Remote sensing of sea ice parameters plays a key role in polar research and climate change investigations. New sensors such as high resolution passive microwave scanners (AMSR-E) and visible/infrared radiometers (MODIS) provide new information from which, given appropriate algorithms, products including sea ice extent and concentration, snow thickness or ice temperature can be derived. These algorithms depend on approximations and assumptions, which have to be assessed in situ for quality control and/or to readjust the algorithms parameters. An Australian sea ice dedicated expedition in (austral) early spring 2003 to the East Antarctic marginal sea ice zone (RSV Aurora Australis, Voyage 1 - 2003/04) offered the opportunity for cross validation of diverse geophysical tools such as the AWIs helicopter-borne EM ice thickness profiler, as well as a helicopter-borne system containing a digital nadir looking camera combined with a thermal infrared radiometer, and remote sensing data from AMSR-E, SSM/I, MODIS, AVHRR, MISR, SAR, etc. satellite sensors. The airborne platforms could be precisely validated against ground truth data acquired on 13 ice stations and consequently could be used to validate remote sensing data.On two days during the expedition exceptionally good weather conditions with clear sky along several hundred kilometres provided a superb dataset. Flight tracks of altogether more than 500 km were profiled synoptically with the EM ice thickness platform and the aerial photography + IR radiometer system. Photography flights were carried out at 5000 feet altitude while EM bird was usually flown at around 100 ft allowing the EM operators to document the general ice conditions and take detailed geocoded digital pictures of the ice and snow conditions along the track, giving a ground truth dataset for the high altitude photos as well as structures found in satellite pictures.On both days near real time MODIS scenes containing the flight tracks were acquired and provide an excellent overview of the general ice conditions in the area. Along 109.3°E in the vicinity of the Australian Antarctic research station Casey, a 155 km long meridional flight transect from 65.75°S to 64.4°S passes a variety of different ice classes varying from a freshly refrozen polynya west of an iceberg grounding line along Peterson Bank to vast, snow - covered drifting floes at 65°S. Accounting for the different footprints and spatial resolutions of the systems, statistical properties are compared such as HEM derived ice thickness distribution with ice/snow surface temperature distributions from the helicopter IR radiometer and MODIS IR channel. Huge structures at the mentioned polynya extending for almost 10 km along the flight track, or the biggest drift floe measuring roughly 15 x 7 km can be described by the HEM thickness distribution computed from profile subsets with length equal to the highest spatial resolution for the AMSR-E (6x4 km @ 89 GHz) resulting in an average snow + ice thickness of 0.06 m with standard deviation 0.09 m and 3.49 m thickness (1.17 m SD) respectively, corresponding to a brightness of 2% and 80% in the visual MODIS channel. HEM thickness distributions from this 155 km long transect (including open water) were compared to AMSR-E ice concentrations.
Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL1-Processes and interactions in the polar climate system