Glacial-interglacial dynamics of Antarctic firn columns: comparison between simulations and ice core air- δ 15N measurements

• Published in: Climate of the Past
• Main Authors: Capron, E., Landais, A., Buiron, D., Cauquoin, A., Chappellaz, J., Debret, Maxime, Jouzel, Jean, Leuenberger, M., Martinerie, P., Masson-Delmotte, Valérie, Mulvaney, R., Parrenin, F., Prie, F.
• Other Authors: 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), British Antarctic Survey (BAS), Natural Environment Research Council (NERC), 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)), 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), Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS), Climate and Environmental Physics Bern (CEP), Physikalisches Institut Bern, Universität Bern / University of Bern (UNIBE)-Universität Bern / University of Bern (UNIBE), Laboratoire Chrono-environnement (UMR 6249) (LCE), Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté COMUE (UBFC)-Université Bourgogne Franche-Comté COMUE (UBFC)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; [SDE.MCG]Environmental Sciences/Global Changes; [SDU]Sciences of the Universe [physics]; Antarc*; Antarctic; Antarctica; Berkner Island; Dronning Maud Land; EPICA; ice core; James Ross Island; Ross Island
• Online Access: https://hal.science/hal-00861133; https://hal.science/hal-00861133/document; https://hal.science/hal-00861133/file/cp-9-983-2013.pdf; https://doi.org/10.5194/cp-9-983-2013

International audience Correct estimation of the firn lock-in depth is essential for correctly linking gas and ice chronologies in ice core studies. Here, two approaches to constrain the firn depth evolution in Antarctica are presented over the last deglaciation : outputs of a firn densification model, and measurements of 15N of N2 in air trapped in ice core, assuming that 15N is only affected by gravitational fractionation in the firn column. Since the firn densification process is largely governed by surface temperature and accumulation rate, we have investigated four ice cores drilled in coastal (Berkner Island, BI, and James Ross Island, JRI) and semi-coastal (TALDICE and EPICA Dronning Maud Land, EDML) Antarctic regions. Combined with available ice core air- 15N measurements from the EPICA Dome C (EDC) site, the studied regions encompass a large range of surface accumulation rates and temperature conditions. Our 15N profiles reveal a heterogeneous response of the firn structure to glacial-interglacial climatic changes. While firn densification simulations correctly predict TALDICE 15N variations, they systematically fail to capture the large millennial-scale 15N variations measured at BI and the 15N glacial levels measured at JRI and EDML - a mismatch previously reported for central East Antarctic ice cores. New constraints of the EDML gas-ice depth offset during the Laschamp event ( 41 ka) and the last deglaciation do not favour the hypothesis of a large convective zone within the firn as the explanation of the glacial firn model- 15N data mismatch for this site. While we could not conduct an indepth study of the influence of impurities in snow for firnification from the existing datasets, our detailed comparison between the 15N profiles and firn model simulations under different temperature and accumulation rate scenarios suggests that the role of accumulation rate may have been underestimated in the current description of firnification models.