| Titre | Observation of internal tides and sediment transport processes at the head of Logan Canyon on central Scotian Slope, eastern Canada |
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| Auteur | Li, M Z ;
Prescott, R H; Robertson, A G |
| Source | Journal of Marine Systems vol. 193, 2019 p. 103-125, https://doi.org/10.1016/j.jmarsys.2019.02.007 |
| Image |  |
| Année | 2019 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20180333 |
| Éditeur | Elsevier BV |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1016/j.jmarsys.2019.02.007 |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Province | Région extracotière de l'est; Nouvelle-Écosse |
| SNRC | 10 |
| Région | Scotian Slope; Logan Canyon; Sable Island Bank |
| Lat/Long OENS | -60.0833 -59.5000 43.6667 43.1667 |
| Sujets | Holocène; dérive des continents; plate-forme continentale; talus continental; caractéristiques sous-marines; canyons sous-marins; transport des sediments; mécanismes de transport; distribution des
sédiments; marées; courants; courants de fond; tempêtes; océanographie; hydrodynamique; charge de fond; charge en suspension; sédiments marins; sables; instruments d'observation; analyses granulométriques; géologie marine; géologie des dépôts
meubles/géomorphologie; sédimentologie; Nature et environnement; Sciences et technologie; Phanérozoïque; Cénozoïque; Quaternaire |
| Illustrations | cartes de localisation; cartes géolscientiques généralisées; photographies; tableaux; séries chronologiques; spectres; profils; graphiques |
| Programme | Géoscience pour la sécurité publique Géo-risques marins |
| Diffusé | 2019 02 12 |
| Résumé | (disponible en anglais seulement)
An instrumented seabed lander was deployed in the head of Logan Canyon in ~280?m water depth in 2005 to obtain the first observations of near-bed hydrodynamics
and sediment transport processes in a shelf incising canyon on the glaciated Scotian Slope under strong influence of storms and ocean currents. The seafloor at the head of Logan Canyon is quite dynamic. Hourly mean current speeds can reach 35?cm/s
while the maximum instantaneous currents are up to 70?cm/s. Under the forcing of semi-diurnal tides, the bottom currents are dominated by high frequency alternating up- and down-canyon current pulses of internal tides that cause periodic bedload and
suspended load sediment transport. The current and sediment transport processes of the internal tides likely extend down to 800–1000?m depths along the canyon to contribute to the observed distribution of Holocene fine sand in the head and talweg of
Logon Canyon. The high-frequency current and sediment concentration data show that the temporal changes of the current pulses are well correlated with the changes of temperature and sediment resuspension to demonstrate strong asymmetric patterns. The
amplified currents of the internal tides cause the fine sands at the head of Logan Canyon to be transported as bedload in 2.1% of the time and in suspended-load in 1.2% of the time. Suspended-load transport is dominant over bedload transport. The
maximum suspended sediment concentrations may reach ~100?mg/l in strong current events. As down-canyon transport is generally stronger and more frequent and the residual current is down-canyon, the net transport of sediment is in the down-canyon
direction. Summer storms do not seem to directly impact the bottom currents at the head of Logan Canyon. However, sediments resuspended on the shelf during storms can be advected down slope into the canyon to cause events of substantially high
sediment concentration enhancing sediment supply and transport at the head of Logan Canyon. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Des instruments installés sur le fond marin dans un canyon sur le talus néo-écossais en août 2005 ont permis de recueillir les premières
observations des courants près du fond et de la mobilité des sédiments. De forts courants de fond ont été enregistrés et le transport intensif de sédiments qui en résulte pourrait être un mécanisme potentiel d'instabilité des fonds marins et de
formation de courants de turbidité dans les canyons du talus néo-écossais. |
| GEOSCAN ID | 313350 |
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