JIGOG (Surface mass redistribution from Joint Inversion of GPS site displacements, Ocean bottom pressure models and GRACE global gravity models) is a joint project between the Alfred-Wegener-Institute (AWI) in Bremerhaven, the Institute for Planetary Geodesy (IPG) of the Technical University Dresden, the Institute of Geodesy and Geoinformation (IGG) of the University Bonn and GFZ within the DFG Special Priority Program 1257 "Mass Transport and Mass Distribution in the Earth System".

When water, snow and air are redistributed over the Earth's surface the following effects can be observed:

• The gravity field of the Earth changes, because regions with higher mass content yield a stronger gravitational attraction,
• the surface pressure changes because the new column of atmospheric and oceanic masses assert a different weight on the Earth’s surface and
• the shape of the solid Earth changes because it deforms under the surface pressure and the change in gravity (self gravitation).

Within the JIGOG project we develop a strategy to consistently combine data from the satellite mission GRACE (GFZ weekly gravity models available at the Information System and Data Center (ISDC)), ocean bottom pressure simulations from AWI’s FESOM model (Finite Element Sea Ice-Ocean Model) and site displacements from a permanent global GPS station network (consistently reprocessed by IPG), with the aim of retrieving time variable mass transfers on the Earth’s surface. Complementary to these data sets there are several other geodetic techniques which might be used in the (near) future, such as for example satellite laser ranging (SLR) and altimetry. The exchange between the Earth's major mass compartments is currently largely unknown and the retrieval by single techniques is accompanied by data-specific disadvantages. Our combination approach, using least squares techniques, allows for better accuracy, a higher temporal resolution, and it addresses data-specific problems. Our results therefore contribute to the current knowledge of global mass transport on the surface of the Earth.

Further information can be found at the JIGOG project webpage of the SPP1257.