| Title | Modelling seabed disturbance and sediment mobility for the Scotian Shelf bioregion, offshore Nova Scotia |
| Download | Downloads |
| |
| Licence | Please note the adoption of the Open Government Licence - Canada
supersedes any previous licences. |
| Author | Li, M Z ; Wu, Y;
Ma, Y; Wang, Y |
| Source | Geological Survey of Canada, Open File 8952, 2023, 55 pages, https://doi.org/10.4095/331499  Open Access |
| Image |  |
| Year | 2023 |
| Publisher | Natural Resources Canada |
| Document | open file |
| Lang. | English |
| Media | digital; on-line |
| File format | readme
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| File format | pdf |
| Province | Eastern offshore region; Nova Scotia |
| NTS | 11D/09; 11D/10; 11D/11; 11D/12; 11D/13; 11D/14; 11D/15; 11D/16 |
| Lat/Long WENS | -63.0000 -62.0000 45.0000 44.5000 |
| Subjects | marine geology; sedimentology; sediments; marine sediments; sediment transport; shear stress; seafloor topography; bottom currents; currents; modelling; bathymetry; Scotian Shelf |
| Illustrations | location maps; tables; figures; time series; distribution diagrams |
| Program | Marine Geoscience for Marine Spatial Planning |
| Released | 2023 03 09 |
| Abstract | (Summary)
Ocean surface waves and currents can interact to produce strong seabed shear stress and mobilization of sediments that can significantly impact the seabed stability and benthic
habitats on continental shelves. Therefore the knowledge of the magnitude and frequency of seabed disturbance by waves and currents and the resulting mobilization of sediment on continental shelves is critical for the spatial planning and management
of Canada's offshore lands. Modelled waves, near-bottom tidal current and circulation current data for a 3-year period were used in a widely applied sediment transport module to simulate the seabed shear stresses and the mobilization of observed
sediment grain size for the Scotian Shelf bioregion. The modelling results are presented and analyzed to derive updated understanding of seabed disturbance and sediment mobility on the Scotian Shelf. The Scotian Shelf is affected by strong waves and
tidal currents. Maximum mean significant wave height can reach 2.4 m and maximum mean tidal currents can reach 0.5 m·s?1. These waves, currents and/or their interaction cause maximum mean bed shear velocities of 5 - 10 cm·s?1. Sediments on the
Scotian Shelf can be mobilized by tidal currents at least once during the modelled 3 year period over 28% of the shelf area while waves can mobilize sediments at least once over 60% of the shelf area suggesting much stronger sediment mobilization by
waves. Interaction between waves and currents can produce enhanced combined wave-current shear velocity that is capable of mobilizing sediments over 74% of the shelf area. The spatial variation of the sediment mobilization frequencies by component
processes was used to classify the Scotian Shelf into six disturbance types. The seabed disturbance type classification based on near-bed tidal currents and new modelled waves suggests that wave dominant disturbance is predominant accounting for
38.2% of the shelf area. Tide dominant disturbance type accounts for 19.1% of the shelf area, the next highest. In comparison with previous studies using depth-averaged tidal currents, the present study based on near-bottom tidal currents has
resulted in reduced sediment mobilization frequency by tidal currents, smaller extent of high mobility areas and significant changes of the spatial pattern of disturbance type distribution on the Scotian Shelf. The universal Seabed Disturbance Index
and Sediment Mobility Index have also been applied to quantify the seabed exposure to physical processes and sediment mobilization on the Scotian Shelf by accounting for both the magnitude and frequency of these processes. The applications of these
indices provide improved quantification of seabed forcing and sediment mobility for several areas on the Scotian Shelf. |
| Summary | (Plain Language Summary, not published)
Modelled waves, near-bottom tidal current and circulation current data for the period of 2017-2019 were used in a widely applied sediment transport
module to simulate the seabed shear stresses and the mobilization of observed sediment grain size for the Scotian Shelf bioregion. The modelling results represent updated understanding of seabed disturbance and sediment mobility on the Scotian Shelf.
Strong waves and currents produce maximum mean bed shear velocities of 5-10 cm·s-1 and can mobilize sediments over 74% of the shelf area. The relative importance of waves, tidal current and circulation current in mobilizing sediments was used to
classify the Scotian Shelf into six disturbance types. Wave dominant disturbance is predominant on the Scotian Shelf and tide dominant disturbance is second important. The results of the study are important for environmental assessments and for the
spatial planning and management of the bioregion. |
| GEOSCAN ID | 331499 |
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