Proc. of 4 th Int. Symp. on Retrieval of Bio- and Geophysical Parameters from SAR Data for Land Applications Innsbruck, Austria, 16-19 November 2004 Improved monitoring of polar land ice dynamics by means of SAR interferometry: ICEDANCE W. Rack (1) , U. Nixdorf (1) , H. Miller (1) , H. Runge (2) (1) Alfred Wegener Institute for Polar and Marine Research Columbusstrasse, D-27568 Bremerhaven, Germany wrack@awi-bremerhaven.de (2) Deutsches Zentrum für Luft- und Raumfahrt (DLR) Remote Sensing Technology Institute (DLR-IMF), D-82234 Wessling, Germany Hartmut.Runge@dlr.de INTRODUCTION Polar regions play an essential role in the complex climate system. They are characterized by very low temperatures, marked seasonality, huge continental ice sheets and large oceanic areas permanently or seasonally covered by sea ice. Taken together, the present global cryosphere (glaciers and ice sheets) contains enough water to rise sea level by almost 70 m. Thus, a small fraction of change in their volume would have a significant effect on sea level. However, the uncertainties in the knowledge of the cryosphere’s mass balance are large. E.g., the mass imbalance of Antarctica is likely to be small, but even its sign cannot yet be determined [1]. The gross behaviour of ice sheets is controlled by the dynamics at a relatively small number of key areas. These are principally the grounding line and areas of concentrated flow in outlet glaciers and ice streams, which are responsible for the bulk of the ice transport towards the coast. Recent investigations especially based on satellite altimetry and interferometry, show a pattern of high spatial and temporal variability [2]. This is due to changes in mass balance and flow behaviour of outlet glaciers in the West Antarctic Ice Sheet (WAIS) [3] and the Antarctic Peninsula [4] [5]. Spaceborne interferometric SAR proved to be the powerful tool to investigate the changes in the cryosphere at the required high accuracy (Table 1) [6]. Suitable interferometric data are mainly available in C- band and were acquired in 1994 during the ERS-1 Ice Phase (3 day repeat pass), and the ERS-1/2 Tandem Mission (1995-1999). The main draw back of ERS in remote areas as Antarctica was the need for local ground data receiving stations which had not available continuously. The first complete coverage of Antarctica was obtained during the Radarsat Antarctic Mapping Mission (September/October 1997, 24 day repeat pass). The interferometric capabilities of L-, C-, and X-band were simultaneously demonstrated during the 2 nd Space Shuttle SIR-C/X-SAR mission (SRL-2, 30 th Sept. – 11 th October 1994) for varying temporal (1 to 3 days) and spatial baselines. Operating between 60°N and 60°S, coherence was observed over snow and ice in C- and L-Band. In X-Band, coherence was observed only under exceptional conditions. Single pass interferometry was successfully applied with C- and X-Band SAR during the Shuttle Radar Topographic Mission (SRTM), showing up the accuracy differences between both bands. Although no global coverage was obtained with SRTM, these data are a baseline for direct glacier mass balance measurements in low and mid latitudes. Table 1: SAR space missions which provided interferometric ice measurements S/C frequency Band bandwidth (MHz) incidence angle Mission duration repeat cycle ERS-1 C 16 23 ice phase: (Dec.’91- Mar.‘92, Dec.’93-Apr.’94) 3 days ERS-1/2 C 16 23 Tandem Mission (1995- 1999) 1 day Radarsat-1 C 11.6/17.3/30 10-60 AMM (26 th Sept.-14 th Oct. 1997) 24 days SIR-C/X-SAR X/C/L 10/20 (X-band) 15-55 SRL-2 (30 th Sept.-11 th Oct. 1994) 1 to 3 days SRTM X/C 9.5 (X-band) 52 (X-band) 11 th - 22 nd Feb. 2000 single pass At present, no comparable systems are available. ICEDANCE (Ice Mass Transport and Balance of Glaciers and Ice Sheets) is a concept for a dedicated SAR satellite mission for improved monitoring of the dynamics of the cryosphere, 410