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  • 1
    Online Resource
    Online Resource
    Oxygen-18 of O 2 Records the Impact of Abrupt Climate Change on the Terrestrial Biosphere
    American Association for the Advancement of Science (AAAS) ; 2009
    In:  Science Vol. 324, No. 5933 ( 2009-06-12), p. 1431-1434
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 324, No. 5933 ( 2009-06-12), p. 1431-1434
    Abstract: Photosynthesis and respiration occur widely on Earth’s surface, and the 18 O/ 16 O ratio of the oxygen produced and consumed varies with climatic conditions. As a consequence, the history of climate is reflected in the deviation of the 18 O/ 16 O of air (δ 18 O atm ) from seawater δ 18 O (known as the Dole effect). We report variations in δ 18 O atm over the past 60,000 years related to Heinrich and Dansgaard-Oeschger events, two modes of abrupt climate change observed during the last ice age. Correlations with cave records support the hypothesis that the Dole effect is primarily governed by the strength of the Asian and North African monsoons and confirm that widespread changes in low-latitude terrestrial rainfall accompanied abrupt climate change. The rapid δ 18 O atm changes can also be used to synchronize ice records by providing global time markers.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1169473
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2009
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  • 2
    Online Resource
    Online Resource
    Differentiating bubble-free layers from melt layers in ice cores using noble gases
    International Glaciological Society ; 2015
    In:  Journal of Glaciology Vol. 61, No. 227 ( 2015), p. 585-594
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 61, No. 227 ( 2015), p. 585-594
    Abstract: Melt layers are clear indicators of extreme summer warmth on polar ice caps. The visual identification of refrozen meltwater as clear bubble-free layers cannot be used to study some past warm periods, because, in deeper ice, bubbles are lost to clathrate formation. We present here a reliable method to detect melt events, based on the analysis of Kr/Ar and Xe/Ar ratios in ice cores, and apply it to the detection of melt in clathrate ice from the Eemian at NEEM, Greenland. Additionally, melt layers in ice cores can compromise the integrity of the gas record by dissolving soluble gases, or by altering gas transport in the firn, which affects the gas chronology. We find that the easily visible 1 mm thick bubble-free layers in the WAIS Divide ice core do not contain sufficient melt to alter the gas composition in the core, and do not cause artifacts or discontinuities in the gas chronology. The presence of these layers during winter, and the absence of anomalies in soluble gases, suggests that these layers can be formed by processes other than refreezing of meltwater. Consequently, the absence of bubbles in thin crusts is not in itself proof of a melt event.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/2015JoG14J237
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2015
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    SSG: 14
    Location Call Number Limitation Availability
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  • 3
    Online Resource
    Online Resource
    A method to measure Kr/N 2 ratios in air bubbles trapped in ice cores and its application in reconstructing past mean ocean temperature
    American Geophysical Union (AGU) ; 2007
    In:  Journal of Geophysical Research Vol. 112, No. D19 ( 2007-10-10)
    Details
    In: Journal of Geophysical Research, American Geophysical Union (AGU), Vol. 112, No. D19 ( 2007-10-10)
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2006JD008317
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2007
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    SSG: 16,13
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  • 4
    Online Resource
    Online Resource
    CO 2 diffusion in polar ice: observations from naturally formed CO 2 spikes in the Siple Dome (Antarctica) ice core
    International Glaciological Society ; 2008
    In:  Journal of Glaciology Vol. 54, No. 187 ( 2008), p. 685-695
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 54, No. 187 ( 2008), p. 685-695
    Abstract: One common assumption in interpreting ice-core CO 2 records is that diffusion in the ice does not affect the concentration profile. However, this assumption remains untested because the extremely small CO 2 diffusion coefficient in ice has not been accurately determined in the laboratory. In this study we take advantage of high levels of CO 2 associated with refrozen layers in an ice core from Siple Dome, Antarctica, to study CO 2 diffusion rates. We use noble gases (Xe/Ar and Kr/Ar), electrical conductivity and Ca 2+ ion concentrations to show that substantial CO 2 diffusion may occur in ice on timescales of thousands of years. We estimate the permeation coefficient for CO 2 in ice is ∼ 4 × 10 −21 mol m −1 s −1 Pa −1 at −23°C in the top 287 m (corresponding to 2.74 kyr). Smoothing of the CO 2 record by diffusion at this depth/age is one or two orders of magnitude smaller than the smoothing in the firn. However, simulations for depths of ∼930–950 m (∼60–70 kyr) indicate that smoothing of the CO 2 record by diffusion in deep ice is comparable to smoothing in the firn. Other types of diffusion (e.g. via liquid in ice grain boundaries or veins) may also be important but their influence has not been quantified.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/002214308786570764
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2008
    detail.hit.zdb_id: 2140541-4
    SSG: 14
    Location Call Number Limitation Availability
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