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TitleA modeling study of the impact of major storms on waves, surface and near-bed currents on the Grand Banks of Newfoundland
AuthorLi, M Z; Wu, Y; Prescott, R H; Tang, C C L; Han, G
SourceJournal of Geophysical Research, Oceans vol. 120, issue 8, 2015 p. 5358-5386, https://doi.org/10.1002/2015jc010755
Year2015
Alt SeriesEarth Sciences Sector, Contribution Series 20150204
PublisherAmerican Geophysical Union
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceEastern offshore region; Newfoundland and Labrador
AreaGrand Banks
Lat/Long WENS -58.0000 -45.0000 50.0000 42.0000
Subjectssurficial geology/geomorphology; marine geology; modelling; tidal wave; wave propagation; tides; offshore currents; nearshore currents; currents; storms; sediment transport
Illustrationslocation maps; tables; graphs; models
ProgramMarine Geohazards, Public Safety Geoscience
AbstractWave and current processes and seabed stresses during major storms on the Grand Banks of Newfoundland have been simulated using integrated wave model, 3D tidal and ocean current models with an aim to estimate the sediment transport over the Banks. Most of the storms track southwest to northeast and pass to the north or northwest of the Grand Banks. Significant wave heights can reach up to ~14 m and are predominantly to the northeast at the peaks of storms. Extreme surface currents reach approximately 1 m s-1 and are largely to the southeast with nearly uniform spatial distribution. Patterns of bottom currents are more complex. The strongest bottom currents up to 0.8 m s-1 occur on St. Pierre Bank and are dominantly to the south and southeast. Maximum bottom currents range from 0.3 to 0.5 m s-1 on other parts of the model domain and often form counter-clockwise gyres on northeastern or over the entire Grand Bank. While there is an overall trend of increasing wave height and wind-driven current with increasing storm wind speed, storm paths closer to the Grand Banks, shorter distance between storm center and model domain and slower storm translation speed also contribute to stronger wind-driven currents. Surface and near-bed wind-driven currents both rotate clockwise and decrease in strength as the storm moves across the Grand Banks. While the storm impact on the surface currents is largely uniform, bottom currents show significant spatial variation of current magnitude and direction and the time of peak current conditions. On bank tops with shallower depths (~70 m), the direction of the wind-driven current is similar from the surface to the bottom but current speed decreases significantly. For areas with deeper depths, the bottom wind-driven currents not only decrease significantly in magnitude but their direction could also be opposite from the surface wind-driven currents. It is shown that the spatial patterns and vertical variations of the speed and direction of wind-driven currents are controlled by the changes of bathymetry and mixed layer depth over the model domain. Our model predictions establish that storm-generated currents can be 7 to 10 times higher than the background mean currents. These strong currents interact with wave oscillatory flows to produce shear velocities up to 10 cm s-1 and cause wide occurrences of strong sediment transport over nearly the entire Grand Banks.
Summary(Plain Language Summary, not published)
Severe winter storms generate huge waves and strong bottom currents that greatly impact the seabed and mobilize large-sized bedforms on the Grand Banks of Newfoundland. Waves and current processes and seabed stresses during major storms on the Grand Banks were studied using numerical modelling method. Significant wave heights can reach up to ~14 m and surface currents reach ~1 m s-1 during the major storms. The strongest storm-generated currents near the seabed are up to 0.8 m s-1and occur on St. Pierre Bank with dominant directions to the south and southeast. While wave height and wind-driven current increase with increasing wind speed, storm impact is also determined by storm paths, the distance of storm center from the Grand Banks, and how fast the storm moves. Surface and near-bed currents both rotate clockwise and decrease in strength as the storm moves across the Grand Banks. Storm-induced bottom currents show significant spatial variation of current magnitude and direction and the time of peak current conditions.
GEOSCAN ID296906