Simulation of the Norwegian Coastal Current in the vicinity of the Halten Bank: comparison with observations and process study of bank-induced meanders

Results from a high resolution, three-dimensional, real-time simulation of the Norwegian Coastal Current are compared at six current meter moorings deployed during March 1988 in the vicinity of the Halten Bank. The simulation was initialised from a set of fairly arbitrary velocity and density fields. The objectives are to examine (i) how accurately the results reproduce the observed means and variabilities, and (ii) how the dominant flow dynamics may be explained in term of the circulation produced by unstable baroclinic meanders over topography. The simulation reproduces the means fairly well; the rms errors are less than 34% in five of the six moorings for the east/west velocity component, and are less than 32% in three moorings for the north/south component. The agreements in current variabilities are good only at three moorings, for which an averaged rms error of about 22% was obtained. At the other three moorings, the largest errors for the variabilities occur in the subsurface, where energetics are underestimated by as much as 60% or more in the simulation. The discrepancies are most likely due to insufficient vertical resolution, which results in a poor representation of the baroclinic structure, and also due to the smoothed topography used in the simulation. On the other hand, a meander upstream of the Halten Bank on March 26, 1988, is reproduced well by the model. The simulation suggests that the meander is a result of amplification of waves and eddies shed from a smaller bank upstream of the Halten Bank through dynamic instability. A process-oriented simulation has been conducted to support this hypothesis.