1073 / 2024-09-20 09:13:21

Multi-temporal and spatial scale variations of oceanic fronts along the coast of Zhejiang and Fujian and their environmental effects

oceanic fronts,temporal and spatial scale,environmental effects,observation,CTD

Oceanic fronts are common phenomena in marine environments and play a crucial role in the evolution of the ocean environment and the maintenance of ecosystems. This study focuses on the typical development of oceanic fronts along the Zhejiang-Fujian coast. By utilizing hydrological, hydrodynamic, suspended sediment, and chlorophyll data obtained from in-situ large-scale and continuous observation stations, along with remote sensing imagery, wind field data, and tidal levels, the fundamental characteristics and variability of the fronts across multiple temporal and spatial scales were thoroughly investigated.

The findings reveal that the oceanic front along the Zhejiang-Fujian coast is a quasi-stationary, periodic front. At the seasonal scale, the development and spatial variability of the front are highly pronounced, with the front being most developed in winter, weaker in spring and autumn, and not developing in summer due to significant stratification of the water column, though a clear thermocline is observed. At the tidal cycle scale, the front is influenced by tidal ebb and flow, exhibiting diurnal periodic oscillations and is typically most developed during low-tide phases. This is when the interaction between the Zhejiang-Fujian Coastal Current and the Taiwan Warm Current is most pronounced. During low tide, the controlling depth of the front can reach 50 meters. The spatial extent and intensity of the front are influenced by wind fields, particularly the extent of northerly winds in winter.

The development of oceanic fronts along the Zhejiang-Fujian coast significantly impacts the vertical distribution and transport of suspended sediments and chlorophyll, as well as cross-frontal transport processes. As convergence zones for water masses, oceanic fronts facilitate the accumulation of suspended particles such as sediments and chlorophyll, although there are differences in the behavior of suspended matter depending on particle size. With the periodic formation and dissipation of the front over tidal cycles, the concentration of suspended particles and chlorophyll in the region also exhibits cyclical movements. These results contribute to a better understanding of the processes and mechanisms driving regional oceanic environmental changes and help to identify the role of frontogenesis in material transport in marginal seas.