Earth rotation and the ocean's circulation

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The goal of this proposal is to contribute to the interpretation of Earth rotation measurements with a focus on the role of the ocean. We will estimate the oceanic angular momentum for the last fifty years as accurate as possible. Two complementary methods will be applied. The first is advanced numerical ocean modeling which considers all processes of importance and which will be extended to derive the local torques excited by the ocean on the solid Earth and vice versa. The second approach tries to close the angular momentum budget by assimilation of angular momentum time series into a global circulation model. To this end the measured Earth rotation parameters are corrected for best estimates of the contributions by the atmosphere, the cryosphere and hydrology. This ¿measured¿ ocean angular momentum time series is subsequently assimilated into a global ocean model to determine ERP parameters that are consistent with observations and ocean dynamics. The result will also be a major step forward in determining which part of the observed sea level rise is due to global warming in contrast to an increase in ocean mass.