Influence from 'Ocean Weather' on near seabed currents and events at Ormen Lange

The near seabed currents at Ormen Lange have significant spatial and temporal variability under strong influence by the rather rough topography that was formed by the Storegga sub-sea slide. Analysis of current meter records in a given location exhibit periods with relatively calm current conditions accompanied by periods of fairly strong currents, consisting of successions of intermittent events. During such events the near seabed measurements show currents exceeding 60 cm/s. The forcing mechanisms behind such events vary but it is evident that currents and internal waves generated by atmospheric forcing probably dominates, although internal pressure gradients associated with non-linear internal waves and bores/hydraulic jumps are contributing as well. The development of individual events is to a great extent controlled by the interaction between the density stratification and the sloping seabed. In-situ measurements have been combined with numerical simulations in a number of studies with the objective to increase the understanding of events giving rise to extreme currents and internal pressure gradients close to the seabed at Ormen Lange.