Geodynamical interconnections between the atmosphere, ocean, hydrosphere, cryosphere, and solid earth

Mass and angular momentum exchange between the atmosphere, ocean, hydrosphere, cryosphere, and solid earth produce observable changes in global mean sea level, geocenter (mass center of the planet earth system) position, Earth rotation, and gravitational field. These variations are being measured with unprecedented accuracy by space geodetic techniques. We study several space geodetic observations, including the global mean sea level change measured by TOPEX/Poseidon satellite altimeter, geocenter motion derived from Lageos 1 & 2 Satellite Laser Ranging (SLR) observation, polar motion and length-of-day (LOD) variation determined from combined space geodetic measurements, and Lageos-1 nodal precession rate. In a systematic geopotential frame, these variables represent gravitational variations of different wave lengths. We investigate atmospheric, hydrological (including cryospheric), and oceanic contributions to these space geodetic observations, using assimilated climate models and TOPEX/Poseidon altimeter measurements. The steric sea level change has been removed using a simplified model. This investigation shows that seasonal water mass exchange among the atmosphere, land, and ocean can cause seasonal global mean sea level changes of about 6 mm, which is in reasonably good agreement with TOPEX/Poseidon observations in both amplitude and phase. The atmosphere, oceans, and hydrosphere all provide significant contributions to geocenter motion. Both continental hydrological cycle and the oceans play important roles in accounting for the residuals of polar motion and LOD after atmospheric contributions are removed. This study indicates an improved agreement between observed Lageos-1 nodal precession rate change and geophysical contributions, especially those from the hydrosphere. Good correlations at a wide range of frequencies exist between TOPEX/Poseidon measurement and space geodetic observations. This is a strong indication that some of the sea level anomalies are from mass variation, and satellite altimetry has the potential to detect large scale mass variation within the ocean if combined with other space and in situ measurements. Space geodetic measurements provide a means to investigate mass and angular momentum budget in atmospheric, hydrological, cryospheric, and oceanic models, and place observational constraints on these budgets. This research lays down some of the scientific requirements for future investigations using data from the Gravity Recovery and Climate Experiment (GRACE) mission.