Surface topography and ice flow in the vicinity of the EDML deep-drilling site, Antarctica

Abstract

Interpretation of ice-core records requires accurate knowledge of the past and present surface topography and stress-strain fields. The European Project for Ice Coring in Antarctica (EPICA) drilling site (75.00258 8 S, 0.06848 E; 2891.7 m) in Dronning Maud Land, Antarctica, is located in the immediate vicinity of a transient and forking ice divide. A digital elevation model is determined from the combination of kinematic GPS measurements with the GLAS12 datasets from the ICESat. Based on a network of stakes, surveyed with static GPS, the velocity field around the drilling site is calculated. The annual mean velocity magnitude of 12 survey points amounts to 0.74 m a -1 . Flow directions mainly vary according to their distance from the ice divide. Surface strain rates are determined from a pentagonshaped stake network with one center point close to the drilling site. The strain field is characterized by along-flow compression, lateral dilatation and vertical layer thinning.

The deuterium excess records of EPICA Dome C and Dronning Maud Land ice cores (East Antarctica)

“…The horizontal surface velocity at the drilling site is 0.76 m/yr (Wesche et al, 2007). Thus, the ice flow is more complex than at Dome C: instead of a simple vertical thinning, the ice buried below the surface is originating from upstream at higher elevation.…”

Direct evidence for continuous radar reflector originating from changes in crystal-orientation fabric

“…The drill site is located at 0.0684 • E, 75.0025 • S at 2891.7 m above sea level near a transient ice divide, characterised by along-flow compression and lateral extension, causing an overall vertical compression of the ice column (Wesche et al, 2007). ); ordinates are the same for both panels: two-way travel time (TWT) on left ordinate is recording time corrected to the first break of surface reflection, right ordinate refers to depth below the surface for a mean wave speed of 168.7 m µs −1 from the surface to a 2100-m depth; color code indicates signal magnitude (increasing white-blue-black); first breaks of internal reflectors of interest are marked by yellow and red "V" at 0 km (drill site) at travel times of 22 and 24 µs, respectively; dark diagonal line between −3.8 and −2.3 km is a hyperbola leg, caused by reflections from Kohnen station (located at 0 km); white vertical line at 1.3 km is caused by system dropout.…”

Radar diagnosis of the subglacial conditions in Dronning Maud Land, East Antarctica

“…Towards Site-1, the ice becomes thinner from ∼ 2900 m to ∼ 400 m (Fig. 2) and the ice-flow speed decreases to ∼1 m yr −1 (Wesche et al, 2007;Rybak et al, 2007). Along the ME leg, ice thickness varies by ∼ 1000 m with a dominant periodicity of ∼ 20 km and ice flow speeds are relatively high (up to ∼ 18 m yr −1 ) (Motoyama et al, 1995).…”