Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core
An important share of paleoclimatic information is buried within the lowermost layers of deep ice cores. Because improving our records further back in time is one of the main challenges in the near future, it is essential to judge how deep these records remain unaltered, since the proximity of the b...
Published in: | The Cryosphere |
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Online Access: | http://hdl.handle.net/10281/88636 https://doi.org/10.5194/tc-9-1633-2015 |
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ftunivmilanobic:oai:boa.unimib.it:10281/88636 2024-04-21T07:47:10+00:00 Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core Tison, J de Angelis, M Littot, G Wolff, E Fischer, H Hansson, M Bigler, M Udisti, R Wegner, A Jouzel, J Stenni, B Johnsen, S Masson Delmotte, V Landais, A Lipenkov, V Loulergue, L Barnola, J Petit, J Dreyfus, G Dahl Jensen, D Durand, G Bereiter, B Schilt, A Spahni, R Pol, K Lorrain, R Souchez, R Samyn, D. DELMONTE, BARBARA Tison, J de Angelis, M Littot, G Wolff, E Fischer, H Hansson, M Bigler, M Udisti, R Wegner, A Jouzel, J Stenni, B Johnsen, S Masson Delmotte, V Landais, A Lipenkov, V Loulergue, L Barnola, J Petit, J Delmonte, B Dreyfus, G Dahl Jensen, D Durand, G Bereiter, B Schilt, A Spahni, R Pol, K Lorrain, R Souchez, R Samyn, D 2015 http://hdl.handle.net/10281/88636 https://doi.org/10.5194/tc-9-1633-2015 eng eng Copernicus GmbH info:eu-repo/semantics/altIdentifier/wos/WOS:000360661700020 volume:9 issue:4 firstpage:1633 lastpage:1648 numberofpages:16 journal:THE CRYOSPHERE http://hdl.handle.net/10281/88636 doi:10.5194/tc-9-1633-2015 info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-84939813992 info:eu-repo/semantics/openAccess ice cores Antarctica Paleoclimate info:eu-repo/semantics/article 2015 ftunivmilanobic https://doi.org/10.5194/tc-9-1633-2015 2024-03-28T01:09:08Z An important share of paleoclimatic information is buried within the lowermost layers of deep ice cores. Because improving our records further back in time is one of the main challenges in the near future, it is essential to judge how deep these records remain unaltered, since the proximity of the bedrock is likely to interfere both with the recorded temporal sequence and the ice properties. In this paper, we present a multiparametric study (δD-δ18Oice, δ18Oatm, total air content, CO2, CH4, N2O, dust, high-resolution chemistry, ice texture) of the bottom 60 m of the EPICA (European Project for Ice Coring in Antarctica) Dome C ice core from central Antarctica. These bottom layers were subdivided into two distinct facies: the lower 12 m showing visible solid inclusions (basal dispersed ice facies) and the upper 48 m, which we will refer to as the "basal clean ice facies". Some of the data are consistent with a pristine paleoclimatic signal, others show clear anomalies. It is demonstrated that neither large-scale bottom refreezing of subglacial water, nor mixing (be it internal or with a local basal end term from a previous/initial ice sheet configuration) can explain the observed bottom-ice properties. We focus on the high-resolution chemical profiles and on the available remote sensing data on the subglacial topography of the site to propose a mechanism by which relative stretching of the bottom-ice sheet layers is made possible, due to the progressively confining effect of subglacial valley sides. This stress field change, combined with bottom-ice temperature close to the pressure melting point, induces accelerated migration recrystallization, which results in spatial chemical sorting of the impurities, depending on their state (dissolved vs. solid) and if they are involved or not in salt formation. This chemical sorting effect is responsible for the progressive build-up of the visible solid aggregates that therefore mainly originate "from within", and not from incorporation processes of debris from the ice ... Article in Journal/Newspaper Antarc* Antarctica EPICA ice core Ice Sheet Università degli Studi di Milano-Bicocca: BOA (Bicocca Open Archive) The Cryosphere 9 4 1633 1648 |
institution |
Open Polar |
collection |
Università degli Studi di Milano-Bicocca: BOA (Bicocca Open Archive) |
op_collection_id |
ftunivmilanobic |
language |
English |
topic |
ice cores Antarctica Paleoclimate |
spellingShingle |
ice cores Antarctica Paleoclimate Tison, J de Angelis, M Littot, G Wolff, E Fischer, H Hansson, M Bigler, M Udisti, R Wegner, A Jouzel, J Stenni, B Johnsen, S Masson Delmotte, V Landais, A Lipenkov, V Loulergue, L Barnola, J Petit, J Dreyfus, G Dahl Jensen, D Durand, G Bereiter, B Schilt, A Spahni, R Pol, K Lorrain, R Souchez, R Samyn, D. DELMONTE, BARBARA Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core |
