon, the proportion of mobilized terrestrial OC accounted for by ancient carbon has increased by 3-6% between 1985-2004. These findings suggest that, while partly masked by surface-carbon export, climate-change-induced mobilization of old permafrost carbon is well under way in the Arctic.
  • Preprint
    Microbial oxidation of lithospheric organic carbon in rapidly eroding tropical mountain soils
    ( 2018-02-15) Hemingway, Jordon D. ; Hilton, Robert G. ; Hovius, Niels ; Eglinton, Timothy I. ; Haghipour, Negar ; Wacker, Lukas ; Chen, Meng-Chiang ; Galy, Valier
    Lithospheric organic carbon (“petrogenic”; OCpetro) is oxidized during exhumation and subsequent erosion within mountain ranges. This process is a significant source of CO2 to the atmosphere over geologic timescales, but the mechanisms that govern oxidation rates in mountain landscapes remain poorly constrained. We demonstrate that, on average, 67 ± 11 % of OCpetro initially present in bedrock exhumed from the tropical, rapidly eroding Central Range of Taiwan is oxidized within soils, leading to CO2 emissions of 6.1 – 18.6 t C km-2 yr-1. The molecular and isotopic evolution of bulk OC and lipid biomarkers during soil formation reveals that OCpetro remineralization is microbially mediated. Rapid oxidation in mountain soils drives CO2 emissions fluxes that increase with erosion rate, thereby counteracting CO2 drawdown by silicate weathering and biospheric OC burial.
  • Preprint
    Spatial variations in geochemical characteristics of the modern Mackenzie Delta sedimentary system
    ( 2015-01) Vonk, Jorien E. ; Giosan, Liviu ; Blusztajn, Jerzy S. ; Montlucon, Daniel B. ; Graf Pannatier, Elisabeth ; McIntyre, Cameron P. ; Wacker, Lukas ; Macdonald, Robie W. ; Yunker, Mark B. ; Eglinton, Timothy I.
    The Mackenzie River in Canada is by far the largest riverine source of sediment and organic carbon (OC) to the Arctic Ocean. Therefore the transport, degradation and burial of OC along the land-to-ocean continuum for this riverine system is important to study both regionally and as a dominant representative of Arctic rivers. Here, we apply sedimentological (grain size, mineral surface area), and organic and inorganic geochemical techniques (%OC, δ13C-OC and Δ14C-OC, 143Nd/144Nd,δ2H and δ18O, major and trace elements) on particulate, bank, channel and lake surface sediments from the Mackenzie Delta, as well as on surface sediments from the Mackenzie shelf in the Beaufort Sea. Our data show a hydrodynamic sorting effect resulting in the accumulation of finer-grained sediments in lake and shelf deposits. A general decrease in organic carbon (OC) to mineral surface area ratios from river-to-sea furthermore suggests a loss of mineral-bound terrestrial OC during transport through the delta and deposition on the shelf. The net isotopic value of the terrestrial OC that is lost en route, derived from relationships between δ13C, OC and surface area, is -28.5‰ for δ13C and -417‰ for Δ14C. We calculated that OC burial efficiencies are around 55%, which are higher (~20%) than other large river systems such as the Amazon. Old sedimentary OC ages, up to 12 14C-ky, suggest the delivery of both a petrogenic OC source (with an estimated contribution of 19±9%) as well as a pre-aged terrestrial OC source. We calculated the 14C-age of this pre-aged, biogenic, component to be about 6100 yrs, or -501‰, which illustrates that terrestrial OC in the watershed can reside for millennia in soils before being released into the river. Surface sediments in lakes across the delta (n=20) showed large variability in %OC (0.92% to 5.7%) and δ13C (-30.7‰ to -23.5‰). High-closure lakes, flooding only at exceptionally high water levels, hold high sedimentary OC contents (> 2.5%) and young biogenic OC with a terrestrial or an autochthonous source whereas no-closure lakes, permanently connected to a river channel, hold sediments with pre-aged, terrestrial OC. The intermediate low-closure lakes, flooding every year during peak discharge, display the largest variability in OC content, age and source, likely reflecting variability in for example the length of river-lake connections, the distance to sediment source and the number of intermediate settling basins. Bank, channel and suspended sediment show variable 143Nd/144Nd values, yet there is a gradual but distinct spatial transition in 143Nd/144Nd (nearly three ε units; from -11.4 to -13.9) in the detrital fraction of lake surface sediments from the western to the eastern delta. This reflects the input of younger Peel River catchment material in the west and input of older geological source material in the east, and suggests that lake sediments can be used to assess variability in source watershed patterns across the delta.
