CALIBRATION AND COMPARISON OF THE LDGO NEPHELOMETER AND THE OSU TRANSMISSOMETER ON THE NOVA SCOTIAN RISE
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During the survey of the HEBBLE (High Energy Benthic Boundary Layer Experiments) area, two optical instruments were used to determine the spatial and temporal structure of the benthic nepheloid layer. Both instruments showed a linear response to suspended particle mass and volume over the typical range of concentrations found in the ocean (10-250 g 1-1). At higher concentrations the transmissometer response remains linear, but, as previously noted and as shown here by theory, the nephelometer has a predictable second-order response due to multiply scattered light. At the low concentrations found in mid-water, both instruments seem near their limit of sensitivity. Small differences between instruments at low concentrations may result from variations in response to particle types found in mid-water or may be minor second-order effects of temperature or pressure on the instruments. The comparison made here shows that either instrument can be effectively used to study the nepheloid layer, and that data from different study areas using these instruments can consistently be compared. The HEBBLE region was ideal for testing the range of these instruments because it yielded the highest concentrations of particles ever recorded in the deep sea. 1985.
