Interconnections between combined Length-of-Day and polar motion parameters concerning joint atmosphere-ocean-hydrosphere modes

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The project investigates the interrelation of climate variability/climate change and the variations in the Earth Rotation Parameters (ERPs) on interannual to decadal time scales. The extent is determined to which ERPs can be used as a climate indicator which is independent of measurements in the atmosphere and the ocean. Two approaches are combined to achieve this goal: On the one hand, the impact of dynamical processes in the atmosphere-ocean system on ERPs is analysed, taking into account the interdependence of the variability patterns in the two sub-systems. On the other hand, the ERP variations are projected on specific variations in the ocean-atmosphere system. Different patterns (like ENSO, NAO), their interrelation and underlying processes in atmosphere and ocean are investigated. While atmospheric contributions can be estimated from atmospheric reanalysis products the impact of the ocean cannot be deduced from three-dimensional observations. Thus, numerical global ocean models forced by atmospheric data are used. Coupled atmosphere-ocean models are employed for estimating the contribution of long term variations in the climate system to variations of the ERPs.