Two-dimensional impurity imaging in deep Antarctic ice cores: Snapshots of three climatic periods and implications for high-resolution signal interpretation

Abstract:

Due to its micron-scale resolution and micro-destructiveness, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is especially suited for exploring closely spaced layers in the oldest and highly thinned sections of polar ice cores. Recent adaptions of the LA-ICP-MS technique have allowed us to achieve fast washout times as the basis for introducing state-of-the-art 2D imaging techniques to ice core analysis. This new technique has great potential in its application for investigating the location of impurities on the ice sample surface, crucial to avoid misinterpretation of ultra-fine resolution signals. Here we present first results from applying LA-ICP-MS chemical imaging to glacial and interglacial samples of the Talos Dome and EPICA Dome C ice cores from central Antarctica. We discuss the localization of impurities with marine and terrestrial sources and find generally a strong connection with the network of grain boundaries but also distinct differences among climatic periods. Scale-dependent image analysis shows that the spatial significance of a single line profile along the main core axis increases systematically as the imprint of grain-boundaries weakens. With this, we propose how settings can be adapted specifically fit-for-purpose, i.e. either to employ LA-ICP-MS to study the impurity-microstructure interplay or to investigate highly thinned climate proxy signals in deep polar ice.