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  • 1
    Electronic Resource
    Electronic Resource
    A stable-isotope tree-ring timescale of the Late Glacial/Holocene boundary (1991)
    [s.l.] : Nature Publishing Group
    Nature 353 (1991), S. 647-649 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Through the stepwise cross-dating of more than 6,000 tree-ring curves, we established the absolute German oak dendrochronology, continuous to the year 7938 BC. It consists of subfossil river oaks linked with prehistoric, historic and modern oak samples. The statistical significance of the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/353647a0
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Anatolian tree rings and the absolute chronology of the eastern Mediterranean, 2220–718 BC (1996)
    [s.l.] : Nature Publishing Group
    Nature 381 (1996), S. 780-783 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A tree-ring chronology of 1,503 years has been constructed from large groups of timbers in major archaeological monuments, principally at Gordion, Porsuk, Acemhoyuk and Kiiltepe in Anatolia2, and might provide a solution to many currently impenetrable or ambiguous issues in eastern Mediterranean ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/381780a0
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Possible solar origin of the 1,470-year glacial climate cycle demonstrated in a coupled model (2005)
    [s.l.] : Nature Publishing Group
    Nature 438 (2005), S. 208-211 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Many palaeoclimate records from the North Atlantic region show a pattern of rapid climate oscillations, the so-called Dansgaard–Oeschger events, with a quasi-periodicity of ∼1,470 years for the late glacial period. Various hypotheses have been suggested to explain these rapid ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature04121
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Field determination of air-sea gas exchange by continuous measurement of radon-222 (1978)
    Springer
    Pure and applied geophysics 116 (1978), S. 476-485 
    Details
    ISSN: 1420-9136
    Keywords: Air-sea exchange ; Mixed layer ; Radon-222 ; Wind speed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Equipment has been developed for automatic measurement of the radon dissolved in sea water, with the aim of determining gas exchange rates at sea on the basis of the radon-222 deficiency in the mixed layer with respect to its parent nuclide radium-226. The equipment will be employed to obtain, over an extended period at fixed position, repeated measurements of the vertically integrated radon deficiency. The repetition period will be 2 hours, and sampling will be by a winch-operated submersible pumping system which will continuously scan the radon-deficient layer. The repeated measurements will allow to derive gas exchange rates even under transient meteorological conditions. As opposed to this, radon work carried out to date relied on isolated deficiency measurements and stationary conditions were commonly assumed (the deficiency relaxation time is about 5 days), which, under transient conditions, may lead to considerable errors. Equipment tests have been made at sea and the first integrated-deficiency measurements were obtained on the RSSChallenger in July 1977. Field programs are in preparation for JASIn (Joint Air-Sea Interaction, July–September 1978) and FGGE (First GARP Global Experiment, January–July 1979). The ultimate goal is a parameterization of the gas exchange rate in terms of external parameters, primarily wind speed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01636901
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    Paper (German National Licenses)
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  • 5
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    Measurement of Small Volume Oceanic 14C Samples by Accelerator Mass Spectrometry (1987)
    Department of Geosciences, University of Arizona
    In:  Radiocarbon, 29 (3). pp. 347-352.
    Details
    Publication Date: 2020-06-04
    Description: A technique for 14C measurement of small volume (0.5L) oceanic water samples by Accelerator Mass Spectrometry (AMS) is described. Samples were taken from a CTD/rosette system used for standard hydrographic work. After CO2 extraction and target preparation, the samples were measured at the Zürich tandem accelerator facility. On the basis of 14C data from samples collected on a station in the northern Weddell Sea, the precision of the measurements is estimated to ca ±8‰. The error in the present AMS results is dominated by the statistical error in 14C detection. From results of duplicate targets, it is concluded that a precision of ±5° can be reached. The 14C data are discussed in relation to the Weddell Sea hydrography.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1017/S0033822200043757
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    On the 14C and 39Ar Distribution in the Central Arctic Ocean: Implications for Deep Water Formation (1994)
    Department of Geosciences, University of Arizona
    In:  Radiocarbon, 36 (3). pp. 327-343.
