Characterising dust particles in the RECAP ice core with a multi-method approach to investigate abrupt climate changes

Ice cores can supply high-resolution insights into abrupt changes within the climate system. The RECAP ice core from the Renland ice cap, East Greenland, contains a substantial variety in dust particle size throughout its record, reaching back to the Eemian. Changes in dust particle sizes have been shown to reflect smaller ice cap extent during interglacial periods. Thus, local dust sources are only periodically available and can be characterised by large dust particles. For abrupt changes during the last glacial period, it is necessary to disentangle the potential imprint of dust sources and the role of snow accumulation. To better understand dust chemistry and size changes at high resolution, we apply several analytical methods in an ongoing investigation: Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) 2D imaging, coulter counter (CC), time-of-flight single particle analysis (SP ICP-TOFMS), and Low- Background Instrumental Neutron Activation Analysis (LB-INAA). We show that high-resolution (10-40 µm) 2D chemical images, focusing on Na, Al, Mg, and Fe, reveal the clustering of particles in the microstructure and a species-dependent preferred localisation. Subsequent measurements, taken where possible on the same samples provide new insoluble particle size and concentration data (CC) and further in-depth elemental characterisation of the dust particles (LB-INAA). Furthermore, first results from SP analyses display their potential for ice core research regarding largely unexplored areas, such as the characterisation of rare earth elements of dust deposited in Greenland. The expertise and insight on high-resolution dust chemistry and size gained during this multi-method approach on ice with partly highly thinned annual layers will eventually be crucial for interpreting the dust signal stored in future Antarctic ice cores reaching back up to 1.5 Myr.