Preprints
https://doi.org/10.5194/tc-2022-259
https://doi.org/10.5194/tc-2022-259
31 Jan 2023
 | 31 Jan 2023
Status: a revised version of this preprint is currently under review for the journal TC.

Impact of subsurface crevassing on the depth-age relationship of high-alpine ice cores extracted at Col du Dôme between 1994 and 2012

Susanne Preunkert, Pascal Bohleber, Michel Legrand, Hubertus Fischer, Adrien Gilbert, Tobias Erhardt, Roland Purtschert, Lars Zipf, Astrid Waldner, and Joseph R. McConnell

Abstract. Three seasonally-resolved ice-core records covering the 20th century were extracted in 1994, 2004 and 2012 at a nearly identical location at the Col du Dôme (4250 m above sea level, m asl, Mont Blanc, French Alps) drill site. Here we complete and combine chemical records of major ions and radiometric measurements of 3H and 210Pb obtained on these three cores together with a 3D ice flow model of the Col du Dôme glacier, to investigate in detail the origin of the discontinuities observed in the depth-age relation of the ice cores drilled in 2004 and 2012. Taking advantage of the granitic bedrock at Col du Dôme, which makes the 210Pb ice-core records sensitive to the presence of upstream crevasses, and the fact that the depth-age disturbances are observed at depths for which absolute time markers were available, we draw an overall picture of a dynamic crevasse formation which can explain the non-disturbed depth-age relation of the ice core drilled in 1994 as well as the perturbations observed in those drilled in 2004 and 2012. Since crevasses are common at high alpine glacier sites, our study points out the mandatory need of rigorous investigations of the depth-age scale before using high alpine sites to interpret atmospheric changes.

Susanne Preunkert, Pascal Bohleber, Michel Legrand, Hubertus Fischer, Adrien Gilbert, Tobias Erhardt, Roland Purtschert, Lars Zipf, Astrid Waldner, and Joseph R. McConnell

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2022-259', Anonymous Referee #1, 28 Feb 2023
  • RC2: 'Comment on tc-2022-259', Anonymous Referee #2, 22 Mar 2023
Susanne Preunkert, Pascal Bohleber, Michel Legrand, Hubertus Fischer, Adrien Gilbert, Tobias Erhardt, Roland Purtschert, Lars Zipf, Astrid Waldner, and Joseph R. McConnell
Susanne Preunkert, Pascal Bohleber, Michel Legrand, Hubertus Fischer, Adrien Gilbert, Tobias Erhardt, Roland Purtschert, Lars Zipf, Astrid Waldner, and Joseph R. McConnell

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Short summary
Being close to European pollution source regions makes ice cores from Alpine glaciers important to reconstruct past anthropogenic changes over Europe. Three ice cores covering the 20th century were extracted at the same place at the Col du Dôme (4250 masl, French Alps) in 1994, 2004, and 2012. Combining chemical profiles, bomb test markers and 210Pb profiles, used as footprints of crevasses, allowed to highlight changes over time of the depth-age characteristics at an Alpine drill site.