Earth is a dynamic planet subject to many processes. Detectable changes in the shape of the solid Earth and its gravity field arise due to the varying mass distribution of the surface fluids (oceans, atmosphere and terrestrial water storage). These include variations related to climate change such as sea level changes, loss of ice sheets, post-glacial rebound, and changes in precipitation, water storage, and runoff. These shape changes are called loading effects and can reach significant amplitudes (several mm). Besides global climate changes, loads exhibit regional variations over all time scales.
Space geodesy provides unprecedented coverage of the Earth's surface and can contribute to monitoring the interaction between climate change and Earth’s time-dependent shape and gravity field. The Global Positioning System (GPS) has become the essential tool for the mm to cm level positioning requirements within the geosciences. Gravity satellite missions such as the Gravity Recovery and Climate Experiment (GRACE) can also observe the global movement of environmental fluids. These two techniques give very long time series of observations that are extremely complementary in spatial and temporal resolution, for monitoring loading effects and enhancing global understanding of the mass transport at the Earth’s surface. Loading effects can explain much of the annual signal in position time series. Nevertheless, the errors in the geophysical models are still significant and discrepancies exist between models and observations.
The GEOCLIME (Climate change and Geodetic deformation) project aimed to better infer crustal deformation processes related to the water cycle, and the impact of climate change on Earth’s shape via the study of loading effects. This project addressed key science questions related to surface deformation associated with water distribution and water cycle change, as well as the processes controlling variations in relative land and sea levels. It also contributed to other major unresolved scientific problems concerning the effective rheology and structure of the lithosphere and mantle. The main objective was to explore the impact of changing rheological properties in loading deformation models and to improve and validate these forward models. To achieve this, the project adopted a multi-disciplinary approach using highly accurate space geodesy datasets and state of the art modelling. This offered a unique opportunity to identify climate change signals, improving our understanding of how Earth responds to the water cycle. Better understanding this interaction is essential for applications such as how coasts react to relative sea level change and storms as well as natural hazard mitigation.
