Velocity and bottom-stress measurements in the bottom boundary layer, outer Norton Sound, Alaska

Abstract

We have used long-term measurements of near-bottom velocities at four heights above the sea floor in Norton Sound, Alaska, to compute hourly values of shear velocity u., roughness zo. and bottom-drag coefficient cD. Maximum sediment resuspension and transport, predicted for periods when the computed value of u- exceeds a critical level, occur during peak tidal currents associataed with spring tides. The fortnightly variation in u, is correlated with a distinct nepheloid layer that intensifies and thickens during spring tides and diminishes and thins during neap tides. The passage of a storm near the end of the experiment caused significantly higher u, values than those found during fair weather. We attribute these increases in u. to stronger bottom currents and larger surface waves.