Abstract

A 614 kHz acoustic Doppler current profiler was deployed through land-fast ice in Resolute Passage, in the Canadian Archipelago for 30 days in April and May 1992. It was demonstrated that in the mean, at tidal and at high frequencies the instrument was stable and aligned within 0.5° of vertical, permitting unambiguous measurement of the horizontal, and more importantly, the vertical velocity structure. The flow was dominated by tidal and high frequency (15 min period) oscillations. The K1 and M2 tidal currents were both approximately 10.0 cm s−1, oriented along-channel. The K1 component was constant with depth while the M2 component changed in magnitude and its sense of rotation. The corresponding vertical velocities showed maximum spectral power density in the semi-diurnal frequency band but were insignificant in the diurnal band. At high frequencies, 31 events, or groups of oscillations with vertical velocities greater than 3.5 cm s−1 were found. They were identified as finite amplitude internal waves trapped to the pycnocline, finite amplitude internal waves at greater depth (corresponding to a change in the density structure) and linear internal waves. The horizontal kinetic energy of the oscillations was dependent on the spring-neap tidal cycle. It is proposed that many were generated through interaction of the tidal flow with a compression ridge in the ice, located approximately 15 km from the measurement site.

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