A Three Stream Ocean Optics Model

A Three Stream Ocean Optics Model: Regional Implementation and Validation. Adapted by OOI from Miller M., 2022. 

(Figure 3.10 from Miller (2022) Top: The black line shows the mean OOI absorption as a function of wavelength for OOI Endurance CSPP Oregon shelf deployment 15 (August – Sept 2019). The gray shading shows the OOI absorption extent between the 20% and 80 % quantiles. The tan shading shows the maximum and minimum extent of OOI absorption. The colored lines correspond to the modeled absorption for different single species approximations. Bottom: Same as top, but for scattering instead of absorption.

Miles Miller used OOI data as part of this MS thesis awarded September 2022 from the Univ. California, Santa Cruz.  The goal of his work was to develop the potential to estimate phytoplankton community structure from remotely sensed optical information and not direct in situ phytoplankton observations. As a step towards this goal, he estimated phytoplankton community structure using spectrally dependent optical absorption and scattering data from an AC-S on the Oregon Shelf profiler. Miller developed linear relationships between modeled phytoplankton absorption and scattering and corresponding observations and solved them by constrained least squares inversion over a field of thirteen wavelengths using six phytoplankton types.  He solved the problem for independent absorption and scattering as well as coupled absorption and scattering. He estimated phytoplankton communities as a function of profile depth and for multiple profiles in time.

The model produced accurate downward irradiance fields when using observed absorption and scattering profiles obtained from the Ocean Observatories Initiative’s Oregon Shelf Surface Piercing Profiler Mooring. Through this forward modeling-based comparison to observations it was found that the optical model can produce accurate profiles under certain conditions, making it promising for data assimilation of remote sensing reflectance as a function of wavelength.  Miller identified several outstanding issues remaining to be addressed to move from using in situ measured absorption and scattering to estimates from remote sensing reflectance.  Because the optical model accuracy is primarily dependent on absorption and scattering, he argued that remote sensing reflectance accuracy can be improved with enhanced phytoplankton community structure and CDOM estimations (see Figure 3.10 from Miller (2022). This figure shows that the modeled phytoplankton light attenuation agrees well with the measurements but that modeled absorption underestimates measurements. This underestimation hints that chromophoric dissolved organic matter (CDOM) is not being properly resolved as CDOM affects only total absorption and not scattering.

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Miller, M. (2022). A Three Stream Ocean Optics Model: Regional Implementation and Validation (master’s thesis). University of California, Santa Cruz. 62 pp.