Polar ice cores are an indispensable key to understanding the natural dynamics of our climate system. One of today’s most pressing research questions concerns the prediction and mechanics of abrupt climate change (ACC). This has particular significance for the Arctic, one of the fastest warming regions on the planet. Ice cores drilled on polar ice sheets have informed us of past abrupt climate transitions, such as the abrupt onset of “Dansgaard-Oeschger events” (DO) in Greenland. Happening over just a few years to decades, the study of the events can serve as past analogues to present and future ACC. Polar ice cores archive proxies for past changes in atmospheric transport of soluble and insoluble chemistry. However, fine temporal detail is required to decipher the fundamental processes and precursors of ACC. Due to continuous thinning of layers with depth, conventional cm-resolution melting techniques may not always provide adequate detail, motivating the use of novel high- resolution analysis. At micron scale resolution, however, it is pivotal to avoid misinterpretation by taking into account post-depositional layer disturbances, especially the interaction of impurities with the ice crystal matrix. This can be achieved by carefully mapping the spatial impurity distribution in 2D. The technique of Laser-Ablation Inductively-Coupled Plasma Mass Spectrometry (LA-ICP-MS) is unique in offering micron scale-resolution ice core impurity analysis AND imaging the spatial impurity distribution. The combination of the two strengths has not yet been exploited, however. The MSCA Global Fellowship MICRO-CLIMATE has used a unique opportunity to take a leap forward in LA-ICP-MS ice core analysis of ACC, by having two leading groups join forces: Among few existing LA-ICP-MS setups used for ice core analysis, the Climate Change Institute (CCI) at the University of Maine, USA has pioneered a system with a large cryogenic chamber. Recently, LA-ICP-MS at Ca’Foscari University of Venice (UNIVE) has been optimized with state-of-the-art 2D imaging techniques to investigate the impurity distribution in small ice core samples at high resolution, thus providing the tool to avoid misinterpretation at the micro-scale. During the course of the project, the fellow was awarded with the ERC Consolidator grant “AiCE”, which impacted also the course of the MSCA-GF fellowship: it was decided to conclude MICRO- CLIMATE at the end of 2023, in order to enable starting the ERC project in 2024. In spite of having been compressed into two instead of three years, the majority of the research, training and dissemination objectives has been completed or partially reached. The main limitation to the scientific objectives regards the amount of ACC events studied, while at the same time, an individual event has been studied in even more detail than originally anticipated. This sets a method that can be further exploited in follow-up projects. In conclusion, MICRO-CLIMATE has led to significant scientific insight, technological developments and strengthening of institutional partnerships. The strong career boost to the fellow can only be regarded as highly positive but had a strong impact on the project by leading to finishing one year earlier than anticipated.
