Spatial and temporal dynamics of three East Antarctic outlet glaciers and their floating ice tongues

Recent observations show that some outlet glaciers in Greenland and Antarctica undergo rapid changes in flow velocity and ice thickness. There is concern about the implications of this for global sea levels and ocean circulation. At least part of the changes has been ascribed to changes in the dynamics of these glaciers. Measuring ice flow velocity and gradients in velocity are first steps in studying their dynamics and possible response to climatic changes. With the launch of the RADARSAT-1 satellite and the RADARSAT-1 Antarctic Mapping Project (RAMP) a great opportunity arose to derive ice flow velocity of Antarctica's glaciers remotely.; This study uses RAMP imagery to derive ice flow velocity and, in combination with various other datasets, including BEDMAP, VELMAP, OSUDEM, ICESat and InSAR derived velocity, to study spatial and temporal fluctuations in the velocity and stress fields of selected Antarctic glaciers. In particular we focus on the flow regimes of David Glacier, Mertz Glacier and Stancomb-Wills Glacier. These are all major East Antarctic outlet glaciers that have floating termini. We explore the role of these so-called ice tongues on their feeding glaciers. This is relevant especially in the wake of recent evidence that suggests the significant speed up and thinning of some glaciers in the Antarctic Peninsula is triggered by the collapse of a buttressing ice shelf.; The derived high-resolution 2-dimensonal surface velocity maps form an important benchmark for gauging possible (future) changes in velocity and dynamics and form one of the major contributions of this study. The maps are derived using pre-established feature tracking techniques that we improved, optimized and streamlined in order to extract as much reliable velocity data as possible from the wealth of data provided by the RAMP project. This included pre-processing of the images by using a speckle reduction filter, the addition of an adaptive window extraction routine and the design and application of a noise removal filter.; To determine the important flow governing forces we use pre-existing force-budget theory. We include a detailed error analysis and investigate the implications of a recently established flow law on derived stresses. The investigations of our study areas suggest that flow has been rather constant over decadal timescales. Based on this we infer that the stress field has not changed significantly either, permitting the combination of various data sets (averaged over different time spans) to optimize the velocity field in order to study dynamics in greater detail then previously possible. We find that the relative contribution of side drag declines along the fjords, but demonstrate that, once they leave the valley walls, the glaciers are not immediately true free floating ice shelves. Measurements show that ice tongues spread faster in the across flow direction than the along flow direction for a considerable length. In addition there appears to be some lateral drag, once a glacier leaves the coast, which could be associated with sub-surface valley walls or an adjacent ice shelf. This could lead to an increase in along flow creep if the ice tongue were to break off. Finally we conclude that ice tongues are important, because they can provide clues to past ice sheet behavior and fluctuations.