Building an Integrated View of Antarctica Using Products from the Radarsat Antarctic Mapping Project

From the IGY through the early 1970's, scientific knowledge about Antarctica was gleaned primarily from observations made at points along traverse routes or along sparsely spaced aircraft flight lines. Analysis of these observations provided tantalizing clues about the nature and behavior of the ice sheet and the bedrock beneath. But the data themselves could not provide a continental scale assessment of how different glaciological and geophysical regimes interacted. The situation began to change rapidly in the mid-1970's with the launch of several active and passive sensors on satellites positioned in polar orbit. Still, none of the instruments alone or together could provide important large-scale information on several key geophysical variables. For that reason, NASA and the Canadian Space Agency began planning in the early 1980's for an imaging campaign using the Synthetic Aperture Radar to be carried by RADARSAT 1. The science driving the campaign was to obtain a benchmark for detecting changes in the continent by comparison with earlier and subsequent data. The resulting RAMP Antarctic image mosaic helped reach that goal and has been used to map the coastline of the continent in great detail, to study and contrast glaciological regimes about the continent, and to examine glaciological process such as the evolution of ice shelves by observing ice shelves at various stages of development about the continent. But a single instrument or data set is rarely ever able to answer complex scientific questions. For that reason it becomes useful and very interesting to use the RAMP mosaic as a basis for integrating other continental scale observations into a common framework referencable to features observable on the surface. In this paper, we present an ensemble of several continental data sets including velocities so far computed from the RAMP data set. We compare the RAMP image mosaic with: surface topography patterns using the RAMP Digital Elevation Model; BEDMAP compiled basal topography; a RAMP prepared model of surface balance velocities; and interferometric surface velocities derived from the RAMP data set. We find good correlations between the basal topography and backscatter strength in the vicinity of the Belgica Highlands. The result is exciting because it suggests that inferences about basal topography and properties can be made using the image mosaic in regions where basal topography data are sparse or completely absent. We also find that there is good correlation between image-mosaic-inferred glaciological structures and the surface balance velocity field. For example, the modeled velocities patterns capture the extensive network of ice streams draining into the Filchner Ice Shelf. These ice streams are revealed in the RAMP mosaic by the intense crevassing that occurs along their margins and which appears bright in radar imagery. Comparisons between the balance velocity model and measured RAMP velocities also reveal where the ice flow is more complex than predicted. West of the Amery ice shelf, measured velocities reveal the presence of numerous small ice streams or outlet glaciers that snake through the region but which are absent in the velocity model.