Optical atomic clocks: new sensors for monitoring geodynamic processes?

The measurement of time has always been closely related to the observation of the Earth. Today, the best optical atomic frequency standards can reach inacurracies around 10?18 in terms of relative frequency. Because time flow is affected by gravity, it means optical clock comparisons could measure gravity potential differences with an accuracy of 0.1 m2/s2, which is equivalent to 1-cm in height difference, opening new fields of fundamental and applied research. In this talk, we will introduce what is an optical atomic clock and how remote clock comparisons could help us improve the knowledge of the Earth's gravity field. Then, we will present various applications that could bring the exploitation of clock measurements in geodesy: determination of the geopotential with high spatial resolution, vertical reference system, and we will discuss the possible applications associated to the geodynamic processes related to mass transfers.