| Title | Synthesis of near-bed currents and sediment mobility on the Beaufort Shelf edge and upper slope, offshore Northwest Territories |
| Download | Downloads |
| |
| Licence | Please note the adoption of the Open Government Licence - Canada
supersedes any previous licences. |
| Author | Li, M Z ; King, E
L; Forest, A; Melling, H; Osborne, P D |
| Source | Geological Survey of Canada, Open File 8579, 2020, 58 pages, https://doi.org/10.4095/326562  Open Access |
| Image |  |
| Year | 2020 |
| Publisher | Natural Resources Canada |
| Document | open file |
| Lang. | English |
| Media | on-line; digital |
| File format | pdf |
| Province | Northern offshore region; Northwest Territories; Yukon |
| NTS | 107C/10; 107C/11; 107C/12; 107C/13; 107C/14; 107C/15; 107C/16; 107D/13; 107E/03; 107E/04; 107E/05; 107E/06; 107E/11; 107E/12; 117C/08; 117C/09; 117C/16; 117D/05; 117D/06; 117D/07; 117D/08; 117D/09; 117D/10;
117D/11; 117D/12; 117D/13; 117D/14; 117D/15; 117D/16 |
| Area | Beaufort Sea |
| Lat/Long WENS | -140.5000 -130.0000 70.5833 69.2500 |
| Subjects | marine geology; surficial geology/geomorphology; Science and Technology; Nature and Environment; continental margins; continental shelf; continental slope; depositional environment; depositional cycles;
currents; bottom currents; storms; marine sediments; muds; landslides; permafrost; periglacial features; pingos; sediment transport; erosion; suspended sediments; sediment dispersal; grab samples; core samples; piston cores; grain size analyses;
oceanography; unconformities; water circulation patterns; current circulation; source areas; hydrodynamics; Beaufort Shelf; Beaufort Shelf-Break Jet; Mackenzie Trough; colluvial and mass-wasting deposits; alluvial sediments; Phanerozoic; Cenozoic;
Quaternary |
| Illustrations | location maps; geoscientific sketch maps; tables; plots; spectra; time series; profiles |
| Program | Public Safety Geoscience Assessing landslides and marine geohazards |
| Program | Program of Energy Research and Development (PERD) |
| Released | 2020 07 29 |
| Abstract | (Summary)
Limited wind-driven current modelling and moored current measurements suggest the presence of strong currents associated with the amplified Beaufort Shelf-break Jet (BSJ) on the
Beaufort shelf edge and upper slope. Zones of erosion and non-deposition have also been mapped along the shelf break. However, knowledge of near-bed current intensity and erosion and transport of sediments on the Beaufort shelf break and upper slope
is lacking. This report addresses the lack of near-bed current data and the gap in our understanding of the spatial distribution of bottom currents and sediment mobility on the Beaufort shelf edge and upper slope through the compilation and analysis
of existing moored current data. The spatial patterns of bottom currents and sediment mobility are compared with the mapped distribution of the erosion and non-deposition zones for insights of the correlation between modern oceanographic processes
and the distribution of the erosion and non-deposition zones on the Beaufort shelf break and upper slope.
Mooring water-column and near-bed current data have been compiled from11 sites that occur in water depths of 75-660 m and span the entire
Beaufort shelf break and upper slope environments. The measured and extrapolated near-bed current data, largely at 6-10 m above bottom, were analyzed and compared with the threshold for sediment erosion to derive a regional framework of near-bed
currents and sediment mobility on the Beaufort Shelf break and upper slope. Events with maximum bottom currents of 60-80 cm/s periodically occur and maximum sediment erosion frequency can reach 17% and 7% of the time on the Beaufort shelf break and
upper slope respectively. These estimates suggest that currents and sediment mobility on the Beaufort shelf break and upper slope are greater than the mid- and outer shelf. The direction of peak currents is roughly parallel to the local isobaths,
predominantly to the NE and the ENE on the central Beaufort shelf break. The bottom currents and inferred sediment mobility also show strong seasonal and inter-annual variabilities.
Estimated near-bottom currents and sediment erosion frequency
along cross-slope transects demonstrate that currents and sediment erosion are the strongest along the shelf break and decrease both seaward on the upper slope and landward on the outer shelf. The width of the impact zone of the amplified Beaufort
Shelf-break Jet currents is 20-25 km. Intensity of currents and sediment erosion also decreases from the west to the east. These observations are in qualitative agreement with the width and along-slope trend of the mapped erosion and non-deposition
zone, suggesting that the presence and amplification of the BSJ are responsible for this seabed phenomenon. |
| Summary | (Plain Language Summary, not published)
An erosional zone has recently been mapped along the shelf break and upper slope of the Canadian Beaufort Sea. Measured or extrapolated near-bottom
current data have been compiled for several along-shelf geographic areas. The bottom current data have been compared with the threshold for sediment erosion to compute the level and time percentage of seabed erosion. At the shelf break, the 95
percentile current speeds range 17-25 cm/s and cause sediment erosion in 3.4-12% of the time. On the upper slope in slightly deep water, the 95 percentile current speeds are 13-17 cm/s and sediment erosion occurs in 2-3% of the time. The current
intensity and sediment erosion frequency are also found to decrease from the west to the east along the shelf break. The cross-slope variation of the current and sediment erosion intensity are in qualitative agreement with the spatial pattern of the
mapped erosional zone on the Beaufort shelf break and upper slope. |
| GEOSCAN ID | 326562 |
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