Observations show that some glaciers in Greenland and Antarctica undergo rapid changes in flow velocity and thickness. There is concern about the implications for global sea levels and ocean circulation. Part of the changes has been ascribed to changes in glacier dynamics. Measuring velocity and velocity gradients are first steps in studying their dynamics and possible response to climatic changes. With the RADARSAT-1 Antarctic Mapping Project (RAMP) a great opportunity arose to derive flow velocity of Antarctica's glaciers remotely.
This study uses RAMP imagery to derive ice flow velocity and, in combination with other datasets, to study spatial and temporal fluctuations in velocity and stress fields of selected Antarctic glaciers.
The derived high-resolution surface velocity maps form an important benchmark for gauging possible changes in velocity and dynamics. The maps are derived using pre-established feature tracking techniques that we improved and streamlined in order to extract as much velocity data as possible.
To determine important flow governing forces we use 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 stress fields have not changed significantly either, permitting combinations of various data sets 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 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.
|School:||The Ohio State University|
|School Location:||United States -- Ohio|
|Source:||DAI-B 79/10(E), Dissertation Abstracts International|
|Keywords:||Antarctica, Glacier dynamics, Glaciology, Remote sensing|
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