Light scattering properties of marine particles in coastal and open ocean waters asrelated to the particle mass concentration

Abstract

Variations in the spectral scattering coefficient of marine particles [b p ()] were measured at 241 locations in oceanic (case 1) and coastal (case 2) waters around Europe. The scattering coefficient at 555 nm normalized to the dry mass of particles [b (555)] was, on average, 1.0 and 0.5 m 2 g Ϫ1 in case 1 and case 2 waters, respectively. characterized by a high density that counterbalances the effect of a higher refractive index. In the Baltic Sea, b (555) was similar to values found in other coastal waters despite the fact that particles were dominantly organic, m p which may result from higher absorption relative to scattering. A smaller than expected increase of b p () toward short wavelengths is attributed to significant absorption that increases toward the shorter wavelengths and reduces scattering, whether particles are living, detrital, or mineral. Our analyses suggest that the determination of b may m p be significantly sensitive to the porosity of the filter used to assess the dry mass of particles.Light scattering by suspended particles is generally the first-order determinant of reflectance variability in coastal 1 Corresponding author (marcel@obs-vlfr.fr). AcknowledgmentsThis study was mainly funded by the European Commission (Environment and Climate Program, contract ENV4-CT96-0310), and partially by the European Space Agency and by the U.S. Office of Naval Research Environmental Optics Program (grant N00014-98-1-0003). Ship time was provided by the Reedereigemeinschaft Forschungsschiffahrt and Institut National des Sciences de l'Univers. We thank Louis Prieur, who made possible our participation in the Almofront-2 cruise aboard R.V. L'Atalante. We are grateful to the crews of R.V. Victor Hensen and R.V. Tethys 2, and to Commerc'Air SA staff for their support during field experiments. We also thank G. M. Ferrari, G. Obolensky, N. Hoepffner, F. Lahet, K. Oubelkheir, and E. Roussier for their help during measurements,

Optical techniques for remote and in-situ characterization of particles pertinent to GEOTRACES

“…Twardowski et al, 2001;Fournier et al, 2014). When the optical properties such as attenuation and scattering are normalized by dry-mass (that is without the interstitial water, as when obtaining dry weight PM), the mass specific optical property varies by only a factor of two between organic and inorganic particles (Babin et al, 2003).…”

In situ variability of mass‐specific beam attenuation and backscattering of marine particles with respect to particle size, density, and composition

“…Second-order effects are caused by variations in particle size, material composition (i.e., refractive index), shape, and internal structure. Strong relationships are generally found between IOPs and suspended particulate matter concentration, [SPM] (Babin et al 2003;Boss et al 2009a), or chlorophyll a concentration, [Chl a], widely used as an index of phytoplankton biomass (Bricaud et al 1998;Loisel and Morel 1998). Such relationships were derived from in situ measurements, whereas our present understanding of the effect of particle characteristics on IOPs is mainly based on laboratory measurements and theoretical calculations.…”

Patterns of suspended particulate matter across the continental margin in the Canadian Beaufort Sea

“…bution of particle assemblages (Kitchen et al, 1982;Bunt et al, 1999;Babin et al, 2003b;Reynolds et al, 2010;Woźniak et al, 2010;Hill et al, 2011), and may thus show regional differences. The proportion of organic to inorganic material is important because mineral particles have typically higher refractive index compared to organic particles, and thus generally produce higher scattering (e.g., Babin et al, 2003b;Woźniak et al, 2010).…”

“…The proportion of organic to inorganic material is important because mineral particles have typically higher refractive index compared to organic particles, and thus generally produce higher scattering (e.g., Babin et al, 2003b;Woźniak et al, 2010). Beam attenuation is also affected by variable absorption.…”

“…Particle size is of importance because the scattering crosssection of individual particles typically increases as particle size increases (Morel and Bricaud, 1986;Stramski and Kiefer, 1991). However, particle concentration often decreases significantly with an increase in particle size so that relatively small particles can have higher contribution to bulk scattering per unit mass concentration of particles than larger particles (Babin et al, 2003b;Reynolds et al, 2010;Hill et al, 2011). In this section, we provide a description of the bulk composition and size distribution of particle assemblages sampled during the MALINA cruise in August 2009.…”