Air–snow transfer of nitrate on the East Antarctic Plateau – Part 2: An isotopic model for the interpretation of deep ice-core records

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Erbland, J, Savarino, J, Morin, Samuel, France, J.L, Frey, M.M., King, M.D
• Other Authors: Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-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 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 recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), Royal Holloway University of London (RHUL), British Antarctic Survey (BAS), Natural Environment Research Council (NERC)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Antarctic; East Antarctica; The Antarctic; Antarc*; Antarctica; ice core
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-01320986; https://hal-insu.archives-ouvertes.fr/insu-01320986/document; https://hal-insu.archives-ouvertes.fr/insu-01320986/file/ATMOSPHERIC%20CHEMISTRY%20AND%20PHYSICS%20-%20Air-snow%20transfer%20of%20nitrate%20on%20the%20East%20Antarctic%20Plateau.pdf; https://doi.org/10.5194/acp-15-12079-2015

International audience Unraveling the modern budget of reactive nitrogen on the Antarctic Plateau is critical for the interpretation of ice-core records of nitrate. This requires accounting for nitrate recycling processes occurring in near-surface snow and the overlying atmospheric boundary layer. Not only concentration measurements but also isotopic ratios of nitrogen and oxygen in nitrate provide constraints on the processes at play. However, due to the large number of intertwined chemical and physical phenomena involved, numerical mod-eling is required to test hypotheses in a quantitative manner. Here we introduce the model TRANSITS (TRansfer of Atmospheric Nitrate Stable Isotopes To the Snow), a novel conceptual , multi-layer and one-dimensional model representing the impact of processes operating on nitrate at the air–snow interface on the East Antarctic Plateau, in terms of concentrations (mass fraction) and nitrogen (δ 15 N) and oxygen isotopic composition (17 O excess, 17 O) in nitrate. At the air– snow interface at Dome C (DC; 75 • 06 S, 123 • 19 E), the model reproduces well the values of δ 15 N in atmospheric and surface snow (skin layer) nitrate as well as in the δ 15 N profile in DC snow, including the observed extraordinary high positive values (around +300 ‰) below 2 cm. The model also captures the observed variability in nitrate mass fraction in the snow. While oxygen data are qualitatively reproduced at the air–snow interface at DC and in East Antarctica, the simulated 17 O values underestimate the observed 17 O values by several per mill. This is explained by the simplifications made in the description of the atmospheric cycling and oxidation of NO 2 as well as by our lack of understanding of the NO x chemistry at Dome C. The model reproduces well the sensitivity of δ 15 N, 17 O and the apparent fractiona-tion constants (15 ε app , 17 E app) to the snow accumulation rate. Building on this development, we propose a framework for the interpretation of nitrate records measured from ice cores. ...