Using Cryo-Raman spectroscopy to analyse the location and chemistry of micro-inclusions in the EastGRIP ice core

• Main Authors: Stoll, Nicolas, Eichler, Jan, Weikusat, Ilka, Dahl-Jensen, Dorthe
• Format: Conference Object
• Language: unknown
• Published: 2020
• 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/57457/

One of the major uncertainties regarding future sea-level rise is the physics behind the flow of ice, which significantly impacts the amount of solid ice discharge into the oceans. Various physical properties of polar ice are affected by impurities in ice, ranging from electrical conductivity to internal deformation and thus, ice flow. Our goal is to better understand the impact of impurities on the deformation of ice by analysing the East Greenland Ice Core Project (EastGRIP) ice core. The on-going EastGRIP drilling delivers the first deep ice core from a fast-flowing ice stream, the Northeast Greenland Ice Stream, enabling novel in-situ information on the flow of ice. We analysed seven samples from various depths of the first 900 m of the ice core in our cold lab (-15°C). First, we used an optical microscope to map the surface of the sample and the same area focused 500 μm below the surface. These maps allow us to locate micro-inclusions, solid impurities of μm- size, inside the ice while preserving the original microstructure and preventing contamination . Following this, a WITec alpha 300 M+ confocal cryo-Raman system with a Nd:YAG laser (532 nm) is used to analyse the chemical composition of these inclusions. We present impurity distribution and mineralogical data from seven different depths of the EastGRIP ice core. Preliminary key findings are 1) a homogenous spatial distribution of impurities in the microstructure, 2) distinct layers of impurity-rich grains, 3) a strong relationship between identified minerals and the bulk chemistry, and 4) a diverse chemical range of micro-inclusions mainly consisting of sulfates (e.g., gypsum) and insoluble terrestrial minerals such as quartz, mica or feldspar.