Constraints on N 2 O budget changes since pre-industrial time from new firn air and ice core isotope measurements

• Main Authors: Bernard, Serge, Röckmann, T., Kaiser, J., Barnola, J.-M., Fischer, H., Blunier, T., Chappellaz, J.
• Other Authors: 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), Max Planck Institute for Nuclear Physics (MPIK), Max-Planck-Gesellschaft, Institute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht University Utrecht, Department of Geosciences Princeton, Princeton University, Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Climate and Environmental Physics Bern (CEP), Physikalisches Institut Bern, Universität Bern Bern (UNIBE)-Universität Bern Bern (UNIBE)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2006
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Arctic; Antarctic; Greenland; Berkner Island; Antarc*; Greenland ice core; Greenland Ice core Project; ice core; NGRIP; North Greenland; North Greenland Ice Core Project
• Online Access: https://hal.science/hal-00328418; https://hal.science/hal-00328418/document; https://hal.science/hal-00328418/file/acp-6-493-2006.pdf

International audience A historical record of changes in the N 2 O isotope composition is important for a better understanding of the global N 2 O atmospheric budget. Here we have combined measurements of trapped gases in the firn and in ice cores of one Arctic site (North GReenland Ice core Project - NGRIP) and one Antarctic site (Berkner Island). We have performed measurements of the 18 O and position dependent 15 N isotopic composition of N 2 O. By comparing these data to simulations carried out with a firn air diffusion model, we have reconstructed the temporal evolution of the N 2 O isotope signatures since pre-industrial times. The decrease observed for all signatures is consistent from one pole to the other. Results obtained from the air occluded in the ice suggest a decrease of about -2.8, -2.4, -3.2 and -1.6 for d 15 N, 1 d 15 N, 2 d 15 N and d 18 O, respectively, since 1700 AD. Firn air data imply a decrease of about -1.1, -1.2, -1.0 and -0.6 for d 15 N, 1 d 15 N, 2 d 15 N and d 18 O, respectively, since 1970 AD. These results imply consistent trends from firn and ice measurements for d 15 N and d 18 O. The trends for the intramolecular distribution of 15 N are less well constrained than the bulk 15 N trends because of the larger experimental error for the position dependent 15 N measurements. The decrease in the heavy isotope content of atmospheric N 2 O can be explained by the increasing importance of agriculture for the present atmospheric N 2 O budget.