New surface features of the Antarctic ice sheet from radar and visible-NIR mapping

The authors examine several recent image maps of the Antarctic ice sheet (AIS) and describe a host of new features visible in them. The image maps come from the Radarsat Antarctic Mapping Project (RAMP), Landsat TM and ETM, and enhanced AVHRR images. A comparison of these new maps highlights the advantages of the new radar images, and the value of combining visible and near infrared (`Vis-NIR´) images with synthetic aperture radar in studies of glaciological surface and shallow subsurface features. The new images provide a broad perspective on the major ice stream systems draining the AIS. This overview clarifies the significant morphological changes ice streams systems exhibit along flow, from (proceeding upstream) ice shelves and ice plains, through an ice stream trunk/interstream-ridge region, to the more diffuse boundaries in the onset regions. The images have facilitated the identification of areas in both the ice shelves and the upper trunk and onset areas where flow direction inferred from surface morphology does not agree with present-day ice flow measurements-implying significant recent reorganizations of flow. The new maps also reveal the full extent of unique `megadune´ features in the Antarctic plateau, and provide clues to their formation