Time Variable Gravity: An Emerging Frontier in Interdisciplinary Geodesy

The interdisciplinary potential of gravity is stressed with special emphasis on the synergistic use of gravity with other data types. Satellite gravity measurements expected from GRACE and CHAMP will provide unprecedented views of the Earth’s gravity field and its changes with time. These measurements will be complementary with those of GOCE, which will provide unprecedented determination of the high-resolution static field. Gravity changes directly reflect changes in the masses of the ocean (thus allowing the separation of steric (heat induced) and non-steric contributions to sea level rise), the Greenland and Antarctic ice sheets, and the water stored in the continents. Not only can measurements of those changes provide a truly global integrated view of the Earth; they have, at the same time, sufficient spatial resolution to aid in the study of individual regions of the Earth. These data should yield information on water cycling previously unobtainable and be useful to both fundamental studies of the hydrologic cycle and practical assessments of water availability and distribution. Together with complementary geophysical data, satellite gravity data represent a new frontier in studies of the Earth and its fluid envelope.