The Gravity Field in Antarctica: Geodetic Modelling and Geophysical Inversion (AntGrav)

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The gravity field reflects the mass distribution of the Earth. Thus, it allows studying its inner structure and tectonic evolution. In this respect, it is important to gain precise knowledge of the geometry of specific boundary surfaces respectively surfaces of distinct density contrast such as the topography and the crust-mantle boundary (Mohorovicic discontinuity). In Antarctica, the subglacial topography that is covered by an ice sheet of up to 4,000 m thickness is of special interest. Additionally, the geoid as a distinct equipotential surface serves as a reference surface, for instance, in oceanography (for dynamic ocean topography) and in geodesy (for height systems and a globally unified height datum).For the very first time it will now be possible to study the gravity field in Antarctica on a continental scale and in a homogeneous and consistent way. This is facilitated by the recent availability of a new Antarctic-wide compilation of ground-based gravity data published by an international consortium with one of the applicants being lead author (Scheinert et al., 2016). Thus, we aim to unite the expertise of both applicants in global gravity field modelling based on modern satellite gravity missions such as GRACE and GOCE on the one hand, and in regional gravity field improvement in Antarctica based on terrestrial and near-surface gravity measurements on the other hand. Hence, the main objective of our proposal is to determine a combined, consistent, high-resolution gravity field model of Antarctica. This will be based on a thorough validation and homogenization of the Antarctic terrestrial gravity data and their combination with satellite data. We will develop innovative methods for an optimal combination of all gravity data investigating regional and regionally tailored global approaches taking different properties like accuracy and spectral resolution into account. Using this improved continental-wide gravity field model a further objective is to investigate the lithospheric inversion including density and geometry (subglacial topography, Moho depths). For this, we will make use of additional data like ice thickness measurements from radio echo sounding (RES) and grounding line locations. The inversion of the gravity data will utilize sophisticated methods with different ways of constraining by those additional data. Thus, we aim to contribute to overcoming the deficiencies of our knowledge of subglacial topography and lithospheric structure in Antarctica. Both the methods for combined gravity field modelling and gravity inversion with constraints have to be further developed and adapted to the specific situation in Antarctica.The gravity field model as well as the lithospheric model will be complemented by realistic uncertainty estimates. Finally, the impact of these models on several geoscientific disciplines will be assessed, and their usability will be outlined in a scientific roadmap.