| 21 Apr 2026
Fidelity and stratigraphy of the Antarctic Allan Hills old ice archive from Continuous Flow Analysis
Abstract. The Allan Hills blue ice area, East Antarctica, offers a unique opportunity to extend the ice core record beyond 800 thousand years (kyr), with ice as old as 6 million years recently recovered. The ice in this area demonstrates several peculiarities—such as strong layer thinning and folding—that warrant an in-depth investigation of its stratigraphy and the fidelity of the climate record it contains. Here, we present a high-resolution Continuous Flow Analysis (CFA) of two shallow ice cores from the Allan Hills (ALHIC 2201 and ALHIC 2302), spanning the upper 69 m and 46 m, respectively.
Our CFA analysis includes methane, water stable isotopes, and particle concentrations, allowing us to characterize their variability and assess how well geochemical measurements are recorded and preserved in Allan Hills ice. Dating of the ice (using the 40Ar chronometer) revealed ages ranging from ~150–1200 kyr with substantial age discontinuities and folding, highlighting the complex stratigraphy of ice in this region. To assess glacial-interglacial variability, we conduct descriptive statistical analyses of each measurement relative to the EPICA Dome C (EDC) deep ice core record, which served as a reference benchmark over the last 800 kyr. Relative to EDC, we find data representing warm climate states are overrepresented at Allan Hills, and the Allan Hills records typically exhibit a narrower distribution compared to the EDC record. These observations confirm previous suggestions of interglacial bias and glacial cycle averaging in some sections of Allan Hills records. Differences between ALHIC 2201 and ALHIC 2302 further suggest that coring location within the Allan Hills region affects signal preservation in the record. Our high-resolution investigation of this ice is a critical step toward improved interpretation of the discrete, multi-million-year records from the Allan Hills.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Climate of the Past.
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