The Atlantic Water flow along the Vøring Plateau: Detecting frontal structures in oceanic station time series

摘要

The topographic steering of the baroclinic western branch of the Norwegian AtlanticCurrent (NwAC) determines the extent of Atlantic Water and location of the ArcticFront in the Nordic Seas. In this paper the geographical spread of hydrographicmeasurements at the Ocean Weather Station M (OWSM, 66°N 2°E) is utilisedto create mean sections across the Vøring Plateau Escarpment in the NorwegianSea. In concert with a theoretical framework involving the impact of low pressuresystems on frontal jets over steep bathymetry, the behaviour of the front-currentsystem at this location is described. It is shown that the halocline and thermoclineare sloped from about 200 m in the west and down to 400 m in the east over 40 kmcentred on the station, indicating that the western branch of the NwAC is locatedhere. The horizontal gradients introduced by this slope are 2°C and 0.1 for salinity.The frontal slope is not seen to change its inclination on seasonal, multi-annual,nor decadal timescales, indicating that the dynamic control of this frontal slopedoes not change appreciably. Further supported by the theoretical framework it isshown that the subsurface part of this front and the associated western branch ofthe NwAC is strongly locked by topography along the Vøring Plateau also on shorttimescales. From large scale bathymetry it is also shown how this kind of frontallocking can be expected over most of the ridges and continental slopes in the NordicSeas.