Beaufort Sea Sediment Dynamics

📖 The Scoop

Numerous scientific studies have been conducted in the Beaufort Sea since the original Beaufort Sea Project of 1974 and 1975, but, to date, these studies have not been synthesized with respect to sediment dispersal. This report provides a state-of-the-art interpretation of information related to sediment dynamics and outlines a revised sediment dispersal model for the Beaufort Sea. Analysis of the sediment budget indicates that the Mackenzie River is the major contributor of sediment to the southern Beaufort Sea system, contributing over 95 percent of the total. Analysis of mud volumes and sedimentation rates on the shelf indictes that the major portion of the sediment contributed by the Mackenzie River is deposited in shallow water near the delta. This observation is supported by analysis of suspended sediment concentrations (SSC), which were derived from LANDSAT imagery enhancement. The processed images often show very high SSC values (>100 mg/l) inside the 10-m contour and low SSC values (10 mg/l) seaward of the 10-m contour with a strong SSC gradient in the 5-m to 10-m water depths. These analyses indicate that the proximal delta area serves as the primary sediment sink for river sediment. The enhanced LANDSAT imagery also shows that the turbid water of the Mackenzie River plume is frequently deflected to the north and east from the delta and serves as a sediment source to these areas of the shelf, although sedimentation rates (0.2 mm/yr) are nearly one order of magnitude less than those near the delta (2 mm/yr). Wave climate data and current meter data were analyzed for potential transport frequency and potential transport directions. The results show that the shelf seaward of the 20-m contour is dormant in terms of transport potential except on the western shelf where slightly stronger currents occur. Landward of the 20-m contour sediments can be transported by combined wave and current action; transport is most active inside the 5-m contour where waves may suspend material over 50 percent of the time. On the central and eastern part of the shelf net transport is directed to the northeast; longshore transport at the coast is controlled by the dominant northwest storm wave approach and is directed to the east or south, depending on shoreline orientation. Shelf transport on the western shelf may be directed to either the northwest or southeast. Geologically recent changes in sea level and supply pattern have affected shelf sediment dispersal. Areas of the shelf with little or no ongoing sedimentation (the eastern-most and western-most parts of the shelf) have coarse surficial sediments, which are thought to be relict and deposited under different hydrodynamic conditions than exist at present. As such, the shelf morphology and sediment character is a product of both present and past (early to mid-Holocene) sedimentary process -- ASTIS (online) database.

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