    Details
    Publication Date: 2017-03-09
    Description: We present ΔA14C and 39Ar data collected in the Nansen, Amundsen and Makarov basins during two expeditions to the central Arctic Ocean (RV Polarstern cruises ARK IV/3, 1987 and ARK VIII/3, 1991). The data are used, together with published Δ14C values, to describe the distribution of Δ14C in all major basins of the Arctic Ocean (Nansen, Amundsen, Makarov and Canada Basins), as well as the 39Ar distribution in the Nansen Basin and the deep waters of the Amundsen and Makarov Basins. From the combined Δ14C and 39Ar distributions, we derive information on the mean “isolation ages” of the deep and bottom waters of the Arctic Ocean. The data point toward mean ages of the bottom waters in the Eurasian Basin (Nansen and Amundsen Basins) of ca. 250-300 yr. The deep waters of the Amundsen Basin show slightly higher 3H concentrations than those in the Nansen Basin, indicating the addition of a higher fraction of water that has been at the sea surface during the past few decades. Correction for the bomb 14C added to the deep waters along with bomb 3H yields isolation ages for the bulk of the deep and bottom waters of the Amundsen Basin similar to those estimated for the Nansen Basin. This finding agrees well with the 39Ar data. Deep and bottom waters in the Canadian Basin (Makarov and Canada Basins) are very homogeneous, with an isolation age of ca. 450 yr. Δ14C and 39Ar data and a simple inverse model treating the Canadian Basin Deep Water (CBDW) as one well-mixed reservoir renewed by a mixture of Atlantic Water (29%), Eurasian Basin Deep Water (69%) and brine-enriched shelf water (2%) yield a mean residence time of CBDW of ca. 300 yr.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1017/S003382220001451X
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    THE INTCAL20 NORTHERN HEMISPHERE RADIOCARBON AGE CALIBRATION CURVE (0–55 CAL kBP) (2020)
    Department of Geosciences, University of Arizona | Cambridge University Press
    In:  Radiocarbon, 62 (4). pp. 725-757.
    Details
    Publication Date: 2021-01-08
    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.
    Type: Article , PeerReviewed
    Format: text
    Format: archive
    DOI: 10.1017/RDC.2020.41
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Marine20—The Marine Radiocarbon Age Calibration Curve (0–55,000 cal BP) (2020)
    Department of Geosciences, University of Arizona | Cambridge University Press
    In:  Radiocarbon, 62 (4). pp. 779-820.
    Details
    Publication Date: 2021-01-08
    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/.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1017/RDC.2020.68
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Field measurements of air-sea gas exchange by the radonn deficit method during JASIN 1978 and FGGE 1979 (1983)
    Bornträger
    Details
    Publication Date: 2022-06-27
    Description: We present field measurements of air-sea gas exchange by the radon deficit method that were carried out during JASIN 1978 (NE Atlantic) and FGGE 1979 (Equatorial Atlantic). Both experiments comprised repeated deficit measurements at mixed position over periods of days or longer, using a previously described precise and fast-acquisition, automatic radon measuring system. The deficit time series exhibit variations that only partly reflect the expected changes in gas transfer. By evaluating averages over each time series we deduce the following average gas transfer velocities (average wind velocity and water temperature in parentheses): JASIN phase 1: 1.6 ± 0.8 mid (at -6 mis, 13 °C) JASIN phase 2: 4.3 ± 1.2 mid (at -8 mis, 13 °C) FGGE: 1.2 ± 0.4 mid (at -5 mis, 28 °C) 0.9 ± 0.4 mid (at -7 mis, 28 °C) 1.5 ± 0.4 mid (at -7 mis, 28 °C) The large difference between the JASIN phase 2 and FGGE values despite quite similar average wind velocity becomes even larger when the values are corrected to a common temperature. Both values are, however, fully compatible with the range of gas transfer velocities observed in laboratory experiments and the conclusion is suggested that their difference is caused by the highly different wind variability in JASIN and FGGE. We conclude that in gas exchange parameterization it is not sufficient to consider wind velocity only. A comparison of our observations with laboratory results outlines the range of variation of air-sea gas transfer velocities with wind velocity and sea state. We also reformulate the radon deficit method, in the light of our observed deficit variations, to account explicitely for non-stationarity and horizontal inhomogeneity in the near-surface radon deficit layer (i.e., mixed-layer and upper thermocline). We show that neglection of non-stationarity and horizontal inhomogeneity in previous radon work introduces considerable uncertainty in deduced gas transfer velocities. We furthermore discuss the observational requirements that have to be met for an adequate exploitation of the radon deficit method, of which an observation area of minimum horizontal inhomogeneity and monitoring of the remaining inhomogeneities are thought to be the most stringent ones.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP) (2020)
    Cambridge University Press
    In:  EPIC3Radiocarbon, Cambridge University Press, 62(4), pp. 725-757, ISSN: 0033-8222
    Details
    Publication Date: 2020-09-24
    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.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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