THINICE · An Arctic analogue for the impurity-based stratigraphy in Antarctica’s Oldest Ice

Polar ice cores are our most precise archives of past climate. Anticipating future change requires resolving the dynamics behind major transitions, most notably the Mid-Pleistocene Transition (MPT) with the characteristic shift from 41 kyr to 100 kyr cycles, yet the decisive information is preserved in the deepest, thinnest ice where up to ~20,000 years can be compressed into a single metre of ice. Such compression obscures stratigraphic features and places high demands on the spatial resolution of analytical techniques. A new path is therefore needed: a micrometre-resolution stratigraphic method that preserves fine-scale variability beyond the reach of centimetre-scale melting and explicitly accounts for microstructural effects that distort the signal. This project will establish an integrated 1D-2D Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) approach at true micrometre resolution for impurity-based stratigraphy, working on the newly established LA-ICP-MS facility in Bremerhaven and leveraging Prof. Dr. Pascal Bohleber's expertise in glaciochemistry and micrometre-scale impurity imaging. Two-dimensional impurity imaging is combined with micro-scale line profiles and quantifies line-to-line coherence to identify the resolution at which heterogeneous signals converge into a repeatable pattern indicative of preserved layering. Using the Greenland RECAP core as a thinning analogue, we will establish objective criteria and thresholds for stratigraphic interpretability and derive an acquisition regime that yields spatially coherent profiles. The resulting framework will be then applied to exemplar intervals from Beyond EPICA, testing transfer to the oldest Antarctic ice. Arriving as Beyond EPICA, the oldest ice core ever retrieved to date covering the MPT, enters its analysis phase, this project converts micro-scale chemistry into robust stratigraphy, maximizing its scientific yield and positioning Europe at the forefront of ice-core science.