Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core

• Published in: The Cryosphere
• Main Authors: Tison, J.-L, 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, Valérie, Landais, A., Lipenkov, V, Loulergue, L, Barnola, J.-M, Petit, J.-R, Delmonte, B, Dreyfus, G, Dahl-Jensen, D, Durand, G, Bereiter, B, Schilt, A, Spahni, R, Pol, K, Lorrain, R, Souchez, R, Samyn, D
• Other Authors: Département des Sciences de la Terre et de l'Environnement, Université libre de Bruxelles (ULB), Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), British Antarctic Survey (BAS), Natural Environment Research Council (NERC), Climate and Environmental Physics Bern (CEP), Physikalisches Institut Bern, Universität Bern / University of Bern (UNIBE)-Universität Bern / University of Bern (UNIBE), Stockholm University, Chemistry Department, Università degli Studi di Firenze = University of Florence = Université de Florence (UniFI), Department of Bentho-pelagic processes, Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung = Alfred Wegener Institute for Polar and Marine Research = Institut Alfred-Wegener pour la recherche polaire et marine (AWI), Helmholtz-Gemeinschaft = Helmholtz Association-Helmholtz-Gemeinschaft = Helmholtz Association, Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Dipartimento di Scienze Ambientali, Informatica e Statistica, University of Ca’ Foscari Venice, Italy, Niels Bohr Institute Copenhagen (NBI), Faculty of Science Copenhagen, University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH), Arctic and Antarctic Research Institute (AARI), Russian Federal Service for Hydrometeorology and Environmental Monitoring (Roshydromet), Dipartimento di Scienze dell'Ambiente e del Territorio (DISAT), Università degli Studi di Milano = University of Milan (UNIMI), Oak Ridge Institute for Science and Education Climate Change Policy and Technology Fellow with the US Department of Energy Office of Policy and International Affairs, Nagaoka University of Technology
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: [SDE]Environmental Sciences; Antarc*; Antarctica; EPICA; ice core; Ice Sheet; The Cryosphere
• Online Access: https://insu.hal.science/insu-01286552; https://insu.hal.science/insu-01286552/document; https://insu.hal.science/insu-01286552/file/THE%20CRYOSPHERE-%20Retrieving%20the%20paleoclimatic%20signal%20from%20the%20deeper%20part%20of%20the%20EPICA%20Dome%20C%20ice%20core.pdf; https://doi.org/10.5194/tc-9-1633-2015

International audience 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 paleocli-matic 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.