The proportions and variations of the light absorption coefficients of major ocean color components in the East China Sea

The East China Sea (ECS), one of the largest continental seas, has dynamic hydrology and complex optical characteristics that make ocean color remote-sensing retrieval difficult. The distributions and proportions of the light absorption coefficients of major ocean color components based on two large-scale investigations in the ECS are presented, showing these features in typical summer and winter seasons. The absorption coefficient a_CDOM, a_NAP and a_phy of colored dissolved organic matter, non-algal particle, and pigment of phytoplankton show a decreasing trend from the coast to the outer shelf. According to the a_CDOM distribution at 440 nm, the Changjiang River plume shows an abnormal southeastward transport. An extremely high a_NAP value patch at 440 nm is present in the middle coast. The chlorophyll-a-specific phytoplankton pigment absorption (a_phy^*) is much higher in winter than in summer, which may cause serious underestimated results when applying the averaged a_phy^* into remote-sensing algorithms for chlorophyll concentration retrieval. The importance of phytoplankton size was evident in outer shelf waters. The absorption of a_CDOM(440) is a dominant component accounting for over half of the total seawater absorption in summer. The a_NAP(440) accounts for 64% of the absorption of the ECS coastal area in winter.