Estimating dissolved organic carbon inventories in the East China Sea using remote-sensing data

The coastal ocean is characterized by a high dissolved organic carbon (DOC) concentration due to large terrestrial inputs and high primary production. Monitoring the dynamic variation of DOC inventories in coastal oceans provide more information on carbon flux, but is very challenging in practice. We propose a method of estimating DOC inventories in the East China Sea (ECS) by integrating the surface DOC distribution with a vertical model of the DOC profile via satellite data. Surface DOC concentration was retrieved from satellite-derived chromophoric dissolved organic matter and chlorophyll concentration. Two vertical DOC profile models (uniform model and stratified model) were established based on water-density profiles, and the usage of these two models was corresponded to water mass classification determined by a water mass index. The average bias of the satellite-derived DOC inventory, in the euphotic layer was 23.8% in spring, 24.8% in autumn and 14.7% in winter, and in the water column was 15.6% in spring, 12.3% in autumn, and 10.2% in winter. The total satellite-derived DOC inventory integrated in the water column was about 31.84, 31.96, 28.59, and 31.18 Tg in four seasons in the ECS (5.84 x 10(5) km(2)). Sensitivity analysis indicated that the remote-sensing method of estimating DOC inventory is stable and reliable. The available long-term and large-scale satellite-derived DOC inventories in marginal sea would provide us basic information on carbon cycle, and the difference between the seasonal DOC inventories would help to understand the DOC export and relative biogeochemical processes in the ECS.