An analysis of the influence of deformation and recrystallisation on microstructures of the EastGRIP ice core

• Main Authors: Stoll, Nicolas, Kerch, Johanna, Kleitz, Ina, Eichler, Jan, Shigeyama, Wataru, Homma, Tomoyuki, Jansen, Daniela, Bayer-Giraldi, Maddalena, Kuiper, Ernst-Jan, Westhoff, Julien, Saruya, Tomotaka, Faria, Sérgio H., Kipfstuhl, Sepp, Dahl-Jensen, Dorthe, Weikusat, Ilka
• Format: Conference Object
• Language: unknown
• Published: 2018
• Subjects: Alfred Wegener Institute; East Greenland; Greenland; ice core; Polar Research; Polar Science
• Online Access: https://epic.awi.de/id/eprint/48740/; https://epic.awi.de/id/eprint/48740/1/NIPR_Poster_vertical_A0.pdf; https://hdl.handle.net/10013/epic.ac5aa782-8bd7-4ec6-9d42-0618afa24d7d

New and more detailed investigations from the EGRIP physical properties dataset down to 1650m of the ice core will be presented. EGRIP is the first deep ice core through one of our Earth’s ice sheets partly motivated by ice dynamics’ research. It is drilled just downstream of the onset of the largest ice stream in Greenland (North East Greenland Ice Stream). Data processing of the collected ice core physical properties data was done at the Alfred Wegener Institute Helmholtz Centre for Marine and Polar Research. The two main findings regarding CPO (c-axes fabric) pattern, 1) a rapid evolution of c-axes anisotropy and 2) partly novel characteristics, were further, and in more detail, investigated. To gain a better understanding of the dominating deformation mechanisms of NEGIS, different approaches considering different length scales were chosen (1650m versus 0.55m and 0.09m scale), including several case studies. A large-scale statistical analysis of the entire dataset results in new information about the depth-dependent evolution of parameters as for example the strength of c-axes anisotropy and grain-size in the polycrystal. In general, mean grain-size decreases with depth as we drill through the Holocene ice and approach the Glacial material. The grain size variability with fine and coarse grain layers is extreme in the Holocene ice but decreases in the Glacial ice. Microstructure properties were examined, with the aim to investigate the relationship between the remarkable rapid evolution of CPO-pattern and grain properties evolution. Furthermore, the evolution of a grain-size dependent anisotropy, found in the first 350m of the ice core, is investigated and examined also in deeper sections of the core. The large-scale evolution of density distributions of c-axes orientations differ significantly from observations in deep ice cores made so far: A novel "hourglass shaped" girdle was observed, characterized by a high density of horizontally oriented c-axes within the vertical girdle. In some parts of the core, ...