HR: 0800h
AN: H41B-0509    [Abstracts]
TI: Tracking Changes in Coastal and Nearshore Morphology in the Southern Beaufort Sea Using Synthetic Aperture Radar
AU: * Solomon, S M
EM: ssolomon@nrcan.gc.ca
AF: Geological Survey of Canada, PO Box 1006, Dartmouth, NS B2Y 4A2, Canada
AU: Fraser, P
EM: pfraser@nrcan.gc.ca
AF: Geological Survey of Canada, PO Box 1006, Dartmouth, NS B2Y 4A2, Canada
AU: Whalen, D
EM: dwhalen@nrcan.gc.ca
AF: Geological Survey of Canada, PO Box 1006, Dartmouth, NS B2Y 4A2, Canada
AB: Nearshore morphology in the Mackenzie Delta region of the Beaufort Sea is poorly known because much of the region is very shallow (< 2 m) and the water is highly turbid. Synthetic Aperture Radar (SAR) has been used to map nearshore morphology of lakes in Alaska by taking advantage of the ability of radar waves to penetrate freshwater ice. This technique has been extended to the Mackenzie Delta nearshore region where winter ice forms from river water that is sufficiently fresh so as to be transparent at SAR frequencies. SAR allows the delineation of sea ice that freezes to the seabed (bottom-fast ice or BFI). A time series of imagery throughout a winter depicts the progressive growth of areas where BFI occurs and if sea ice thickness is known at the time of imaging, the delineation of BFI zones represents a proxy for bathymetry. Progressive development of BFI was mapped through the winters of 2003-07 and isolated images from other years are available. The nearshore morphology of the region as revealed by BFI mapping is characterized by extensive nearshore shoals that form at the mouths of active distributaries and are separated by wide, slightly deeper embayments. Narrow channels can be seen to transect the shoals both aligned with and orthogonal to the river outflow. Detailed images from thick ice years depict channels fanning out to feed distributary mouth bars. Comparison of images acquired over more than 10 years suggest that shoal migration can exceed 100 m per year and channel incision of the shoals to depths of >5 m has occurred. The BFI imagery suggests that there is sufficient room beneath the sea ice cover to permit river discharge to reach the shelf without requiring extensive networks of sub- ice channels. The distribution of bottomfast ice also constrains discharge during winter and spring. High inflows occurring during winter surges may lift the ice canopy or over flow onto the surface of the ice disrupting transportation networks. Negative surges in winter can seal off channels. Rising spring discharge is routed over the surface of the nearshore ice when the capacity of the constrained sub-ice drainage network is exceeded causing extensive flooding of the ice surface and strudel drainage to occur.
DE: 0750 Sea ice (4540)
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 4275 Remote sensing and electromagnetic processes (0689, 2487, 3285, 4455, 6934)
DE: 4546 Nearshore processes
DE: 9315 Arctic region (0718, 4207)
SC: Hydrology [H]
MN: 2007 Fall Meeting