Sub and superharmonics of the lunar nodal tides and the solar radiative forcing in global sea level changes

Abstract

The working hypothesis of this study is that periodic lunar nodal tides and almost periodic solar radiation variations influence sea level changes through their harmonic beating of nearby natural and/or forced broadband oscillations of the sea level at multi-decadal frequencies. The presence of the harmonics of the lunar nodal tides and the solar radiation variations, including the pole tides, is investigated by modeling and estimating the amplitudes of the corresponding periodicities in 27 globally distributed long tide gauge records. Statistically significant signatures of sub and superharmonics of lunar nodal tides and forced sea level variations due to solar radiation are detected in all station records.Meta-analysis of the harmonic amplitudes from all stations reveals that the effect sizes are statistically significant and provide evidence for the harmonic beating of sea level changes as a global phenomenon. Consequently, the compounding of the lunar nodal tides and forced sea level changes due to solar radiation with other broadband natural and forced sea level oscillations is a plausible explanation for the recent sea level accelerations and decelerations detected by satellite altimetry measurements and long tidal records.

Keywords

• Climate change
• Lunar nodal subharmonics and superharmonics
• Sea level rise
• Satellite altimetry
• Solar radiation
• Tide gauge
• Variable acceleration