EQUILIBRIUM- AND FIRN-LINE DETECTION WITH MULTI-POLARIZATION SAR – FIRST RESULTS

• Main Authors: Max König, Jan-gunnar Winther, Niels Tvis Knudsen, Tore Guneriussen
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Norway; Ela; austre Okstindbreen; Okstindbreen; glacier
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.547.7338; http://las.physik.uni-oldenburg.de/eProceedings/vol01_1/01_1_koenig1.pdf

We examine the capability of multipolarisation SAR for glacier monitoring on Austre Okstindbreen in mid-Norway using airborne and geocoded EMISAR images in C- and L-Band from the EMAC '95 campaign. The crosspolarisation SAR images (HV and VH) contain more backscatter variation and reveal more details on the glacier than the HH and VV polarised images. HH and VV images are very similar, as well are HV and VH images. An icefall is clearly visible, and crevasses are visi-ble in L-Band. The present year's equilibrium line cannot be seen on the SAR images, however a distinct line is visible on the C-Band SAR images. Photographs from Austre Okstindbreen show that this line represents the firn line created by previous year's layers. Monitoring of the firn line will be a valuable source of information. The firn line is itself not affected by yearly variations in equilibrium-line altitude, but a permanent change in the average equilibrium-line altitude will eventually result in a change in firn-line altitude. The firn-line altitude serves thus as a valuable climate indicator and appears to be easily detectable on SAR images due to strong difference in backscatter between ice and firn. Eventually, this may call for the development of correlation fac-tors between firn-line altitude (FLA) and mass balance in contrast to today's use of equilibrium-line altitude (ELA) in order to use SAR for routine mass-balance monitoring.