Identifying optimal drilling sites in Antarctic Blue Ice Areas using a flowline model

Blue ice areas have attracted growing interest over the past decade, notably following the recovery of ice older than the current record of deep ice core drilling, in the Allan Hills region of Antarctica (snapshots up to 6 million of years). In this study, we assess the suitability of flowline modelling for surface age prediction in blue ice environments. To this end, we perform 10,000 theoretical experiments covering a wide range of site conditions, using an ice-dynamical flowline model, to determine which factors most strongly favor the preservation of old ice at the surface. Our results show that a strong negative surface mass balance (i.e. high ablation) and slow surface velocities along the flowline are the primary controls on the emergence of old ice at the surface, whereas ice thickness and distance from the upstream accumulation zone play only secondary roles. Moreover, based on statistical and machine learning analyses, we illustrate that the occurrence of very old ice at the surface appears to be mostly correlated with exceptionally low surface velocities, with high ablation rates being insufficient on their own. We compare these findings with recently measured surface mass balance and surface velocities in the Sør Rondane Mountains blue ice areas (Dronning Maud Land, East Antarctica) to inform the selection of future ice core drilling site in the region.