  • Article
    Multimolecular tracers of terrestrial carbon transfer across the pan-Arctic : 14C characteristics of sedimentary carbon components and their environmental controls
    (John Wiley & Sons, 2015-11-02) Feng, Xiaojuan ; Gustafsson, Orjan ; Holmes, Robert M. ; Vonk, Jorien E. ; van Dongen, Bart E. ; Semiletov, Igor P. ; Dudarev, Oleg V. ; Yunker, Mark B. ; Macdonald, Robie W. ; Wacker, Lukas ; Montlucon, Daniel B. ; Eglinton, Timothy I.
    Distinguishing the sources, ages, and fate of various terrestrial organic carbon (OC) pools mobilized from heterogeneous Arctic landscapes is key to assessing climatic impacts on the fluvial release of carbon from permafrost. Through molecular 14C measurements, including novel analyses of suberin- and/or cutin-derived diacids (DAs) and hydroxy fatty acids (FAs), we compared the radiocarbon characteristics of a comprehensive suite of terrestrial markers (including plant wax lipids, cutin, suberin, lignin, and hydroxy phenols) in the sedimentary particles from nine major arctic and subarctic rivers in order to establish a benchmark assessment of the mobilization patterns of terrestrial OC pools across the pan-Arctic. Terrestrial lipids, including suberin-derived longer-chain DAs (C24,26,28), plant wax FAs (C24,26,28), and n-alkanes (C27,29,31), incorporated significant inputs of aged carbon, presumably from deeper soil horizons. Mobilization and translocation of these “old” terrestrial carbon components was dependent on nonlinear processes associated with permafrost distributions. By contrast, shorter-chain (C16,18) DAs and lignin phenols (as well as hydroxy phenols in rivers outside eastern Eurasian Arctic) were much more enriched in 14C, suggesting incorporation of relatively young carbon supplied by runoff processes from recent vegetation debris and surface layers. Furthermore, the radiocarbon content of terrestrial markers is heavily influenced by specific OC sources and degradation status. Overall, multitracer molecular 14C analysis sheds new light on the mobilization of terrestrial OC from arctic watersheds. Our findings of distinct ages for various terrestrial carbon components may aid in elucidating fate of different terrestrial OC pools in the face of increasing arctic permafrost thaw.
  • Preprint
    Carbon isotopic (13C and 14C) composition of synthetic estrogens and progestogens
    ( 2012-06) Griffith, David R. ; Wacker, Lukas ; Gschwend, Philip M. ; Eglinton, Timothy I.
    Steroids are potent hormones that are found in many environments. Yet, contributions from synthetic and endogenous sources are largely uncharacterized. The goal of this study was to evaluate whether carbon isotopes could be used to distinguish between synthetic and endogenous steroids in wastewater and other environmental matrices. Estrogens and progestogens were isolated from oral contraceptive pills using semi-preparative liquid chromatography/diode array detection (LC/DAD). Compound purity was confirmed by gas chromatography-flame ionization detection (GC-FID), gas chromatography/time-of-flight mass spectrometry (GC/TOF-MS) and liquid chromatography/mass spectrometry using negative electrospray ionization (LC/ESI-MS). 13C content was determined by gas chromatography/isotope ratio mass spectrometry (GC/IRMS) and 14C was measured by accelerator mass spectrometry (AMS). Synthetic estrogens and progestogens are 13C depleted (δ13Cestrogen = -30.0 ± 0.9 ‰; δ13Cprogestogen = -30.3 ± 2.6 ‰) compared to endogenous hormones (δ13C ~ -16 ‰ to -26 ‰). The 14C content of the majority of synthetic hormones is consistent with synthesis from C3 plant-based precursors, amended with “fossil” carbon in the case of EE2 and norethindrone acetate. Exceptions are progestogens that contain an ethyl group at carbon position 13 and have entirely “fossil” 14C signatures. Carbon isotope measurements have the potential to distinguish between synthetic and endogenous hormones in the environment. Our results suggest that 13C could be used to discriminate endogenous from synthetic estrogens in animal waste, wastewater effluent, and natural waters. In contrast, 13C and 14C together may prove useful for tracking synthetic progestogens.
  • Article
    Short communication : Massive erosion in monsoonal central India linked to late Holocene land cover degradation
    (Copernicus Publications on behalf of the European Geosciences Union, 2017-12-01) Giosan, Liviu ; Ponton, Camilo ; Usman, Muhammed ; Blusztajn, Jerzy S. ; Fuller, Dorian Q. ; Galy, Valier ; Haghipour, Negar ; Johnson, Joel E. ; McIntyre, Cameron P. ; Wacker, Lukas ; Eglinton, Timothy I.
