Calibration and validation of the CryoSat radar altimeter - Devon Ice Cap, Spring/Fall 2004

Field experiments towards calibration/validation of the CryoSat radar altimeter were performed on the Devon ice cap in the Canadian Arctic during the spring (April - May) and fall (August-September) of 2004. Field measurements were synchronized with overflights of an airborne radar altimeter (ASIRAS) operated by the Alfred Wegener Institute along a 50 km transect extending from the central divide to the south margin of the ice cap. Direct measurements of surface elevation, elevation change, surface roughness, and subsurface structure were performed at 4 main study sites that were established during the spring campaign in the percolation/dry snow (1800 m a.s.l.), wet snow (1400 m a.s.l.), superimposed ice (1000 m a.s.l.), and ablation (670m a.s.l.) zones. Surface elevations at each study site were measured using static differential global positioning (DGPS) techniques and along the entire transect using kinematic DGPS. Rates of ice thickness change were measured using the 'coffee can' technique at all study sites and from horizontal strain data combined with long term (41 year) mass balance estimates at study sites 2 and 3. Surface roughness was quantified along the entire transect at the centimeter, decimeter, and meter scales using digital photography, optical leveling, and kinematic DGPS techniques respectively. Subsurface properties (to depths of ~2 m) and seasonal mass balance were also measured along the entire transect from snow pits and shallow ice cores during the spring and fall campaigns. During the fall campaign only, the continuity of the main subsurface layers was tracked between snow pit and ice core locations using 1 GHz ground penetrating radar (GPR) surveys. Meteorological conditions were recorded at 3 automatic weather stations and 15 HOBOTM temperature loggers installed during the spring campaign. Field measurement techniques and preliminary results are presented.