Microstructure and ice dynamics – Integrating Grain Properties, Fabric, and Borehole Data in the NEEM Ice Core

Abstract. The physical properties of ice grains, including grain size and orientation, are fundamental to understanding ice flow and deformation processes in polar ice sheets. This study leverages a newly developed large-area scanning microscope (xLASM) and an automated microtome to non-destructively analyze the NEEM ice core's microstructure across 55 cm segments. The resulting microstructural data are compared with continuous flow analysis (CFA) measurements of impurity concentrations, fabric orientation, and shear strain rates over a 16-meter section (2004–2020 m depth) that spans the Last Glacial Maximum and abrupt climatic transitions during Dansgaard-Oeschger event GS-20. Our results reveal strong associations between grain size, impurity concentrations, and shear deformation rates, with impurity-rich, fine-grained stadial ice exhibiting higher shear strain rates. The ice fabric remains stable despite the changes in shear deformation, indicating that, in this case, the fabric is not the cause of the changing deformation.