Experiences with the use of ground based interferometric radar near the calving front of Kronebreen, Svalbard. (Invited)
Abstract
Data of temporal variation of calving events and velocities directly from the calving fronts are very valuable because they inform about calving processes, which are still poorly understood. However, such data are rare, due to the dangers and the technological difficulties connected to measuring. Ground based interferometric radar at high temporal rate (2 Hz) has successfully been used for velocity measurements and monitoring of calving events during about one week at Kronebreen, Svalbard for three test seasons (2007, 2008 and 2009). The radar is placed ~4 km from the glacier calving front, and the antenna lobe covers a width of ~700 m of the front. By tracking natural permanent scatterers we find that relative velocities of mm accuracy can be measured on the calving front and up-glacier, and that larger calving events (> 4 m depth of calving blocks) can be identified in the amplitude radar return-signal data. Daily terrestrial optical photogrammetry, and continuous visual observation and registration of calving events are conducted to facilitate the interpretation of a 116 hour radar data record from August/September 2008. The calving front geometry is extracted from the optical images. Interpretation of the radar amplitude return signal plot is conducted according to the calving front geometry and the measured velocities. Detection of calving events in the radar data is demonstrated by change detection image processing, and 92 % of the larger calving events registered by continuous visual observations are detected (85 % of all calving events). It is of interest to determine whether the glacier velocities are influenced by the tidal cycles. In our radar back scatter data set we have observed a pattern perfectly correlated with the tidal cycles, however this is explained as electromagnetic interference due to multipath scattering, recording geometry and tidal cycles. We thus find that the glacier velocities and measurement accuracies are not influenced by the tidal cycles. The radar has also successfully been tested from Ny-Ålesund research station, ~15 km from the glacier front. Continuous radar monitoring of the calving activity of Kronebreen is therefore possible, so that seasonal variations could be identified.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.C14A..03R
- Keywords:
-
- 0720 CRYOSPHERE / Glaciers;
- 0732 CRYOSPHERE / Icebergs;
- 0758 CRYOSPHERE / Remote sensing;
- 0762 CRYOSPHERE / Mass balance