Projected Changes in Extreme Sea Level and Sea‐Level Distribution in the China Marginal Seas Using Dynamical Downscaling

Abstract

Future global and regional mean sea level (MSL) changes have been widely quantified, yet projections of extreme sea level (ESL) remain limited, despite their substantial environmental and socioeconomic risks to densely populated coastal regions such as the marginal seas near China. Here, we use a high‐resolution (∼8 km) regional ocean model to project sea‐level changes over the marginal seas near China, resolving shallow‐shelf dynamics and enabling process‐based attribution of dynamic ESL changes. The model is forced by a coupled climate model for historical (1985–2005) and future (2080–2100) periods under a high‐emission scenario. Evaluation against tide‐gauge records shows that the model reasonably reproduces observed dynamic sea level (DSL) variability, distributional characteristics and extremes. The projections show that local time‐mean DSL change dominates the increase in extreme high sea level (EHSL), primarily through a shift in the sea‐level distribution. The distribution shape is projected to become increasingly asymmetric, which further enhances EHSL but plays a dominant role in weakening extreme low sea‐level (ELSL) events. Perturbation experiments using decomposed atmospheric forcing reveal that changes in high‐frequency forcing, from daily to intraseasonal timescales, dominate the evolution of distribution‐shape changes. In the Bohai Sea and Yellow Sea, strengthened high‐frequency southerly winds and weakened northerly winds enhance EHSL and weaken ELSL relative to MSL, producing increased skewness and reduced kurtosis. These results highlight the critical role of high‐frequency atmospheric variability in shaping future sea‐level distributions and underscore the importance of accurately representing such variability in climate projections of coastal sea‐level risk.