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TitreProcesses and seabed impact of major storms on Grand Banks
AuteurLi, M Z; Prescott, R H; Wu, Y; Tang, C L; Han, G
SourceL'Association géologique du Canada-L'Association minéralogique du Canada, Réunion annuelle conjointe, Recueil des résumés vol. 35, 2012.
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20110345
RéunionGAC/MAC2012 Joint Meeting; St. John's, NL; CA; mai 27-29, 2012
Documentpublication en série
ProvinceRégion extracotière de l'est
Sujetsetudes des ondes de surface; transport des sediments; moyens de transport; transport sous-marin; courants; courants de fond; courants dirigés vers le large; tempêtes; dépôts de tempête; géologie marine
ProgrammeGéoscience en mer, La géoscience pour les développements extracôtiers de la côte est
Résumé(disponible en anglais seulement)
Storms can generate significant surface waves and strong wind-driven currents on the Grand Banks, Newfoundland. The strong waves and wind-driven currents induced by the major storms can cause seabed scouring and bedform mobility, and hence impact the engineering design and safety of offshore seabed installations. The wind-driven current pattern and sediment transport processes during storms are also important for predicting the dispersion of material from oil spill incidents. Wind, wave hindcast data, and ocean and wind-driven currents predicted from a 3D ocean model for 22 selected major storms for the past 50 years were used to investigate the pattern, processes, and impact on the seabed by major storms on the Grand Banks. These wave and ocean current data, together with model-predicted tidal current and observed grain size data, were coupled in a sediment transport model to predict seabed shear stresses, magnitude and frequency of sediment mobility, and sediment transport flux for the selected major storms. Wind and waves are to the NE during most of the major storms on Grand Banks, and the associated storm-induced currents are predominantly to the SE. Although stronger wind tends to generate stronger currents, significant variance exists and suggests that other factors, e.g. storm track and storm center translation speed, also affect the storm impact. Storms significantly alter current patterns on Grand Banks. At the peaks of major storms, surface wind-driven currents are dominantly to the SE and can reach as high as 140 cm/s, more than 4 times stronger than that under non-storm conditions. In the near-bottom layer, strongest currents up to 50-70 cm/s occur on the western Grand Banks and are dominantly to the southeast and east. Near-bottom currents reach about 30 cm/s and are to the north and northwest on the NE Grand Bank. Under non-storm conditions, seabed shear velocity is < 2 cm/s and low sediment transport occurs only in isolated spots. During major storms, bottom shear velocity is increased to >10 cm/s due to strong waves and wind-driven currents and significant sediment transport is widely predicted on the Grand Banks. Maximum sediment transport rate reaches about 2-3 kg/m/s and occurs on the SE Grand Bank. Maximum seabed forcing during major storms can transport up to small pebbles, and intermittent transport of sediment should occur on most bedorms during these storms.