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Titel |
Phase relationships between orbital forcing and the composition of air trapped in Antarctic ice cores |
VerfasserIn |
Lucie Bazin, Amaëlle Landais, Valérie Masson-Delmotte, Catherine Ritz, Ghislain Picard, Emilie Capron, Jean Jouzel, Marie Dumont, Markus Leuenberger, Frédéric Prié |
Konferenz |
EGU General Assembly 2015
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 17 (2015) |
Datensatznummer |
250111288
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Publikation (Nr.) |
EGU/EGU2015-11393.pdf |
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Zusammenfassung |
Orbital tuning is central for ice core chronologies beyond annual layer counting, available
back to 60 ka (i.e. thousands of years before 1950) for Greenland ice cores. While
several complementary orbital tuning tools have recently been developed using
δ18Oatm, δO2/N2 and air content with different orbital targets, quantifying their
uncertainties remains a challenge. Indeed, the exact processes linking variations of
these parameters, measured in the air trapped in ice, to their orbital targets are not
yet fully understood. Here, we provide new series of δO2/N2 and δ18Oatm data
encompassing Marine Isotopic Stage (MIS) 5 (between 100-160 ka) and the oldest
part (380-800 ka) of the East Antarctic EPICA Dome C (EDC) ice core. For the
first time, the measurements over MIS 5 allow an inter-comparison of δO2/N2 and
δ18Oatm records from three East Antarctic ice core sites (EDC, Vostok and Dome
F). This comparison highlights a site-specific relationship between δO2/N2 and
its local summer solstice insolation that increases the uncertainty associated with
the use of δO2/N2 as a tool for orbital tuning. Combining records of δ18Oatm and
δO2/N2 from Vostok and EDC, we evidence a loss of orbital signature for these two
parameters during periods of minimum eccentricity (~400 ka, ~720-800 ka). Our dataset
reveals a time-varying lag between δO2/N2 and δ18Oatm over the last 800 ka that we
interpret as variations of the lag between δ18Oatm and precession. Large lags of
~5 ka are identified during Terminations I and II, associated with strong Heinrich
events. On the opposite, minimal lags (~1-2 ka) are identified during four periods
characterized by high eccentricity, intermediate ice volume and no Heinrich events
(MIS 6-7, the end of MIS 9, MIS 15 and MIS 17). We therefore suggest that the
occurrence of Heinrich events influences the response of δ18Oatm to precession. |
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