SYSU_Topo: A Global Bathymetric Model Derived from SWOT Altimetry and the Gravity-Geological Method

The Surface Water and Ocean Topography (SWOT) mission provides novel perspectives for ocean observations, including ocean dynamics, marine gravity, and seafloor topography. Based on the gravity anomaly of the grav_SWOT_02 model (released by Scripps Institution of Oceanography), this study uses a high-precision gravity geological method to construct a global seafloor topography model SYSU_Topo with 1 arc-min resolution, focusing on the marine region between 180°W–180°E and 80°S–80°N. To reliably obtain the optimal density contrast for GGM, a sliding window strategy of partition inversion is adopted, and a fusion method with boundary constraint points is developed to effectively eliminate the splicing effect of partition inversion. The model was validated with approximately 11,167,583 independent single-beam bathymetric points and newly added multibeam grid points from GEBCO_2024. The single-beam validation for SYSU_Topo model shows that approximately 87% of the checkpoints have absolute errors within 100 m, while around 89% of the checkpoints exhibit relative errors within 5%. The error distribution of SYSU_Topo model is more concentrated and smaller compared to the topo_27.1 and SDUST2023BCO models. During the multibeam validation, each model demonstrates distinct advantages in specific regions. Notably, the SYSU_Topo model achieves superior performance in the South China Sea, with a std of about 132.07m which is 8%-26% better than other models. Compared to traditional altimeter-derived gravity anomalies, SWOT data exhibits greater potential in filling regions lacking high-precision bathymetry, thereby enhancing seafloor topography inversion accuracy. Even when modelled solely with single-beam data, the SYSU_Topo model achieves reliable precision. This research provides a new benchmark framework for integrating multi-source bathymetric data to construct high-resolution seafloor topography, contributing to the advancement of global ocean mapping efforts.