Basal topography and ice flow in the Bailey/Slessor region of East Antarctica

Abstract

An airborne radio‐echo sounding campaign carried out in the upper reaches of Bailey Ice Stream and Slessor Glacier, in Coats Land, East Antarctica, has revealed that tributaries of enhanced flow lie within well‐defined basal troughs and are separated from each other by bed highs. These new data indicate significant differences in ice thickness compared with those estimated in the Bedmap database. A numerical modeling study has revealed that driving stresses are high enough to account for flow by ice deformation alone in intertributary areas. Most flow in the enhanced flow tributaries of Slessor Glacier may also be explained by ice deformation alone. However, although ice deformation is also significant in the Bailey Ice Stream tributary, a large amount of basal motion is also required to fully explain flow velocities here. It is proposed that the trough in which Bailey tributary lies is sufficiently deep that marine sediments may have accumulated here in preglacial times. Along with water produced by geothermal heating, frictional heating, and through a reduction in the pressure melting point, basal motion may therefore be facilitated by the presence of a deformable, saturated till layer at the bed.

A comparison of basal reflectivity and ice velocity in East Antarctica

“…Deformational velocity is proportional to the fourth power of ice thickness and it is possible, therefore, that fast flow features in East Antarctica do not require an additional mechanism to account for their existence. For the deepest, thickest tributary feeding Slessor Glacier, however, basal sliding was found to be important to the ice motion (Rippin et al, 2003). This appears also to be the case here.…”

“…Where investigated, fast flow features in East Antarctica appear to be controlled to some extent by bedrock topography (e.g. Rippin et al, 2003), lying in troughs. Deeper, thicker ice is warmer at depth, resulting in a lower viscosity and a higher driving stress.…”

Subglacial topography inferred from ice surface terrain analysis reveals a large un‐surveyed basin below sea level in East Antarctica

“…Extracts from one basal topography transect available from the region [Lythe et al, 2001] show a strong agreement with the PC analysis (Figures 4a and 4b). More recent data are available for an area covering the Slessor Glacier tributaries [Rippin et al, 2003]; the correlation between an extract from this dataset and the PC is also good (Figure 4c). Figure 4b highlights the difficulty in distinguishing between areas of bedrock above sea level and areas which are likely to be frozen to their bed; between 175 km and 240 km along the profile, the measured bed is well below sea level, though it corresponds to a convex PC value.…”

“…Ice surface analysis methods have been used to infer subglacial lakes in the low-slope region (slope <0.45 m km À1 , Figure 1, inset) at the onset of fast flow [Bell et al, 2007]. Indirect magnetic evidence of a sedimentary basin up to 800 m below sea level has been found in a neighboring tributary region of Slessor Glacier (L7, Figure 1) [Rippin et al, 2003;Bamber et al, 2006], causing basal motion to dominate the flow in the tributary . As a result of these findings, it is feasible that there are water saturated deformable sediments present in the Recovery Glacier catchment, causing enhanced flow and surface drawdown.…”

In situ radioglaciological measurements near Taylor Dome, Antarctica and implications for ultra-high energy (UHE) neutrino astronomy

“…This is interpreted as direct observation of birefringence due to the asymmetry in the crystal orientation fabric ("COF"), caused by the ice flow itself along the gravitational gradient and resulting in crystal orientation perpendicular to the flow direction [24]. Schematically, the geometry of the crystal orientation, relative to the putative birefringence axes, is shown in Figure 26.…”