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

Journal metrics

Journal metrics

  • IF value: 3.470 IF 3.470
  • IF 5-year value: 4.009 IF 5-year
    4.009
  • CiteScore value: 3.45 CiteScore
    3.45
  • SNIP value: 1.166 SNIP 1.166
  • IPP value: 3.28 IPP 3.28
  • SJR value: 1.929 SJR 1.929
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 64 Scimago H
    index 64
  • h5-index value: 43 h5-index 43
Discussion papers
https://doi.org/10.5194/cp-2019-159
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/cp-2019-159
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 14 Jan 2020

Submitted as: research article | 14 Jan 2020

Review status
This preprint is currently under review for the journal CP.

Mysteriously high Δ14C of the glacial atmosphere: Influence of 14C production and carbon cycle changes

Ashley Dinauer1, Florian Adolphi1,2, and Fortunat Joos1 Ashley Dinauer et al.
  • 1Climate and Environmental Physics, Physics Institute and Oeschger Centre for Climate Change Research, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
  • 2Quaternary Sciences, Department of Geology, Lund University, Sölvegatan 12, 22362 Lund, Sweden

Abstract. Despite intense focus on the ~ 190 permil drop in atmospheric Δ14C across the deglacial “mystery interval”, the specific mechanisms responsible for the apparent Δ14C excess in the glacial atmosphere have received considerably less attention. The computationally efficient Bern3D earth system model of intermediate complexity, designed for long-term climate simulations, allows us to address a very fundamental but still elusive question concerning the atmospheric Δ14C record: How can we explain the persistence of relatively high Δ14C values during the millennia after the Laschamp event? Large uncertainties in the pre-Holocene 14C production rate, as well as in the older portion of the Δ14C record, complicate our qualitative and quantitative interpretation of the glacial Δ14C elevation. Here we begin with sensitivity experiments that investigate the controls on atmospheric Δ14C in more idealized settings. We show that the long-term process of sedimentation may be much more important to the simulation of Δ14C than had been previously thought. In order to provide a bounded estimate of glacial Δ14C change, the Bern3D model was integrated with five available estimates of the 14C production rate as well as reconstructed and hypothesized paleoclimate forcing. Model results demonstrate that none of the available reconstructions of past changes in 14C production can reproduce the elevated Δ14C levels during the last glacial. In order to increase atmospheric Δ14C to glacial levels, a drastic reduction of air-sea exchange efficiency in the polar regions must be assumed, though discrepancies remain for the portion of the record younger than ~ 33 kyr BP. We end with an illustration of how the 14C production rate would have had to evolve to be consistent with the Δ14C record, by combining an atmospheric radiocarbon budget with the Bern3D model. The overall conclusion is that the remaining discrepancies with respect to glacial Δ14C may be linked to an underestimation of 14C production and/or a biased-high reconstruction of Δ14C over the time period of interest. Alternatively, we appear to still be missing an important carbon cycle process for atmospheric Δ14C.

Ashley Dinauer et al.

Interactive discussion

Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
[Login for Authors/Editors] [Subscribe to comment alert] Printer-friendly Version - Printer-friendly version Supplement - Supplement

Ashley Dinauer et al.

Ashley Dinauer et al.

Viewed

Total article views: 341 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
249 88 4 341 2 5
  • HTML: 249
  • PDF: 88
  • XML: 4
  • Total: 341
  • BibTeX: 2
  • EndNote: 5
Views and downloads (calculated since 14 Jan 2020)
Cumulative views and downloads (calculated since 14 Jan 2020)

Viewed (geographical distribution)

Total article views: 172 (including HTML, PDF, and XML) Thereof 171 with geography defined and 1 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 

Cited

Saved

No saved metrics found.

Discussed

No discussed metrics found.
Latest update: 04 Apr 2020
Publications Copernicus
Download
Short summary
Despite intense focus on the ~190 permil drop in Δ14C across the deglacial "mystery interval", the specific mechanisms responsible for the apparent Δ14C excess in the glacial atmosphere have received considerably less attention. Sensitivity experiments with the computationally efficient Bern3D earth system model suggest that our inability to reproduce the elevated Δ14C levels during the last glacial may reflect an underestimation of 14C production and/or a biased-high reconstruction of Δ14C.
Despite intense focus on the ~190 permil drop in Δ14C across the deglacial "mystery interval",...
Citation