Strong near-bed current events off the shelf edge

摘要

The shelf edge and the slope into the deep ocean are regions where the coastal sea meets therndeep ocean. These regions represent a transition zone where a number of physical processesrnoccur as a result of the adjustment between shelf sea and deep ocean dynamics. Thernintersection between density surfaces and the steep bathymetry gives rise to special processesrnand modelling challenges. One of these is run-up of internal waves at the shelf slope, which isrnthe subject of the present paper.rnThe origin of this paper is a series of current and temperature measurements at Ormen Lange,rnan offshore gas field located off mid-Norway. The bottom topography in the area is veryrnvariable due to the Storegga slide, which took place about 8000 years ago. A significant densityrngradient between the cold Norwegian Sea Arctic Intermediate Water and the Atlantic Water isrnalso present. The measurements include recordings of current and density profiles at thernplanned production site, and several near bottom observations along possible pipeline routes.rnThe data shows a number of near seabed intermittent current events with high speedrnaccompanied by a corresponding change of temperature. By combining the fieldrnmeasurements with a fine scale hydrodynamic model, selected events are described, and thernprocesses and triggering mechanisms causing these events are discussed.