    Soil erosion plays a crucial role in transferring sediment and carbon from land to sea, yet little is known about the rhythm and rates of soil erosion prior to the most recent few centuries. Here we reconstruct a Holocene erosional history from central India, as integrated by the Godavari River in a sediment core from the Bay of Bengal. We quantify terrigenous fluxes, fingerprint sources for the lithogenic fraction and assess the age of the exported terrigenous carbon. Taken together, our data show that the monsoon decline in the late Holocene significantly increased soil erosion and the age of exported organic carbon. This acceleration of natural erosion was later exacerbated by the Neolithic adoption and Iron Age extensification of agriculture on the Deccan Plateau. Despite a constantly elevated sea level since the middle Holocene, this erosion acceleration led to a rapid growth of the continental margin. We conclude that in monsoon conditions aridity boosts rather than suppresses sediment and carbon export, acting as a monsoon erosional pump modulated by land cover conditions.
  • 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
    Rapid 14C analysis of dissolved organic carbon in non-saline waters
    ( 2016-06) Lang, Susan Q. ; McIntyre, Cameron P. ; Bernasconi, Stefano M. ; Fruh-Green, Gretchen L. ; Voss, Britta M. ; Eglinton, Timothy I. ; Wacker, Lukas
    The radiocarbon content of dissolved organic carbon (DOC) in rivers, lakes, and other non-saline waters can provide valuable information on carbon cycling dynamics in the environment. DOC is typically prepared for 14C analysis by accelerator mass spectrometry (AMS) either by ultraviolet (UV) oxidation or by freeze-drying and sealed tube combustion. We present here a new method for the rapid analysis of 14C of DOC using wet chemical oxidation (WCO) and automated headspace sampling of CO2. The approach is an adaption of recently developed methods using aqueous persulfate oxidant to determine the δ13C of DOC in non-saline water samples and the 14C content of volatile organic acids. One advantage of the current method over UV oxidation is higher throughput: 22 samples and 10 processing standards can be prepared in one day and analyzed in a second day, allowing a full suite of 14C processing standards and blanks to be run in conjunction with samples. A second advantage is that there is less potential for cross-contamination between samples.
  • Article
    Climate control on terrestrial biospheric carbon turnover
    (National Academy of Sciences, 2021-02-23) Eglinton, Timothy I. ; Galy, Valier ; Hemingway, Jordon D. ; Feng, Xiaojuan ; Bao, Hongyan ; Blattmann, Thomas M. ; Dickens, Angela F. ; Gies, Hannah ; Giosan, Liviu ; Haghipour, Negar ; Hou, Pengfei ; Lupker, Maarten ; McIntyre, Cameron P. ; Montlucon, Daniel B. ; Peucker-Ehrenbrink, Bernhard ; Ponton, Camilo ; Schefuß, Enno ; Schwab, Melissa S. ; Voss, Britta M. ; Wacker, Lukas ; Wu, Ying ; Zhao, Meixun
    Terrestrial vegetation and soils hold three times more carbon than the atmosphere. Much debate concerns how anthropogenic activity will perturb these surface reservoirs, potentially exacerbating ongoing changes to the climate system. Uncertainties specifically persist in extrapolating point-source observations to ecosystem-scale budgets and fluxes, which require consideration of vertical and lateral processes on multiple temporal and spatial scales. To explore controls on organic carbon (OC) turnover at the river basin scale, we present radiocarbon (14C) ages on two groups of molecular tracers of plant-derived carbon—leaf-wax lipids and lignin phenols—from a globally distributed suite of rivers. We find significant negative relationships between the 14C age of these biomarkers and mean annual temperature and precipitation. Moreover, riverine biospheric-carbon ages scale proportionally with basin-wide soil carbon turnover times and soil 14C ages, implicating OC cycling within soils as a primary control on exported biomarker ages and revealing a broad distribution of soil OC reactivities. The ubiquitous occurrence of a long-lived soil OC pool suggests soil OC is globally vulnerable to perturbations by future temperature and precipitation increase. Scaling of riverine biospheric-carbon ages with soil OC turnover shows the former can constrain the sensitivity of carbon dynamics to environmental controls on broad spatial scales. Extracting this information from fluvially dominated sedimentary sequences may inform past variations in soil OC turnover in response to anthropogenic and/or climate perturbations. In turn, monitoring riverine OC composition may help detect future climate-change–induced perturbations of soil OC turnover and stocks.
