Sea level budget in the China Seas over 2005–2023

The observed fluctuations in regional sea levels on seasonal to decadal timescales can be budgeted as the sum of a manometric (mass-related) component and a steric (density-related) component. We assess the sea level budget (SLB) of the China Seas (the Bohai Sea, Yellow Sea, East China Sea, and South China Sea) for the period 2005–2023, utilizing datasets from satellite observations and ocean objective analysis. Our results demonstrate that the sum of manometric and steric components is generally consistent with the observed sea level variations across seasonal to decadal timescales, indicating a preliminary closure of SLB in the China Seas. On the seasonal timescale, the manometric component dominates sea level change on the continental shelf of the South China Sea, with peaks in winter (December), while the steric component plays a more significant role in other basins, peaking in autumn (September). On the interannual to decadal timescales, the manometric component predominates in influencing sea level change in the shallow seas, while the steric component plays a more significant role in the South China Sea deep basin. Further analysis suggests that the observed positive long-term trend of manometric sea level over shallow seas comes not only from the melting of land ice, but also from the global-warming-induced seawater redistribution from the open ocean to the shallow areas.