POSTER Session 2

DETAILED ANALYSIS OF ATMOSPHERIC AND OCEANIC CONSTITUENTS GOVERNING TOP-OF-ATMOSPHERE AND IN-WATER RADIATION DURING A LARGE BLOOM OF EMILIANIA HUXLEYI IN HARDANGERFJORD

Blooms of calcifying phytoplankton in marine environments are accompanied by characteristic optical features observable by satellite sensors, however constituents remain challenging to quantify with traditional ocean color retrieval algorithms. We study Sentinel-3 top-of-atmosphere radiance together with concurrently measured radiance and irradiance just below the water surface in a Norwegian fjord during a bloom of the highly scattering coccolithophore Emiliania huxleyi. In situ measured optical properties and a coupled atmosphere-ocean radiative transfer code are used to analyze step-by-step how atmospheric gases, aerosols, molecular water, particles, and colored dissolved organic matter in the fjord are individually contributing to closure between modeled and measured radiation spectra. In addition, we attempt to estimate measurement uncertainties for these highly scattering waters because of darkening from surrounding mountains, instrument self-shading, and subsurface radiation enhancement induced by internal surface reflection. After obtaining a fit between the measured and modeled spectra, we also analyze the relative water-leaving contribution to the top-of-atmosphere radiance in the near infrared part of the spectrum, which indicate that the merit of the black-pixel approximation is appropriate for the aerosol levels encountered during the coccolithophore bloom. Finally, we do the same step-by-step analysis for contrasting waters representing non-bloom conditions.

Børge Hamre, University of Bergen, Norway, https://orcid.org/0000-0002-0135-0542

Elinor Tessin, University of Bergen, Norway

Daniel Koestner, University of Bergen, Norway

Arne Kristoffersen, University of Bergen, Norway

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