The absorption coefficient of chromophoric dissolved organic matter (CDOM) is a major variable used in developing robust bio‐optical models and understanding biogeochemical processes. Over the last decade, the
optical properties of CDOM in the open sea have been intensely studied. However, their variations in clear water are poorly documented, particularly in the Red Sea, owing to the absence of
in situ measurements. We performed several cruises in the Red Sea to investigate the
spatial distribution of the absorption coefficient of CDOM. The
spectral absorption coefficients were determined from 400 nm to 740 nm using a WETLabs ac-s hyper-spectral
spectrophotometer. In general, we found a
latitudinal gradient in the CDOM absorption coefficient at 443 nm (a
CDOM(443)) from south to north that is likely influenced by the exchange of water through the strait of Bab-el-Mandeb and the
thermohaline circulation of the Red Sea. However, high a
CDOM(443) values were observed in the northern Red Sea due to the existence of a sub-mesoscale feature that may induce an increase in
phytoplankton production and lead to CDOM production. The a
CDOM(443) covaried with the
chlorophyll a concentration ([Chl a],) despite a high scatter. Furthermore, the a
CDOM(443) for a given [Chl a] concentration was higher than those predicted by
global ocean bio-optical models. This study advances our understanding of CDOM concentration in the Red Sea and may help improve the accuracy of the algorithms used to obtain CDOM absorption from
ocean color.