Spatio‐Temporal Variability of Suspended Sediment Fronts (SSFs) on the Inner Shelf of the East China Sea: The Contribution of Multiple Factors

• Published in: Journal of geophysical research. Oceans 2022-09, Vol.127 (9), p.n/a
• Main Authors: Du, Yunfei, Zhang, Jicai, Wei, Zilu, Yin, Wenbin, Wu, Hui, Yuan, Yeping, Wang, Ya Ping
• Format: Article
• Language: English
• Subjects: Algorithms; Archipelagoes; Bottom topography; Coastal currents; Coastal zone; Datasets; East China Sea; Edge detection; El Nino; El Nino phenomena; Estuaries; Fisheries; Frontogenesis; Fronts; Geophysics; GOCI; Identification; Image processing; Interannual variability; Intrusion; Isobaths; Marine pollution; Ocean circulation; Ocean color; Ocean colour; Offshore; Orthogonal functions; Physiographic features; Pollutants; Pollution dispersion; Pollution transport; Probability theory; Resuspension; River discharge; River flow; Rivers; Sea pollution; Seasonal variability; Seasonal variations; Sediment concentration; Sediment transport; Sediments; Shelving; Southern Oscillation; Stratification; Subsurface water; suspended sediment fronts; Suspended sediments; Temporal variability; Temporal variations; tide; Topography; Upwelling; Variability; Water discharge; Wind; Winds
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1029/2021JC018392

Modulated by a host of complex processes, suspended sediment fronts (SSFs) on the inner shelf of the East China Sea persist strongly and vary notably. Using hourly suspended sediment concentration data collected by the Geostationary Ocean Color Imager over the period 2011–2021, a gradient‐based edge detection algorithm was implemented to extract SSFs; the frontal probability (FP) and seasonal and interannual variability were identified and interpreted. Pronounced frontal activity is principally confined to the nearshore waters within the 60‐m isobaths and decreases with increasing offshore distance. Frontogenesis is mainly determined by the bottom topography and tide‐induced mixing. Empirical orthogonal function decompositions reveal that the seasonal cycle dominates the variability of SSFs, which responds to the cycles of winds and related changes in coastal currents and upwelling. The highest FPs are identified in winter when wind‐induced suspended sediment transport and resuspension reach their annual maxima. In summer, stratification and the intrusion of Kuroshio subsurface water are not conducive to frontogenesis. Furthermore, the discharge of the Yangtze River has a certain influence on the frontal variability in the waters around the Zhoushan Archipelago. Notably, the interannual variability of SSFs is modulated by the El Niño‐Southern Oscillation. These findings, based on a comprehensive dataset of SSFs over 10 years, can usefully inform the studies of marine pollutant transport, sedimentary dynamics, fisheries, and wider ecological processes in the study area. Plain Language Summary Suspended sediment fronts (SSFs) are a common and influential phenomenon in major estuaries and coastal areas of the world, and are of great significance for oceanic material transport and biological productivity. For this study, a 10‐year dataset of satellite‐derived suspended sediment concentrations was used to identify the spatiotemporal variations in SSFs on the inner shelf of the East China Sea. The mean distribution of SSFs is consistent with the bottom topography, and most fronts do not extend offshore across the 60‐m isobath. Frontogenesis is controlled primarily by topographic features and tide‐induced mixing. The noticeable seasonal variability of frontal activity can be attributed to the changes in wind forcing and wind‐related processes. Local differences in frontal displacement can be associated with stratification, the intrusion of Kuroshio subsurface wat