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

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. Front the southern end of the shelf, velocity decreases front a high of about 800 m a(-1) to around 300 m a(-1) and then increases to a maximum of about 1350 m a(-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 front 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 oil the octahedral shear stress term.