Gravity and the hydrosphere: new frontier

Satellite gravity measurements expected in the next few years will provide unprecedented views of the Earth's gravity field and, given sufficient dura tion, its changes with time. Gravity changes directly reflect changes in th e masses of the ocean (thus allowing the separation of steric (heat induced ) and non-steric contributions to sea-level rise), the Greenland and Antarc tic ice sheets, and the water stored in the continents. Not only can measur ements 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 informati on on water cycling previously unobtainable and be useful to both fundament al studies of the hydrologic cycle and practical assessments of water avail ability and distribution. Together with complementary geophysical data, sat ellite gravity data represent a new frontier in studies of the Earth and it s fluid envelope.