Optimizing rapid access englacial sampling location to date deep radiostratigraphy for old ice

The Center for Oldest Ice Exploration (COLDEX) aims to unearth a stratigraphically intact ice core record going back to 1.5 million years. The target area is the corridor between South Pole and the southern flank of Dome A. While our current survey has yielded dated stratigraphy extending to 93.9 thousand years ago across the region, a significant portion of the stratigraphy remains undated. Our approach has involved leveraging englacial connections with existing ice cores and dust loggers, yet much of the stratigraphy awaits dating. Rapid ice access tools are capable of sampling the ice sheet using far fewer resources as compared to conventional drilling. By optimizing the site for such sampling, we can preemptively maximize the information that can be extracted eventually.

Our study’s objective in selecting a rapid ice access site is twofold: firstly, to maximize the age-depth scale extraction by dating the hitherto undateable deeper isochrones, and secondly, to strategically sample the pervasive basal layer in the survey region to understand its role in preserving old ice. To achieve an optimal age-depth scale extraction, we aim to target sites containing a larger portion of undated stratigraphy while maintaining the optimum resolution to understand ice age dust cycles. For instance, Ice Diver, a melt probe by COLDEX, houses an optical dust logger capable of counting ice age dust cycles.

Previous research (e.g., Chung et al., 2023) indicates that a basal layer identified through radar sounding may exhibit a distinct flow regime compared to the stratigraphic portion of the ice sheet column. Accessing this layer in advance could provide insights into the interface between the echo-free zone and stratigraphic ice, thereby refining our understanding of current ice sheet models and how to exploit them in the pursuit of old ice. An ideal access site would facilitate quick sampling without requiring deep drilling to reach the basal layer. Our aim is to reconcile these methodologies by identifying the most suitable site(s) for deploying such probes or drills.