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| Titel |
Glacial–interglacial dynamics of Antarctic firn columns: comparison between simulations and ice core air-δ¹⁵N measurements |
| VerfasserIn |
E. Capron, A. Landais, D. Buiron, A. Cauquoin, J. Chappellaz, M. Debret, J. Jouzel, M. Leuenberger, P. Martinerie, V. Masson-Delmotte, R. Mulvaney, F. Parrenin, F. Prié |
| 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 ; 9, no. 3 ; Nr. 9, no. 3 (2013-05-02), S.983-999 |
| Datensatznummer |
250018049
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| Publikation (Nr.) |
 copernicus.org/cp-9-983-2013.pdf |
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| Zusammenfassung |
Correct estimation of the firn lock-in depth is essential for correctly
linking gas and ice chronologies in ice core studies. Here, two approaches
to constrain the firn depth evolution in Antarctica are presented over the
last deglaciation: outputs of a firn densification model, and measurements
of δ15N of N2 in air trapped in ice core, assuming that
δ15N is only affected by gravitational fractionation in the
firn column. Since the firn densification process is largely governed by
surface temperature and accumulation rate, we have investigated four ice
cores drilled in coastal (Berkner Island, BI, and James Ross Island, JRI)
and semi-coastal (TALDICE and EPICA Dronning Maud Land, EDML) Antarctic
regions. Combined with available ice core air-δ15N measurements from the EPICA
Dome C (EDC) site, the studied regions encompass a large
range of surface accumulation rates and temperature conditions.
Our δ15N profiles reveal a heterogeneous response of the firn
structure to glacial–interglacial climatic changes. While firn densification
simulations correctly predict TALDICE δ15N variations, they
systematically fail to capture the large millennial-scale δ15N
variations measured at BI and the δ15N glacial levels measured
at JRI and EDML – a mismatch previously reported for central East Antarctic
ice cores.
New constraints of the EDML gas–ice depth offset during the Laschamp event
(~41 ka) and the last deglaciation do not favour the
hypothesis of a large convective zone within the firn as the explanation of
the glacial firn model–δ15N data mismatch for this site. While
we could not conduct an in-depth study of the influence of impurities in
snow for firnification from the existing datasets, our detailed comparison
between the δ15N profiles and firn model simulations under
different temperature and accumulation rate scenarios suggests that the role
of accumulation rate may have been underestimated in the current description
of firnification models. |
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