Airborne sea ice surveys: [R] APPLS

 

Jan Lieser, Adam Steer, Peter Jansen

While sea ice extent can be measured routinely from satellites, there are no data available to detect change in sea ice thickness, and this effect of climate change could currently be going unnoticed.

Techniques of estimating sea-ice thickness, such as satellite radar and laser altimetry, are emerging but for accurate estimates these techniques need calibration and validation with ‘ground truth’ data.

During the SIPEX-2 voyage, one of the most important goals is to calibrate satellite radar data, laser altimetry data and other remote sensing techniques, by taking measurements on, in and under the sea-ice simultaneously with collecting data by remote sensing. This includes conducting airborne remote sensing using a helicopter deployed from the Aurora australis.

For airborne remote sensing, a suite of instruments will be mounted in an Aerospatiale AS350 helicopter, fitted with an inertial navigation and differential GPS system (OxTS RT 4003) for post-processing of data.

  The remote sensing instruments include:

(i) a scanning laser altimeter (Riegl LMS-Q240i-60),

(ii) thermal infrared radiometer (Heitronics KT-19),

(iii) a high resolution, medium format, digital camera (Hasselblad H3D-II),

(iv) a frequency modulated, continuous wave snow thickness radar, and

(v) 36 GHz passive microwave radiometer.

Components of this system have been successfully deployed during previous campaigns and used to characterise snow and ice conditions on sea ice floe (<1 km) to regional (100 km) scales. The combination of instruments and integration into one platform is new during SIPEX-2. Key parameters obtained are sea ice floe-size distribution, surface elevation used for ice thickness determination, and snow thickness on sea ice. These data will be used to calibrate and validate space-borne estimates from CryoSat-2.

The airborne data will be analysed using a suite of purpose-built analysis routines that have been developed at AAD, ACE CRC and NIPR. Analysis products will consist of geo-referenced surface elevation (500 m scanner swath width), infrared and passive microwave radiation as well as aerial photography floe-size distribution data for investigation of per cent cover of open water, thin snow-free and snow-covered sea ice.