ESTIMATION OF ICE-SHEET MOTION USING SATELLITE RADAR INTERFEROMETRY -METHOD AND ERROR ANALYSIS WITH APPLICATION TO HUMBOLDT GLACIER, GREENLAND

Satellite radar interferometry provides glaciologists with an importan t new tool for determining the motion and topography of large ice shee ts. We examine the sources of error in interferometrically derived ice -motion measurements, including those errors due to inaccurate estimat es of tile interferometric baseline. Several simulations are used to a ssess baseline accuracy in terms of tie-point error and the number and distribution of tie points. These results give insight into how best to select tie points, and also demonstrate the level of accuracy that can be achieved. Examination of two representative cases likely to occ ur in mapping ice-sheet motion leads to the conclusion that with adequ ate tie-point information ice velocity can be measured accurately to w ithin a few meters per year. A method to correct horizontal velocity e stimates for the, effect of vertical displacement using surface slopes is also developed. Finally we estimate the single-component velocity field for an area on Humboldt Glacier, northern Greenland, using inter ferograms formed from ERS-1 SXR images. We estimate that these velocit y measurements are accurate to within 2.3 m year(-1).