  • Article
    Consistently dated Atlantic sediment cores over the last 40 thousand years
    (Nature Research, 2019-09-02) Waelbroeck, Claire ; Lougheed, Bryan C. ; Vazquez Riveiros, Natalia ; Missiaen, Lise ; Pedro, Joel ; Dokken, Trond ; Hajdas, Irka ; Wacker, Lukas ; Abbott, Peter ; Dumoulin, Jean-Pascal ; Thil, Francois ; Eynaud, Frederique ; Rossignol, Linda ; Fersi, Wiem ; Albuquerque, Ana Luiza ; Arz, Helge W. ; Austin, William E. N. ; Came, Rosemarie E. ; Carlson, Anders E. ; Collins, James A. ; Dennielou, Bernard ; Desprat, Stéphanie ; Dickson, Alex ; Elliot, Mary ; Farmer, Christa ; Giraudeau, Jacques ; Gottschalk, Julia ; Henderiks, Jorijntje ; Hughen, Konrad A. ; Jung, Simon ; Knutz, Paul ; Lebreiro, Susana ; Lund, David C. ; Lynch-Stieglitz, Jean ; Malaizé, Bruno ; Marchitto, Thomas M. ; Martínez-Méndez, Gema ; Mollenhauer, Gesine ; Naughton, Filipa ; Nave, Silvia ; Nürnberg, Dirk ; Oppo, Delia W. ; Peck, Vicky L. ; Peeters, Frank J. C. ; Penaud, Aurélie ; Portilho-Ramos, Rodrigo da Costa ; Repschläger, Janne ; Roberts, Jenny ; Ruhlemann, Carsten ; Salgueiro, Emilia ; Sanchez Goni, Maria Fernanda ; Schönfeld, Joachim ; Scussolini, Paolo ; Skinner, Luke C. ; Skonieczny, Charlotte ; Thornalley, David J. R. ; Toucanne, Samuel ; Van Rooij, David ; Vidal, Laurence ; Voelker, Antje H. L. ; Wary, Mélanie ; Weldeab, Syee ; Ziegler, Martin
    Rapid changes in ocean circulation and climate have been observed in marine-sediment and ice cores over the last glacial period and deglaciation, highlighting the non-linear character of the climate system and underlining the possibility of rapid climate shifts in response to anthropogenic greenhouse gas forcing. To date, these rapid changes in climate and ocean circulation are still not fully explained. One obstacle hindering progress in our understanding of the interactions between past ocean circulation and climate changes is the difficulty of accurately dating marine cores. Here, we present a set of 92 marine sediment cores from the Atlantic Ocean for which we have established age-depth models that are consistent with the Greenland GICC05 ice core chronology, and computed the associated dating uncertainties, using a new deposition modeling technique. This is the first set of consistently dated marine sediment cores enabling paleoclimate scientists to evaluate leads/lags between circulation and climate changes over vast regions of the Atlantic Ocean. Moreover, this data set is of direct use in paleoclimate modeling studies.
  • Article
    Organic carbon aging during across‐shelf transport
    (John Wiley & Sons, 2018-08-22) Bao, Rui ; Uchida, Masao ; Zhao, Meixun ; Haghipour, Negar ; Montlucon, Daniel B. ; McNichol, Ann P. ; Wacker, Lukas ; Hayes, John M. ; Eglinton, Timothy I.
    Compound‐specific radiocarbon analysis was performed on different grain‐size fractions of surficial sediments to examine and compare lateral transport times (LTTs) of organic carbon. 14C aging of long‐chain leaf wax fatty acids along two dispersal pathways of fluvially derived material on adjacent continental margins implies LTTs over distances of ~30 to 500 km that range from hundreds to thousands of years. The magnitude of aging differs among grain size fractions. Our finding suggests that LTTs vary both temporally and spatially as a function of the specific properties of different continental shelf settings. Observations suggest that 14C aging is widespread during lateral transport over continental shelves, with hydrodynamic particle sorting inducing age variations among organic components residing in different grain sizes. Consideration of these phenomena is of importance for understanding carbon cycle processes and interpretation on sedimentary records on continental margins.
  • Article
    Constraining instantaneous fluxes and integrated compositions of fluvially discharged organic matter
    (American Geophysical Union, 2018-06-07) Freymond, Chantal V. ; Lupker, Maarten ; Peterse, Francien ; Haghipour, Negar ; Wacker, Lukas ; Filip, Florin ; Giosan, Liviu ; Eglinton, Timothy
    Fluvial export of organic carbon (OC) and burial in ocean sediments comprises an important carbon sink, but fluxes remain poorly constrained, particularly for specific organic components. Here OC and lipid biomarker contents and isotopic characteristics of suspended matter determined in depth profiles across an active channel close to the terminus of the Danube River are used to constrain instantaneous OC and biomarker fluxes and integrated compositions during high to moderate discharges. During high (moderate) discharge, the total Danube exports 8 (7) kg/s OC, 7 (3) g/s higher plant‐derived long‐chain fatty acids (LCFA), 34 (21) g/s short‐chain fatty acids (SCFA), and 0.5 (0.2) g/s soil bacterial membrane lipids (brGDGTs). Integrated stable carbon isotopic compositions were TOC: −28.0 (−27.6)‰, LCFA: −33.5 (−32.8)‰ and Δ14C TOC: −129 (−38)‰, LCFA: −134 (−143)‰, respectively. Such estimates will aid in establishing quantitative links between production, export, and burial of OC from the terrestrial biosphere.
  • 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.
  • 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.