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

Understanding the current Vertical Land Motion (VLM), including subsidence or uplift, is the basis for projecting Relative Sea Level Rise (RLSR) and estimating related risks. However, in Shanghai, the impacts of the spatiotemporal change of VLM are little known. The purpose of this study was to quantify the impact of VLM on 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 indicated 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. The VLM, especially subsidence, is the main driver of 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 have mostly underestimated or overlooked the impact of VLM on the risks of RSLR and subsequent 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 planning of coastal cities worldwide.