Particulate Scattering and Backscattering in Relation to the Nature of Particles in the Red Sea

Measurements of light scattering can be used to quantify the concentration and composition of oceanic particles, and resolve biogeochemical processes spanning different time and space scales. In this paper, we analyze the first dataset, collected over wide spatial scales in the Red Sea, of particula...

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Bibliographic Details
Published in:Journal of geophysical research. Oceans 2021-04, Vol.126 (4), p.n/a
Main Authors: Kheireddine, Malika, Brewin, R. J. W., Ouhssain, M., Jones, B. H.
Format: Article
Language:English
Subjects:
Absorption
Algae
Aquatic environment
Backscatter
Backscattering
Biogeochemistry
Chlorophyll
Chlorophyll a
Coefficients
Color
Colour
Components
Composition
Geophysics
Light scattering
Ocean models
Oceans
Optical measurement
Phytoplankton
Plankton
Primary production
Regional development
Remote sensing
Scattering coefficient
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Summary:Measurements of light scattering can be used to quantify the concentration and composition of oceanic particles, and resolve biogeochemical processes spanning different time and space scales. In this paper, we analyze the first dataset, collected over wide spatial scales in the Red Sea, of particulate scattering (bp(λ)), particulate backscattering (bbp(λ)), particulate absorption and chlorophyll‐a concentration [Chl_a]. We fit a three‐component conceptual model relating bbp(λ) to [Chl_a], assuming a fixed background component (bbpk(λ)), and two additional components driven by small (2μm) (bbp,1(λ) and bbp,2(λ), respectively). We extend the approach, for the first time, to the modeling of total particulate scattering (bp(λ)), allowing us to retrieve the backscattering ratio for each component in the model. We observe a high backscattering ratio for the background component which, when analyzed alongside measurements of particulate absorption, suggests it is likely dominated by non‐algal (rather than algal) particles. The high contribution of non‐algal particles to bbp(λ) at low [Chl_a] may be related to the unique conditions in the Red Sea, or more broadly, characteristic of other oceanic conditions. The work illustrates how we can combine optical measurements with conceptual models, to understand better the composition of oceanic particles and ultimately, improve monitoring of marine biogeochemical processes. Our work will also be useful for developing regional ocean‐color models for the Red Sea. Plain Language Summary The ocean contains a large variety of suspended particles that cover a broad size range, from 0.1 nm to 1 mm, and vary in origin, shape and internal composition. The pool of suspended particles is often divided into non‐algal particles and phytoplankton. Most particles play an important role in ocean processes like primary production that modulate the biological carbon pump in the ocean. Concentration and various type of marine particles can be estimated and studied from measurements of light scattering (i.e., particulate backscattering and scattering), and help study and understand biogeochemical processes in aquatic environments. However, separating the contribution from non‐algal particles and phytoplankton to scattering properties is challenging given they often co‐vary with phytoplankton biomass in open ocean waters. The particulate backscattering and scattering coefficients were fit to a chlorophyll‐a de
ISSN:2169-9275
2169-9291
DOI:10.1029/2020JC016610