The layered evolution of fabric and microstructure of snow at Point Barnola, Central East Antarctica

• Published in: Earth and Planetary Science Letters
• Main Authors: Calonne, Neige, Montagnat, Maurine, Matzl, Margret, Schneebeli, Martin
• Other Authors: Institut des Géosciences de l’Environnement (IGE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut de Recherche pour le Développement (IRD)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), Institut Fédéral de Recherches sur la Forêt, la Neige et le Paysage (WSL), Institut Fédéral de Recherches Suisse
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: temperature gradient metamorphism; c-axis orientation; Antarctica; snow microstructure; [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; East Antarctica; Point Barnola; Antarc*; ice core; Ice Sheet
• Online Access: https://hal.archives-ouvertes.fr/hal-01832198; https://hal.archives-ouvertes.fr/hal-01832198/document; https://hal.archives-ouvertes.fr/hal-01832198/file/Calonne_2016_Fabric-Micros_AuthorCopy.pdf; https://doi.org/10.1016/j.epsl.2016.11.041

International audience Snow fabric, defined as the distribution of the c-axis orientations of the ice crystals in snow, is poorly known. So far, only one study exits that measured snow fabric based on a statistically representative technique. This recent study has revealed the impact of temperature gradient metamorphism on the evolution of fabric in natural snow, based on cold laboratory experiments. On polar ice sheets, snow properties are currently investigated regarding their strong variability in time and space, notably because of their potential influence on firn processes and consequently on ice core analysis. Here, we present measurements of fabric and microstructure of snow from Point Barnola, East Antarctica (close to Dome C). We analyzed a snow profile from 0 to 3 m depth, where temperature gradients occur. The main contributions of the paper are (1) a detailed characterization of snow in the upper meters of the ice sheet, especially by providing data on snow fabric, and (2) the study of a fundamental snow process, never observed up to now in a natural snowpack, namely the role of temperature gradient metamorphism on the evolution of the snow fabric. Snow samples were scanned by micro-tomography to measure continuous profiles of microstructural properties (density, specific surface area and pore thickness). Fabric analysis was performed using an automatic ice texture analyzer on 77 representative thin sections cut out from the samples. Different types of snow fabric could be identified and persist at depth. Snow fabric is significantly correlated with snow microstructure, pointing to the simultaneous influence of temperature gradient metamorphism on both properties. We propose a mechanism based on preferential grain growth to explain the fabric evolution under temperature gradients. Our work opens the question of how such a layered profile of fabric and microstructure evolves at depth and further influences the physical and mechanical properties of snow and firn. More generally, it opens the way to ...