Journal cover Journal topic
Climate of the Past An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

IF value: 3.536
IF3.536
IF 5-year value: 3.967
IF 5-year
3.967
CiteScore value: 6.6
CiteScore
6.6
SNIP value: 1.262
SNIP1.262
IPP value: 3.90
IPP3.90
SJR value: 2.185
SJR2.185
Scimago H <br class='widget-line-break'>index value: 71
Scimago H
index
71
h5-index value: 40
h5-index40
Volume 8, issue 4
Clim. Past, 8, 1239–1255, 2012
https://doi.org/10.5194/cp-8-1239-2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: AICC2012: a new ice core chronology

Clim. Past, 8, 1239–1255, 2012
https://doi.org/10.5194/cp-8-1239-2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 02 Aug 2012

Research article | 02 Aug 2012

On the gas-ice depth difference (Δdepth) along the EPICA Dome C ice core

F. Parrenin1,2, S. Barker3, T. Blunier4, J. Chappellaz2, J. Jouzel5, A. Landais5, V. Masson-Delmotte5, J. Schwander6, and D. Veres2,7 F. Parrenin et al.
  • 1Laboratoire Chrono-Environnement, Besançon, France
  • 2UJF Grenoble 1, UMR5183, CNRS – Laboratoire de Glaciologie et Géophysique de l'Environnement (LGGE), Grenoble 38041, France
  • 3School of Earth and Ocean Sciences, Cardiff University, UK
  • 4Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
  • 5Laboratoire des Sciences du Climat et de l'Environnement, Gif-sur-Yvette, France
  • 6Physics Institute, University of Bern, Bern, Switzerland
  • 7Institute of Speleology, Romanian Academy, Cluj-Napoca, Romania

Abstract. 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.

Publications Copernicus
Download
Citation