NASA and the German Space Agency launched the GRACE satellite gravity mission in 2002. The mission is projected to last through 2013. GRACE provides highly accurate solutions for the Earth’s global gravity field every month. Differences between fields for different months provide information about time-variability in the gravity field, and so about month-to-month fluctuations in the Earth’s mass distribution, at scales of a few hundred km and greater. The results can be used to study a wide range of geophysical signals, from changes in the water and snow stored on land and in the ground, ice mass loss in the polar ice sheets, changes in ocean bottom pressure and ocean mass variability, and processes in the solid Earth (e.g post-glacial-rebound; very large earthquakes).
In this talk I will describe the GRACE mission, putting it in the context of earlier time-variable gravity measurements from satellites. I will focus on cyrospheric and hydrological applications: those that involve changes in the distribution of snow and ice in the Greenland and Antarctic ice sheets and of water and snow on continents.