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Abstract:
Improving the current conventional model of short period ocean tidal effects in polar motion and changes in lengthof-
day is a key challenge of present Earth rotation research. Accurate estimates of ocean tidal angular momentum
(OTAM) that are required to this end can be inferred from a purely altimetry-based method, in which measured
elevations determine the OTAM mass signal and also the horizontal velocity field through an inversion of the
classical shallow water equations. Some of the subtleties of this global adjustment, which we investigate here in
the context of Earth rotation, include the weighting schemes for different observation equations, the treatment of
closed boundaries, as well as the choice of bathymetry and the amount of bottom friction. We perform a range of
test inversions, where the optimal parameter set for diurnals and semi-diurnals is found by working with a dataassimilative
global tide model for which both heights and barotropic currents are known. Having completed the
fit of tidal velocities to elevations from an up-to-date altimetric model of major constituents, OTAM values are
computed and supplemented by the contributions from minor tides using admittance assumptions. We assess the
quality of the derived high-frequency Earth rotation model by deploying it as an a priori in the analysis of VLBI
(Very Long Baseline Interferometry) observations and comparing its performance to that of the conventional model and those of empirical solutions.
