The 1500 m South Pole ice core: recovering a 40 ka environmental record

Ice-flow reorganization within the East Antarctic Ice Sheet deep interior

“…Additional model configurations each resulted in basal temperatures within the range of −6.9 to 10.9°C Q4 . All fits were obtained with a surface accumulation of 8 cm a −1 , which was consistent with observational evidence in the South Pole region (Mosley- van der Veen et al 1999;Casey et al 2014), as well as with the 4.6-0 ka submergence rate from englacial reflector geometry described below. …”

“…In validation of the submergence model, the patterns of submergence for the uppermost layer (Fig. 4c) in the South Pole proximal locations had the same magnitude (7.5-8.5 cm a −1 ice equivalent) as ice-core estimates of accumulation van der Veen et al 1999) and modelling with ice-core age constraints (Casey et al 2014). Both magnitudes and spatial patterns of the submergence rate matched remotely sensed accumulation estimates (Arthern et al 2006).…”

“…Fischer et al 2013) because periods of basal melt would remove the oldest layers and the deformation of englacial layers could complicate stratigraphic interpretation. Increased complexity of interpretation would also be true for the South Pole ice core (Casey et al 2014) that reached a maximum depth of approximately 1750 m. Based on our observations, the 51.4 and 16.8 ka reflectors are situated at approximately 1780 and 1040 m depth at the South Pole.…”

“…Control points, where two radar transects cross, ensured the same reflector was traced in multiple profiles. Where reflectors intersected the South Pole borehole, we were able to transfer the agedepth timescale measured from the dust record (Casey et al 2014) to date individual reflectors from 93.9 to 4.7 ka Q2 . We then devised a 1D vertical velocity model that assumed a constant strain rate at all depths (Nye 1963) to calculate ice submergence rates (b) between traced reflectors:…”

“…This coupled with a previously published examination of radar basal reflectivity in the South Pole region (Carter et al 2007) demonstrates the existence of a former ice-stream tributary in the South Pole region. Identifying regions of former fast flow in the South Pole region has implications for a variety of ongoing investigations, including interpretation of ice-core climate records (Casey et al 2014), the search for recoverable million year old ice (e.g. Fischer et al 2013;van Liefferinge & Pattyn 2013) and possible expansion of the IceCube neutrino detector (Aartsen et al 2014).…”