Automated microstructure characterization through deep ice cores using sublimation etching

Polar ice sheets can be regarded as unique deformation experiments carried out by nature. Compared to other geological materials forming the earth‘s crust, the microstructure of ice is directly and depthcontinuously accessible in deep ice cores and can be mapped to a great extent utilizing controlled sublimation etching of polished surfaces. This technique is limited in the quantification of crystal orientation, but shows high sensitivity in locating low-angle lattice distortions such as detecting regions of high sub-grain boundary densities. Grain boundary networks extracted and diversely parameterized allow to validate the presence of different recrystallization processes depending on changing (climatic) conditions and deformation history. A dedicated method of digital image processing has been developed to overcome the need for tedious manual analysis. This contribution outlines how small grains (only a few micrometers in cross-section) can be extracted and are optionally considered in grain size analysis. Grain boundaries are characterized by their shape in high resolution and acting driving forces are estimated. Based on large extracted data sets different micro-structural parameterizations are performed and principally analyzed