Ocean currents in the Iceland-Faeroe area, measured by a bottom-mounted ADCP

Abstract

Horizontal currents as a function of depth, measured by a bottommounted

acoustic doppler current profiler (ADCP) in the Iceland-Faeroe area have been analysed. Because of instrumental limitations it was expected that currents measured in the upper 15% of the water column would be 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. The uncontaminated data are of high quality and cover about 75% of the water column. By means of least-squares methods, tidal currents have been extracted. The semidiurnal tide M2 is dominant, its barotropic portion has been estimated from vertically averaged currents. After removing the tides, the only significant variance peak left is for clockwise rotating currents around the inertial period. Vertical coherence between currents at different depth levels has been investigated and a decomposition into empirical orthogonal eigenfunctions (EOFs) has been performed. A surprisingly high correlation has been found between low-pass filtered current velocities at the (contaminated) near-surface level and wind velocities from the wind archive of the UK Meteorological Office.