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  • 1
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    Cambridge University Press
    In:  EPIC3Antarctic Science, Cambridge University Press, 33(6), pp. 575-595, ISSN: 0954-1020
    Publication Date: 2022-01-13
    Description: The waters along the West Antarctic Peninsula (WAP) have experienced warming and increased freshwater inputs from melting sea ice and glaciers in recent decades. Challenges exist in understanding the consequences of these changes on the inorganic carbon system in this ecologically important and highly productive ecosystem. Distributions of dissolved inorganic carbon (CT), total alkalinity (AT) and nutrients revealed key physical, biological and biogeochemical controls of the calcium carbonate saturation state (Ωaragonite) in different water masses across the WAP shelf during the summer. Biological production in spring and summer dominated changes in surface water Ωaragonite (ΔΩaragonite up to +1.39; ∼90%) relative to underlying Winter Water. Sea-ice and glacial meltwater constituted a minor source of AT that increased surface water Ωaragonite (ΔΩaragonite up to +0.07; ∼13%). Remineralization of organic matter and an influx of carbon-rich brines led to cross-shelf decreases in Ωaragonite in Winter Water and Circumpolar Deep Water. A strong biological carbon pump over the shelf created Ωaragonite oversaturation in surface waters and suppression of Ωaragonite in subsurface waters. Undersaturation of aragonite occurred at 〈 ∼1000 m. Ongoing changes along the WAP will impact the biologically driven and meltwater-driven processes that influence the vulnerability of shelf waters to calcium carbonate undersaturation in the future.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
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  • 2
    Publication Date: 2022-06-22
    Description: Pliocene–Quaternary faults are relevant structures with which to constrain the seismotectonic context and contribute to the evaluation of the seismic hazard of a region. Many of these faults, however, do not show clear surface evidence even when releasing earthquakes. For these reasons they can be extremely dangerous as they receive relatively little attention and can be difficult to identify. From among the various surface geology studies and/or palaeoseismological investigations, we focus our attention on the integration of different datasets such as seismic reflection profiles, surface kinematic data and the relocation of seismological data, which make it possible to identify and characterize active faults whose dimension and earthquake potential would otherwise not be large enough to make them identifiable. We take as an example the Montespertoli NE-trending fault in southern Tuscany (central Italy) with which we associate the 2016 M=3.9 Castelfiorentino earthquake. This structure is part of a wider (in the order of 15–20 km) crustal-scale shear zone, which may be responsible for strong historical earthquakes in the area.
    Description: Published
    Description: 853 - 872
    Description: 4T. Sismicità dell'Italia
    Description: JCR Journal
    Keywords: active faults ; seismic faults ; Earthquakes ; strike-slip faults ; inner Northern Apennines ; solid earth
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hughen, K. A., & Heaton, T. J. Updated Cariaco Basin C-14 calibration dataset from 0-60 cal kyr BP. Radiocarbon, 62(4), (2020): 1001-1043, doi:10.1017/RDC.2020.53.
    Description: We present new updates to the calendar and radiocarbon (14C) chronologies for the Cariaco Basin, Venezuela. Calendar ages were generated by tuning abrupt climate shifts in Cariaco Basin sediments to those in speleothems from Hulu Cave. After the original Cariaco-Hulu calendar age model was published, Hulu Cave δ18O records have been augmented with increased temporal resolution and a greater number of U/Th dates. These updated Hulu Cave records provide increased accuracy as well as precision in the final Cariaco calendar age model. The depth scale for the Ocean Drilling Program Site 1002D sediment core, the primary source of samples for 14C dating, has been corrected to account for missing sediment from a core break, eliminating age-depth anomalies that afflicted the earlier calendar age models. Individual 14C dates for the Cariaco Basin remain unchanged from previous papers, although detailed comparisons of the Cariaco calibration dataset to those from Hulu Cave and Lake Suigetsu suggest that the Cariaco marine reservoir age may have shifted systematically during the past. We describe these recent changes to the Cariaco datasets and provide the data in a comprehensive format that will facilitate use by the community.
    Description: K.A. Hughen was supported by funds from U.S. NSF grant #OCE-1657191, and by the Investment in Science Fund at WHOI. T.J. Heaton is supported by a Leverhulme Trust Fellowship RF-2019-140\9, “Improving the Measurement of Time Using Radiocarbon”.
    Keywords: Calibration ; Climate ; Radiocarbon
    Repository Name: Woods Hole Open Access Server
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  • 4
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Baker, M. G., Aster, R. C., Wiens, D. A., Nyblade, A., Bromirski, P. D., Gerstoft, P., & Stephen, R. A. Teleseismic earthquake wavefields observed on the Ross Ice Shelf. Journal of Glaciology, 67(261), (2021): 58-74, https://doi.org/10.1017/jog.2020.83.
    Description: Observations of teleseismic earthquakes using broadband seismometers on the Ross Ice Shelf (RIS) must contend with environmental and structural processes that do not exist for land-sited seismometers. Important considerations are: (1) a broadband, multi-mode ambient wavefield excited by ocean gravity wave interactions with the ice shelf; (2) body wave reverberations produced by seismic impedance contrasts at the ice/water and water/seafloor interfaces and (3) decoupling of the solid Earth horizontal wavefield by the sub-shelf water column. We analyze seasonal and geographic variations in signal-to-noise ratios for teleseismic P-wave (0.5–2.0 s), S-wave (10–15 s) and surface wave (13–25 s) arrivals relative to the RIS noise field. We use ice and water layer reverberations generated by teleseismic P-waves to accurately estimate the sub-station thicknesses of these layers. We present observations consistent with the theoretically predicted transition of the water column from compressible to incompressible mechanics, relevant for vertically incident solid Earth waves with periods longer than 3 s. Finally, we observe symmetric-mode Lamb waves generated by teleseismic S-waves incident on the grounding zones. Despite their complexity, we conclude that teleseismic coda can be utilized for passive imaging of sub-shelf Earth structure, although longer deployments relative to conventional land-sited seismometers will be necessary to acquire adequate data.
    Description: This research was supported by NSF grants PLR-1142518, 1141916, 1142126, 1246151, 1246416 and OPP-1744852 and 1744856.
    Keywords: Glacier geophysics ; Ice shelves ; Seismology
    Repository Name: Woods Hole Open Access Server
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  • 5
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    Cambridge University Press
    Publication Date: 2022-10-26
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in McNichol, A., Key, R., & Guilderson, T. Global ocean radiocarbon programs. Radiocarbon, (2022): 1–13, https://doi.org/10.1017/rdc.2022.17.
    Description: The importance of studying the radiocarbon content of dissolved inorganic carbon (DI14C) in the oceans has been recognized for decades. Starting with the GEOSECS program in the 1970s, 14C sampling has been a part of most global survey programs. Early results were used to study air-sea gas exchange while the more recent results are critical for helping calibrate ocean general circulation models used to study the effects of climate change. Here we summarize the major programs and discuss some of the important insights the results are starting to provide.
    Description: Authors received funding from the National Science Foundation OCE-85865400 (APM) and a Woods Hole Oceanographic Technical Staff Award (APM).
    Keywords: Dissolved inorganic carbon ; Ocean models ; Oceanography ; Radiocarbon
    Repository Name: Woods Hole Open Access Server
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  • 6
    Publication Date: 2022-10-20
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ackley, S. F., Perovich, D. K., Maksym, T., Weissling, B., & Xie, H. Surface flooding of Antarctic summer sea ice. Annals of Glaciology, 61(82), (2020): 117-126, doi:10.1017/aog.2020.22.
    Description: The surface flooding of Antarctic sea ice in summer covers 50% or more of the sea-ice area in the major summer ice packs, the western Weddell and the Bellingshausen-Amundsen Seas. Two CRREL ice mass-balance buoys were deployed on the Amundsen Sea pack in late December 2010 from the icebreaker Oden, bridging the summer period (January–February 2011). Temperature records from thermistors embedded vertically in the snow and ice showed progressive increases in the depth of the flooded layer (up to 0.3–0.35 m) on the ice cover during January and February. While the snow depth was relatively unchanged from accumulation (〈10 cm), ice thickness decreased by up to a meter from bottom melting during this period. Contemporaneous with the high bottom melting, under-ice water temperatures up to 1°C above the freezing point were found. The high temperature arises from solar heating of the upper mixed layer which can occur when ice concentration in the local area falls and lower albedo ocean water is exposed to radiative heating. The higher proportion of snow ice found in the Amundsen Sea pack ice therefore results from both winter snowfall and summer ice bottom melt found here that can lead to extensive surface flooding.
    Description: This work was supported by the National Science Foundation grant to UTSA, ANT-0839053-Sea Ice System in Antarctic Summer (S.F. Ackley, H. Xie and B. Weissling), and to WHOI, ANT-1341513 (T. Maksym), and by the NASA Center for Advanced Measurements in Extreme Environments or NASA-CAMEE at UTSA, NASA #80NSSC19M0194 (S.F. Ackley, H. Xie, B.Weissling).
    Keywords: Ice/ocean interactions ; Sea ice ; Sea-ice growth and decay ; Snow/ice surface processes
    Repository Name: Woods Hole Open Access Server
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  • 7
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Reimer, P. J., Austin, W. E. N., Bard, E., Bayliss, A., Blackwell, P. G., Ramsey, C. B., Butzin, M., Cheng, H., Edwards, R. L., Friedrich, M., Grootes, P. M., Guilderson, T. P., Hajdas, I., Heaton, T. J., Hogg, A. G., Hughen, K. A., Kromer, B., Manning, S. W., Muscheler, R., Palmer, J. G., Pearson, C., van der Plicht, J., Reimer, R. W., Richards, D. A., Scott, E. M., Southon, J. R., Turney, C. S. M., Wacker, L., Adolphi, F., Buentgen, U., Capano, M., Fahrni, S. M., Fogtmann-Schulz, A., Friedrich, R., Koehler, P., Kudsk, S., Miyake, F., Olsen, J., Reinig, F., Sakamoto, M., Sookdeo, A., & Talamo, S. The Intcal20 Northern Hemisphere radiocarbon age calibration curve (0-55 cal kBP). Radiocarbon, 62(4), (2020): 725-757, doi:10.1017/RDC.2020.41.
