Aerial imaging of sea ice with LiDAR and photos

An integrated airborne imaging system with scanning LiDAR (Light Detecting And Ranging) and high resolution, digital aerial photography is used by the Australian Antarctic Program for various purposes, in East Antarctica. One of the main objectives is the measurement of surface elevation of sea ice (ice freeboard) and glacial ice to estimate its thickness. To understand the effects and feedbacks of a changing climate in polar regions information on the rate of change of ice thickness is vital. Large-scale coverage of the East Antarctic ice sheet, ice shelves, and the sea ice zone is currently very sparse, with latterly relying on satellite altimetry measurements that are unvalidated and uncalibrated. We describe the combined instrument system and present in-situ results acquired over sea ice in the vicinity of 122° East, 65° South. Validation of the airborne surface elevation data is done by drill-hole measurements of sea ice freeboard and shows agreement to within the centimetre-level. This allows confidence to use the system for large-scale aerial surveys (up to 200 km range) to calibrate and validate space-borne sea ice thickness products, for example from CryoSat-2.