Liam Reed Kirkpatrick, Austin Joseph Carter, Julia Marks Peterson, Sarah Shackleton, T.J. Fudge

Recent ice cores from the Allan Hills, a blue ice area in Antarctica, are nearly 3 million years old. These cores extend ice core chronologies, enabling new insight into key climate periods such as the Mid-Pleistocene Transition. The interpretation of these climate records is complex because of the disturbed stratigraphy in this ice. Here we present a new three- dimensional multitrack electrical conductivity measurement method (3D ECM) to resolve layer structure. We demonstrate this technique on a cumulative 60 m of two large-diameter (241 mm) ice cores, ALHIC2201 and ALHIC2302. We find well defined and dipping layering in both cores, averaging 28° and 68° from horizontal, respectively. Both cores show a statistically significant but gradual decrease in dip angle with depth. We discuss how this new method can be applied to enable accurate, high- resolution multi-proxy record development even in ice cores with steeply dipping layers. 3D ECM improves interpretation of blue ice area cores by providing accurate, non-destructive constraints on stratigraphy.