    Description: 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.
    Description: We would like to thank the National Natural Science Foundation of China grants NSFC 41888101 and NSFC 41731174, the 111 program of China (D19002), U.S. NSF Grant 1702816, and the Malcolm H. Wiener Foundation for support for research that contributed to the IntCal20 curve. The work on the Swiss and German YD trees was funded by the German Science foundation and the Swiss National Foundation (grant number: 200021L_157187). The operation in Aix-en-Provence is funded by the EQUIPEX ASTER-CEREGE, the Collège de France and the ANR project CARBOTRYDH (to EB). The work on the correlation of tree ring 14C with ice core 10Be was partially supported by the Swedish Research Council and the Knut and Alice Wallenberg foundation. M. Butzin was supported by the German Federal Ministry of Education and Research (BMBF) as Research for Sustainable Development (FONA; http://www.fona.de) through the PalMod project (grant number: 01LP1505B). S. Talamo and M. Friedrich are funded by the European Research Council under the European Union’s Horizon 2020 Research and Innovation Programme (grant agreement No. 803147-RESOLUTION, awarded to ST). CA. Turney would like to acknowledge support of the Australian Research Council (FL100100195 and DP170104665). P. Reimer and W. Austin acknowledge the support of the UKRI Natural Environment Research Council (Grant NE/M004619/1). T.J. Heaton is supported by a Leverhulme Trust Fellowship RF-2019-140\9. Other datasets and the IntCal20 database were created without external support through internal funding by the respective laboratories. We also would like to thank various institutions that provided funding or facilities for meetings.
    Keywords: Calibration curve ; Radiocarbon ; IntCal20
    Repository Name: Woods Hole Open Access Server
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  • 8
    Publication Date: 2022-10-26
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Druffel, E., Beaupre, S., Grotheer, H., Lewis, C., McNichol, A., Mollenhauer, G., & Walker, B. Marine organic carbon and radiocarbon – present and future challenges. Radiocarbon, (2022): 1-17, https://doi.org/10.1017/RDC.2021.105.
    Description: We discuss present and developing techniques for studying radiocarbon in marine organic carbon (C). Bulk DOC (dissolved organic C) Δ14C measurements reveal information about the cycling time and sources of DOC in the ocean, yet they are time consuming and need to be streamlined. To further elucidate the cycling of DOC, various fractions have been separated from bulk DOC, through solid phase extraction of DOC, and ultrafiltration of high and low molecular weight DOC. Research using 14C of DOC and particulate organic C separated into organic fractions revealed that the acid insoluble fraction is similar in 14C signature to that of the lipid fraction. Plans for utilizing this methodology are described. Studies using compound specific radiocarbon analyses to study the origin of biomarkers in the marine environment are reviewed and plans for the future are outlined. Development of ramped pyrolysis oxidation methods are discussed and scientific questions addressed. A modified elemental analysis (EA) combustion reactor is described that allows high particulate organic C sample throughput by direct coupling with the MIniCArbonDAtingSystem.
    Keywords: CSRA ; Dissolved organic carbon ; Methodology ; Organic carbon ; Radiocarbon
    Repository Name: Woods Hole Open Access Server
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  • 9
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Priscu, J. C., Kalin, J., Winans, J., Campbell, T., Siegfried, M. R., Skidmore, M., Dore, J. E., Leventer, A., Harwood, D. M., Duling, D., Zook, R., Burnett, J., Gibson, D., Krula, E., Mironov, A., McManis, J., Roberts, G., Rosenheim, B. E., Christner, B. C., Kasic, K., Fricker, H. A., Lyons, W. B., Barker, J., Bowling, M., Collins, B., Davis, C., Gagnon, A., Gardner, C., Gustafson, C., Kim, O-S., Li, W., Michaud, A., Patterson, M. O., Tranter, M., Ryan Venturelli, R., Trista Vick-Majors, T., & Elsworth, C. Scientific access into Mercer Subglacial Lake: scientific objectives, drilling operations and initial observations. Annals of Glaciology, 62(85–86), (2021): 340–352, https://doi.org/10.1017/aog.2021.10.
    Description: The Subglacial Antarctic Lakes Scientific Access (SALSA) Project accessed Mercer Subglacial Lake using environmentally clean hot-water drilling to examine interactions among ice, water, sediment, rock, microbes and carbon reservoirs within the lake water column and underlying sediments. A ~0.4 m diameter borehole was melted through 1087 m of ice and maintained over ~10 days, allowing observation of ice properties and collection of water and sediment with various tools. Over this period, SALSA collected: 60 L of lake water and 10 L of deep borehole water; microbes 〉0.2 μm in diameter from in situ filtration of ~100 L of lake water; 10 multicores 0.32–0.49 m long; 1.0 and 1.76 m long gravity cores; three conductivity–temperature–depth profiles of borehole and lake water; five discrete depth current meter measurements in the lake and images of ice, the lake water–ice interface and lake sediments. Temperature and conductivity data showed the hydrodynamic character of water mixing between the borehole and lake after entry. Models simulating melting of the ~6 m thick basal accreted ice layer imply that debris fall-out through the ~15 m water column to the lake sediments from borehole melting had little effect on the stratigraphy of surficial sediment cores.
    Description: This material is based upon work supported by the US National Science Foundation, Section for Antarctic Sciences, Antarctic Integrated System Science program as part of the interdisciplinary (Subglacial Antarctic Lakes Scientific Access (SALSA): Integrated study of carbon cycling in hydrologically-active subglacial environments) project (NSF-OPP 1543537, 1543396, 1543405, 1543453 and 1543441). Ok-Sun Kim was funded by the Korean Polar Research Institute. We are particularly thankful to the SALSA traverse personnel for crucial technical and logistical support. The United States Antarctic Program enabled our fieldwork; the New York Air National Guard and Kenn Borek Air provided air support; UNAVCO provided geodetic instrument support. Hot water drilling activities, including repair and upgrade modifications of the WISSARD hot water drill system, for the SALSA project were supported by a subaward from the Ice Drilling Program of Dartmouth College (NSF-PLR 1327315) to the University of Nebraska-Lincoln. J. Lawrence assisted with manuscript preparation. Finally, we are grateful to C. Dean, the SALSA Project Manager, and R. Ricards, SALSA Project Coordinator at McMurdo Station, for their organizational skills, and B. Huber of Lamont-Doherty Earth Observatory for providing the SBE39 PT sensors and the Nortek Aquadopp current meter and assisting with interpretation of the data. B. Huber also provided helpful input on programing and calibrating the SBE19PlusV2 6112 CTD.
    Keywords: Antarctic glaciology ; Basal ice ; Biogeochemistry ; Glacial sedimentology ; Subglacial lakes
    Repository Name: Woods Hole Open Access Server
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  • 10
    Publication Date: 2022-05-27
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tison, J.-L., Maksym, T., Fraser, A. D., Corkill, M., Kimura, N., Nosaka, Y., Nomura, D., Vancoppenolle, M., Ackley, S., Stammerjohn, S., Wauthy, S., Van der Linden, F., Carnat, G., Sapart, C., de Jong, J., Fripiat, F., & Delille, B. Physical and biological properties of early winter Antarctic sea ice in the Ross Sea. Annals of Glaciology, 61(83), (2020): 241–259, https://doi.org/10.1017/aog.2020.43.
    Description: This work presents the results of physical and biological investigations at 27 biogeochemical stations of early winter sea ice in the Ross Sea during the 2017 PIPERS cruise. Only two similar cruises occurred in the past, in 1995 and 1998. The year 2017 was a specific year, in that ice growth in the Central Ross Sea was considerably delayed, compared to previous years. These conditions resulted in lower ice thicknesses and Chl-a burdens, as compared to those observed during the previous cruises. It also resulted in a different structure of the sympagic algal community, unusually dominated by Phaeocystis rather than diatoms. Compared to autumn-winter sea ice in the Weddell Sea (AWECS cruise), the 2017 Ross Sea pack ice displayed similar thickness distribution, but much lower snow cover and therefore nearly no flooding conditions. It is shown that contrasted dynamics of autumnal-winter sea-ice growth between the Weddell Sea and the Ross Sea impacted the development of the sympagic community. Mean/median ice Chl-a concentrations were 3–5 times lower at PIPERS, and the community status there appeared to be more mature (decaying?), based on Phaeopigments/Chl-a ratios. These contrasts are discussed in the light of temporal and spatial differences between the two cruises.
    Description: S. Stammerjohn was supported by the PIPERS and LTER Programs of the U.S. National Science Foundation, ANT-1341606 (S. Stammerjohn and J. Cassano, U Colorado) and ANT-0823101 (H. Ducklow, LDEO/Columbia University), respectively. Steve Ackley (UTSA) was supported by the PIPERS program of the U.S. National Science Foundation ANT-1341717 and by NASA Grant 80NSSC19M0194 to the Center for Adv. Meas. in Extreme Environments at UTSA.Ted Maksym (WHOI) was supported by the PIPERS program of the U.S. National Science Foundation ANT-1341513. This research was supported by the Belgian F.R.S-FNRS (project ISOGGAP and IODIne, contract T.0268.16 and J.0262.17, respectively). Fanny Van der Linden, Sarah Wauthy, Gauthier Carnat, Célia Sapart and Bruno Delille are PhD students, postdoctoral researchers and research associate, respectively, of the Belgian F.R.S.-FNRS. This work was also supported by the Australian Government's Cooperative Research Centre program through the Antarctic Climate & Ecosystems Cooperative Research Centre, and by the Australian Research Council's Special Research Initiative for Antarctic Gateway Partnership (Project ID SR140300001). Daiki Nomura was supported by grants from the Japan Society for the Promotion of Science (#17H04715) and the National Institute for Polar Research through Project Research KP-303 (ROBOTICA) and #28-14.
