Surface velocities of the east Antarctic ice streams from RADARSAT-1 interferometric synthetic aperture radar data.

摘要

The newly discovered East Antarctic Ice Streams drain a significant portion of the Antarctic Ice Sheet. Therefore, changes in their flow behavior can significantly alter ice-sheet mass-balance and influence global sea level. This dissertation research created the most comprehensive measurements to date of surface velocity across the East Antarctic Ice Streams using RADARSAT-1 interferometric synthetic aperture radar (InSAR) data acquired in 1997. Two-dimensional surface velocity was derived by combined interferometric and speckle matching techniques. Improvements in both techniques mediated some of the unique problems and limitations associated with imaging the Antarctic Ice Sheet using RADARSAT-1. The improvements included Delaunay triangulation based co-registration of SAR images, phase reconciliation of disconnected phase patches, and two-dimensional velocity calibration using extended velocity control points. The research produced a highly dense, highly accurate, two-dimensional surface velocity map of the East Antarctic Ice Streams, and a by-product coherence map reflecting surface changes. The velocity uncertainty is better than 15 m/year and velocity direction error is within 5° on the ice shelf and ice streams. Ice-stream shear-margins were mapped and the comparison between the ice stream margins and BEDMAP subglacial topography suggests that ice stream flow is controlled by bedrock topography. Mass balance calculations indicate that the ice stream and Filchner Ice Shelf system is not significantly thinning or thickening. There is evidence to suggest that at least one of the individual ice streams (Bailey Glacier) is thickening at a rate of 0.25 ± 0.06 m/year. Ice stream surfaces are generally convex and Slessor Glacier and Bailey Ice Stream driving stresses are large compared to the concave shaped West Antarctic Ice Streams. The surface topography of Recovery Glacier varies the most from an equilibrium profile and stretches of the Recovery Glacier have low driving stress, suggestive of flow on a lubricated bed. The convexity of the surface profiles, high driving stress, evidence of streaming flow and the shape of the glacier bed suggest that a change in ice stream dynamics could potentially result in an imbalanced discharge of large amounts of ice into the sea.