PARTICLE-SIZE, LIGHT-SCATTERING AND COMPOSITION OF SUSPENDED PARTICULATE MATTER IN THE NORTH-ATLANTIC
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Suspended particulate matter characteristics were studied on the Iceland Rise and in the western North Atlantic southeast of New York. Comparison of suspended particulate matter (SPM) and light-scattering in the Iceland Rise area suggests a second-order response due to particle size and/or composition or a nonlinear response with increasing concentration. Correlations of light scattering to SPM concentration also differ regionally. Particle size distributions are more peaked in the nepheloid layer than those in clear water. The nepheloid layer samples have a mean modal size between 3 and 9 m, interpreted as being primarily due to resuspension and advection of sediment into the region in the bottom boundary layer. Apparent densities are relatively high, though density differences between SPM in clear water and the nepheloid layer are not distinguishable in the Iceland Rise area. Apparent densities increase in the nepheloid layer in the western North Atlantic where 1.1 g cm-3 adequately separates clear water from nepheloid layer samples. Compared to clear water, the nepheloid layer in both regions includes lower percentages of small coccoliths and increased clays and mineral matter. These compositional variations are more dramatic in the western North Atlantic region, due to dissolution of carbonate at the seafloor, and later resuspension of the clays and mineral matter into the nepheloid layer. 1987.
