SEA WATER TURBIDITY VARIABILITY AND ITS ASSOCIATIONS WITH TIDAL DYNAMICS AND ENVIRONMENTAL CONDITIONS IN THE KOREAN COASTAL ZONE OF THE YELLOW SEA

Abstract

This study investigates the variability of sea surface water turbidity in the coastal region of the Yellow Sea and its relationship with environmental factors. Using spectral analysis, harmonic analysis, wavelet transformation, and multivariate linear regression, we analyzed in situ turbidity measurements to examine the temporal fluctuations and the contributions of tidal currents and atmospheric components. Multivariate linear regression was applied to identify the daily variations in the fractional contributions of tidal currents and atmospheric influences on turbidity. The results indicated that turbidity fluctuations in the Yellow Sea were primarily associated with major tidal harmonics (M2, S2, K1, O1), as well as shallow-water tides (MS4, M4) and semi-diurnal tides (H1, H2). The amplitude of turbidity variations related to shallow-water and semi-diurnal tides was found to be linearly related to tidal variations, with a rate of 0.24 NTU cm？¹, four times greater than the 0.06 NTU cm？¹ rate observed for major tidal components. This suggests that non-linear tidal processes play a significant role in turbidity changes in shallow regions. Additionally, inertial motion in coastal turbidity (19.56 h) was detected during periods of relatively weak external forces. The influence of tidal currents on turbidity fluctuations decreased significantly during typhoon periods due to strong atmospheric influences. High-resolution Sentinel-2 turbidity data from the past 6 years (2018？2023) further revealed more pronounced responses to extreme environmental conditions. Moreover, a detailed investigation of satellite-derived turbidity estimates was conducted to assess the accuracy and reliability of Sentinel-2 data in capturing the spatiotemporal dynamics of turbidity variations. This aspect of the study focused on refining turbidity retrieval algorithms and resolving discrepancies between in situ measurements and satellite observations. The high-resolution Sentinel-2 data provided crucial insights into the large-scale turbidity patterns and variability in the Yellow Sea, particularly during extreme weather events. This study contributes to a deeper understanding of turbidity fluctuations in the Yellow Sea, specifically the interactions between tidal currents and atmospheric conditions. It also emphasizes the importance of satellite-based monitoring tools for assessing turbidity in coastal ecosystems, improving the reliability of turbidity estimates, and offering a valuable resource for future environmental monitoring in the region.