Drivers of spectral optical scattering by particles in the upper 500 m of the Atlantic Ocean

• Published in: Optics express 2020-11, Vol.28 (23), p.34147-34166
• Main Authors: Organelli, Emanuele, Dall’Olmo, Giorgio, Brewin, Robert J. W., Nencioli, Francesco, Tarran, Glen A.
• Format: Article
• Language: English
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.408439

Optical models have been proposed to relate spectral variations in the beam attenuation (c p ) and optical backscattering (b bp ) coefficients to marine particle size distributions (PSDs). However, due to limited PSD data, particularly in the open ocean, optically derived PSDs suffer from large uncertainties and we have a poor empirical understanding of the drivers of spectral c p and b bp coefficients. Here we evaluated PSD optical proxies and investigated their drivers by analyzing an unprecedented dataset of co-located PSDs, phytoplankton abundances and optical measurements collected across the upper 500 m of the Atlantic Ocean. The spectral slope of c p was correlated (r>0.59) with the slope of the PSD only for particles with diameters >1 µm and also with eukaryotic phytoplankton concentrations. No significant relationships between PSDs and the spectral slope of b bp were observed. In the upper 200 m, the b bp spectral slope was correlated to the light absorption by particles (a p ; r