The bottom boundary layer of the deep ocean

Some aspects of the bottom boundary layer of the deep ocean are exhibited in profiles of salinity and temperature made with a Woods Hole Oceanographic Institution/Brown CTD microprofiler. Profiles from the center of the Hatteras Abyssal Plain have a signature that is characteristic of mixing up a uniformly stratified region. Over rough or sloping topography, to the east and west of the abyssal plain, the profiles have more complicated structure. All profiles show a well-mixed layer above the bottom; the penetration height of the layer varies from about 10 to 100 m and is correlated with the one-day mean velocity, inferred from current meters located above the bottom boundary layer. Over the Hatteras Abyssal Plain the mixed layer extends above the bottom about 6 times the turbulent Ekman layer height. Over rough and sloping topography the penetration height is between the Ekman layer height and the height observed on the flat abyssal plain.