    Keywords: Antarctic glaciology ; biogeochemistry ; sea ice
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  • 11
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    Cambridge University Press
    In:  EPIC3Climate Change 2022: Impacts, adaptation and vulnerability. Contribution of the WGII to the 6th assessment report of the intergovernmental panel on climate change, IPCC AR WGII, Cambridge University Press
    Publication Date: 2022-08-23
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , NonPeerReviewed
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  • 12
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    Cambridge University Press
    In:  EPIC3Climate Change 2022: Impacts, adaptation and vulnerability. Contribution of the WGII to the 6th assessment report of the intergovernmental panel on climate change, ,, IPCC AR6 WGII, https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_FinalDraft_Chapter03.pdf, Cambridge University Press
    Publication Date: 2022-08-23
    Repository Name: EPIC Alfred Wegener Institut
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  • 13
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    Cambridge University Press
    In:  EPIC3Climate Change 2022: Impacts, adaptation and vulnerability. Contribution of the WGII to the 6th assessment report of the intergovernmental panel on climate change, IPCC AR6 WGII, Climate Change 2022: Impacts, adaptation and vulnerability. Contribution of the WGII to the 6th assessment report of the intergovernmental panel on climate change, IPCC AR6 WGII, https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_FinalDraft_Chapter02.pdf, Cambridge University Press, 5 p., pp. 22-26
    Publication Date: 2022-06-17
    Repository Name: EPIC Alfred Wegener Institut
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  • 14
    Publication Date: 2022-07-20
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tan, S., Pratt, L. J., Voet, G., Cusack, J. M., Helfrich, K. R., Alford, M. H., Girton, J. B., & Carter, G. S. Hydraulic control of flow in a multi-passage system connecting two basins. Journal of Fluid Mechanics, 940, (2022): A8, https://doi.org/10.1017/jfm.2022.212.
    Description: When a fluid stream in a conduit splits in order to pass around an obstruction, it is possible that one branch will be critically controlled while the other remains not so. This is apparently the situation in Pacific Ocean abyssal circulation, where most of the northward flow of Antarctic bottom water passes through the Samoan Passage, where it is hydraulically controlled, while the remainder is diverted around the Manihiki Plateau and is not controlled. These observations raise a number of questions concerning the dynamics necessary to support such a regime in the steady state, the nature of upstream influence and the usefulness of rotating hydraulic theory to predict the partitioning of volume transport between the two paths, which assumes the controlled branch is inviscid. Through the use of a theory for constant potential vorticity flow and accompanying numerical model, we show that a steady-state regime similar to what is observed is dynamically possible provided that sufficient bottom friction is present in the uncontrolled branch. In this case, the upstream influence that typically exists for rotating channel flow is transformed into influence into how the flow is partitioned. As a result, the partitioning of volume flux can still be reasonably well predicted with an inviscid theory that exploits the lack of upstream influence.
    Description: This work was supported by the National Science Foundation under grants OCE-1029268, OCE-1029483, OCE-1657264, OCE-1657795, OCE-1657870 and OCE-1658027.
    Repository Name: Woods Hole Open Access Server
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  • 15
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Heaton, T. J., Koehler, P., Butzin, M., Bard, E., Reimer, R. W., Austin, W. E. N., Ramsey, C. B., Grootes, P. M., Hughen, K. A., Kromer, B., Reimer, P. J., Adkins, J., Burke, A., Cook, M. S., Olsen, J., & Skinner, L. C. Marine20-the marine radiocarbon age calibration curve (0-55,000 cal BP). Radiocarbon, 62(4), (2020): 779-820, doi:10.1017/RDC.2020.68.
    Description: 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/.
    Description: We would like to thank Jeremy Oakley and Richard Bintanja for informative discussions during the development of this work. T.J. Heaton is supported by a Leverhulme Trust Fellowship RF-2019-140\9, “Improving the Measurement of Time Using Radiocarbon”. M Butzin is supported by the German Federal Ministry of Education and Research (BMBF), as Research for Sustainability initiative (FONA); www.fona.de through the PalMod project (grant numbers: 01LP1505B, 01LP1919A). E. Bard is supported by EQUIPEX ASTER-CEREGE and ANR CARBOTRYDH. Meetings of the IntCal Marine Focus group have been supported by Collège de France. Data are available on the PANGAEA database at doi:10.159/ANGAEA.914500.
    Keywords: Bayesian modeling ; calibration ; carbon cycle ; computer model ; marine environment
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  • 16
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in [Schiller, C. M., Whitlock, C., Elder, K. L., Iverson, N. A., & Abbott, M. B. Erroneously old radiocarbon ages from terrestrial pollen concentrates in Yellowstone Lake, Wyoming, USA. Radiocarbon, 63(1), (2021): 321-342, https://doi.org/10.1017/RDC.2020.118.
    Description: Accelerator mass spectrometry (AMS) dating of pollen concentrates is often used in lake sediment records where large, terrestrial plant remains are unavailable. Ages produced from chemically concentrated pollen as well as manually picked Pinaceae grains in Yellowstone Lake (Wyoming) sediments were consistently 1700–4300 cal years older than ages established by terrestrial plant remains, tephrochronology, and the age of the sediment-water interface. Previous studies have successfully utilized the same laboratory space and methods, suggesting the source of old-carbon contamination is specific to these samples. Manually picking pollen grains precludes admixture of non-pollen materials. Furthermore, no clear source of old pollen grains occurs on the deglaciated landscape, making reworking of old pollen grains unlikely. High volumes of CO2 are degassed in the Yellowstone Caldera, potentially introducing old carbon to pollen. While uptake of old CO2 through photosynthesis is minor (F14C approximately 0.99), old-carbon contamination may still take place in the water column or in surficial lake sediments. It remains unclear, however, what mechanism allows for the erroneous ages of highly refractory pollen grains while terrestrial plant remains were unaffected. In the absence of a satisfactory explanation for erroneously old radiocarbon ages from pollen concentrates, we propose steps for further study.
    Description: This research was supported by NSF Grant No. 1515353 to C. Whitlock and sampling in Yellowstone National Park was conducted under permits YELL-SCI-0009 and YELL-SCI-5054.
    Keywords: AMS dating ; Chronology ; Contamination ; Paleoecology ; Pine
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  • 17
    Publication Date: 2022-10-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Roberts, Mark L., Elder, Kathryn L., Jenkins, William J., Gagnon, Alan R., Xu, Li, Hlavenka, Joshua D., & Longworth, Brett E. C-14 Blank Corrections for 25-100 mu G samples at the National Ocean Sciences AMS Laboratory. Radiocarbon, 61(5), (2019): 1403-1411, Doi: 10.1017/RDC.2019.74.
    Description: Replicate radiocarbon (14C) measurements of organic and inorganic control samples, with known Fraction Modern values in the range Fm = 0–1.5 and mass range 6 μg–2 mg carbon, are used to determine both the mass and radiocarbon content of the blank carbon introduced during sample processing and measurement in our laboratory. These data are used to model, separately for organic and inorganic samples, the blank contribution and subsequently “blank correct” measured unknowns in the mass range 25–100 μg. Data, formulas, and an assessment of the precision and accuracy of the blank correction are presented.
    Description: This work is supported by a Cooperative Agreement (OCE-1755125) with the U.S. National Science Foundation.
    Keywords: AMS ; AMS dating ; Blank corrections
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  • 18
    Publication Date: 2022-10-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Baker, M. G., Aster, R. C., Anthony, R. E., Chaput, J., Wiens, D. A., Nyblade, A., Bromirski, P. D., Gerstoft, P., & Stephen, R. A. Seasonal and spatial variations in the ocean-coupled ambient wavefield of the Ross Ice Shelf. Journal of Glaciology, 65(254), (2019): 912-925, doi:10.1017/jog.2019.64.
    Description: The Ross Ice Shelf (RIS) is host to a broadband, multimode seismic wavefield that is excited in response to atmospheric, oceanic and solid Earth source processes. A 34-station broadband seismographic network installed on the RIS from late 2014 through early 2017 produced continuous vibrational observations of Earth's largest ice shelf at both floating and grounded locations. We characterize temporal and spatial variations in broadband ambient wavefield power, with a focus on period bands associated with primary (10–20 s) and secondary (5–10 s) microseism signals, and an oceanic source process near the ice front (0.4–4.0 s). Horizontal component signals on floating stations overwhelmingly reflect oceanic excitations year-round due to near-complete isolation from solid Earth shear waves. The spectrum at all periods is shown to be strongly modulated by the concentration of sea ice near the ice shelf front. Contiguous and extensive sea ice damps ocean wave coupling sufficiently so that wintertime background levels can approach or surpass those of land-sited stations in Antarctica.
    Description: This research was supported by NSF grants PLR-1142518, 1141916, 1142126, 1246151 and 1246416. JC was additionally supported by Yates funds in the Colorado State University Department of Mathematics. PDB also received support from the California Department of Parks and Recreation, Division of Boating and Waterways under contract 11-106-107. We thank Reinhard Flick and Patrick Shore for their support during field work, Tom Bolmer in locating stations and preparing maps, and the US Antarctic Program for logistical support. The seismic instruments were provided by the Incorporated Research Institutions for Seismology (IRIS) through the PASSCAL Instrument Center at New Mexico Tech. Data collected are available through the IRIS Data Management Center under RIS and DRIS network code XH. The PSD-PDFs presented in this study were processed with the IRIS Noise Tool Kit (Bahavar and others, 2013). The facilities of the IRIS Consortium are supported by the National Science Foundation under Cooperative Agreement EAR-1261681 and the DOE National Nuclear Security Administration. The authors appreciate the support of the University of Wisconsin-Madison Automatic Weather Station Program for the data set, data display and information; funded under NSF grant number ANT-1543305. The Ross Ice Shelf profiles were generated using the Antarctic Mapping Tools (Greene and others, 2017). Regional maps were generated with the Generic Mapping Tools (Wessel and Smith, 1998). Topography and bathymetry data for all maps in this study were sourced from the National Geophysical Data Center ETOPO1 Global Relief Model (doi:10.7289/V5C8276M). We thank two anonymous reviewers for suggestions on the scope and organization of this paper.
