News from the EastGRIP ice core - on microstructure, impurities and the bridging of different scales

• Main Authors: Stoll, Nicolas, Hörhold, Maria, Westhoff, Julien, Erhardt, Tobias, Bohleber, Pascal, Eichler, Jan, Svensson, Anders, Zeising, Ole, Gerber, Tamara, Franke, Steven, Rathmann, Nicholas, Jansen, Daniela, Richards, Daniel, Streng, Kyra, Kerch, Johanna, Eisen, Olaf, Dahl-Jensen, Dorthe, Barbante, Carlo, Weikusat, Ilka
• Format: Conference Object
• Language: unknown
• Published: 2023
• Subjects: East Greenland; East Greenland Ice-core Project; Greenland; Greenland ice core; Greenland Ice core Project; ice core
• Online Access: https://epic.awi.de/id/eprint/58251/; https://epic.awi.de/id/eprint/58251/1/AGU2023_Stoll.pdf; https://hdl.handle.net/10013/epic.e89661a6-d9bd-4b83-b0d2-aafa647039f0

A better understanding of ice flow and deformation is needed to improve the projections of future sea level rise. Especially ice streams, the main contributors to solid ice discharge, still require more observational data to be represented sufficiently in computer models. The East Greenland Ice-core Project (EastGRIP) thus successfully drilled the first continuous deep ice core from an ice stream, the Northeast Greenland Ice Stream (NEGIS) while serving as a hub for geophysical measurements. A major unknown is the ice microstructure, i.e. the size and orientation of ice crystals (CPO) and its interplay with chemical impurities. Impurities are a climate proxy but are also assumed to impact microstructural processes, such as deformation and grain growth, and it is thus crucial to investigate where impurities are located in the microstructure. By combining microstructural (fabric analyser, microstructure-mapping, large area scanning macroscope) and impurity (Raman spectroscopy, inductively coupled plasma mass spectrometry 2D imaging) methods, we here present a systematic overview of the evolution of the microstructure and of the location of impurities throughout the EastGRIP ice core. Solid impurities, such as dust, are preferably located in the grain interior, while soluble impurities are mainly in the grain boundaries. This shows that microstructure should be considered when using impurities as a climate proxy due to the large spatial variability on the (sub-) millimetre scale. The analysed microstructure in the EastGRIP ice core further assists in reconstructing the original orientation of the ice core via visual stratigraphy, delivering the ground-truthing for an improved method of interfering horizontal fabric with co-polarised phase-sensitive radar and gaining new insights into the spatial variability of anisotropy and ice viscosity within NEGIS. Combining microstructural data with numerical modelling enables new insights into the processes underlying CPO formation and the bridging of different spatial scales ...