Long‐term in situ calculations of kinetic energy and Reynolds stress in a deep sea boundary layer

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Abstract
Long‐term measurements of Reynolds stress and kinetic energy are necessary to characterize the bottom boundary layer during storms which transport sediment in the High Energy Benthic Boundary Layer Experiment area on the Nova Scotia Rise. The benthic acoustic stress sensor current meter system employed an on‐board microcomputer to process 2‐Hz velocity vector data into 20‐min averages of velocity vectors and the turbulent Reynolds stress tensor. The data indicate a bottom boundary layer, which is usually transitional, with bottom roughness scaling between viscous (z0 = v/9u*) and rough (z0 = ks/30). During the periods of transitional flow the logarithmic layer was not a useful indicator of boundary stress. Direct stress and energy measurements showed that the stress was much less than that indicated by the slope of the transitional mean logarithmic velocity profile. Several westward high‐velocity events, which were modulated by a significant tidal component, were recorded. It appears from this data set that the mean westward flow must be accompanied by a train of internal tidal waves to achieve the velocities necessary to be the sediment transport events identified as “benthic storms”.