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| Titel |
On the gas-ice depth difference (Δdepth) along the EPICA Dome C ice core |
| VerfasserIn |
F. Parrenin, S. Barker, T. Blunier, J. Chappellaz, J. Jouzel, A. Landais, V. Masson-Delmotte, J. Schwander, D. Veres |
| 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 ; 8, no. 4 ; Nr. 8, no. 4 (2012-08-02), S.1239-1255 |
| Datensatznummer |
250005710
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| Publikation (Nr.) |
 copernicus.org/cp-8-1239-2012.pdf |
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| Zusammenfassung |
| We compare a variety of methods for estimating the gas/ice depth offset
(Δdepth) at EPICA Dome C (EDC, East Antarctica). (1) Purely based on
modelling efforts, Δdepth can be estimated combining a firn
densification with an ice flow model. (2) The diffusive column height can be
estimated from δ15N and converted to Δdepth using an
ice flow model and assumptions about past average firn density and thickness
of the convective zone. (3) Ice and gas synchronisation of the EDC ice core
to the GRIP, EDML and TALDICE ice cores shifts the ice/gas offset problem
into higher accumulation ice cores where it can be more accurately
evaluated. (4) Finally, the bipolar seesaw hypothesis allows us to
synchronise the ice isotopic record with the gas CH4 record, the later
being taken as a proxy of Greenland temperature. The general agreement of
method 4 with methods 2 and 3 confirms that the bipolar seesaw antiphase
happened during the last 140 kyr. Applying method 4 to the deeper section of
the EDC core confirms that the ice flow is complex and can help to improve
our reconstruction of the thinning function and thus, of the EDC age scale.
We confirm that method 1 overestimates the glacial Δdepth at EDC and
we suggest that it is due to an overestimation of the glacial lock-in
depth (LID) by the firn densification model. In contrast, we find that
method 1 very likely underestimates Δdepth during Termination II,
due either to an underestimated thinning function or to an underestimated
LID. Finally, method 2 gives estimates within a few metres of methods 3 and
4 during the last deglacial warming, suggesting that the convective zone at
Dome C cannot have been very large at this time, if it existed at all. |
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