Ice-flow measurements and deformation at marginal shear zones on Sørsdal Glacier, Ingrid Christensen Coast, East Antarctica

Abstract

Observations of crevasse and crevasse trace geometry recorded along marginal shear zones of Sørsdal Glacier, East Antarctica, are presented with fine-spatial-resolution measurements of ice flow collected at three selected study sites. Strain grids established at each site, comprising 254 points, were repeatedly surveyed during the summers 2000/01 and 2001/02 using a semi-kinematic global positioning system technique with relative coordinate precisions at the order of ±2 cm in horizontal and ±5 cm in vertical. The annual results show ice-flow velocities of 2–114 m a–1 across a 2.7 km section of the Sørsdal margin. Comparable ice-flow velocities were also obtained using a Doppler system DORIS. At one study site, covering a planar area of 0.04 km2, a preliminary comparison is made between the crevasse pattern and strain-rate tensors computed for 64 discrete points using the method developed by Nye (1959). The comparison indicates that the most recent crevasses are directly related to the principal strain rates in this zone of simple shear.

The International DORIS Service

“…Four years latter, in August 2003, the International DORIS Service (IDS) was accepted as a new IAG Service (Willis et al, 2004b) and started its activities. This procedure is parallel to what was conducted for the International GPS Service (IGS) (Beutler et al, 1999), and more recently for the International Laser Ranging Service (ILRS) (Pearlman et al, 2002) and for the International VLBI Service (IVS) (Schluter et al, 2002). In fact all these services are the backbone on which the IAG plan to organize its Global Geodetic Observing System (GGOS) (Rummel et al, 2002) in which DORIS can play a specific role (Altamimi et al, 2005;Willis et al, 2005b).…”

“…During the December 12, 2001 to February 5, 2002 period, Geoscience Australia deployed a DORIS beacon on the Sorsdal Glacier (Patrick et al, 2003), which is located in the vicinity of the Davis Station (68°S-78°E), Australian Antarctic Territory. It was the first site selected for the IDS DORIS Pilot Experiment.…”

A DORIS determination of the absolute velocities of the Sorsdal and Mellor glaciers in Antarctica

“…from the Davis base. The DORIS antenna was placed on a zone that is affected by complex fracture patterns and anomalously high flow rates (Patrick et al, 2003), at an elevation of approximately 440 m. During the first Sorsdal campaign, from December 2001 to January 2002, SPOT-2, SPOT-4, TOPEX/Poseidon and Jason-1 satellites were available. As per the data acquisition plan, the DORIS instrument onboard the three satellites, SPOT-2, SPOT-4 and TOPEX/Poseidon and the Sorsdal beacon were programmed accordingly.…”

“…The orbit determination analysis used the NASA GEODYN orbit determination and geodetic parameter estimation program (Pavlis et al, 2006). The GGM01S GRACE-derived earth gravity field model (Tapley et al, 2004) was applied to degree and order 90.…”

“…During the first Sorsdal occupation, the DORIS antenna was surveyed using GPS both at the time of deployment and when the equipment was retrieved (Patrick et al, 2003). The comparison results are shown in Table 6.…”