Vertical profiles of beam attenuation coefficients in East China Sea

Abstract

The vertical profiles of beam attenuation coefficient (c) can provide information about the distribution and variability of suspended particles in the water column. Vertical profiles of particulate beam attenuation coefficient at 660 nm (c p (660)), Chlorophyll a (chla) and Particulate Organic Carbon(POC) were analyzed to examine patterns and controlling factors of vertical distributions in the East China Sea (ECS), based on two cruises in summer and late autumn. In late autumn, the c p (660) profiles showed uniform distribution with depth in most of shelf regions, and high value of c p (660) was observed in some inshore stations caused by strong resuspension. In summer, c p (660) exhibited weak subsurface maxima phenomenon in outer shelf, while with the well vertical mixed structures in the northern coast areas of ECS. The variability of c p (660) between summer and autumn were mainly influenced by the changes of thermocline distribution in the ECS. In the late autumn, water potential density were characterized as fully vertical mixed, on the contrary, the strong stratifications of water column were observed in summer. Except for several inshore stations with highly influenced by terrestrial input, significant relationships between POC and c P (660) were observed in both late autumn and summer. The close relationship between POC and c p (660) could be an potential application to retrieve the POC profiles from in situ c P (660) measurements, and be applied to the surface POC estimated from space.