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FP5

GLACIORISK Informe resumido

Project ID: EVG1-CT-2000-00018
Financiado con arreglo a: FP5-EESD
País: France

Alpine glacier dynamics observed by synthetic aperture radar interferometry

Measurements of the spatial distribution of surface velocity and its changes on various time scales are an important tool for studying deformational and basal processes on glaciers [3]. The surface velocity of glaciers is traditionally measured by repetitive terrestrial surveying of markers on the ice surface. This method allows evaluation of mean velocities over interannual to sub-daily time-scales. A drawback to this method is that usually only a few markers can be monitored, whose spatial distribution is often unable to reveal interesting two-dimensional (2D) features of the velocity field. The traditional method requires ground occupation, which can be expensive and time consuming on large glaciers and ice fields.

This work presents a use of SAR interferometry to obtain full 2D-measurements on the displacement field over the Mer de Glace and Argentiere glaciers. The team has used a SAR interferogram obtained from the two European Remote-sensing Satellite (ERS1-2) [1]. Synthetic-aperture radar (SAR) images, acquired on 10 and 11 March 1996. The team has investigated whether the interferometric data are quantitatively consistent with terrestrial velocity measurements along two transverse profiles and two longitudinal profiles. These terrestrial data are from different years (1996 and 1997) and cover the period from 15 September 1996 to 14 September 1997 (a whole year).

Terrestrial ice velocity at the date of the SAR imagery was obtained via seasonal and annual corrections that were calculated from other terrestrial velocity measurements available at higher time resolution for selected sites on the glacier. Interferometric and terrestrial velocities are in agreement if a (terrestrially measured) surface-normal velocity component is properly accounted for. This suggests that both the interferometric velocities and the conversions of terrestrial data to the winter period are reliable. Finally, the team showed that the application of repeat-pass SAR interferometry to the glaciers enable precise mapping of ice flow dynamics at a much higher level than the levels usually obtained [2].

References:
[1] Hanssen, R. F., “Radar Interferometry, Data Interpretation and Error Analysis” in “Remote sensing and Digital Image Processing”, vol 2, Kluwer Academic Publishers, 275 pp, 2001.

[2] Massonnet, D., T. Rabaute, Radar Interferometry : Limits and Potential, IEE Trans. Geosci. Remote Sensing, 31, (2), pp. 455-464, 1993.

[3] Rabus, B. T., D. R. Fatland, Comparison of SAR-interferometric and surveyed velocities on a mountain glacier : Black Rapids Glaciers, Alaska, U.S.A., J. Glaciol., 46, (152), pp. 119-128, 2000.

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