© 2014 H. Bâki Iz, licensee De Gruyter Open. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License. J. Geod. Sci. 2014; 4:150–165 Research Article Open Access H. Bâki Iz* 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 pe- riodic lunar nodal tides and almost periodic solar radia- tion variations influence sea level changes through their harmonic beating of nearby natural and/or forced broad- band oscillations of the sea level at multi-decadal frequen- cies. 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 am- plitudes of the corresponding periodicities in 27 globally distributed long tide gauge records. Statistically signifi- cant 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 har- monic 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 phe- nomenon. Consequently, the compounding of the lunar nodal tides and forced sea level changes due to solar ra- diation 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; So- lar radiation; Tide gauge; Variable acceleration. DOI 10.2478/jogs-2014-0016 Received April 29, 2014; accepted November 5, 2014 It begins as a noise in the background keeping steady beat as it makes its round it can be found at any time of day it’s so simple, just push and play. The Loudest Shadow by Anthony *Corresponding Author: H. Bâki Iz: Dept. of Land Surveying and Geo-Informatics The Hong Kong Polytechnic University, Hong Kong, China; Email: H.Baki.Iz@gmail.com 1 Introduction A plethora of investigations during the last two decades indicates global sea level accelerations and decelera- tions. Some of them are: Woodworth (1990), deceleration and acceleration; Douglas (1992) deceleration; Holgate and Woodworth (2004), acceleration; Church and White (2006), acceleration followed by deceleration; Jevrejeva et al. (2008), acceleration; International Panel on Climate Change (2007), acceleration; Woodworth et al. (2009) ac- celeration followed by deceleration; Houston and Dean (2011), no acceleration; Watson (2011), a regional deceler- ation. Most recently Iz et al. (2013) showed that a variable global sea level velocity/acceleration model can represent these divergent estimates about global sea level rise, as in- ferred from tide gauge and satellite altimetry data. Nonetheless, all these current models do not explain the origin of the variable sea level velocities and accel- erations coherently at the global scale. It is likely that variable-accelerations could be due to a number of hidden periodicities in sea level changes with small amplitudes. Their periods, exceeding decadal or longer time span how- ever, cannot be easily detected using spectral methods. This is due to various reasons, such as: the need for series longer than a century, episodic phase reversals, small am- plitude of periodicities and noisy records, a wide spread broadband behavior of sea level variations in all perti- nent frequencies, presence of autocorrelations and long- memory processes in tide gauge records. Alternatively, a top-down approach can be used in search of such hidden periodicities. Along these lines, compounding of lunar nodal tides and/or forced sea level changes induced by solar radiation variations together with other natural and/or forced broadband oscillations of sea levels with periods of up to multi-decades is submitted as the working hypothesis of this study. In the following sections, we first examine and discuss 27 tide gauge stations with records over 80 years (Fig. 1), and their power spectra (Fig. 2). This is followed by a dis- Unauthenticated Download Date | 1/10/15 2:21 AM