Decadal Variation and Regulation Mechanisms of the Suspended Sediment Concentration in the Bohai Sea, China

Abstract

Bohai Sea, with the highest suspended sediment concentration in the world, has experienced a sharp decrease in sea surface suspended sediment concentration (SSSC) in the latest two decades. However, limited by the shortage of long‐term field observations, the spatiotemporal characteristics and mechanisms of the long‐term variation in the SSSC are still unclear. Based on remote sensing data, this study reconstructed the spatiotemporal SSSC distribution from 2003 to 2016, and found significant spatial difference in decadal SSSC variation in the Bohai Sea. The largest decadal SSSC decrease was observed in the southern Bohai Sea with an average annual decrease of 1.3 mg/L (decrease of 4.4% per year), while significant SSSC increase was observed in the central Bohai Sea with largest annual increase of 0.4 mg/L (increase of 5.0% per year). Significant seasonal differences in the SSSC decreasing were also revealed, and the SSSC decrease in winter and spring (0.46 mg/L/a) was 27.8% higher than that in summer and autumn (0.36 mg/L/a). Decadal wind speed data measured at 14 meteorological stations around the Bohai Sea indicated that wind speed reduction played the most important role in the decadal decrease in SSSCs, and significant SSSC decrease can only be found in sea areas with a significantly reduced wind speed. In addition, although the runoff and sediment discharge of the Yellow River also decreased during 2003–2016, they were not related to the spatiotemporal variation of SSSCs and their direct impact was limited to the range of 15 km from the estuary.

Multiple Timescale Variations in Water Transparency in the Eastern China Seas over the Period 1997–2019

“…According to the fifth generation reanalysis products, the wind speed of the BS shows a significant declining trend over the study period (Figure 14b), resulting in a significant TSM decrease in the three bays (Figure 14d). Our results are consistent with those of Zhou et al (2017) and Zhao et al (2022). Owing to the empirical relationship between Z sd and b bp (555) in the BS (Figures 8 and 9a), we can conclude that the weakening of the wind speed plays a key role in the positive Z sd trends in the three bays of the BS.…”

“…(2017) and Zhao et al. (2022). Owing to the empirical relationship between Z sd and b bp (555) in the BS (Figures 8 and 9a), we can conclude that the weakening of the wind speed plays a key role in the positive Z sd trends in the three bays of the BS.…”

“…Zhao et al. (2022) found that wind speed reduction is the main factor leading to the linear decline in TSM (2003–2014) for the Laizhou Bay, Bohai Bay, and Liaodong Bay, and the proportion of plankton in TSM in the three bays is negligible. According to the fifth generation reanalysis products, the wind speed of the BS shows a significant declining trend over the study period (Figure 14b), resulting in a significant TSM decrease in the three bays (Figure 14d).…”

Drivers of suspended sediment dynamics along the shorelines of the Yellow River Delta detected from satellite data

“…Even along Section 4, just in front of the river mouth, there was a poor relationship between TSS and YSD (Tables 2 and 3). Zhao et al (2022) mentioned that the Yellow River run‐off mainly influences TSS within the estuarine zone, and seldom changes of sediment concentration has been delivered into the Bohai sea. Approximately 90% of the sediment input deposits in the subaqueous delta region nearby the river mouth (Bi et al, 2010; Wang et al, 2007).…”

“…Seasonal variability of TSS in Bohai Sea is caused by monsoons, with TSS about three to 10 times higher in the cold season (Bi et al, 2011). Wind speed reduction also played an important role in the TSS decrease in the Bohai sea (Zhao et al, 2022). Although many studies have explored the processes that drive TSS in the YRD, few have provided a detailed analysis of TSS dynamics along the shoreline.…”