Local Enhancement of Marine Gravity Field over the Spratly Islands by Combining Satellite SAR Altimeter-Derived Gravity Data

Abstract

The marine gravity field recovery close to land/island is challenging owing to the scarcity of measured gravimetric observations and sorely contaminated satellite radar altimeter-derived data. The satellite missions that carried the synthetic aperture radar (SAR) altimeters supplied data with improved quality compared to that retrieved from the conventional radar altimeters. In this study, we combine the satellite altimeter-derived gravity data for marine gravity field augmentation over island areas; in particular, the feasibility for regional augmentation by incorporating the SAR altimeter-derived gravity data is investigated. The gravity field modeling results over the Spratly Islands demonstrate that the marine gravity field is augmented by the incorporation of newly published satellite altimeter-derived gravity data. By merging the gravity models computed with the Sentinel-3A/B SAR altimetry data, the quasi-geoid and mean dynamic topography are dramatically improved, by a magnitude larger than 4 cm around areas close to islands, in comparison with the results directly derived from a combined global geopotential model alone. Further comparison of regional solutions computed from heterogeneous gravity models shows that the ones modeled from the SAR-based gravity models have better performances, the errors of which are reduced by a magnitude of 2~4 cm over the regions close to islands, in comparison with the solutions modeled with the gravity models developed without SAR altimetry data. These results highlight the superiority of using the SAR-based gravity data in marine gravity field recovery, especially over the regions close to land/island.

An Adaptive Nonlinear Iterative Method for Predicting Seafloor Topography From Altimetry‐Derived Gravity Data

“…The DTU21GRA gravity model is provided by Y. Wu et al. (2022). The GEBCO_08 (Goodwillie, 2008) can be downloaded from https://www.gebco.net/data_and_products/historical_data_sets/.…”

“…The DTU21GRA gravity model is provided by Y. Wu et al (2022). The GEBCO_08 (Goodwillie, 2008) The CRUST1.0 model (Laske et al, 2013) is available at https://igppweb.ucsd.edu/∼gabi/crust1.html.…”

“…In this study, the DTU21GRA released by Technical University of Denmark space (Andersen & Knudsen, 2019) was used to predict the ST of the study area. Compared with DTU17GRA, DTU21GRA was computed by combining 5 years of Sentinel‐3A and 3 years of Sentinel‐3B and reprocessed CryoSat‐2 data (Y. Wu et al., 2022). The grid resolution of DTU21GRA is one arc‐minute, as shown in Figure 3a.…”

“…Compared with DTU17GRA, DTU21GRA was computed by combining 5 years of Sentinel-3A and 3 years of Sentinel-3B and reprocessed CryoSat-2 data (Y. Wu et al, 2022). The grid resolution of DTU21GRA is one arc-minute, as shown in Figure 3a.…”

Bathymetry Refinement over Seamount Regions from SAR Altimetric Gravity Data through a Kalman Fusion Method

“…The global marine gravity field has been significantly improved using multi-satellite altimetry data, and the currently released gravity model maps the marine gravity field at a mean resolution of several kilometers with an accuracy of 3-5 mGal in open seas [10]. Furthermore, the data extracted from synthetic aperture radar (SAR) altimeters have denser spatial coverage than observations derived from conventional radar altimeters, and SAR altimetry data have a higher signal-to-noise ratio and lower speckle noise [11][12][13]. As a result, the incorporation of SAR-based gravity data may be beneficial for bathymetry modeling.…”