Subtidal and Tidal Currents in the Vicinity of the Iceland-Færœs Front

Abstract

A tidal analysis carried out on a combination of ship-mounted and moored ADCP (acoustic Doppler current profiler) data is presented for the Iceland-Færœs front region, an area where tidal flows are expected to be of the same magnitude as those of the frontal jet and the eddylike instabilities that appear near it. More than 15 days of ship-mounted ADCP data and 29 days of moored ADCP data were available for the analyses, which were carried out for four tidal components: M2, S2, 01, and K1. The strong influence of topography near the Iceland-Færœs ridge causes large spatial variations in the amplitude and phase of the tide. Simple first- and second-order polynomials are used to empirically model the variation in phase and amplitude of the tidal components with latitude, longitude, and water depth by least-squares fitting techniques. The success of the analysis techniques is assessed by making quantitative comparisons of the results and with predictions from a numerical tidal model of the North Atlantic. Additionally, streamfunctions calculated from the residual subtidal currents are examined and compared with hydrographic data. The empirical analysis techniques and the tidal currents predicted by the numerical model product similar residual velocities, and comparison with hydrographic measurements indicates that the streamfunctions obtained from the residual velocities are significantly more realistic than those obtained from the full velocity measurements. The incorporation of bathymetry data in the empirical analysis techniques appears to improve the estimation of the tidal currents.