Watching the changing Earth

The melting of ice during the summer and the regrowth of ice shields in winter or any variation of mass on the surface of the Earth and inside the Earth, in general, are reflected in the change of its gravity field. By monitoring the gravity field from space, we can infer the mass variations necessary to result in the measured gravity changes. Satellite missions like GRACE (Gravity Recovery and Climate Experiment) offer us a monthly view of the Earth's changing gravity field since 2002. Providing a look into the mass redistribution driven geophysical processes, climate, and human civilisation. Furthermore, the combination of gravity with additional types of measurements allows us to get a better understanding of our planet. The objective of this presentation is not to discuss the last significant decimal in some indicator of climate change. A look at the gravity field offers much more information, e. g., continental and global hydrology, changing ocean currents, mass flow in the mantle. This talk will give a brief introduction into space geodetic techniques used to monitor the gravity field of the Earth with a focus on the GRACE mission, its scientific results and applications. I will explain their working principle and the process which leads to a mathematical representation of the gravity field. We will look at a few selected examples, and try to answer the questions as mentioned above. Fortunately, the necessary data products are freely available. Additionally, there are services which spare us the math and offer tools to generate visualisations for a straightforward approach to this topic.