Detection and Dispersion of Small-Scale Oil Spills in Pristine Coastal Waters Using Sentinel-2 Satellite Imagery: A Case Study From Jeju Island

Small-scale oil spills can exert substantial ecological impacts on pristine coastal environments, even when the discharged volume is relatively limited. This study investigates a diesel oil spill that occurred on 4 July 2022 along the coast of Jeju Island, Korea, following a fire on moored fishing vessels. Using high-resolution Sentinel-2 optical imagery, we developed a remote sensing-based framework to detect, quantify, and analyze the dispersion of the oil spill. Nonocean pixels, including land, ships, and clouds, were first removed through spectral thresholding. A spectral unmixing algorithm was then applied to extract endmembers representing oil and seawater. The spectral angle mapper method was used to delineate the spatial extent of the spill and a two-beam interference model was employed to estimate oil thickness and total volume. The resulting oil-covered area and volume estimates showed reasonable consistency with reported values. A particularly notable observation was the bifurcation of the oil slick into two distinct branches after exiting the harbor. Hydrodynamic simulations, combined with near-surface wind data, revealed a strong temporal correlation between surface current direction and oil advection, with statistical significance. In addition, bathymetric analysis derived from Sentinel-2 imagery identified two small seamounts near the harbor outlet, which contributed to the divergence of the oil’s trajectory. This study demonstrates the utility of high-resolution optical satellite data for detecting thin oil sheens and highlights the combined influence of wind, surface currents, and local bathymetry on oil dispersion dynamics in shallow, environmentally sensitive coastal waters.