CURRENTS UNDER LAND-FAST ICE IN THE CANADIAN ARCTIC ARCHIPELAGO .1. VERTICAL VELOCITIES

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 degrees of vertical, permitting unambiguous measurement of the hori zontal, and more importantly, the vertical velocity structure. The flo w was dominated by tidal and high frequency (15 min period) oscillatio ns. The K-1 and M(2) tidal currents were both approximately 10.0 cm s( -1), oriented along-channel. The K-1 component was constant with depth while the M(2) component changed in magnitude and its sense of rotati on. The corresponding vertical velocities showed maximum spectral powe r density in the semi-diurnal frequency band but were insignificant in the diurnal band. At high frequencies, 31 events, or groups of oscill ations 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 (corresp onding to a change in the density structure) and linear internal waves . The horizontal kinetic energy of the oscillations was dependent on t he spring-neap tidal cycle. It is proposed that many were generated th rough interaction of the tidal flow with a compression ridge in the ic e, located approximately 15 km from the measurement site.