ApRES time series from Roi Baudouin Ice Shelf, 2016/02-2017/01

The ApRES (Brennan et al., 2014; Nicholls et al., 2015) was deployed from January to December in 2016 on the RBIS about 90 km from the ice shelf front and 5 km seaward from the grounded ice on the fast-flowing portion of the West Ragnhild glacier, which is the third largest outlet glacier along the Dronning Maud Land Coast (Callens et al., 2014). The ice thickness at the site was ∼300 m in the trough of a channel (Drews, 2015) but increases up to 600 m in the grounding zone upstream, and ice flow velocities in this region range between 250 and 300 m/a (Rignot et al., 2013). By transmitting an electromagnetic signal and receiving the echo, the radar system can detect the ice base (ice-ocean interface) as well as relatively weak internal reflecting layers that are due to changes in ice permittivity. Between two consecutive measurements, the relative vertical motion of internal layers and the base can therefore be tracked. The displacements of the internal layers determine how the thickness of the column evolves due to vertical strain and bottom melting.