Characterization of cm-scale variations of crystal orientation fabric in cold Alpine ice core from Colle Gnifetti

• Main Authors: Kerch, Johanna, Weikusat, Ilka, Eisen, Olaf, Wagenbach, Dietmar, Bohleber, Pascal, Spaulding, Nicole
• Format: Conference Object
• Language: unknown
• Published: 2015
• Subjects: ice core; Polarforschung
• Online Access: https://epic.awi.de/id/eprint/40821/; https://hdl.handle.net/10013/epic.47836

Crystal orientation fabric – i.e. the spatial distribution of crystal c-axes in a defined depth interval – and its evolution with depth contain information on deformation processes in the ice column. Recent pilot studies on Alpine and polar ice indicate that fabric evolution provides more information than just on deformation if examined on the sub-meter scale, where the interaction between climate-related impurities and fabric evolution, i.e. their mutual influence, comes into focus and needs to be investigated. We studied crystal orientation fabric from an Alpine ice core from Colle Gnifetti (4450 m asl, Monte Rosa, Switzerland), a small glacier saddle with low net accumulation which is uniquely suited as a test site for studies under polar conditions. We calculated orientation tensor eigenvalues as measure for fabric strength in cm-resolution for several depth ranges of about 1 m between the firn-ice-transition and bed rock of the 73 m long ice core drilled in 2013. We found significant variations of fabric strength occurring within only 10 cm in all assessed depth ranges, revealing a complex anisotropic ice structure. In order to understand the mechanisms that lead to the observed short-scale variability we evaluated impurity data in cm-resolution from continuous flow analysis of the ice core. As a new approach we collected sub-mm impurity data from several features of the ice microstructure, where fabric changes occur, by means of a new laser ablation-inductively coupled plasma-mass spectrometry technique to explore the direct comparison of sub-mm impurity data and ice microstructure.