Yangjiang is situated in southwestern Guangdong Province, China, adjacent to the Pearl River Delta (PRD). It acts as a vital coastal corridor for material exchange among the PRD, the eastern Guangdong coast, and Hainan Island, and represents a core economic belt of western Guangdong. Over the past few decades, the rapid construction of offshore wind farms and marine ranches across the coastal and shelf waters off Yangjiang has generated an urgent demand to clarify how extreme weather events alter coastal and shelf hydrodynamic and sediment dynamics, providing theoretical and practical guidance for the construction and maintenance of marine infrastructures. In this study, a fully coupled ocean circulation-wave-sediment transport modeling system was used to explore the hydrodynamic and sediment transport processes triggered by four representative typhoons featuring different tracks and intensities within the study area. The results indicate that all typhoons generated intense currents and waves, broke down water-column stratification, and elevated bed shear stress as well as bottom sediment resuspension - except for the typhoon whose track passed to the right of the study domain. Storm waves dominated the generation of bed shear stress and sediment resuspension in both nearshore zones and the continental shelf, with the exception of the typhoon that traversed the study area directly. Although typhoon forcing acts on the study area for less than 5
The radial sand ridge system in the South Yellow Sea, the world’s largest tide-dominated sand ridge system, features tidal channels and sand ridges that are key geomorphic units for understanding tidal-current dynamics and geomorphic evolution. Previous studies have relied mainly on satellite remote sensing and numerical modeling, whereas in-situ observations remain limited owing to the complex hydrodynamics and topography. Focusing on Tiaozini, located in the inner margin of the system, we integrate time-series satellite imagery, topographic surveys, in-situ hydrodynamic observations, and sediment grain-size analysis to examine the evolutionary trend of the major tidal channels from 2020 to 2025, and to reconstruct in detail the morphological evolution during the 2022–2023 reorganization and analyze its underlying driving mechanisms. The main conclusions are as follows: (1) Over 2020–2025, the tidal channels exhibited an overall landward migration, with the most significant morphological adjustments occurring during 2022–2023: the Xidagang channel shrank, while a newly formed channel captured and reorganized the tidal channels in the middle segment. Cross-sectional results show that four tidal channels underwent lateral migration of up to 2 km, with a maximum incision depth of 2.8 m. (2) Tidal-channel evolution is largely controlled by local hydrodynamics. Flood-tide dominance under tidal asymmetry, coupled with strong tidal currents during flood phases, may serve as an important driver of the landward migration of tidal channels. The sandbar formed by the breaching of the tidal flat between Xidagang and Dongdagang is likely a key cause of the tidal-channel reorganization during 2022–2023. (3) Surface sediments are dominated by sand and silt with low cohesiveness, which facilitates lateral migration. Decreasing proportions of fine-grained end-members indicate enhanced hydrodynamic conditions, whereas coarse-grained end-members reflect higher-energy environments. This study documents the recent evolution and driving mechanisms of tidal channels in Tiaozini, providing a scientific basis for the sustainable management of tidal-flat resources.
In this study, we reconstructed the late Pleistocene seawater temperatures using hydroxylated isoprenoid and isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) of bulk sediments from core 19ESDP-101 in the Hupo Trough of the southwestern East Sea (Japan Sea). Two temperature proxies (TEX₈₆L and RI-OH′) were compared, alongside GDGTs-derived indices (BIT, IIIa/IIa,
This study evaluates seawater intrusion (SWI) in the sandy unconfined coastal aquifer of Pehuen Có (Buenos Aires Province, Argentina) through the integration of hydrodynamic analysis and vertical electrical soundings (VES). The objective was to characterize the geometry of the freshwater–saltwater interface and identify mechanisms controlling salinization in a low-exploitation coastal system. Hydraulic gradients indicate active groundwater discharge toward the sea under present conditions. The Ghyben–Herzberg relation predicts interface depths of about − 80 m at the beach front relative to mean sea level. However, geoelectrical data suggest that the main saline wedge is located between − 90 and − 140 m and is preferentially hosted in lower-permeability units underlying the sandy aquifer, highlighting the influence of stratigraphic heterogeneity on intrusion geometry. Additionally, a shallow salinization process (0–11 m depth) was identified in the beach sector. The observed resistivity patterns are consistent with a tide-influenced salinization process linked to the flooding of semipermeable Holocene marine deposits exposed in the intertidal zone, which may temporarily retain saline water and promote localized vertical mixing. Similar processes have been described in the literature under different conceptual frameworks, and are here inferred for the first time in the study area. Under sea-level rise scenarios, increased tidal inundation may intensify shallow salinization and modify vertical salinity distribution. The proposed conceptual model provides a useful framework for supporting groundwater management and coastal conservation strategies in similar sandy coastal environments, while acknowledging the limitations associated with the absence of independent validation of salinity distribution.
Coastal seas are critical interfaces where sediment transport, hydrodynamic processes, and biological productivity interact. Understanding the spatially heterogeneous drivers of phytoplankton dynamics in such systems is essential for deciphering coastal environmental evolution and mitigating ecological disasters. Using satellite-derived sea surface Chlorophyll-a (Chl-a) concentration data and multi-source environmental data from January 2003 to December 2022, we employed an integrated machine learning approach to investigate the spatiotemporal patterns and environmental controls of sea surface Chl-a concentrations in the waters off the Shandong Peninsula, China. By combining Empirical Orthogonal Function (EOF) analysis, K-means clustering, Random Forest (RF) modeling, and Shapley Additive Explanations (SHAP), we objectively delineated five subregions with distinct seasonal Chl-a patterns. These subregions exhibited contrasting phenology: summer high values occurred in the nearshore bays and the adjacent Bohai Sea (Subregion 1, 4, and 5), whereas autumn-winter and winter-spring high values characterized the eastern coastal current zone (Subregion 2) and the offshore Yellow Sea (Subregion 3), respectively. SHAP analysis revealed that the influence of sea surface temperature (SST), suspended sediment concentration (SSC, a proxy for sediment resuspension and light availability), and mixed layer depth (MLD) varied substantially across subregions—in both magnitude and direction. Furthermore, subregion-specific nonlinear thresholds were identified for these drivers, indicating shifts in dominant limiting factors (e.g., from nutrient to light limitation with increasing SSC). These findings provide quantitative insights into the linkages between sediment dynamics and coastal biogeochemical responses, with implications for understanding eutrophication events, harmful algal blooms, and sedimentary environmental evolution under changing hydroclimatic conditions.
