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| Titel |
New constraints on the gas age-ice age difference along the EPICA ice cores, 0–50 kyr |
| VerfasserIn |
L. Loulergue, F. Parrenin, T. Blunier, J.-M. Barnola, R. Spahni, A. Schilt, G. Raisbeck, J. Chappellaz |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 3, no. 3 ; Nr. 3, no. 3 (2007-08-28), S.527-540 |
| Datensatznummer |
250001079
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| Publikation (Nr.) |
 copernicus.org/cp-3-527-2007.pdf |
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| Zusammenfassung |
| Gas is trapped in polar ice sheets at ~50–120 m below the surface and
is therefore younger than the surrounding ice. Firn densification models are
used to evaluate this ice age-gas age difference (Δage) in the past.
However, such models need to be validated by data, in particular for periods
colder than present day on the East Antarctic plateau. Here we bring new
constraints to test a firn densification model applied to the EPICA Dome C
(EDC) site for the last 50 kyr, by linking the EDC ice core to the EPICA
Dronning Maud Land (EDML) ice core, both in the ice phase (using volcanic
horizons) and in the gas phase (using rapid methane variations). We also use
the structured 10Be peak, occurring 41 kyr before present (BP) and due
to the low geomagnetic field associated with the Laschamp event, to
experimentally estimate the Δage during this event. Our results seem
to reveal an overestimate of the Δage by the firn densification
model during the last glacial period at EDC. Tests with different
accumulation rates and temperature scenarios do not entirely resolve this
discrepancy. Although the exact reasons for the Δage overestimate at
the two EPICA sites remain unknown at this stage, we conclude that current
densification model simulations have deficits under glacial climatic
conditions. Whatever the cause of the Δage overestimate, our finding
suggests that the phase relationship between CO2 and EDC temperature
previously inferred for the start of the last deglaciation (lag of CO2
by 800±600 yr) seems to be overestimated. |
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