Document Type

Article

Date of Original Version

1982

Department

Oceanography

Abstract

Velocity and temperature measurements from the bottom boundary layer (BBL) over the Eastward Scarp of the Bermuda Rise in water depth of 4620 m show little variability over an 8‐month period. The free‐stream flow 62 m above the bottom was south‐southeasterly following the isobaths in the region with an average speed of 22 cm/s. The current vector in the BBL rotated an average of 5° in a counterclockwise sense between 62 and 0.8 m above the bottom. The thickness of the BBL was ∼40 m and the average magnitude of the bottom stress was ∼0.7 dynes/cm2. Mean speed profiles, height of the BBL, and the magnitude of the bottom stress predicted by a model compare favorably with the observations, but the model predicts a rotation of the current vector between 62 and 0.8 m more than twice that measured. The time‐dependent nature of the flow field is also reproduced by the model. The Bermuda Rise data and speed profile measurements at the base of the Scotian Rise show that the M2 clockwise polarized tide is damped more than the mean current as the bottom is approached in the BBL. This phenomenon is reproduced by the model and can be explained by differing effective Ekman layer thicknesses associated with tidal and steady components of the flow.

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