    Keywords: Antarctic glaciology ; Ice shelves ; Seismology
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  • 19
    Publication Date: 2022-10-26
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Xu, L., Roberts, M., Elder, K., Hansman, R., Gagnon, A., & Kurz, M. Radiocarbon in dissolved organic carbon by UV oxidation: an update of procedures and blank characterization at NOSAMS. Radiocarbon, 64(1), (2022): 195-199, https://doi.org/10.1017/rdc.2022.4.
    Description: This note describes improvements of UV oxidation method that is used to measure carbon isotopes of dissolved organic carbon (DOC) at the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS). The procedural blank is reduced to 2.6 ± 0.6 μg C, with Fm of 0.42 ± 0.10 and δ13C of –28.43 ± 1.19‰. The throughput is improved from one sample per day to two samples per day.
    Description: We gratefully acknowledge support from the U.S. National Science Foundation, via NSF-OCE-1755125.
    Keywords: Blank ; Dissolved organic carbon ; Radiocarbon ; UV-oxidation
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  • 20
    Publication Date: 2022-10-21
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ackley, S. F., Stammerjohn, S., Maksym, T., Smith, M., Cassano, J., Guest, P., Tison, J., Delille, B., Loose, B., Sedwick, P., DePace, L., Roach, L., & Parno, J. Sea-ice production and air/ice/ocean/biogeochemistry interactions in the Ross Sea during the PIPERS 2017 autumn field campaign. Annals of Glaciology, 61(82), (2020): 181-195, doi:10.1017/aog.2020.31.
    Description: The Ross Sea is known for showing the greatest sea-ice increase, as observed globally, particularly from 1979 to 2015. However, corresponding changes in sea-ice thickness and production in the Ross Sea are not known, nor how these changes have impacted water masses, carbon fluxes, biogeochemical processes and availability of micronutrients. The PIPERS project sought to address these questions during an autumn ship campaign in 2017 and two spring airborne campaigns in 2016 and 2017. PIPERS used a multidisciplinary approach of manned and autonomous platforms to study the coupled air/ice/ocean/biogeochemical interactions during autumn and related those to spring conditions. Unexpectedly, the Ross Sea experienced record low sea ice in spring 2016 and autumn 2017. The delayed ice advance in 2017 contributed to (1) increased ice production and export in coastal polynyas, (2) thinner snow and ice cover in the central pack, (3) lower sea-ice Chl-a burdens and differences in sympagic communities, (4) sustained ocean heat flux delaying ice thickening and (5) a melting, anomalously southward ice edge persisting into winter. Despite these impacts, airborne observations in spring 2017 suggest that winter ice production over the continental shelf was likely not anomalous.
    Description: NSF supported PIPERS award numbers: ANT-1341717 (S.F. Ackley, UTSA); ANT-1341513 (E. Maksym, WHOI); ANT-1341606 (S. Stammerjohn and J. Cassano, U Colorado); ANT-1341725 (P. Guest, NPS). P. Sedwick was supported by NSF ANT-1543483. S.F. Ackley was also supported by NASA Grant 80NSSC19M0194 to the Center for Advanced Measurements in Extreme Environments at UTSA. S. Stammerjohn was also supported by the LTER Program under NFS award number ANT-0823101 (H. Ducklow, LDEO/Columbia University). Additional support was by the Belgian F.R.S-FNRS (project ISOGGAP and IODIne, contract T.0268.16 and J.0262.17, respectively). Bruno Delille is a research associate of the F.R.S.-FNRS. Terra-Sar-X quicklook imagery was coordinated by Kathrin Hoeppner at DLR, and Andy Archer (with the Antarctic Support Contractor) provided selected (cloud-free) MODIS scenes and daily maps of AMSR2 sea-ice concentration.
    Keywords: Atmosphere/ice/ocean interactions ; Ice/ocean interactions ; Sea ice ; Sea-ice growth and decay
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  • 21
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    Cambridge University Press
    In:  Cambridge, 342 pp., Cambridge University Press, vol. 13, no. XVI:, pp. 227-235, (ISBN 3-540-43528-X)
    Publication Date: 1983
    Keywords: Textbook of geophysics ; Seismology ; Seismics (controlled source seismology) ; Waves
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  • 22
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    Cambridge University Press
    In:  Boston, 227 pp., Cambridge University Press, vol. Developments in Petroleum Science vol. 15B, no. Publ. No. 12, pp. 9, (ISBN 0-521-66023-8 hc (0-521-66953-7 pb))
    Publication Date: 1982
    Keywords: Textbook of geophysics ; Seismics (controlled source seismology)
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  • 23
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    Cambridge University Press
    In:  Boston, 227 pp., Cambridge University Press, vol. Developments in Petroleum Science vol. 15B, no. Publ. No. 12, pp. 9, (ISBN 0-521-66023-8 hc (0-521-66953-7 pb))
    Publication Date: 1983
    Keywords: Textbook of geophysics ; Seismics (controlled source seismology)
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  • 24
    Publication Date: 1984-01-01
    Description: The following radiocarbon date list contains dates of samples measured since our previous list (R, 1982, v 24, p 352–371). As before, age calculations are based on the Libby half-life (5570 ± 30) yr and reported in years before 1950. The modern standard is 0.95 of the NBS oxalic acid activity. Sample pretreatment, combustion, and counting technique are essentially the same as described in R, 1971, v 13, p 135–140, supplemented by new techniques for groundwater processing (R, 1979, v 21, p 131–137).
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  • 25
    Publication Date: 1983-01-01
    Description: Radiocarbon determinations, employing both decay and direct counting, were obtained on various organic fractions of four human skeletal samples previously assigned ages ranging from 28,000 to 70,000 years on the basis of their D/L aspartic acid racemization values. In all four cases, the 14C values require an order of magnitude reduction in age.
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  • 26
    Publication Date: 1983-01-01
    Description: In the past 30 years many hundreds of archaeologic samples have been dated by radiocarbon laboratories. Yet, one cannot say that 14C dating is fully integrated into archaeology. For many archaeologists, a 14C date is an outside expertise, for which they are grateful, when it provides the answer to an otherwise insoluble chronologic problem and when it falls within the expected time range. But if a 14C date contradicts other chronologic evidence, they often find the ‘solution’ inexplicable. Some archaeologists are so impressed by the new method, that they neglect the other evidence; others simply reject problematic 14C dates as archaeologically unacceptable. Frequently, excavation reports are provided with an appendix listing the relevant 14C dates with little or no discussion of their implication. It is rare, indeed, to see in archaeologic reports a careful weighing of the various types of chronologic evidence. Yet, this is precisely what the archaeologist is accustomed to do with the evidence from his traditional methods for building up a chronology: typology and stratigraphy. Why should he not be able to include radiocarbon dates in the same way in his considerations?
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  • 27
    Publication Date: 1983-01-01
    Description: 14C dates of a medieval settlement with archaeologically well-dated strata are compared with the true ages of the respective layers. The 14C values indicate that each layer may contain older material reaching up to the beginning of settlement. Therefore, the 14C measurement of only a few wood or charcoal samples may lead to age estimations several hundred years too old.
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  • 28
    Publication Date: 1983-01-01
    Description: 13C isotope analyses of different stages of benzene synthesis have been made to study partial isotope fractionation. More than 60 analyses of carbonates, charcoal, carbon dioxide, and benzene were made in a double collector mass spectrometer. In the first stage of the synthesis (conversion to carbon dioxide) little or no fractionation was observed, beyond the analytical error of the method. Later stages of the process, show a greater and systematic fractionation. The experimental techniques are described.
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  • 29
    Publication Date: 1983-01-01
    Description: A mini-gas-proportional counter prototype of 10ml capacity (at NTP) was constructed of oxygen-free Finnish copper. The counter tube will be one of 16 equivalent tubes of a small-sample gas counting system, which is equipped with passive graded shield made of lead, cadmium, and copper and a dual active anticoincidence shield, consisting of an external cosmic gas-proportional and an internal plastic scintillation guard. The aim of this study was to evaluate the parameters leading to the design of a cost-effective and compact shielding package for mini-counters.
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  • 30
    Publication Date: 1983-01-01
    Description: The preparation and calibration of a secondary standard for the INGEIS Radiocarbon Dating Laboratory are presented. This standard is barium carbonate with a specific activity almost twice that of NBS oxalic acid. It was prepared from BaCO3 with high specific activity and commercial potassium carbonate by an isotopic dilution technique. The advantages of this standard are: 1) the preparation is simple and can be achieved with ordinary labware; 2) the production of CO2 by acid attack from this carbonate shows minimum isotopic fractionation. At least, it has less fractionation than wet oxidation of oxalic acid, the problems of which are described in the literature. This standard ensures better reproducibility in activity measurements; 3) despite some problems of activity exchange with atmospheric CO2 concerning carbonates, measurements of activity over a period of about two years have shown no significant deviation from the mean value. A tentative explanation of this phenomenon is also given. The activity ratio between BaCO3 and NBS oxalic acid is given with its error, and the statistical tests used in the calibration are briefly explained. Finally, a control chart for the activity of the standard over a long period is drawn, showing non-significant deviation and supporting the usefulness of this standard.
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  • 31
    Publication Date: 1983-01-01
    Description: Computer storage and surveys of large sets of data should be an attractive technique for users of 14C dates. Our pilot project demonstrates the effectiveness of a text retrieval system, NOVA STATUS. A small database comprising ca 100 dates, selected from results of the Trondheim 14C laboratory, is generated. Data entry to the computer is made by feeding typewritten forms through a document reader capable of optical character recognition. A text retrieval system allows data input to be in a flexible format. Program systems for text retrieval are in common use and easily implemented for a 14C database.
