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

Abstract

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.

Effects of spatial bottom friction parameterization scheme on the tidal dynamics in the macrotidal East China Seas

“…The SH number has been tested by field observations and the databases of temperature and salinity profiles which determined the positions of fronts in the shelf seas (Garrett et al, 1978;Lie, 1989;Glorioso and Flather, 1995;Kobayashi et al, 2006). Du et al (2022) used a 10-year dataset of satellite-derived suspended sediment concentrations to identify the spatiotemporal variations in suspended sediment fronts on the inner shelf of the East China Seas. They found that the local high-value and low-value SH regions corresponded to the local low-value and high-value frontal probability regions, respectively.…”

Multiscale Spatio‐Temporal Variations of Suspended Sediment Fronts in the Semi‐Enclosed Bohai Sea, China

“…Zhai et al (2021) found that the interannual anomaly of Chlorophyll-a concentration in the Bohai Sea had a significant negative correlation with the ENSO index, although the correlation between the two was slightly weaker than that with the Pacific decadal oscillation index. The effects of ENSO on global well-known estuarine and offshore SSCs and SSFs have also been generally investigated (Du et al, 2022;Nagy et al, 2008;Romero-Rodriguez et al, 2020;Saldias et al, 2016). The occurrence of ENSO events could explain the significant anomalous fluctuation of FP in some years in most regions except the North Yellow Sea.…”

“…Over the past 20 years, spatio‐temporal variations of suspended sediment fronts (SSFs) have gained increasing attention globally (Du et al., 2022; Framinan & Brown, 1996; Hu et al., 2016; Nagy et al., 2008; Y. Zhou et al., 2020). SSF often forms in estuaries, coasts, and shallow shelf seas with sufficient sediment sources and drastic changes in dynamic environments, separating water masses with significant turbidity differences.…”

“…In the Río La Plata Estuary system, for instance, seasonal, and interannual variability of the turbidity fronts is mainly due to the seasonality of runoff and wind field characteristics superimposed on interannual dynamics associated with El Niño‐Southern Oscillation (ENSO) (Framinan & Brown, 1996; Nagy et al., 2008). The combined effects of bottom topography and tidal dynamics were also suggested as the dominant factors for the formation of SSFs in many estuarine and coastal areas (Du et al., 2022; Hu et al., 2016; H. Yang et al., 2016).…”

“…Hafeez et al (2021) used the SSC data derived from Himawari-8 with a temporal resolution of 15 min to track the diurnal variation of turbidity fronts. For long-term monitoring, Du et al (2022) extracted the seasonal and interannual variability in the SSFs along the Zhejiang-Fujian coast using GOCI data over 10 years and identified multiple influencing factors. The coupling of SSF with multi-source satellite fronts and numerical modeling has also received attention.…”