On the capability of an upward-looking ADCP deployed in the Iceland-Faeroe frontal area

Abstract

An upward looking acoustic Doppler current profiler (ADCP), deployed in the Iceland-Faeroe area, recorded horizontal currents as function of depth over a period of some 200 days from August 1991 to March 1992. The water depth at the mooring was about 400 m and the vertical resolution 16 m. Differently from the point measurements of conventional current meters the ADCP performs vertical integration within the resolution cells. This feature is used to determine the barotropic tides. Through instrumental limitations it is expected that currents measured in the upper 15% of the water column are contaminated by side-lobe reflections from the sea surface. Some evidence has been found that this effect is less important in the upper part of the contaminated layer, where currents are significantly correlated with winds. Variance spectra of high resolution may be obtained from the ADCP data by performing spectral averaging over depth instead of time. This is demonstrated with respect to inertial oscillations. The ADCP allows to study the vertical coherence over nearly continuous spacings.