Abstract Record‐breaking flooding occurred in the Bohai Sea on 21 October 2024. During this event, coastal sea levels along the Bohai Sea abruptly rose by more than 2.0 m under calm weather conditions, inundating several densely populated coastal communities. Hydrodynamics and associated tempo‐spatial variability in the Bohai Sea during this severe flooding are examined using a nested‐grid ocean circulation model. Analyses of model results reveal that this severe coastal flooding resulted from three major drivers: (a) remotely generated coastal trapped waves (CTWs), (b) large spring tides, and (c) positive sea surface elevations associated with the large‐scale ocean circulation over the northwestern Pacific Ocean. These CTWs are generated by atmospheric forcing over remote regions including the Yellow Sea, Korea Strait, and Sea of Japan and propagate into the Bohai Sea with propagation speeds of ∼28.9 m s −1 over the Korean west shelf and ∼24.4 m s −1 around the Bohai Sea. The remotely generated CTWs account for ∼30% of the peak sea‐level rise during the flooding event. The Complex Empirical Orthogonal Function analysis reveals that these CTWs are dominated by the double Kelvin waves, with noticeable contributions from low‐mode shelf waves. Our findings demonstrate that the role of non‐local atmospheric forcing could not be ignored for operational forecasting of the Bohai Sea and other semi‐enclosed coastal waters.
Yang et al. (2026) studied this question.