Eddies of Vestfjorden, Norway

Vestfjorden, the large fjord between the Lofoten Islands and mainland Norway, is an area of complex oceanography ruled by the interaction of two major currents, the Norwegian Atlantic Current (NAC) and the Norwegian Coastal Current (NCC). The currents are affected by the strong tides in this region and by the bathymetry of the continental shelf; meanders in the currents coincide with the troughs and banks of the continental shelf. Many dynamical features can be observed in sea surface temperature (SST) imagery derived from infrared measurements. Variability in the SST data is associated with seasons, the effects of wind forcing and bathymetric steering. There is distinct seasonality in the SST patterns with the most marked changes occurring in late spring/early summer when the NCC becomes warmer than the NAC, a period for which there is usually less cloud seen in the imagery. Eddy features in Vestfjorden were visible in several sequences of images that allow the formation and decay of features to be traced, e.g. eddies and meanders of the currents and fronts. The eddies observed in the imagery have been compared with results of drifter experiments in Vestfjorden which independently confirm the presence of eddy features in the fjord. Eddies have been found in several locations and their size varies accordingly, the widest eddies have been observed over the sill region, with the narrowest in inner Vestfjorden near the mouth of Ofotfjorden. Inspection of the imagery indicates that, in general, the eddies occurring over the sill are anticyclonic whilst those further into the fjord are cyclonic.