SUSPENDED MATTER ALONG CONTINENTAL MARGIN OF NORTH AMERICAN BASIN

Vertical profiles of light scattering at 31 stations along the western margin of the North American Basin establish the bottom nepheloid layer as a permanent (non-seasonal) feature of the bottom waters of this region in depths greater than 3000 m. Its thickness ranges from 300 to 2400 m, the greatest thickness occurring toward the south off the Blake Plateau and Bahama Islands. Scattering intensities are greatest on the lower continental rise and abyssal plain north of Cape Hatteras. This layer represents sediment in suspension in the southerly bottom current along the western margin. Frequently near the outer ridges, the water is relatively clear adjacent to the bottom under the main nepheloid layer. In the Gulf Stream at about 500 m, the approximate depth of a high gradient in horizontal velocity, a marked increase in light scattering may mark the Sargasso Sea Water-Slope Water boundary. © 1969.