Glaciares de Chile


"Mapping Blue Ice Areas and Crevasses in West Antarctica Using ASTER Images, GPS and Radar"

Rivera A, Cawkwell F, Wendt A, Zamora R (2014) : «Mapping Blue Ice Areas and Crevasses in West Antarctica Using ASTER Images, GPS and Radar» Global Land Ice Measurements from Space, Springer-Praxis, ISBN: 978-3540798170, chapter 31, 743-757

Resumen / Abstract.

Before the satellite era, relatively little was known about the interior of the West Antarctic Ice Sheet (WAIS). Of special interest are the rock outcrops associated with blue-ice areas (BIAs), which have been exploited for logistical purposes as well as being the subject of scientific research. The blue ice consists of relatively snow-free glacier ice that is undergoing ablation. One of these BIAs is Patriot Hills (80º18’S, 81º22’W) where aircraft with conventional landing gear have been landing for more than 20 years. This is now the main hub supporting large terrestrial expeditions conducted by Chilean scientists within Antarctica. Kinematic GPS has been used to map BIAs since 1996, with areas delineated on ASTER images since 2001 using both manual and automated approaches. The GPS method typically delimits the largest area, and supervised classification of the images by an algorithm demarcates the smallest area due to thin patchy snow cover overlying blue ice. These areas do not display a unique spectral response when mostly snow covered, so that they can only be visually discriminated. This detailed record of BIA extent shows no significant areal change with time, but does display interannual variability, which most likely is connected to prevailing meteorological conditions. BIAs around other nunataks in the region have been mapped from ASTER imagery, with the aim of identifying other landing sites for aircraft, as well as providing a detailed map for meteorite seekers. ASTER composite images have also been used to map safe routes for terrestrial traverses through crevasse zones. High-pass filters enhanced crevasse features, but visual analysis proved to be the most reliable method of identifying all crevasses. ASTER images were superior to microwave imagery for crevasse detection, as the latter can lack sufficient contrast; however, only Radarsat imagery provided coverage of higher latitude regions. Information gleaned from visible imagery can be combined with that of field-based radio-echo sounding and groundpenetrating radar profiles through the ice to map internal layers and bedrock topography with the objective of enhancing our knowledge of this remote region.