Seasonal and yearly variations of optical and environmental properties using in situ and remotely sensed data in the East China Sea

Abstract

Intricate and striking patterns of suspended sediments created by a complex interplay of physical, chemical, and geological processes in the East China Sea (ECS) and southern Yellow Sea (YS) have been investigated using in situ measurements and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data. For this study about 200 water samples were collected in the ECS and YS during 1998 to 2007, we analyzed the concentrations and absorption coefficients of sea water constituents such as phytoplankton, Suspended Sediment (SS) and Dissolved Organic Matter (DOM). The concentration ranges of surface chlorophyll and SS showed the 0.10 - 4.38 mg/m3 and 0.12 - 24 g/m3, respectively. Phytoplankton exhibited pronounced absorption features at 440nm, 465nm and 675nm. Some cases had the absorption features at 550 nm. Absorption coefficient values of phytoplankton at 443nm are appeared ranged of 0.02 to 0.11 m-1. The structure of SS patterns by the remotely sensed data can reveal a great deal about the processes underlying their formation. A careful analysis of these patterns in conjugation with other data gave birth to the definition of the evolution of SS into four stages: activation, younger, mature and extinction. Each of these stages experiences the different characteristics of waters and numerous physical mechanisms that control pattern formation during the winter monsoon. In situ data related to vertical and horizontal profiles of SS concentration and particle size distributions had good potential in predicting and confirming the evolution of the younger stage. The most significant result inferred from these profiles was that the high density sediment plume appeared to be propagating from the southwest coastal sea of Korea to the southern YS, leading to eventual collision with the massive plume originating from the Yangtze banks of the ECS. The SS plume, which was analysed by SeaWiFS, of Yangtze river after 2003 was abruptly decreased.