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  • 32
    Publication Date: 1983-01-01
    Description: This paper discusses the characteristics of the commoner classes of writing materials and textiles deriving from ancient and more recent historical sources and the problems they present for 14C dating. The materials under consideration are, firstly, paper in various forms, parchment, and vellum (ancient papyrus, which poses different kinds of dating problems, is not considered) and secondly, fabrics such as linen, cotton, and woolen textiles, to which, from the dating point of view, similar technical considerations apply. Our main concern is with problems associated with the dating of paper.
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  • 33
    Publication Date: 1983-01-01
    Description: Variability in temperature and 14C levels are recorded in coralline aragonite that grew in the Gulf Stream during the past four centuries. In particular, 18O/16O ratios reflect a decrease of ca 1°C in surface water temperature during the latter part of the Little Ice age. 14C levels also rose in the surface waters of the Gulf Stream and in atmospheric CO2 during the Maunder minimum. These observations indicate that ocean circulation may have been significantly different in the North Atlantic around the beginning of the 18th century.
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  • 34
    Publication Date: 1982-01-01
    Description: The following list consists of dates for archaeologic samples mostly measured from July 1976 to December 1977. The dates were obtained by liquid scintillation counting of benzene using the laboratory procedures outlined in previous lists (see, eg, BM-VIII, R, 1976, v 18, p 16). Dates are expressed in radiocarbon years relative to ad 1950 based on the Libby half-life for 14C of 5570 yr, and are corrected for isotopic fractionation (δ13C values are relative to PDB). No corrections have been made for natural 14C variations (although in some instances approximate calibrated dates taken from the tables of R M Clark (1975) have been given in the comments where this aids interpretation of results). The modern reference standard is NBS oxalic acid (SRM 4990). Errors quoted with the dates are based on counting statistics alone and are equivalent to ± 1 standard deviation (± 1σ), Dates in this and the next list (BM-XIV) reported to submitters or published elsewhere before the introduction of the new guidelines for rounding of computed figures have deliberately been left unrounded. From BM-XV onwards all BM dates will be rounded before publication in conformity with the recently recommended procedures (R, 1977, v 19, p 362). Descriptions, comments, and references to publications are based on information supplied by submitters.
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  • 35
    Publication Date: 1983-01-01
    Description: 14C ages were obtained for the Australian lakes recorded below in order to complement research into their magnetic stratigraphy and sedimentology. It has been possible to establish precise 14C chronologies in six separate lakes, and also to compare ages obtained from stratigraphically equivalent horizons in different parts of the same lake so as to determine the reproducibility of these ages.
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  • 36
    Publication Date: 1984-01-01
    Description: We demonstrate the feasibility of pulse time of arrival information for early detection of periodic events in low level counting. Time of arrival data allows us to apply time series analysis and serial correlation tests which, in graphic form, give the user an illustrative view of the parameters affecting the validity of counting statistics. The decision to discontinue counting can already be made on the basis of less than 100 counts from the time information alone if more than 10 of these are non-Poisson periodic counts. The analyses also serve as a means of quality control for low level counting, being directly based upon the interval distribution of the Poisson process.
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  • 37
    Publication Date: 1980-01-01
    Description: A bibliography of the radiocarbon dating literature for the years 1948-68, which is in the process of compilation, is examined and a format is proposed. A survey of literature growth has also been undertaken. This enables projections of the numbers of publications referring to radiocarbon dating to be made. The estimated number of publications for the year 1978 is compared to literature retrieval obtained by interrogating eight relevant computer data bases. It is concluded that computer information retrieval is not satisfactory. Bibliographic control of radiocarbon dating literature would be best achieved by a bibliography dedicated to the subject and updated at regular intervals.
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  • 38
    Publication Date: 1983-01-01
    Description: The real-time measurement of net photosynthesis and dark respiration of plants has been possible since the development of the infra-red analyzer and its application in the 1940's. This technique has allowed intensive investigations of the mechanisms and dynamics of carbon dioxide assimilation by green plants (Sestak, Catsky, and Jarvis, 1971). As a result, physiologic and ecologic aspects of net carbon dioxide exchange are the subject of much research (eg, Osmond, Bjorkman and Anderson, 1980).
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  • 39
    Publication Date: 1984-01-01
    Description: This series reports some of the measurements made since publication of the last list (R, 1981, v 23, p 94–135). Also included are a number of earlier dates previously withheld pending submitter evaluation. For some the authors have been unable to obtain appropriate comment. References to other publication of these dates are given where known.Acetylene proportional gas counting methods essentially remain as described in Saskatchewan II (R, 1960, v 2, p 73). Bone dating is carried out on soluble collagen extract (Longin, 1971) since 1978.
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  • 40
    Publication Date: 1984-01-01
    Description: Facilities for radiocarbon dating were established at the University of Frankfurt/Main in the Institute of Anthropology. The Radiocarbon Laboratory provides assistance to the Amino-Acid-Dating Laboratory. This list reports on 14C dates measured up to September 1983.The laboratory is installed in the basement of a three-story building and is equipped with a 2L copper proportional counter filled to 1013 mbar with purified CO2. The counter is protected against cosmic and surrounding radiation by a 3.5 ton lead shield and a copper multiwire anticoincidence ring-counter flushed with purified 90Ar/10CH4. Electronics are of the commercial NIM type. Charcoal and wood samples are treated by standard acid-alkali-acid methods. Bone samples are treated according to the collagen methods described by Berger, Horney, and Libby (1964), Longin (1971), Protsch (1972; 1975), and Protsch and Berger (1973).
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  • 41
    Publication Date: 1980-01-01
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  • 42
    Publication Date: 1984-01-01
    Description: The following list consists of dates for archaeologic and geologic samples mostly measured from June 1982 to June 1983. The dates were obtained by liquid scintillation counting of benzene using the laboratory procedures outlined in previous lists (see, eg, BM-VIII, R, 1976, v 18, p 16). Dates are expressed in radiocarbon years relative to ad 1950 based on the Libby half-life for 14C of 5570 yr, and are corrected for isotopic fractionation (δ13C values are relative to PDB). No corrections have been made for natural 14C variations. The modern reference standard is NBS oxalic acid (SRM 4990). Errors quoted with dates are based on counting statistics alone and are equivalent to ± 1 standard deviation (± 1σ). Descriptions, comments, and references to publications are based on information supplied by submitters.
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  • 43
    Publication Date: 1984-01-01
    Description: This radiocarbon laboratory began operation in 1980 using the benzene scintillation method. The benzene synthesizer is essentially identical with that of Ikeda (1976). A liquid scintillation counter is Aloca LSC-LB1. Samples dated are wood, charcoal, shell, and coral.Pretreatment of wood and charcoal is a standard acid-alkali procedure, using 2% HCl and 2% NaOH at elevated temperatures. Charcoal is further heated in concentrated HNO3 for one hour, diluted in water, stands one night, and is washed and dried. Pretreated wood and charcoal are carbonized before combustion. The combustion products are passed over CuO, and are collected in an ammonium hydroxide bubbler system, and precipitated with calcium chloride.
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  • 44
    Publication Date: 1980-01-01
    Description: Archaeologists began to participate in cross-disciplinary endeavors in the 1930's, albeit on a very limited basis. The passage of time found members of that discipline unprepared for collaboration with physical scientists when W F Libby announced the development of the radiocarbon dating method. Libby proposed to apply to archeologic and geologic samples techniques based on ideas that were completely foreign to archeology …. The initial reactions of archeologists were sometimes amusing but more often significant, for they led to the foundation and emergence of the radiocarbon chronology that has so profoundly affected our understanding of prehistory (Johnson, 1967, p 165).To date, our historical knowledge about the nature, function, and impact of the early (1946-1948) relations between Libby and American archaeologists has come to us in the form of published anecdotes, many of which contain inaccurate information. The author's access to W F Libby's private 14C correspondence, combined with data obtained from interviews with some of the principal participants throughout this period, offers many new or different insights into the nascent years of radiocarbon dating. When, and under what unexpected cricumstances, did Libby first encounter representatives of the achaeologic community? What strategies were employed to facilitate diffusion of knowledge about 14C dating across disciplinary boundaries? How did archaeologists respond to the introduction or “intrusion” into their field of Libby's radioactive age-measurement tool?
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  • 45
    Publication Date: 1980-01-01
    Description: A new 14C detector system containing nine, independently working, CO2 proportional counters is described. The system is designed for a sufficient measuring capacity at a precision level better than σ = ± 2‰, which requires a counting time of about one week per sample. The size of the installation requires a simple and economic design of counters and electronics. A single anticoincidence shield for all counters consists of five newly developed flat counters. The modern counting rate (52cpm) is sensitively checked by running Heidelberg sodium carbonate standard samples wth a counting rate of about 10 times modern. A microcomputer (DEC PDP-11 /03) is used for data acquisition. Recent developments in laboratory techniques (preparation and gaschromatographic purification of samples) are also reported.
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  • 46
    Publication Date: 1980-01-01
    Description: Amino acid composition data and stable isotope ratios (14N, D, and13C) are being evaluated as sources of information to indicate the presence of non-indigenous organics in bone samples intended for 14C analyses. The study is being conducted in the context of the planned measurement of Pleistocene bone samples by a high energy mass spectrometric 14C detection system.
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  • 47
    Publication Date: 1980-01-01
    Description: Annual atmospheric radiocarbon concentrations for the year 1957 to 1978 are measured through oat seeds grown in the rural region of La Pocatière, Québec (70° W, 47° N). Results follow the general pattern of other curves obtained from grains elsewhere in the northern hemisphere. Some disagreements suggest a non-uniform mixing process with faster response to stratospheric contamination in definite regions.
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  • 48
    Publication Date: 1984-01-01
    Description: A sodium bicarbonate solution with a 10-fold activity compared to oxalic acid is used as a secondary standard in the Heidelberg 14C Laboratory. All routine checks and counter tests are greatly facilitated because of the high activity of the solution.
