Evaluation of the CDOM Absorption Coefficient in the Arctic Seas Based on Sentinel-3 OLCI Data

Dmitry Glukhovets,Svetlana Vazyulya,Polina Karalli,Inna Sahling,Anna Yushmanova,Sergey Sheberstov,Oleg Kopelevich

doi:10.3390/rs12193210

Abstract

Our work’s primary goal is to reveal the problematic issues related to estimates of the colored organic matter absorption coefficient in the northern seas from data of the Ocean and Land Color Instrument (OLCI) installed on the Sentinel-3 satellites, e.g., a comparison of the OLCI standard error assessment ADG443_NN_err relating to the measurement and the retrieval of the geophysical products and the uncertainties in the northern seas’ real situation. The natural conditions are incredibly unfavorable there, mainly due to frequent cloudiness and low sun heights. We conducted a comprehensive multi-sensor study of the uncertainties using various approaches. We directly compared the data from satellites (OLCI Sentinel-3 and four other ocean color sensors) and field measurements in five sea expeditions (2016–2019) using the different processing algorithms. Our analysis has shown that the final product’s real uncertainties are significantly (≥100%) higher than the calculated errors of the ADG443_NN_err (~10%). The main reason is the unsatisfactory atmospheric correction. We present the analysis of the various influential factors (satellite sensors, processing algorithms, and other parameters) and formulate future work goals.

Highlights

The content of our study is an analysis of problematic issues related to estimates of the absorption coefficient of colored dissolved organic matter (CDOM) in the northern seas from data of the Ocean and Land Color Instrument (OLCI) on the Sentinel-3 satellites
Three factors determine the importance of the problem: firstly, a subject of our research, the CDOM absorption coefficient, which is usually the essential part of the seawater absorption of solar radiation in the visible range; secondly, the area of our study, the Arctic Basin, the region where global warming is most pronounced; third, OLCI, a new generation of ocean color scanners designed to replace well-known devices such as MEdium Resolution Imaging Spectrometer (MERIS) and Moderate Resolution Imaging Spectroradiometer (MODIS)
We compare them with the data of direct measurements of the absorption coefficient by the ICAM device ag_icam (Section 2.2)

Summary

Introduction

The content of our study is an analysis of problematic issues related to estimates of the absorption coefficient of colored dissolved organic matter (CDOM) in the northern seas from data of the Ocean and Land Color Instrument (OLCI) on the Sentinel-3 satellites. Three factors determine the importance of the problem: firstly, a subject of our research, the CDOM absorption coefficient, which is usually the essential part of the seawater absorption of solar radiation in the visible range; secondly, the area of our study, the Arctic Basin, the region where global warming is most pronounced; third, OLCI, a new generation of ocean color scanners designed to replace well-known devices such as MEdium Resolution Imaging Spectrometer (MERIS) and Moderate Resolution Imaging Spectroradiometer (MODIS). We have to consider the CDOM absorption when calculating the visible solar radiation entering the water column in a wavelength range of 400–700 nm, called photosynthetically available radiation (PAR), a fundamental factor for ocean primary bio-productivity. The visible radiation entering the water column contributes to the ocean heat budget [5], determines underwater visibility, and practical use of various equipment for activity, studying, and monitoring of the marine environment

Results

Discussion

Conclusion