Chemical and visual characterisation of EGRIP glacial ice and cloudy bands within

Abstract

Abstract. Impurities in polar ice play a critical role in ice flow, deformation, and the integrity of the ice core record. Especially cloudy bands, visible layers with high impurity concentrations, are prominent features in ice from glacial periods. Their physical and chemical properties are poorly understood, highlighting the need to analyse them in more detail. We bridge the gap between decimetre and micrometre scales by combining the visual stratigraphy line scanner, fabric analyser, microstructure mapping, Raman spectroscopy, and laser ablation inductively coupled plasma mass spectrometry 2D impurity imaging. We classified approximately 1300 cloudy bands from glacial ice from the East Greenland Ice-core Project (EGRIP) ice core into seven different types. We determine the localisation and mineralogy of more than 1000 micro-inclusions at 13 depths. The majority of the minerals found are related to terrestrial dust, such as quartz, feldspar, mica, and hematite. We further found carbonaceous particles, dolomite, and gypsum in high abundance. Rutile, anatase, epidote, titanite, and grossular are infrequently observed. The 2D impurity imaging at 20 µm resolution revealed that cloudy bands are clearly distinguishable in the chemical data. Na, Mg, and Sr are mainly present at grain boundaries, whereas dust-related analytes, such as Al, Fe, and Ti, are located in the grain interior, forming clusters of insoluble impurities. We present novel vast micrometre-resolution insights into cloudy bands and describe the differences within and outside these bands. Combining the visual and chemical data results in new insights into the formation of different cloudy band types and could be the starting point for future in-depth studies on impurity signal integrity and internal deformation in deep polar ice cores.

The new frontier of microstructural impurity research in polar ice

“…Recent technological and methodological progress in e.g., cryo-Raman spectroscopy (Eichler and others, 2019; Stoll and others, 2021a, 2022; Kawakami and others, 2023; Stoll and others, 2023) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) (Bohleber and others, 2020, 2021c) opened up new pathways in deciphering the localisation of impurities in ice. We briefly summarise the latest developments and perspectives for combining these methods in the future and ongoing research efforts.…”

“…Fluorescence hampers the identification of dozens of inclusions (e.g. Stoll and others, 2022, 2023) and is related to the laser wavelength. Switching between lasers with different wavelengths (e.g.…”

Quantitative Insights on Impurities in Ice Cores at the Micro‐Scale From Calibrated LA‐ICP‐MS Imaging

“…(2021) and samples 7 and 8 in Stoll, Westhoff, et al. (2023), respectively. Samples were measured in pairs of Holocene and glacial samples, with two images collected immediately after another.…”

“…Table 1 provides an overview. The EGRIP samples were previously analyzed by Cryo-Raman Spectroscopy, bags 253, 3316, and 3424 correspond to sample 1 in Stoll, Eichler, Hörhold, Erhardt, et al (2021) and samples 7 and 8 in Stoll, Westhoff, et al (2023), respectively. Samples were measured in pairs of Holocene and glacial samples, with two images collected immediately after another.…”

“…For mostly water‐soluble species such as Na, the chemical maps have revealed a high degree of localization at grain boundaries and mostly signal‐free grain interiors (Bohleber et al., 2021). Conversely, using 2D LA‐ICP‐MS imaging of dust‐rich samples, such as “cloudy bands,” showed localized particle clusters dispersed within the grains, especially for crustal elements such as Al, Si, and Fe (Bohleber et al., 2023; Stoll, Westhoff, et al., 2023).…”