AUTHOR=Rasse Rafael , Dall'Olmo Giorgio , Graff Jason , Westberry Toby K. , van Dongen-Vogels Virginie , Behrenfeld Michael J. 

TITLE=Evaluating Optical Proxies of Particulate Organic Carbon across the Surface Atlantic Ocean

JOURNAL=Frontiers in Marine Science

VOLUME=4

YEAR=2017

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2017.00367

DOI=10.3389/fmars.2017.00367

ISSN=2296-7745

ABSTRACT=<p>Empirical relationships between particulate organic carbon (POC) and inherent optical properties (IOPs) are required for estimating POC from ocean-color remote sensing and autonomous platforms. The main relationships studied are those between POC and particulate attenuation (<italic>c</italic><sub><italic>p</italic></sub>) and backscattering (<italic>b</italic><sub><italic>bp</italic></sub>) coefficients. The parameters of these relationships can however differ considerably due to differences in the methodologies applied for measuring IOPs and POC as well as variations in particle characteristics. Therefore, it is important to assess existing relationships and explore new optical proxies of POC. In this study, we evaluated empirical relationships between surface POC and IOPs (<italic>c</italic><sub><italic>p</italic></sub>, <italic>b</italic><sub><italic>bp</italic></sub> and the particulate absorption coefficient, <italic>a</italic><sub><italic>p</italic></sub>) using an extensive dataset collected during two Atlantic Meridional Transect (AMT 19 and 22) cruises spanning a wide range of oceanographic regimes. IOPs and POC were measured during the two cruises using consistent methodologies. To independently assess the accuracy of the POC-IOPs relationships, we predicted surface POC for AMT-22 using relationships developed based on independent data from AMT-19. We found typical biases in predicting POC ranging between 2–3, 4–9, and 6–13% for <italic>c</italic><sub><italic>p</italic></sub>, <italic>b</italic><sub><italic>bp</italic></sub>, and <italic>a</italic><sub><italic>p</italic></sub>, respectively, and typical random uncertainties of 20–30%. We conclude that (1) accurate POC-<italic>c</italic><sub><italic>p</italic></sub> and POC-<italic>b</italic><sub><italic>bp</italic></sub> relationships were obtained due to the consistent methodologies used to estimate POC and IOPs and (2) <italic>a</italic><sub><italic>p</italic></sub> could be considered as an alternative optical proxy for POC in open-ocean waters, only if all physiological variability in the POC:<italic>chl</italic> ratio could be modeled and used to correct <italic>a</italic><sub><italic>p</italic></sub>.</p>