| dc.description.abstract | Increasing human activities have brought about a global warming trend, and cause
global sea level rise. Investigations of variations in coastal margins of Antarctica and in
the glacial dynamics of the Antarctic Ice Sheet provide useful diagnostic information
for understanding and predicting sea level changes. This research investigates the
coastal dynamics of the Antarctic Ice Sheet in terms of changes in the coastal margin
and ice flow velocities. The primary methods used in this research include image
segmentation based coastline extraction and image matching based velocity derivation.
The image segmentation based coastline extraction method uses a modified
adaptive thresholding algorithm to derive a high-resolution, complete coastline of
Antarctica from 2000 orthorectified SAR images at the continental scale. This new
coastline is compared with the 1997 coastline also derived from orthorectified Radarsat
SAR images, and the 1963 coastline derived from Argon Declassified Intelligence
Satellite Photographs for change detection analysis of the ice margins. The analysis
results indicate, in the past four decades, the Antarctic ice sheet experienced net retreat
and its areal extent has been reduced significantly. Especially, the ice shelves and
glaciers on the Antarctic Peninsula reveal a sustained retreating trend. In addition, the advance, retreat, and net change rates have been measured and inventoried for 200 ice
shelves and glaciers.
A multi-scale image matching algorithm is developed to track ice motion and to
measure ice velocity for a number of sectors of the Antarctic coast based on 1997 and
2000 SAR image pairs. The results demonstrate that a multi-scale image matching
algorithm is much more efficient and accurate compared with the conventional
algorithm. The velocity measurements from the image matching method have been
compared with those derived from InSAR techniques and those observed from
conventional ground surveys during 1970-1971. The comparison reveals that the ice
velocity in the front part of the Amery Ice Shelf has increased by about 50-200 m/a.
The rates of ice calving and temporal variation of ice flow pattern have been also
analyzed by integrating the ice margin change measurement with the ice flow velocity
at the terminus of the outlet glacier. | en |
