Improved ice-mass balance and GIA-induced sea-level change by assimilation of GRACE and SLI data to 3D viscoelastic earth model and joint gravity field inversion

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The Antarctic ice sheet (AIS) and the Greenland ice sheet (GIS) are important components of the Earth’s climate system, contributing significantly to present-day sea-level change. The knowledge of their past and present state will enhance our understanding of changes in the climate system, and improve the modelling of the near-future evolution of global temperature and sea-level change. The temporal variation of mass of the AIS and GIS are important indicators of the ice sheets’ current dynamical state. The Gravity Recovery and Climate Experiment (GRACE) satellite mission monitoring temporal variations of the gravity field provides new constraints on mass changes in the Earth’s system. However, particularly in Antarctica, ice-mass changes are superimposed by the mass redistribution in the Earth’s mantle due to glacial-isostatic adjustment (GIA) contaminating ice-mass balance estimates from GRACE. In turn, GRACE data represents an important new constraint GIA-induced mass changes and surface deformation, which represents an important signal of present-day relative sea-level change. This project aims at simultaneously constraining present-day ice-mass changes and GIA by a joint inversion of the GRACE data for Antarctica and the North America using a three-dimensional viscoelastic earth model. To reduce ambiguities in the inversion, ICESat data and sea-level indicators for the past 10,000 years will be assimilated by the adjoint technique. The results of AGIA will provide an improved estimate of the GIA-induced and eustatic contribution caused by the ice sheets to present-day relative sea-level change.