Sub and superharmonics of the lunar nodal tidesand the solar radiative forcing in global sea levelchanges

Abstract

The working hypothesis of this study is that periodiclunar nodal tides and almost periodic solar radiationvariations influence sea level changes through theirharmonic beating of nearby natural and/or forced broadbandoscillations of the sea level at multi-decadal frequencies.The presence of the harmonics of the lunar nodaltides and the solar radiation variations, including the poletides, is investigated by modeling and estimating the amplitudesof the corresponding periodicities in 27 globallydistributed long tide gauge records. Statistically significantsignatures of sub and superharmonics of lunar nodaltides and forced sea level variations due to solar radiationare detected in all station records.Meta-analysis of the harmonicamplitudes from all stations reveals that the effectsizes are statistically significant and provide evidence forthe harmonic beating of sea level changes as a global phenomenon.Consequently, the compounding of the lunarnodal tides and forced sea level changes due to solar radiationwith other broadband natural and forced sea leveloscillations is a plausible explanation for the recent sealevel accelerations and decelerations detected by satellitealtimetry measurements and long tidal records.