Effective coefficient of diffusion and permeability of firn at Dome C and Lock In, Antarctica, and of various snow types - estimates over the 100-850 kg m −3 density range

• Published in: The Cryosphere
• Main Authors: Calonne, Neige, Burr, Alexis, Philip, Armelle, Flin, Frédéric, Geindreau, Christian
• Other Authors: Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Laboratoire sols, solides, structures - risques Grenoble (3SR), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), ANR-10-LABX-0056,OSUG@2020,Innovative strategies for observing and modelling natural systems(2010), ANR-11-LABX-0030,TEC XXI,Ingénierie de la Complexité : la mécanique et ses interfaces au service des enjeux sociétaux du 21iè(2011)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: [SDU]Sciences of the Universe [physics]; Antarc*; Antarctica; Greenland; The Cryosphere
• Online Access: https://insu.hal.science/insu-03668389; https://insu.hal.science/insu-03668389/document; https://insu.hal.science/insu-03668389/file/tc-16-967-2022.pdf; https://doi.org/10.5194/tc-16-967-2022

International audience Modeling air transport through the entire firn column of polar ice sheets is needed to interpret climate archives. To this end, different regressions have been proposed in the past to estimate the effective coefficient of diffusion and permeability of firn. These regressions are often valid for specific depth or porosity ranges only. Also, they constitute a source of uncertainty as evaluations have been limited by the lack of reliable data of firn transport properties. To contribute with a new dataset, this study presents the effective coefficient of diffusion and the permeability at Dome C and Lock In, Antarctica, from the near-surface to the close-off (23 to 133 m depth). Also, microstructure is characterized based on density, specific surface area, closed porosity ratio, connectivity index, and structural anisotropy through the correlation lengths. All properties were estimated based on pore-scale computations from 3D tomographic images of firn samples. The normalized diffusion coefficient ranges from 1.9 × 10 −1 to 8.3 × 10 −5 , and permeability ranges from 1.2 × 10 −9 to 1.1 × 10 −12 m 2 , for densities between 565 and 888 kg m −3 . No or little anisotropy is reported. Next, we investigate the relationship of the transport properties with density over the firn density range (550-850 kg m −3 ), as well as over the entire density range encountered in the ice sheets (100-850 kg m −3 ), by extending the datasets with transport properties of alpine and artificial snow from previous studies. Classical analytical models and regressions from literature are evaluated against the estimates from pore-scale simulations. For firn, good agreements are found for permeability and the diffusion coefficient with two existing regressions of the literature based on open porosity despite the rather different site conditions (Greenland). Over the entire 100-850 kg m −3 density range, permeability is accurately reproduced by the Carman-Kozeny and self-consistent (spherical bi-composite) models when ...