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Schaller, Christoph Florian; Freitag, Johannes; Eisen, Olaf (2017): Firn microstructure in the lock-in zone for three polar ice cores [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.879577, Supplement to: Schaller, CF et al. (2017): Gas enclosure in polar firn follows universal law. Climate of the Past Discussions, 12 pp, https://doi.org/10.5194/cp-2017-94

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Abstract:
In order to interpret the paleoclimatic record stored in the air enclosed in polar ice cores, it is crucial to understand the fundamental lock-in process. Within the porous firn, bubbles are sealed continuously until the respective horizontal layer reaches a critical porosity. Present-day firn models use a postulated temperature dependence of this value as the only parameter to adjust to the surrounding conditions of individual sites. However, no direct measurements of the firn microstructure could confirm these assumptions. Here we show that the critical porosity is a universal constant by providing a statistically solid data set of µm-resolution 3D X-ray computer tomographic measurements for ice cores representing different extremes of the temperature and accumulation ranges. We demonstrate why indirect measurements yield misleading data and substantiate our observations by applying percolation theory as a theoretical framework for bubble trapping. Incorporation of our results does significantly influence the dating of trace gas records, changing gas age-ice age differences by up to more than 1000 years. This will help resolve inconsistencies, such as differences between East Antarctic d15N records (as a proxy for firn height) and model results. We expect our findings to be the basis for improved firn air and densification models, leading to lower dating uncertainties. The reduced coupling of proxies and surrounding conditions may allow for more sophisticated reinterpretations of trace gas records in terms of paleoclimatic changes and will foster the development of new proxies, such as the air content as a marker of local insolation.
Project(s):
Glaciology @ AWI (AWI_Glac)
Coverage:
Median Latitude: -33.988802 * Median Longitude: 6.105492 * South-bound Latitude: -76.790000 * West-bound Longitude: -26.715778 * North-bound Latitude: 71.304194 * East-bound Longitude: 31.910000
Date/Time Start: 2013-01-15T00:00:00 * Date/Time End: 2015-05-15T00:00:00
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
7 datasets

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Datasets listed in this publication series

  1. Schaller, CF; Freitag, J; Eisen, O (2017): Closed versus total porosity for ice core B49, 73-90 m. https://doi.org/10.1594/PANGAEA.879570
  2. Schaller, CF; Freitag, J; Eisen, O (2017): Coordination number versus total porosity for ice core B49, 73-90 m. https://doi.org/10.1594/PANGAEA.879574
  3. Schaller, CF; Freitag, J; Eisen, O (2017): Closed versus total porosity for ice core B53, 76-106 m. https://doi.org/10.1594/PANGAEA.879572
  4. Schaller, CF; Freitag, J; Eisen, O (2017): Closed versus total porosity for ice core B53, 76-106 m, with cut-bubble effect. https://doi.org/10.1594/PANGAEA.879571
  5. Schaller, CF; Freitag, J; Eisen, O (2017): Coordination number versus total porosity for ice core B53, 76-106 m. https://doi.org/10.1594/PANGAEA.879575
  6. Schaller, CF; Freitag, J; Eisen, O (2017): Closed versus total porosity for ice core RECAP_S2, 49-73 m. https://doi.org/10.1594/PANGAEA.879573
  7. Schaller, CF; Freitag, J; Eisen, O (2017): Coordination number versus total porosity for ice core RECAP_S2, 49-73 m. https://doi.org/10.1594/PANGAEA.879576