Remote sensing reflectance (Rrs) of the surface water of the Mackenzie Delta Region during 4 expeditions from spring to fall in 2019


Vertical profiles of downwelling irradiance (Ed) and upwelling radiance (Lu) were measured during legs 2, 3, and 4 using a Compact-Optical Profiling System (C-OPS) in an ICE-Pro frame from Biospherical Instruments, Inc. (for a detailed description see Morrow et al. 2010 (see further details)). Additionally, above-surface incident downward irradiance (Es(0+)) was measured at about two meters above sea level and was used to correct in-water Ed and Lu for changes in the incident light field during Lu profiling (Zibordi et al., 2019; doi:10.25607/OBP-691). All radiometric quantities were measured at 19 wavelengths spanning from 380 to 875 nm. In-water profiles were obtained from the boat using a 3 m long pole, deployed towards the sun to avoid shading from the boat. The data that were acquired with a tilt of more than 5 degrees were discarded (Hooker et al., 2013; doi:10.5194/bg-10-4511-2013). Due to the high absorption and scattering coefficients in the sampled waters and considering relatively large dimensions of the ICE-Pro, self-shading correction was not negligible. Absorption observed in the present study were mostly outside the limits examined by Gordon and Ding (1992; doi:10.4319/lo.1992.37.3.0491), suggesting the application of the correction questionable. To overcome this issue, we performed Monte-Carlo simulations using the SimulO software (Leymarie et al., 2010; doi:10.1364/AO.49.005415) for examining the self-shading correction factor on Lu at null depth (Gerbi et al., 2016 (doi:10.1175/JTECH-D-16-0067.1); Leymarie et al., 2018 (doi:10.3389/fmars.2018.00437)). The exact dimensions of the ICE-Pro were simulated and virtually placed at a depth of 0.5 m. A wide range of IOPs was considered to cover the conditions encountered in the field. The simulations provide a robust relationship between the computed self-shading and the quantity x = a + bb, where a is the total measured absorption coefficient (i.e., the contributions of pure water, CDOM, algal and non-algal particles) and bb is the total backscattering coefficient (i.e., the contributions of water molecules and particles). The shade-corrected upwelling radiance (Lu corrected) can be expressed as a function of the measured radiance (Lu measured) as: (1) L_u(corrected)=(L_u(measured))/((1-ε)), (2) ε=1-e^(-0.14(a+bb)), where (2) is fitted for solar zenith angles > 45° and bb (which was not measured in the field) was calculated using an empirical relationship from the Malina-cruise dataset (Doxaran et al., 2012 (doi:10.5194/bg-9-3213-2012); Massicotte et al., 2020 (doi:10.5194/essd-13-1561-2021)). Subsurface downward irradiance and upward radiance Ed(0-) and Lu(0-) were estimated with an iterative linear fitting of the log-transformed Ed(z) and Lu(z) vs depth z. Fitting was applied to successively greater depths until the correlation coefficient (r2) exceeded 0.99 or until the layer thickness reached 2.5 m (Bélanger et al., 2017; doi:10.1175/JTECH-D-16-0176.1). Remote Sensing Reflectance (Rrs) was calculated following Mobley (1999; doi:10.1364/AO.38.007442) with: Rrs(λ)=(0.54L_u (0^-,λ))/(E_s(0^+,λ)). To calculate the Rrs we used the R "Cops" package ( (Bélanger 2017: doi:10.1175/JTECH-D-16-0176.1).

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Creator Matsuoka, Atsushi ORCID logo; Juhls, Bennet ORCID logo; Bécu, Guislain ORCID logo; Oziel, Laurent ORCID logo; Leymarie, Edouard; Lizotte, Martine ORCID logo; Ferland, Joannie; Doxaran, David ORCID logo; Maury, Juliette; Babin, Marcel ORCID logo
Publisher PANGAEA
Publication Year 2021
Funding Reference Horizon 2020 Crossref Funder ID 773421 NUNATARYUK, Permafrost thaw and the changing Arctic coast, science for socioeconomic adaptation
Rights Creative Commons Attribution 4.0 International;
OpenAccess true
Resource Type Dataset
Format text/tab-separated-values
Size 856 data points
Discipline Biogeochemistry; Biospheric Sciences; Geosciences; Natural Sciences
Spatial Coverage (-138.135W, 68.264S, -133.031E, 69.649N); Mackenzie Delta, Canada
Temporal Coverage Begin 2019-04-20T15:34:00Z
Temporal Coverage End 2019-09-08T12:00:00Z