Separation of mass signals by common inversion of gravimetric and geometric observations

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The integral signals of mass variations observed by GRACE result, e.g., from atmospheric mass changes, ocean variability, variations in continental water storage, seasonal snow cover and ice volume changes. To identify and separate the contributions of each individual process is a fundamental requirement for understanding the procedure of mass transport. The present project will (i) analyse geophysical models which allow for the assessment of mass variations, (ii) derive the most appropriate functional models to describe these mass variations and (iii) estimate the parameters of these models by a common adjustment of all available gravimetric and geometric observations. The last step, an utmost rigorous combination of all precise space techniques, is necessary to account for the mutual interdependencies between observations and geophysical processes which are up to now often disregarded: seasonal mass variations are derived from GRACE data, but seasonal displacements of stations used for satellite tracking are not accounted for. Similar, the orbits of altimeter satellites refer to a reference system which does not include periodic variations, but altimetry is applied to derive such variations. Thus, parts of the mass variations identified today might be apparent effects due to these geometric effects. The present project aims to solve these inconsistencies by separating mass signals from a common inversion of gravimetric and geometric observations.