The influence of vertical coastal land movement on relative sea level rise: a case study of Shanghai, China

Abstract Understanding the current Vertical Land Motion (VLM), subsidence or uplift, is the basis for Relative Sea Level Rise (RLSR) projection and related risks estimation. However, in Shanghai, the impacts of the spatiotemporal change of VLM are little known. The purpose of this study is to quantify how VLM impacts RSLR and investigate the spatiotemporal evolution characteristics of VLM through tide gauge records, satellite altimetry observations, and Interferometric Synthetic Aperture Radar (InSAR) measurements. The calculations indicate that the RSLR (5.67±0.58 mm/year) from 1969 to 2019 was approximately twice the SLR trend (2.44±0.28 mm/year) from 1993 to 2019, and the VLM, especially subsidence, is the main driver for RSLR. Moreover, spatial and temporal patterns of VLM are highly uneven and nonlinear. These results reveal that VLM is the main driver of RSLR. Unfortunately, previous studies mostly underestimated or even overlooked the impact of VLM on risks of RSLR and subsequential coastal flooding. Thus, prevention strategies for controlling VLM are warranted to minimize the negative impact related to the RSLR. Our research provides a theoretical basis for urban disaster prevention in Shanghai and the construction planning of coastal cities around the world.