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  • 49
    Publication Date: 1983-01-01
    Description: Huon pine is endemic to Tasmania. It has well-defined annual rings, may live for over 2000 years, and is particularly resistant to decay. Celery-top pine has similar characteristics and may live for 800 years. As part of a multi-disciplinary study of these trees and their habitat, a simple wood pretreatment method for isotope analysis is described. The solvent-acid-alkali-acid sequence yields a value of Δ14C = −16 ± 6‰ for AD 1941–45 Huon pine heartwood; Δ14C for extracts containing various proportions of post-AD 1955 carbon are also presented. Δ14C measurements on super-canopy and sub-canopy leaves from Celery-top pines are compared and used to place an upper limit of 10% on the amount of sub-canopy CO2 assimilated by sapling leaves, originating from decaying litter-mass. 14C ages from well-preserved logs illustrate the potential for a continuous Holocene chronology from 7400 years BP to the present. A 12,000-year-old Celery-top log has also been found.
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  • 50
    Publication Date: 1983-01-01
    Description: Procedures and equipment have been described in previous date lists. Except as otherwise indicated, wood, charcoal, and peat samples are pretreated with dilute NaOH–Na4P2O7 and dilute H3PO4 before conversion to the counting gas methane; marls and lake cores are treated with acid only. Very calcareous materials are treated with HCl instead of H3PO4. Pretreatment of bone varies with the condition of the bone sample; solid bone with little deterioration is first cleaned manually and ultrasonically. The bone is treated with 8% HCl for 15 minutes, then dilute NaOH–Na4P2O7 for 3 hours at room temperature, washed until neutral, and the collagen extracted according to Longin (1971). Charred bone is treated with dilute HCl, NaOH–Na4P2O7, and then dilute HCl again.
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  • 51
    Publication Date: 1983-01-01
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  • 52
    Publication Date: 1984-01-01
    Description: Procedures and equipment used in the University of Wisconsin laboratory have been described in previous date lists. Except as otherwise indicated, wood, charcoal, and peat samples are pretreated with dilute NaOH-Na4P2O7 and dilute H3PO4 before conversion to the counting gas methane; marls and lake cores are treated with acid only. Very calcareous materials are treated with HCl instead of H3PO4. Pretreatment of bone varies with the condition of the bone sample; solid bone with little deterioration is first cleaned manually and ultrasonically. The bone is treated with 8% HCl for 15 minutes, then dilute NaOH-Na4P2O7 for 3 hours at room temperature, washed until neutral, and the collagen extracted according to Longin (1971). Charred bone is treated with dilute HCl, NaOH-Na4P2O7, and then dilute HCl again.
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  • 53
    Publication Date: 1983-01-01
    Description: The geomagnetic field is one of the major physical fields of the earth. Because its source is fluid motion in the outer core, it exhibits temporal changes, called secular variation, which are quite rapid compared to most geologic phenomena. The prehistoric secular variation is usually inferred from paleomagnetic data. We will discuss here how changes in the atmospheric 14C content can be used to gain additional insight into the behavior of the dipole moment over the past 8500 years. By rewriting the differential equations representing the 14C geochemical cycle in finite-difference form, we are able to convert the atmospheric 14C activity record into an equivalent radiocarbon dipole moment.
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  • 54
    Publication Date: 1981-01-01
    Description: The following radiocarbon date list contains dates of samples measured since our previous list (R, 1979, v 21, p 131-137). As before, age calculations are based on the Libby half-life 5570 ± 30 yr and reported in years before 1950. The modern standard is 0.95 of the activity of NBS oxalic acid. Sample pretreatment, combustion, and counting technique are essentially the same as described in R, 1971, v 13, p 135-140, supplemented by new techniques for groundwater processing (R, 1979, v 21, p 131-137) and for soil sample treatment (R, 1977, v 19, p 465-475).
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  • 55
    Publication Date: 1982-01-01
    Description: The radiocarbon laboratory of the Center of Applied Research and Documentation of Udine (CRAD), became operative early in 1977 and uses a benzene liquid scintillation counting method. Benzene is prepared as outlined by Legers and Tamers (1963), Noakes, Kim, and Akers (1967), Belluomini et al (1978). The procedure of chemical synthesis is detailed in CRAD (1977).
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  • 56
    Publication Date: 1981-01-01
    Description: This date list includes most of the archaeologic and geologic samples dated in this laboratory since publication of our last date list (R, 1978, v 20, p 210–233), as well as some samples dated previously which lacked adequate sample information.
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  • 57
    Publication Date: 1980-01-01
    Description: The precision quoted on a radiocarbon date is often misleading. Improvement in the accuracy of measurement is discussed together with the use of appropriate precisions. The effect of high accuracy in 14C dating and meaningful precisions are illustrated and applied to radiocarbon time-scale calibration. Intercomparison of such calibrations reveals a significant continuous saw-tooth pattern of short-term periodicity.
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  • 58
    Publication Date: 1980-01-01
    Description: The University of Washington Model FN tandem Van de Graaff accelerator is being used for the measurement of extremely small isotopic abundance ratios, notably 14C/12C and 10Be/9Be, in a joint project of the Nuclear Physics Laboratory (NPL) and the Quaternary Isotope Laboratory (QL). The experimental arrangements and technical developments are described, and some preliminary results on isotopic ratios in carbon and beryllium are presented.
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  • 59
    Publication Date: 1980-01-01
    Description: Δ14C and δ13C values for organic matter in forest and grassland soils, in the presence or absence of earthworms, indicate that it should be possible to quantify the effects of earthworms on soil organic matter by this means. Without earthworms, both in forest and grassland soils, plant debris tends to accumulate on the surface of the mineral soil and little organic matter is incorporated into or is translocated down the soil profile. Where earthworms are present, there is much more marked incorporation of fresh plant debris in the mineral soil. This is shown especially by the pulse of ‘bomb’ carbon and also by the δ13C values.
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  • 60
    Publication Date: 1980-01-01
    Description: 14C and 13C enrichment values are reported for a series of surface soil profiles which represent the progressive transition from mor to mull humus induced by birch (Betula pendula) colonization.Variations in Δ and δ13C, which range between 85 to 154‰ modern and −28.1 to −25.3‰ (PDB), respectively, reflect changes in the rate and mode of organic decomposition. The most marked alterations in soil character occur over the first few decades following the introduction of birch, with clear isotopic evidence for the deeper penetration and accelerated mineralization of organic material.
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  • 61
    Publication Date: 1982-01-01
    Description: The Radiocarbon Dating Laboratory of The Granada University was established to support the work of archaeologists and geologists. The method of dating is benzene synthesis and liquid scintillation counting developed by a number of investigators (Polach and Stipp, 1967; Tamers, 1969; Pietig and Scharpenseel, 1966) with sample combustion in pure oxygen (Switsur, 1974).
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  • 62
    Publication Date: 1980-01-01
    Description: High precision radiocarbon measurements (±2.5‰ STD) were carried out on absolutely dated European oak material. These showed that significant short-term atmospheric 14C variations of up to 2 percent occurred between AD 200 and 800. These changes, reflecting a 150-to 180-year periodicity, seem to correlate with the average sunspot activity around that time. In comparison with results obtained by other authors, a very regular pattern of natural atmospheric 14C variations is exhibited.
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  • 63
    Publication Date: 1980-01-01
    Description: The evolution of a tandem accelerator 14C dating system at Chalk River is recounted. Background problems and sources of instability are discussed and solutions are described. Details of sample chemistry and source preparation are presented.
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  • 64
    Publication Date: 1981-01-01
    Description: Samples in this paper are a continuation of the Florida geologic samples, reported earlier (R, 1978, v 20, p 436–440). Each specimen analyzed in this list was a carbonate shell. All dates are from single shells as opposed to means of multiple shell samples.
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  • 65
    Publication Date: 1981-01-01
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  • 66
    Publication Date: 1980-01-01
    Description: Pollen analysis as well as 18O/16O results on lake marl show that the Younger Dryas climatic period, between about 11,000 and 10,300 bp, was the last vigorous cold phase of the Würm Glacial. Detailed 14C analyses from a peat bog near Wachseldorn (Switzerland) point to a 14C anomaly in this period. Further indication of a 14C anomaly is given by the observation that, during the Younger Dryas period, the sedimentation rates in several lakes apparently were higher than in adjacent periods; an explanation might be that the 14C time scale was compressed between 11,000 and 10,000 bp, ie, the atmospheric 14C/C ratio varied. If real, this suggested 14C variation would probably be connected to the climatic events during this transition period from Later Glacial to Postglacial.
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  • 67
    Publication Date: 1981-01-01
    Description: The Menlo Park radiocarbon laboratory of the US Geological Survey began operation in January 1976 in a new building with a counting room 9.8m below the ground surface. Shielding above the counters consists of 30cm lead and 8.2m earth. The ionizing cosmic ray flux at the counters is 0.28 cpm/cm2. Background levels obtained thus far are summarized in Table 1.
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  • 68
    Publication Date: 1981-01-01
    Description: Recent experimental work has suggested that the relative fractionation of 14C to 13C may differ from the accepted value of b = 2. In order to explore the implications of this possibility, the standard formulae for correcting radiocarbon dates for fractionation effects are rederived, but without making any of the usual assumptions or approximations. A generalized dating equation is derived (where ASN and AON are normalized sample and standard activities, β is a factor which reflects changes in atmospheric 13C and 14C content, {RST(o)/RST}b accounts for post-depositional changes in sample 13C ratio, and tcal is calendar age in years before ad 1950. The errors in calculated ages which might arise from different b values are estimated and shown to be small relative to other dating uncertainties. The effect of b ≠ 2 may be important in the calibration of radiocarbon dates using tree-ring samples of known age. A theoretical analysis suggests that b ≠ 2 effects may result in a correlation between age anomaly (ie, the difference between radiocarbon age and calendar age) and sample 13C data. However, an analysis of published data reveals no meaningful correlation. This result, while not eliminating the possibility that b ≠ 2, highlights its unimportance even in this high-precision application of radiocarbon dating.
