LIGHT-SCATTERING AND CHLOROPHYLL CONCENTRATION IN CASE-1 WATERS - A REEXAMINATION

An analysis is presented based on a large dataset (N = 2,787) made up of recent measurements of the beam attenuation coefficient at 660 nm a nd of the chlorophyll concentration by using the SeaTech transmissomet er and the high-pressure liquid chromatography technique, respectively . This analysis, restricted to case 1 waters, aims at reassessing a pr evious nonlinear relationship established between the particle scatter ing coefficient, b(p) (very close to the particle attenuation coeffici ent, c(p)), and the chlorophyll concentration, [Chl]. As a first resul t, nonlinearity is fully confirmed over the whole range of oceanic chl orophyll concentration (about 3 orders of magnitude). Despite more acc urate measurements, the scatter in this relationship remains large and is actually comparable to that observed within the old dataset. Rathe r than establishing a single relationship between c(p) (or b(p)) and [ Chl] for the entire upper water column, the deep layer and the near-su rface layer (important for remote-sensing application) have been studi ed separately. This separation has led to two distinct expressions. A more appropriate parameterization is thus proposed when dealing specif ically with, and modeling, the near-surface layer. As a consequence, a modified criterion is also suggested with a view to identifying turbi d case 2 waters.