Research
Ice velocity determined using conventional and multiple-aperture InSARWe combine conventional Interferometric Synthetic Aperture Radar (InSAR) with the novel technique of Multiple Aperture InSAR (MAI) to determine ice velocity using a single SAR image pair. The MAI technique retrieves the component of ice displacement along the satellite ground track, which is not detectable by conventional InSAR, and overcomes limitations associated with poor knowledge of topography and temporal variations in ice properties, each of which affect the precision of InSAR. Using MAI, InSAR, and the assumption that ice flows parallel to the ice surface, we are able to map the three dimensional velocity field of the Langjökull and Hofsjökull ice caps in Iceland in 1994 with fine (90 m) spatial resolution. The root-mean-square departure of the estimated ice velocities relative to a distribution of ground based observations recorded in 2001 was 17 m yr-1.
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| Motion of the Langjökull and Hofsjökull ice caps and topographic contours (colour) superimposed over the terrain in shaded relief (grey). a – Conventional InSAR across-track component of the velocity vector with a map of Iceland showing the study location (inset); b - MAI along-track component of the velocity vector; c – Velocity magnitude determined from combining a and b and assuming surface parallel ice flow; d – Zoom of the velocity over the LIC, the dots represent the position of the GPS surveys and are color coded [-30 30] with respect to the velocity difference between InSAR and GPS measurements. Glaciers identified are Hagafellsjökull Vestari, H.V., Hagafellsjökull Eystri, H.E., Þrístapajökull, P., Sátujökull, S., Illviðrajökull I., Blautukvíslarjökull, B., Múlajökull M., and Geitlandsjökull, G. glaciers. Note the absence of detected motion for the H.E., B., M. and I. glaciers in the conventional interferogram versus the MAI result. |
