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Ice core dating with the 36Cl/10Be ratio

Kappelt, Niklas LU orcid ; Muscheler, Raimund LU orcid ; Baroni, Mélanie ; Beer, Juerg ; Christl, Marcus ; Vockenhuber, Christof ; Bard, Edouard and Wolff, Eric (2025) In Quaternary Science Reviews 355.
Abstract

Extremely thinned layers and possible folding make the dating of the deepest sections of ice cores especially challenging. Cosmogenic radionuclides have the potential to provide independent age estimates. The 36Cl/10Be ratio is largely independent of production rate changes that affect individual radionuclides and has an effective half-life of 384 kyr, making it an ideal tool for dating the new 1.5 Myr old ice core that the Beyond EPICA Oldest Ice Core project aims to retrieve at Little Dome C in East Antarctica. However, the loss of 36Cl through hydrogen chloride outgassing at low accumulation sites complicates its application and the long-term decay of the 36Cl/10Be ratio in ice... (More)

Extremely thinned layers and possible folding make the dating of the deepest sections of ice cores especially challenging. Cosmogenic radionuclides have the potential to provide independent age estimates. The 36Cl/10Be ratio is largely independent of production rate changes that affect individual radionuclides and has an effective half-life of 384 kyr, making it an ideal tool for dating the new 1.5 Myr old ice core that the Beyond EPICA Oldest Ice Core project aims to retrieve at Little Dome C in East Antarctica. However, the loss of 36Cl through hydrogen chloride outgassing at low accumulation sites complicates its application and the long-term decay of the 36Cl/10Be ratio in ice has not been studied. Here, we show that 36Cl is preserved in glacial periods and that the 36Cl/10Be ratio decreases more slowly than expected from physical decay over the last 900 kyr. While the glacial 36Cl flux decreases at the expected rate of physical decay within the uncertainty, the 10Be flux decreases faster, which may be linked to a post-depositional mobility of 10Be in deep ice and leads to the slower decrease of the 36Cl/10Be ratio. In addition to this long-term trend, the 36Cl/10Be ratio fluctuates around a fitted decay curve, which is likely caused by different climate sensitivities of the transport and deposition pathways of the individual radionuclides. Both effects need to be better understood and quantified to improve age estimates based on the 36Cl/10Be ratio.

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author
; ; ; ; ; ; and
author collaboration
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Be, Cl, Ice core, Radionuclide dating
in
Quaternary Science Reviews
volume
355
article number
109254
publisher
Elsevier
external identifiers
  • scopus:85218634046
ISSN
0277-3791
DOI
10.1016/j.quascirev.2025.109254
language
English
LU publication?
yes
id
167ec035-4460-453c-86d7-8ed3556c5feb
date added to LUP
2025-06-19 09:17:03
date last changed
2025-06-19 09:17:46
@article{167ec035-4460-453c-86d7-8ed3556c5feb,
  abstract     = {{<p>Extremely thinned layers and possible folding make the dating of the deepest sections of ice cores especially challenging. Cosmogenic radionuclides have the potential to provide independent age estimates. The <sup>36</sup>Cl/<sup>10</sup>Be ratio is largely independent of production rate changes that affect individual radionuclides and has an effective half-life of 384 kyr, making it an ideal tool for dating the new 1.5 Myr old ice core that the Beyond EPICA Oldest Ice Core project aims to retrieve at Little Dome C in East Antarctica. However, the loss of <sup>36</sup>Cl through hydrogen chloride outgassing at low accumulation sites complicates its application and the long-term decay of the <sup>36</sup>Cl/<sup>10</sup>Be ratio in ice has not been studied. Here, we show that <sup>36</sup>Cl is preserved in glacial periods and that the <sup>36</sup>Cl/<sup>10</sup>Be ratio decreases more slowly than expected from physical decay over the last 900 kyr. While the glacial <sup>36</sup>Cl flux decreases at the expected rate of physical decay within the uncertainty, the <sup>10</sup>Be flux decreases faster, which may be linked to a post-depositional mobility of <sup>10</sup>Be in deep ice and leads to the slower decrease of the <sup>36</sup>Cl/<sup>10</sup>Be ratio. In addition to this long-term trend, the <sup>36</sup>Cl/<sup>10</sup>Be ratio fluctuates around a fitted decay curve, which is likely caused by different climate sensitivities of the transport and deposition pathways of the individual radionuclides. Both effects need to be better understood and quantified to improve age estimates based on the <sup>36</sup>Cl/<sup>10</sup>Be ratio.</p>}},
  author       = {{Kappelt, Niklas and Muscheler, Raimund and Baroni, Mélanie and Beer, Juerg and Christl, Marcus and Vockenhuber, Christof and Bard, Edouard and Wolff, Eric}},
  issn         = {{0277-3791}},
  keywords     = {{Be; Cl; Ice core; Radionuclide dating}},
  language     = {{eng}},
  publisher    = {{Elsevier}},
  series       = {{Quaternary Science Reviews}},
  title        = {{Ice core dating with the <sup>36</sup>Cl/<sup>10</sup>Be ratio}},
  url          = {{http://dx.doi.org/10.1016/j.quascirev.2025.109254}},
  doi          = {{10.1016/j.quascirev.2025.109254}},
  volume       = {{355}},
  year         = {{2025}},
}