Evaluation of the sea-level rise in the northwestern Pacific marginal seas

Because regional sea level rise can threaten coastal communities, understanding and quantifying the underlying process contributing to regional sea level budget are essential. In this study, we assessed whether regional sea level rise budget on the northwestern Pacific marginal seas (including the Yellow and East China Seas, South China Sea, and East/Japan Sea) can be closed with a combination of observations and ocean reanalyses over 1993–2017 but also with independent observations from in situ profiles including Argo floats and satellite gravity measurements since 2003. The sum of estimated components is comparable to the geocentric sea level rise for all marginal seas, representing the major contributions from land ice melt and sterodynamic components. While the mass loss of land ice accounts for a large fraction of the observed trend, the spatial trend and its interannual variability are dominated by the sterodynamic processes. The observation-based estimate further shows that along the continental shelves, the sterodynamic sea levels are substantially induced by ocean mass redistribution due to changes in ocean circulation. In contrast, local steric sea level contributes to the sum differently in spatial patterns, with stronger steric sea level rise in the deep water regions than the surrounding continental shelf regions. This result highlights the circulation-driven ocean mass change between the deep ocean and shallow marginal seas, which is playing a role in driving regional sea level rise trend and its variability along the continental shelves. In addition, our study demonstrates the utility of independent observational platforms for a process-based assessment by achieving the regional sea level budget closure.