Poster Session 3, Wednesday,  October  5, 16:00–18:00

Poster 55

Euphotic Depth Approximation from Remote Sensing Reflectance in Temperate Coastal Waters

Bio-optical characterization of coastal marine ecosystems using remote sensing ocean color satellites remains enigmatic. Our ability to spectrally quantify biogeochemical signatures and quasi-apparent optical properties (AOP) is further compounded by complex spatio-temporal scales in these littoral zones. The accurate estimation of the diffuse attenuation coefficient of natural downwelling irradiance [Kd (lambda)] and derivable euphotic depth [Z1% (PAR)], in particular, remain difficult to model from remote sensing reflectance [Rrs (lambda)]. The present study will examine radiometric profiles and bio-optical properties from 2016-2021 ( n = 75) in the temperate coastal waters of Sagami Bay, Japan towards developing an empirical model to accurately estimate Z1% (PAR) vis-a-vis Kd (490) from Rrs (lambda) based on in-situ measurements. Results show that Rrs (565) / Rrs (490) performed well (RMSE = 0.01/m; MAPE = 12.06%) to estimate Kd (490), and cluster analysis of the time-series revealed three (3) distinct water types based on optical constituents: (1) chromophoric dissolved organic matter (CDOM) dominant, (2) low concentration of particulate and dissolved organic matter water, and (3) phytoplankton dominant. Further, the developed empirical model suggests that the Z1% (PAR) could be robustly estimated using Kd (490) regardless of seasonal variability in transparency. The potential of accurately estimating the Z1% (PAR) in temperate coastal waters from remote sensing ocean color satellites will allow researchers to further elucidate biogeochemical complexity in the euphotic layers of the water column.

Victor Kuwahara, Soka University, [email protected], 0000-0003-4171-3894

Masahiko Kaji, Soka University, [email protected]

Shinji Shimode, Yokohama National University, [email protected], 0000-0001-5103-1366

Toru Hirawake, National Institute of Polar Research, [email protected], 0000-0003-0274-6642

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