Estimation of Lateral DOC Transport in Marginal Sea Based on Remote Sensing and Numerical Simulation

Abstract

Due to high temporal and spatial dynamics and complex biological processes, it is difficult to estimate lateral transportations of the dissolved organic carbon (DOC) in marginal seas by conventional field observations and model simulations. Taking the East China Sea (ECS), for example, this study proposed a novel model for estimating the lateral DOC flux in marginal sea. Three-dimensional distributions of DOC concentrations were retrieved by satellite remote sensing. Furthermore, three-dimensional currents were simulated using the numerical model. Finally, the lateral DOC flux in the whole ECS was estimated based on the satellite-derived DOC concentrations and the simulated currents. The results showed that despite seasonal variations, the unit area lateral DOC flux remained high throughout the year in the Changjiang River estuary, Zhejiang-Fujian Coast, Taiwan Strait, and Kuroshio regions. There were three eastward transportation channels which were strong in summer half year and weak in winter half year. Moreover, a northward transport zone extending from north of Taiwan to the south of the Changjiang River estuary was detected. In terms of annually net flux, highest net DOC import (30.65 TgC yr−1) was from the Taiwan Strait, mainly through the eastern side of the strait. The second highest net DOC import (18.75 TgC yr−1) was from the shelf slope (200 m isobath), mainly through the south part of the slope between 26°N and 26.5°N. Most of the net DOC export (−52.75 TgC yr−1) from the ECS was observed through the northern boundary (32°N), particularly in the outer shelf with water depth of 100–200 m.