Recovery of global marine full-tensor gravity gradients from SWOT wide-swath altimetry

Summary

Global marine full-tensor gravity-gradient (FTGG) products with sufficient spatial resolution to characterize fine-scale oceanic gravity-field structures remain limited. Here, the gravity-gradient tensor denotes the 3×3 symmetric matrix of second-order derivatives of the disturbing potential; FTGG refers collectively to its six unique components, whereas the vertical gravity gradient (VGG) refers specifically to the Tzz component. We recover a global marine FTGG model from high-resolution, wide-swath sea surface height observations acquired by the Surface Water and Ocean Topography (SWOT) mission. The recovery framework first derives the vertical gravity gradient from corrected SWOT sea surface heights using a remove–compute–restore procedure and then reconstructs the remaining tensor components through Fourier-domain relations for a harmonic potential field. This approach exploits SWOT’s dense two-dimensional sampling to recover directional second-order derivatives of the marine gravity field and provides a global representation of gravity-field curvature over the oceans. We evaluate the resulting six tensor components against the independently developed CUGB2023GRAD model at global and regional scales. At the global scale, the components show negligible mean differences and root-mean-square differences ranging from 2.49 to 6.13 Eötvös (E). Regional comparisons across a range of latitudes and tectonic environments show generally consistent agreement, with root-mean-square differences mostly below 5.23 E and a maximum of 8.30 E in structurally complex regions. The larger local differences are concentrated in areas of rugged bathymetry and strong short-wavelength gravity signals, where SWOT’s wide-swath observations may retain features that are smoothed in conventional altimetry-based models. The resulting global FTGG dataset provides a high-resolution, directionally resolved description of the marine gravity field and a valuable resource for bathymetric inversion, lithospheric-structure characterization, and tectonic analysis.