Detection of long term modulation orbital cycles in the sea level oscillations using clean algorithm of spectral analysis

The need for a unified astronomical theory of sea-level changes and associated climatic variations motivates the search for Milankovitch eccentricity rhythms in the global sea level variations. The available latest sea level record exhibits long term trend with superimposed higher order frequency oscillations. A new powerful spectral technique based on the one dimensional clean deconvolution algorithm, is applied to the global sea level fluctuations record of the past 30 million years. The spectrum analysis reveals statistically significant (at 90% confidence level) and »clean« cyclicity of 2000 kyr, 1250 kyr, 880 kyr, 660 kyr, 416 kyr, and 260 kyr. Statistically significant sea level cycles indicate possible link with climate and orbital cycles. A principal cycle (Ep) of 413 kyr corresponds to the well known orbital eccentricity cycle. The remaining higher order periodicities are integral multiples of Ep (e.g., Ep/2, 3Ep/2, 2Ep, 3Ep, 5Ep), equivalent to those of the modulation of orbital eccentricity-precession cycles. Matching periodicities of the sea level changes and climatic rhythms, and long term modulation of orbital variations demonstrate significant role of orbital cycles in these processes and integrate the Milankovitch paradigm of orbital forcing to coupled climate-sea level interactions.