Velocity and strain rates derived from InSAR analysis over the Amery Ice Shelf, East Antarctica

Abstract

We use displacements derived from matching complex synthetic aperture radar data using maximum coherence to generate a dense network of velocity estimates over the Amery Ice Shelf. From these velocities we generate the horizontal strain-rate components and resolve them with respect to the local flow direction. We present the spatial distributions of velocity and transverse shear strain rate and use them to investigate features of the flow regime for the shelf. From the southern end of the shelf, velocity decreases from a high of about 800ma–1 to around 300 ma–1, and then increases to a maximum of about 1350ma–1 at the centre of the front. Strain rates vary systematically across and along the shelf. The pattern of the transverse shear strain rate clearly identifies the shear margins, where values exceed 0.1 a–1 in the southern section of the shelf. The pattern also shows longitudinal bands of enhanced shear strain rate containing ice with a strong preferred crystal fabric that was advected from shear margins upstream. In the northern section of the shelf, significant values of longitudinal and traverse stresses lead to enhanced shear deformation through their effect on the octahedral shear stress term.

Meteoric and marine ice crystal orientation fabrics from the Amery Ice Shelf, East Antarctica

“…Observed flow at the AM01 and AM04 borehole sites Figure 5 shows the computed distribution of Amery Ice Shelf vertical strain rates and shear strain rates transverse to the local flow direction, calculated using the inferometric synthetic aperture radar (InSAR)-derived surface velocities of Young and Hyland (2002). Strain-rate tensors for the AM01 and AM04 borehole sites (Fig.…”

Spatial Sciences on Ice: 50 years of Australian activities on the Amery Ice Shelf, East Antarctica

“…(1) It extends 550 km in length from ~73°S to ~68.5°S (Fricker et al 2002a, Young & Hyland 2002. (2) The width of the ice shelf increases from about 40 km at the grounding zone to about 200 km at the front (Young & Hyland 2002).…”

“…(2) The width of the ice shelf increases from about 40 km at the grounding zone to about 200 km at the front (Young & Hyland 2002). (3) The area of the AIS is approximately 71,260 km 2 (Fricker et al 2002a).…”

“…Although SAR instruments have been accommodated on several satellites, RADARSAT (launched in 1995) was the first to deliver complete coverage of the Antarctic continent (Jezek 1999), and thus initiated numerous studies. For example, Young & Hyland (2002) used RADARSAT data to generate a dense network of velocity estimates (see Plate 8) and to determine strain rates over the AIS, while Fricker et al (2002b) investigated the iceberg-calving cycle on the AIS. A combination of SAR data and satellite imagery was used to monitor the propagation of the 'Loose Tooth' rift system (Fricker et al 2005b).…”

“…The AIS is the outlet of the Lambert Glacier Drainage Basin (LGB) which drains continental ice from an area of more than one million square kilometres (Allison 1991) through a section of coastline that represents approximately 1.7% of the total continental circumference (Budd et al 1967), and it is a very dynamic system. The ice in the AIS flows with velocities of up to approximately 1350 m/yr (at the ice shelf front) (Young & Hyland 2002) and, as it is floating, is affected by ocean tides causing continuous vertical motion at all points north of the grounding zone.…”