An improbable observation of the diurnal core resonance

Agnew, DC.  2018.  An improbable observation of the diurnal core resonance. Pure and Applied Geophysics. 175:1599-1609.

Date Published:



Earth, Geochemistry & Geophysics, interferometry, latitude, liquid, Nearly diurnal free wobble, nutation, ocean tides, parameters, tables, tides


The resonance associated with the ellipticity of the core-mantle boundary is usually measured with observations of either the Earth's nutations, or of tidal gravity, strain, or tilt. But, improbably, it can also be seen in a dataset collected and processed with older and simpler technologies: the harmonic constants for the ocean tides. One effect of the resonance is to decrease the ratio of the amplitude of the constituent to the amplitude of the constituent to 0.96 of the ratio in the equilibrium tidal potential. The compilation of ocean-tide harmonic constants prepared by the International Hydrographic Bureau between 1930 and 1980 shows considerable scatter in this ratio; however, if problematic stations and regions are removed, this dataset clearly shows a decreased ratio. While these data apply only a weak constraint to the frequency of the resonance, they also show that the effect could have been observed long before it actually was.