Hydrological and oceanic excitations to polar motion and length-of-day variation

Water mass redistributions in the global hydrosphere, including continental water storage change and non-steric sea level change, introduce variations in the hydrological angular momentum (HAM) and the oceanic angular momentu m (OAM). Under the conservation of angular momentum, HAM and OAM variations are significant excitation sources of the Earth rotational variations at a wide range of timescales. In this paper, we estimate HAM and OAM variation s and their excitations to polar motion and length-of-day variation using s oil moisture and snow estimates andnon-steric sea level change determined b y TOPEX/Poseidon satellite radar altimeter observations and a simplified st eric sea level change model. The results are compared with the variations o f polar motion and LOD that are not accounted for by the atmosphere. This s tudy indicates that seasonal continental water storage change provides sign ificant contributions to both polar motion and LOD variation, especially to polar motion X, and the non-steric sea level change is responsible for a m ajor part of the remaining excitations at both seasonal scale and high freq uencies, particularly in polar motion Y and LOD. The good correlation betwe en OAM contributions and the remaining excitations shows that large-scale n on-tidal mass variation exists in the oceans and can be detected by TOPEX/P oseidon altimeter observations.