Long-lived halocarbon trends and budgets from atmospheric chemistry modelling constrained with measurements in polar firn

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Martinerie, Patricia, Nourtier-Mazauric, E., Barnola, Jean-Marc, Sturges, W., R. Worton, D., Atlas, E., Gohar, L., Shine, K., P. Brasseur, G.
• 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), School of Environmental Sciences Norwich, University of East Anglia Norwich (UEA), University of Miami, University of Miami Coral Gables, Department of Environmental Science, Policy, and Management Berkeley (ESPM), University of California Berkeley (UC Berkeley), University of California (UC)-University of California (UC), Department of Meteorology Reading, University of Reading (UOR), Met Office Hadley Centre (MOHC), United Kingdom Met Office Exeter, National Center for Atmospheric Research Boulder (NCAR), CEC programmes: EUK2-CT2001-00116 (CRYOSTAT) and ENV4-CT97-0406 (FIRETRACC).
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2009
• Subjects: [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; Antarc*; Antarctic; Arctic
• Online Access: https://insu.hal.science/insu-00421106; https://insu.hal.science/insu-00421106/document; https://insu.hal.science/insu-00421106/file/acp-9-3911-2009.pdf; https://doi.org/10.5194/acp-9-3911-2009

International audience The budgets of seven halogenated gases (CFC- 11, CFC-12, CFC-113, CFC-114, CFC-115, CCl4 and SF6) are studied by comparing measurements in polar firn air from two Arctic and three Antarctic sites, and simulation results of two numerical models: a 2-D atmospheric chemistry model and a 1-D firn diffusion model. The first one is used to calculate atmospheric concentrations from emission trends based on industrial inventories; the calculated concentration trends are used by the second one to produce depth concentration profiles in the firn. The 2-D atmospheric model is validated in the boundary layer by comparison with atmospheric station measurements, and vertically for CFC-12 by comparison with balloon and FTIR measurements. Firn air measurements provide constraints on historical atmospheric concentrations over the last century. Age distributions in the firn are discussed using a Green function approach. Finally, our results are used as input to a radiative model in order to evaluate the radiative forcing of our target gases. Multi-species and multi-site firn air studies allow to better constrain atmospheric trends. The low concentrations of all studied gases at the bottom of the firn, and their consistency with our model results confirm that their natural sources are small. Our results indicate that the emissions, sinks and trends of CFC-11, CFC-12, CFC-113, CFC-115 and SF6 are well constrained, whereas it is not the case for CFC-114 and CCl4. Significant emission-dependent changes in the lifetimes of halocarbons destroyed in the stratosphere were obtained. Those result from the time needed for their transport from the surface where they are emitted to the stratosphere where they are destroyed. Efforts should be made to update and reduce the large uncertainties on CFC lifetimes