Micro-inclusions and cloudy bands in EastGRIP glacial ice

Impurities in polar ice play an essential role in ice flow and deformation and the integrity of the ice core record. In particular, cloudy bands, visible layers with high impurity concentrations, are prominent features in deep ice cores. However, these layers' physical and chemical properties are poorly understood, highlighting the need to analyse them in more detail. For this purpose, we combine measurements on different scales using a variety of methods, such as the visual stratigraphy line scanner, fabric analyser, microstructure mapping, and Raman spectroscopy. Here we report an extensive record of the microstructural spatial distribution and mineralogy of solid micro-inclusions in glacial ice from the Northeast Greenland Ice Core Project (EastGRIP) ice core ranging back to 50 ka before today. We determine major minerals related to terrestrial dust, such as quartz, feldspar, mica and hematite, carbonaceous particles, dolomite, and gypsum. Furthermore, we have identified rare minerals, such as rutile, anatase, epidote, titanite, and grossular. We thus show that inclusions in cloudy bands are of diverse mineralogy and that the respective mineralogy of micro-inclusions within and outside of cloudy bands can differ. We discuss the possible impact of these inclusions on deformation processes, and we systematically investigate and classify cloudy band properties, such as thickness, intensity, and sequences of cloudy bands, to distinguish between different types occurring in EastGRIP glacial ice. This study is thus an interdisciplinary approach to better understand the nature of cloudy bands - a regular feature defining large parts of deep polar ice cores