|Local and global aspects of the bottom nepheloid layers in the world ocean|
McCave, I.N. (1986). Local and global aspects of the bottom nepheloid layers in the world ocean. Neth. J. Sea Res. 20(2-3): 167-181
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579, more
The bottom 1 km of the ocean is appreciably more turbid than the two or more km above it. This bottom nepheloid layer has been mapped principally by nephelometers that are most sensitive to particles <=2 µm in diameter. However, the layers contain larger aggregated particles which play an important role in sedimentation. The thickness of the nepheloid layer is much greater than the height above the bed to which turbulent mixing occurs, a fact explained by lateral transport of turbid mixed layers that have detached from the bottom. The overall upwards decline in turbidity is accounted for by the layers higher above the bed having come farther and being on average older than those lower down. The most intense nepheloid layers are found in areas of strong western boundary currents and in regions where the bottom current regime is thought to be highly variable due to penetration of eddy energy from the surface. Areas under the Gulf Stream and in the Argentine basin are examples. Review of the distribution and characteristics of nepheloid layers examines features contributing critically to these hypotheses. An important contributing factor to the depth distribution of turbidity is that the ratio of water volumes to bed areas in contact with them is eight times higher for water between 4 and 5 km than that between 2 to 3 km.