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  • 69
    Publication Date: 1980-01-01
    Description: 14C measurements on continuous weekly samples of atmospheric CO2 and hydrocarbons, collected in a rather densely populated area are presented. The deviation of the measured 14C data from the clean air level is primarily due to CO2 from the combustion of fossil fuels. This is confirmed by fossil fuel admixture estimates individually calculated with an atmospheric dispersion model. Up to 10 percent admixture is predicted by this model and observed from the 14C shift for weekly averages, particularly during the winter season. Natural CO2 admixture due to soil respiration, however, even in winter, is of the same order of magnitude, but much larger in the warm season: the considerable variations in CO2 concentration in summer are almost exclusively controlled by natural sources. Using tree leaf samples, we have been able to identify boiling water reactors (BWR) as weak sources of 14CO2. Atmospheric samples taken in the environment of the pressurized water reactors (PWR) Biblis show that the 14C release of these reactors is primarily in the form of hydrocarbon 14C. The source strength of the various power plants, calculated on the basis of our observations in their environment, ranges from 0.5 to 7Ci per year.
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  • 70
    Publication Date: 1980-01-01
    Description: An MP tandem Van de Graaff accelerator at the University of Rochester has been employed since May 1977 to detect 14C in various terrestrial samples. The carbon sample sizes required are 1mg or less. Dating accuracies based on reproducibility now approach (± 80 years). Measurements have been made on 1850 wood, Australian sucrose, a carbon sample from Mt Shasta, a baby woolly mammoth, and an Egyptian bull mummy wrapping.
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  • 71
    Publication Date: 1965-01-01
    Description: The I.V.I.C. laboratory started operation in December, 1963 using liquid scintillation techniques and the benzene method. The syntheses are carried out in a Packard benzene synthesizer and the solutions counted by a Packard automatic tri-carb spectrometer. For routine dating, a 4 cc counting vial is used with 2 cc benzene coming from the sample being dated and 2 cc commercial toluene added with the PPO and POPOP scintillators.
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  • 72
    Publication Date: 1980-01-01
    Description: Carbon isotope measurements in soil CO2 are presented and discussed. Soil CO2 concentration and 13C profiles were measured using a new technique. A simple model describing the CO2 transport from the soil to the atmosphere is derived. The finding that CO2 in the soil is richer in 13C than the CO2 leaving the soil is attributed to isotopic fractionation in molecular diffusion.
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  • 73
    Publication Date: 1968-01-01
    Description: Our experience in radiocarbon dating has shown that dates obtained from samples of corn cob and kernels are usually too young compared with dates from wood samples. Since other laboratories have also commented on the same problem, a study of C13/C12 ratios in corn and other plant materials has been undertaken.
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  • 74
    Publication Date: 1980-01-01
    Description: Although initial studies in the 1960's established the feasibility of applying the radiocarbon technique directly to ceramics, subsequent analyses have revealed this category of materials to be more complex than previously believed. Consideration of the points at which various types of organic carbon are introduced into ceramic materials by natural or human agencies allows more effective screening of potential sherd samples. It also suggest ways to overcome some of the limiting factors involved in dating ceramics.
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  • 75
    Publication Date: 1983-01-01
    Description: Data on the depth distribution of the major atmospheric gases and the abundance of gaseous 12CO2, 13CO2, and 14CO2 in the subsoil unsaturated zone have been obtained from several sites in the western Great Plains of the United States. Sample profiles range from land surface to depths of 50m. Although each site must be considered on an individual basis, several general statements can be made regarding the profiles. 1) Diffusion of these gaseous molecules through the unsaturated zone is an important transport mechanism. 2) As predicted by diffusion theory, depth profiles of the various isotopic species of CO2 differ substantially from one another, depending on individual sources and sinks such as root respiration and oxidation of organic carbon at depth. 3) In general, post-bomb (〉 100% modern) 14C activities are not observed in the deep unsaturated zone, in contrast to diffusion model predictions. 4) In spite of generally decreasing 14C activities with depth, absolute partial pressures of 14CO2 in the subsoil unsaturated zone are 1–2 orders of magnitude higher than the partial pressure of 14CO2 in the atmosphere.
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  • 76
    Publication Date: 1983-01-01
    Description: A test for the reliability of 14C dating of soil was made at two sites with buried, autochthonous, and in parts, allochthonous sandy podzols, dated either litho- and pedostratigraphically or palynologically. The differences between the age ranges obtained and the apparent mean residence times (AMRT) calculated from the 14C content of alkaline extracts from fossil soil layers and horizons lean in organic matter exceed 10,000 years, corresponding to a maximum contamination with recent carbon of up to 50 %. The use of correction factors for the apparent mean residence times of podzols is not valid, not even for climate zones, because these values have a broad scatter for the same profile.
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  • 77
    Publication Date: 1968-01-01
    Description: The dates detailed below are based on measurements made from September 1962 to August 1964. Work was often seriously interrupted due to difficulties with electronic equipment and also, from the late summer of 1963, high levels of tritium in the local water supplies used in the synthesis of acetylene (from nuclear weapons tests) made it difficult to obtain accurate measurements with acetylene as a filling gas for the proportional counter. The gas preparation equipment was therefore modified for the preparation of high purity CO2, and from Sample BM-165 onwards, the proportional counter was operated with CO2 as the filling gas at a pressure of 210 cm Hg at 22°C. instead of 140 cm Hg pressure of acetylene at 22°C. as reported previously (British Museum I). Background and net modern count rates under these conditions are 3.59 c.p.m. and 8.35 c.p.m., respectively. (In practice these values are taken as the rolling mean of the past 20 weeks’ measurements and are very constant.) The calculations of age are based on the half-life of 5570 yr and error terms are widened to include contributions of ± 80 yr for possible isotopic fractionation effects and ± 100 yr for de Vries-effects. Safeguards against inaccuracies are as described previously (British Museum I).
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  • 78
    Publication Date: 1980-01-01
    Description: Mollusks living only on ground surface can be expected to give the most reliable results in 14C dating from carbonates of continental origin. One may assume they have a homogeneous biotope and are not affected by any hard-water effect. In order to verify these assumptions and to test shells as routine dating material, results from terrestrial gastropods are compared with other 14C dates from classic biologic material, such as peat, charcoal, or bone, collected in the same archaeologic or geologic levels in miscellaneous places. Two sites were selected for which other chronologic data, such as prehistoric industries or malacologic diagrams were available.All results indicate older values for 14C shell dates. The discrepancy between “normal” and snail dates amounts to 300 to 1200 14C years and remains the same whatever the absolute age of the sample. All 13C values of perfectly cleaned shells are between —5 to —10%, versus PDB. The initial 14C content of shells that is too low may be different according to species, as suggested by 13C variations.Although fairly constant, this deviation of 14C ages generally makes such samples unreliable for most archaeologic studies, which often need more precise results. However, some measurements were performed on microfauna shells from several Würmian loess to show that dating of shells may be useful in fairly ancient geologic sediments for lack of better carbonaceous samples. Good agreement of some snail dates with expected sediment ages point to the importance of proper sample selection and pretreatment that might be checked by 13C measurements.
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  • 79
    Publication Date: 1980-01-01
    Description: Since the publication of our first date list (R, 1966, v 8, p 239-247), our 14C laboratory has produced about 1500 radiocarbon dates, including several hundreds of concordant double determinations, the majority of which were on archaeologic samples. The greater part of the other dates concerned dendrochronologic samples from our Tree Ring Laboratory (Schmidt, 1977; Freundlich, 1977). Several archaeologic dates have already been published in articles on archaeology, preferentially by the respective excavators, in a few instances also by us (eg, Schwabedissen and Freundlich, 1968; Faruggia et al, 1973; Kuper, 1975; Lüning and Zürn, 1977; Hohenschwert, 1978). An extensive compilation of Neolithic dates is in preparation.
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  • 80
    Publication Date: 1983-01-01
    Description: The international radiocarbon community met on June 25, 1982. Two reports were presented, and several measures related to radiocarbon dating discussed and adopted.
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  • 81
    Publication Date: 1983-01-01
    Description: Continuous 14C data of 1 or 2 weekly samples of atmospheric CO2 are presented, collected near two nuclear power plants (NPP-Biblis and NPP-Philippsburg) located in the rather densely populated upper Rhine valley. Tree-leaf and tree-ring samples from the area of a boiling water reactor in northern Germany (NPP-Würgassen) are also presented and discussed. Additional atmospheric 14CO2 samples from two continental ‘clean-air’ stations in Germany and Austria were used as reference for the polluted areas. For January 1982, these samples yield a ‘clean-air’ 14C concentration in central Europe of Δ14C=255±5‰ (7.7pCi/gC = 1.45pCi/m3 air).
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  • 82
    Publication Date: 1983-01-01
    Description: The Harwell system for measuring milligram size samples using Brookhaven miniature gas counters is fully operative. It comprises 12 counters of different sizes which operate simultaneously within a single NaI crystal (300mm diameter × 300mm long) acting as an anti-coincidence guard counter. Brief details are given of the construction and commissioning of the system, including counter assembly, shield design, electronics, data capture, data analysis, and chemical processing and filling procedures. The performance of the system and an overall view of the fields of application for which the counters have important applications are discussed.
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  • 83
    Publication Date: 1983-01-01
    Description: During the past year we have continued to work toward greater stability and flexibility in nearly all elements of our accelerator mass spectrometry (AMS) system, which is based upon an FN tandem Van de Graaff accelerator, and have carried out measurements of 14C/12C and 10Be/9Be isotopic abundance ratios in natural samples. The principal recent developments and improvements in the accelerator system and in our sample preparation techniques for carbon and beryllium are discussed, and the results of a study of 10Be cross-contamination of beryllium samples in the sputter ion source are presented.
