Glaciological characterization of Little Dome C: Influence of ice flow on the future Beyond Epica – Oldest Ice Core drilling project

An ice core is being drilled near Little Dome C, a small promontory about 30km downstream from the summit of Dome C, to extract a continuous record of climate over the last 1.5 million years. Present and past ice flow conditions are important to interpret the ice core because the surface velocity at the drilling site is about 40 mm/yr and the oldest ice in the record was deposited in the surface about 10km upstream of the drilling site. Here we explore newly acquired and existing geophysical data to describe present ice flow and investigate signs of past changes. We present new GNSS data that describes the subtle but complex local surface velocity, and ApRES radar data that provides englacial strain-rates along the flow path from the summit of Dome C and bulk englacial crystal orientation fabric. Ice currently flows from Dome C summit along the ridge to Little Dome C, even though a subtle uphill slope, but basal conditions are variable along the path due to the strong basal topography. Of special interest is an ice unit in contact with the bedrock with variable thickness up to about 300m that is vertically stagnant and produce a strong radar reflection.  This basal unit is not present in an area of strong melting about 5km upstream from the drilling site. The crystal orientation fabric reflects the ice flow horizontal extension along the path and changes with depth on ice flow properties following climatic transitions and, more intriguing, indicate a possible change in ice flow extension at the beginning of the Holocene. We aim to facilitate detailed ice flow models to better interpret the ice core data.