New constraints on the gas age-ice age difference along the EPICA ice cores, 0-50 kyr
Gas is trapped in polar ice sheets at ~50–120 m below the surface and is therefore younger than the surrounding ice. Firn densification models are used to evaluate this ice age-gas age difference (Δage) in the past. However, such models need to be validated by data, in particular for periods colder...
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ftdatacite:10.7892/boris.25256 2023-05-15T13:59:40+02:00 New constraints on the gas age-ice age difference along the EPICA ice cores, 0-50 kyr Barnola, J.-M. Chappellaz, J. Loulergue, L. Blunier, Thomas Parrenin, F. Raisbeck, G. Spahni, Renato Schilt, Adrian 2007 application/pdf https://dx.doi.org/10.7892/boris.25256 http://boris.unibe.ch/25256/ en eng Copernicus Publications info:eu-repo/semantics/openAccess CreativeWork article 2007 ftdatacite https://doi.org/10.7892/boris.25256 2021-11-05T12:55:41Z Gas is trapped in polar ice sheets at ~50–120 m below the surface and is therefore younger than the surrounding ice. Firn densification models are used to evaluate this ice age-gas age difference (Δage) in the past. However, such models need to be validated by data, in particular for periods colder than present day on the East Antarctic plateau. Here we bring new constraints to test a firn densification model applied to the EPICA Dome C (EDC) site for the last 50 kyr, by linking the EDC ice core to the EPICA Dronning Maud Land (EDML) ice core, both in the ice phase (using volcanic horizons) and in the gas phase (using rapid methane variations). We also use the structured 10Be peak, occurring 41 kyr before present (BP) and due to the low geomagnetic field associated with the Laschamp event, to experimentally estimate the Δage during this event. Our results seem to reveal an overestimate of the Δage by the firn densification model during the last glacial period at EDC. Tests with different accumulation rates and temperature scenarios do not entirely resolve this discrepancy. Although the exact reasons for the Δage overestimate at the two EPICA sites remain unknown at this stage, we conclude that current densification model simulations have deficits under glacial climatic conditions. Whatever the cause of the Δage overestimate, our finding suggests that the phase relationship between CO2 and EDC temperature previously inferred for the start of the last deglaciation (lag of CO2 by 800±600 yr) seems to be overestimated. Article in Journal/Newspaper Antarc* Antarctic Dronning Maud Land EPICA ice core DataCite Metadata Store (German National Library of Science and Technology) Antarctic Dronning Maud Land |
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Open Polar |
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DataCite Metadata Store (German National Library of Science and Technology) |
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ftdatacite |
language |
English |
description |
Gas is trapped in polar ice sheets at ~50–120 m below the surface and is therefore younger than the surrounding ice. Firn densification models are used to evaluate this ice age-gas age difference (Δage) in the past. However, such models need to be validated by data, in particular for periods colder than present day on the East Antarctic plateau. Here we bring new constraints to test a firn densification model applied to the EPICA Dome C (EDC) site for the last 50 kyr, by linking the EDC ice core to the EPICA Dronning Maud Land (EDML) ice core, both in the ice phase (using volcanic horizons) and in the gas phase (using rapid methane variations). We also use the structured 10Be peak, occurring 41 kyr before present (BP) and due to the low geomagnetic field associated with the Laschamp event, to experimentally estimate the Δage during this event. Our results seem to reveal an overestimate of the Δage by the firn densification model during the last glacial period at EDC. Tests with different accumulation rates and temperature scenarios do not entirely resolve this discrepancy. Although the exact reasons for the Δage overestimate at the two EPICA sites remain unknown at this stage, we conclude that current densification model simulations have deficits under glacial climatic conditions. Whatever the cause of the Δage overestimate, our finding suggests that the phase relationship between CO2 and EDC temperature previously inferred for the start of the last deglaciation (lag of CO2 by 800±600 yr) seems to be overestimated. |
format |
Article in Journal/Newspaper |
author |
Barnola, J.-M. Chappellaz, J. Loulergue, L. Blunier, Thomas Parrenin, F. Raisbeck, G. Spahni, Renato Schilt, Adrian |
spellingShingle |
Barnola, J.-M. Chappellaz, J. Loulergue, L. Blunier, Thomas Parrenin, F. Raisbeck, G. Spahni, Renato Schilt, Adrian New constraints on the gas age-ice age difference along the EPICA ice cores, 0-50 kyr |
author_facet |
Barnola, J.-M. Chappellaz, J. Loulergue, L. Blunier, Thomas Parrenin, F. Raisbeck, G. Spahni, Renato Schilt, Adrian |
author_sort |
Barnola, J.-M. |
title |
New constraints on the gas age-ice age difference along the EPICA ice cores, 0-50 kyr |
title_short |
New constraints on the gas age-ice age difference along the EPICA ice cores, 0-50 kyr |
title_full |
New constraints on the gas age-ice age difference along the EPICA ice cores, 0-50 kyr |
title_fullStr |
New constraints on the gas age-ice age difference along the EPICA ice cores, 0-50 kyr |
title_full_unstemmed |
New constraints on the gas age-ice age difference along the EPICA ice cores, 0-50 kyr |
title_sort |
new constraints on the gas age-ice age difference along the epica ice cores, 0-50 kyr |
publisher |
Copernicus Publications |
publishDate |
2007 |
url |
https://dx.doi.org/10.7892/boris.25256 http://boris.unibe.ch/25256/ |
geographic |
Antarctic Dronning Maud Land |
geographic_facet |
Antarctic Dronning Maud Land |
genre |
Antarc* Antarctic Dronning Maud Land EPICA ice core |
genre_facet |
Antarc* Antarctic Dronning Maud Land EPICA ice core |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.7892/boris.25256 |
_version_ |
1766268331237572608 |