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  • 84
    Publication Date: 1983-01-01
    Description: One of my former teachers in nuclear physics, H Morinaga, once pointed out to me that essentially all the fundamental discoveries in nuclear physics were done without the use of accelerators. At first, this statement seemed extremely exaggerated, but now I think there is much truth in it. Once we build an instrument to investigate a specific problem we have already realized the existence of the problem and do not need the instrument to discover it. It is almost inevitable that the most interesting discoveries with a new technique will be made in fields for which the technique was not invented. Accelerators, built for nuclear physics, produced a great amount of data on nuclear structure and forces but the most fundamental discoveries were made in elementary particle physics. In any case, for almost 40 years the sole purpose of accelerators was to deliver beams of ever increasing energy and versatility to perform experiments after the accelerator. The analytic properties of accelerators were almost completely ignored even after the very early use of the Lawrence cyclotron at Berkeley as a mass spectrometer to discover 3He in nature (Alvarez and Cornog, 1939 a; b). The enormous analytic power of accelerators is now fully recognized, but the joy of the revival is mixed with some disappointment that the great prospects for studying 14C problems (Muller, 1977; Bennet et al, 1977; Nelson, Korteling, and Stott, 1977) have not yet been fulfilled. Fortunately, some of the papers of this conference show that a big step forward has been taken. But in view of what I said before it is not surprising that most of the studies were actually done with other radioisotopes.
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  • 85
    Publication Date: 1984-01-01
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  • 86
    Publication Date: 1982-01-01
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  • 87
    Publication Date: 1984-01-01
    Description: Radiocarbon dating provides the principal chronometric data for the Middle and Upper Palaeolithic, Epipalaeolithic, and Chalcolithic periods in the southern Levant. It is a secondary source of dating evidence for the Early Bronze age, when archaeological correlations with Syria and especially Egypt become available. For the Middle and Late Bronze age, Iron age, Persian, Hellenistic, Roman, and Byzantine periods, 14C dating has only limited value because the technique is less precise than the normally available archaeologic and historic materials.
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  • 88
    Publication Date: 1983-01-01
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  • 89
    Publication Date: 1980-01-01
    Description: The secular patterns of Δ and δ13C measured in wood cellulose are compared with a palaeotemperature index published for the immediate growth region. 14C enrichment shows an overall decrease of ca 20% (Δ) during the 18th and 19th centuries with shorter term (decade) variations superimposed on the general trend. Measured Δ values correlate significantly with the average mean summer temperatures and indicate a linear coefficient of ca − 10.2% °C–1. Short-term variations in the natural concentration of 14C which are closely related to climatic change may reflect the latitudinal dependence for atmospheric mixing.The secular trend in δ13C covers a range of 2% but variations of this magnitude reflect influences other than those directly associated with climatic change, eg, possible assimilation of recycled biospheric CO2 during early life and post AD 1850 anthropogenic effects. No evidence was found to suggest a significant correlation between δ13C and the mean atmospheric temperature during summer growth periods.
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  • 90
    Publication Date: 1983-01-01
    Description: 14C activities of decadal samples from beech trees growing under extreme calcareous conditions were compared to 14C activities of decadal samples of the same age from a beech tree growing in a normal mold soil in order to see whether part of the carbon assimilated during photosynthesis might originate from 14C-deficient carbonates in the soil. The calcareous soils contained from 18 to 52% calcium carbonate, and this carbonate had a mean 14C age of 10,200 to 17,600 years BP. A comparison was also made with the 14C activity of contemporaneous samples from Douglas Fir from the US North Pacific (Stuiver, 1982).No significant depletion in 14C activity in beech trees growing in the highly calcareous soils was detected. The measured mean difference in 14C activity in beech trees from calcareous and non-calcareous sites corresponds to an uptake of 0.12 ± 0.3% carbon from soil carbonates in the calcareous sites.
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  • 91
    Publication Date: 1982-01-01
    Description: This list reports a portion of the analysis completed on archaeologic and paleo-environmental samples measured in the UCR laboratory between August 1974 and August 1976. Results of measurements made during that period on sample suites which are not as yet completed or lack review by submitters will be reported in a subsequent date list.
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  • 92
    Publication Date: 1983-01-01
    Description: Calcareous deposits known as tufa or travertine contain biogenic carbon and are a potential source of geochronologic information. Many dated samples from Karstic regions in Yugoslavia proved that 14C analyses of tufa can provide reliable data reflecting climatic conditions in the past. Systematic dating of tufa samples revealed two distinct groups of deposits: recent tufa deposits, with a sharp age limit of ∼6000 ± 500 years BP, and old tufa deposits with 14C age ranges from 25,000 ± 2300 years BP to the lowest limit of our 14C dating system (∼37,000 years). A histogram based on the initial activity AO = 0.85 shows the age distribution of randomly sampled tufas vs sample frequency. A time gap between ∼6000 BP and ∼23,000 BP is evident, reflecting cooler climatic conditions. The start of peat deposition is coincident with that of tufa growth in the Holocene.Paleoclimatic implications of tufa growth periods obtained by 14C dating are as follows: climatic conditions that favor tufa formation at least in karstic regions, are very stringent. Therefore, climatic conditions, such as mean annual temperature and humidity, as well as hydrologic and vegetational conditions, must have been very similar in periods of tufa growth. While recent tufa deposits are coincident with the warm Holocene period, old tufa can be associated with warm interstadials in the Würm.
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  • 93
    Publication Date: 1983-01-01
    Description: The following list summarizes the post-1970 laboratory results of 14C dating of ancient sea-level indicators from the coasts of the Soviet Union. One of the aims of the International Geologic Correlation Programme Project No. 61 “Sea level movements during the last deglacial hemicycle” is the global cataloguing and mapping of ancient sea levels. The laboratory, which acts as the USSR National curator for these age measurements obtains dates sampled from its own expeditions and from other institutions of the country.
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  • 94
    Publication Date: 1984-01-01
    Description: The Radiocarbon Laboratory of the Archaeological and Ethnographical Museum in Lódź was established to meet the growing demand for radiocarbon dating of archaeologic and geologic samples. The liquid scintillation technique based on the Polish liquid scintillation counter with a single photomultiplier began operation in 1966. The base for the measurements was ethylbenzene. In 1974 new facilities for the determination of radiocarbon assays were installed. The proportional counter and the electronics supplied by Nuclear Enterprises became routine counting equipment two years later.
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  • 95
    Publication Date: 1983-01-01
    Description: 10Be (T1/2 = 1.5·106y) is mainly produced in the atmosphere by cosmic ray spallation reactions on nitrogen and oxygen. About 70 % of the production takes place in the stratosphere. 10Be becomes attached to aerosols within a very short time. If 10Be is produced in the stratosphere some latitudinal mixing occurs. Most of the 10Be is transferred to the troposphere during spring and early summer when, mainly at median latitudes, large stratospheric air masses enter the troposphere. Tropospheric 10Be is deposited rapidly on the earth's surface by precipitation. The mean residence time of 10Be in the atmosphere is ca 1 to 2 years. 10Be removed from the atmosphere by precipitation is either preserved in snow and ice layers, in the topsoil and the biosphere, or it enters the hydrosphere (oceans and lakes), where it is transported to the sediments.
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  • 96
    Publication Date: 1982-01-01
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  • 97
    Publication Date: 1984-01-01
    Description: This list contains the results of measurements of 167 groundwater samples made between September 1979 and December 1982. An additional 175 samples were measured, but these were submitted without detailed information, such as sampling depth, well location, etc; therefore, they were excluded from the following list.
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  • 98
    Publication Date: 1983-01-01
    Description: The Meade thrust, in southeastern Idaho, is a major element of the Western Overthrust Belt. The allochthon is of geo-economic importance both as a potential hydrothermal area and as the principal mining area within the Western Phosphate Field. To assist in the development of these two resources, an understanding of the regional ground-water circulation was sought. Geologic and hydrologic data from boreholes in this area are virtually nonexistent. Waterwell development in the area has not occurred because of the abundance of springs and only a few hydrocarbon exploration boreholes have been drilled. Thus, the problem lends itself to evaluation by isotope hydrologic and geochemical methods. Ten springs from within the thrust block and around its periphery were sampled for major ions, 2H/18O, and 14C/13C analysis. Data from these analyses and from field geologic evidence have identified two distinct flow regimes within the Meade thrust allochthon. Shallow flow systems lie above the impermeable Phosphoria Formation, usually within a few hundred meters of the surface. Most of the spring waters from this system are recent and cool. In all cases, they have mean subsurface residence times of less than a few hundred years. The deeper flow systems which lie below the Phosphoria formation are hydraulically isolated from the shallow system. Warm waters from these springs have 14C contents suggesting mean ground-water residence times on the order of 15,000 years. Although these waters could have circulated to as deep as 1900m, 2H/18O results show that high temperatures were never reached. There is no evidence to suggest that water from beneath the Meade thrust has contributed to the circulation in the allochthon.
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  • 99
    Publication Date: 1980-01-01
    Description: An interlaboratory comparison experiment for 14C measurements has been organized jointly by the Harwell and British Museum laboratories to include the working radiocarbon laboratories of the United Kingdom. The experiment has been run along the lines of that organized by the IAEA for tritium and has explored the problems of sample preparation, verification of equivalent levels, and presentation of results. Samples of benzene representing 5 age equivalent levels between twice modern and 20,000 years old have been prepared and distributed for measurement either by direct counting (liquid scintillation) or full process tests. Preliminary results received show excellent agreement both between laboratories and in comparison with the known relative activities of the prepared solutions. The possibility of extending the experiment to cover different sample types and a wider distribution of testing laboratories is briefly discussed.
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  • 100
    Publication Date: 1984-01-01
    Description: A major collective effort was made to develop a data base for establishing the relationship between 14C and calendric ages (Stuiver, 1982). The early “cosmic schwung” fit between the two ages (Suess, 1970a, p 310) and the 10,350 yr period of the grand trend (Suess, 1970b, p 596) have recently been replaced by the period of 12,100 yr (Suess, 1980). The period of the grand trend was estimated by correlating the data with an a priori postulated sine function (Suess, 1970, p 596), or more recently a polynomial fit of the sixth degree was used (Klein et al, 1982). In the detrended data, periods (wiggles) of between 2400 yr and 104 yr were identified by conventional time series analysis. This approach could not be used to estimate the period of the grand trend, because the time series includes less than one cycle, whereas several cycles are required in order to get a meaningful result.
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