Data-Driven Enhancement of Ocean Surface Forcing for Accurate Floating Debris Transport Modelling in the East/Japan Sea

Abstract. The accumulation of floating debris is a growing concern in marginal seas. This study presents the largest surface drifter experiment conducted to date in the East/Japan Sea, utilizing 33 GPS-tracked drifters to calibrate particle tracking models. Deployed off the Korean coast in late fall 2021, the drifters revealed a clear transport conduit to the Japanese coastline, with beaching occurring after an average of 37 to 50 days. We systematically evaluated model performance driven by combinations of geostrophic currents, Ekman currents, Stokes drift, and windage using MAE and NCLS metrics. The results indicate that near-surface debris is best modelled by combining geostrophic currents, Stokes drift, and windage, whereas deeper debris (2-m depth) requires the additional inclusion of Ekman currents. These optimized forcing combinations were found to outperform global circulation models such as HYCOM and CMEMS. Furthermore, seasonal experiments revealed that strong winter winds accelerate eastward transport and beaching along the Japanese coast, while weaker summer winds allow mesoscale eddies to broaden dispersion zones across both Korean and Japanese coastlines. Validated by this extensive dataset, these findings enable more accurate tracking of floating debris in similar basins.