topic_facet |
ice cores Antarctica Paleoclimate |
description |
An important share of paleoclimatic information is buried within the lowermost layers of deep ice cores. Because improving our records further back in time is one of the main challenges in the near future, it is essential to judge how deep these records remain unaltered, since the proximity of the bedrock is likely to interfere both with the recorded temporal sequence and the ice properties. In this paper, we present a multiparametric study (δD-δ18Oice, δ18Oatm, total air content, CO2, CH4, N2O, dust, high-resolution chemistry, ice texture) of the bottom 60 m of the EPICA (European Project for Ice Coring in Antarctica) Dome C ice core from central Antarctica. These bottom layers were subdivided into two distinct facies: the lower 12 m showing visible solid inclusions (basal dispersed ice facies) and the upper 48 m, which we will refer to as the "basal clean ice facies". Some of the data are consistent with a pristine paleoclimatic signal, others show clear anomalies. It is demonstrated that neither large-scale bottom refreezing of subglacial water, nor mixing (be it internal or with a local basal end term from a previous/initial ice sheet configuration) can explain the observed bottom-ice properties. We focus on the high-resolution chemical profiles and on the available remote sensing data on the subglacial topography of the site to propose a mechanism by which relative stretching of the bottom-ice sheet layers is made possible, due to the progressively confining effect of subglacial valley sides. This stress field change, combined with bottom-ice temperature close to the pressure melting point, induces accelerated migration recrystallization, which results in spatial chemical sorting of the impurities, depending on their state (dissolved vs. solid) and if they are involved or not in salt formation. This chemical sorting effect is responsible for the progressive build-up of the visible solid aggregates that therefore mainly originate "from within", and not from incorporation processes of debris from the ice ... |
author2 |
Tison, J de Angelis, M Littot, G Wolff, E Fischer, H Hansson, M Bigler, M Udisti, R Wegner, A Jouzel, J Stenni, B Johnsen, S Masson Delmotte, V Landais, A Lipenkov, V Loulergue, L Barnola, J Petit, J Delmonte, B Dreyfus, G Dahl Jensen, D Durand, G Bereiter, B Schilt, A Spahni, R Pol, K Lorrain, R Souchez, R Samyn, D |
format |
Article in Journal/Newspaper |
author |
Tison, J de Angelis, M Littot, G Wolff, E Fischer, H Hansson, M Bigler, M Udisti, R Wegner, A Jouzel, J Stenni, B Johnsen, S Masson Delmotte, V Landais, A Lipenkov, V Loulergue, L Barnola, J Petit, J Dreyfus, G Dahl Jensen, D Durand, G Bereiter, B Schilt, A Spahni, R Pol, K Lorrain, R Souchez, R Samyn, D. DELMONTE, BARBARA |
author_facet |
Tison, J de Angelis, M Littot, G Wolff, E Fischer, H Hansson, M Bigler, M Udisti, R Wegner, A Jouzel, J Stenni, B Johnsen, S Masson Delmotte, V Landais, A Lipenkov, V Loulergue, L Barnola, J Petit, J Dreyfus, G Dahl Jensen, D Durand, G Bereiter, B Schilt, A Spahni, R Pol, K Lorrain, R Souchez, R Samyn, D. DELMONTE, BARBARA |
author_sort |
Tison, J |
title |
Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core |
title_short |
Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core |
title_full |
Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core |
title_fullStr |
Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core |
title_full_unstemmed |
Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core |
title_sort |
retrieving the paleoclimatic signal from the deeper part of the epica dome c ice core |
publisher |
Copernicus GmbH |
publishDate |
2015 |
url |
http://hdl.handle.net/10281/88636 https://doi.org/10.5194/tc-9-1633-2015 |
genre |
Antarc* Antarctica EPICA ice core Ice Sheet |
genre_facet |
Antarc* Antarctica EPICA ice core Ice Sheet |
op_relation |
info:eu-repo/semantics/altIdentifier/wos/WOS:000360661700020 volume:9 issue:4 firstpage:1633 lastpage:1648 numberofpages:16 journal:THE CRYOSPHERE http://hdl.handle.net/10281/88636 doi:10.5194/tc-9-1633-2015 info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-84939813992 |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.5194/tc-9-1633-2015 |
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The Cryosphere |
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9 |
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1633 |
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