Drivers of Sea Level Variability in the Yellow Sea and East Sea (1993–2021): A 29-Year Decomposition Using Satellite Altimetry and Reanalysis Data

Understanding and monitoring regional sea level (SL) variability in semi-enclosed marginal seas such as the Yellow Sea (YS) and East Sea (ES) are essential for climate impact assessment, coastal risk management, and regional model validation. This study presents a 29-year (1993–2021) observational analysis of SL and sea level differences (SLDs) around the Korean Peninsula, primarily based on gridded satellite altimetry and complemented by atmospheric and ocean reanalysis datasets. We implemented a reproducible decomposition framework that partitions satellite-derived monthly SL variations into two primary components: a local steric term driven by surface net heat flux, and a residual term representing lateral oceanic transport and other dynamic effects. Results derived from absolute dynamic topography (ADT) climatology revealed pronounced seasonal variability in SLDs between the YS and ES, with peaks in September and a minimum in December. In September, lateral transport contributed to SL increases of approximately 2.1 cm in the YS and 2.8 cm in the ES, whereas in December, atmospheric cooling and enhanced eastward wind stress dominated SL decline in the ES, accompanied by transport-related SL reduction observed in the YS. Furthermore, the relationship between monthly mean SL and inferred volume transport through the Korea, Tsugaru, and Soya Straits revealed region-specific correlations that highlight the spatial complexity of marginal sea dynamics. By integrating multiple freely available datasets and emphasizing seasonal-to-interannual climatology, this study provides a transparent and transferable framework for decomposing sea level variability in the Northwest Pacific.