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TitleNearshore morphology derived from synthetic aperture radar in the Mackenzie Delta region of the Beaufort Sea
AuthorSolomon, S M; Fraser, P; Manson, G K
SourceCanadian Coastal Conference 2005, proceedings/Conférence canadienne sur le littoral 2005, comptes rendus; 2005, 14 pages
Alt SeriesEarth Sciences Sector, Contribution Series 2005164
MeetingCanadian Coastal Conference 2005; Dartmouth, NS; CA; 2005
ProgramGeoscience for Oceans Management
AbstractNearshore morphology in the Mackenzie Delta region of the Beaufort Sea is poorly known because much of the region is both very shallow (< 2 m) and turbid. Synthetic Aperture Radar (SAR) has been used to map nearshore morphology of lakes by taking advantage of the ability of radar waves to penetrate fresh water ice. This technique has been extended to the Mackenzie Delta nearshore region where winter ice forms from river water that is sufficiently fresh. 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. BFI was mapped through the winter of 2003-04 and isolated images from other years are available. Extensive nearshore shoals form at the mouths of active distributaries that are separated by larger, slightly deeper embayments. Narrow channels can be seen to transect the shoals both aligned with and orthogonal to the river outflow. Detailed images from a thick ice year (1993) 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. A rare winter storm surge reaching 1.5 m above chart datum was captured by the 2004-05 time series. Lift-off of the ice canopy in several locations accompanied the injection and drainage of large volumes of water into the ice-confined delta channels over very short intervals (24-48 hours). Rapid drainage of the confined flood waters may deepen existing channels or scour new ones.

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