On the Feasibility of Seafloor Topography Estimation from Airborne Gravity Gradients: Performance Analysis Using Real Data

Abstract

Compared with airborne gravimetry, a technique frequently used to infer the seafloor topography at places inaccessible to ship soundings due to the presence of ice shelf or ice mélange, airborne gravity gradiometry inherently could achieve higher spatial resolution, thus it is promising for improved inference of seafloor topography. However, its estimation capability has not been demonstrated by real projects. Theoretical analysis through admittance shows that compared with gravity disturbance, gravity gradient is more sensitive to the short-wavelength seafloor topography but diminishes faster with the increase of the distance between the seafloor and airplane, indicating its superiority is recovering short-wavelength topographic features over shallow waters. We present the first numerical experiment that estimates seafloor topography from a 0.4-km resolution, real airborne gravity gradients. It is shown that airborne gravity gradiometry can recover smaller topographic features than typical airborne gravimetry, but the estimation accuracy is only ±17 m due to the presence of subsurface density variations. The long-wavelength effect of the subsurface density variations can be removed with the aid of constraining bathymetry inside the study area, whereas the short wavelengths cannot. This study expands the applications of airborne gravity gradiometry, and helps glaciologists understand its performance in seafloor topography estimation.

A New Global Bathymetry Model: STO_IEU2020

“…The ST inversion method, based on sea surface gravity data, mainly includes the frequency-domain [18,20], regression analysis [10,21,22], Gravity-Geologic Method (GGM) [23][24][25], space domain [26,27] and simulated annealing (SA) [28,29]. Based on previous studies and our experiments, external bathymetric data is usually required to supplement non-inversion band ST information.…”

Bathymetry Beneath the Amery Ice Shelf, East Antarctica, Revealed by Airborne Gravity

“…The measured gravity anomalies at flight altitude integrate the gravitational effects of the density difference between the seafloor topography and the overlying water and/or ice layers, the density variations within the shallow subsurface, and the regional isostatic compensation (Watts, 2001) at the Mohorovicic discontinuity (Yang, Luo, Tu, et al., 2020). The latter two effects are not due to the seafloor topography and should be removed prior to the inversion.…”

Altimetry‐Derived Gravity Gradients Using Spectral Method and Their Performance in Bathymetry Inversion Using Back‐Propagation Neural Network

“…(2020), Yang et al. (2020), and Y. M. Wang (2000); meanwhile the remaining five gravity gradients also contain valuable bathymetric information which makes them worth exploiting. However, the complexities of conventional models which relate gravity gradients with bathymetry make this a discouraging exercise.…”

“…Almost all previous bathymetric applications of gravity gradients use only the vertical gravity gradient (the third gravity gradient tensor, often symbolized as 𝐴𝐴 𝐴𝐴𝑧𝑧𝑧𝑧 in literature). Typical examples are the works of Hu et al (2014), Hu et al (2021), Fan et al (2020), Yang et al (2020), and Y. M. Wang (2000); meanwhile the remaining five gravity gradients also contain valuable bathymetric information which makes them worth exploiting. However, the complexities of conventional models which relate gravity gradients with bathymetry make this a discouraging exercise.…”