Discussion of sea-level forcing by synchronization of 56- and 74-year oscillations with the moon's nodal tide on the northwest European Shelf (Eastern North Sea to Central Baltic Sea)

摘要

There has been a debate about the computation of amplitudes and periodicities of multi-decadal sea level oscillations aimed to prevent claims the relative sea level rates of rise higher than the recent past in some areas may be the result of natural oscillations. We show here that while the relative sea level rates of rise are actually not only higher, but also lower than the recent past, it all depends on the phasing of the oscillations that also changes from one area to the other, the sinusoidal approximation of the oscillations is an imperfect model with nonlinearities applied to describe a much more complex pattern. Therefore, the determination of amplitude, phase and period of the sinusoidal oscillations approximating a more complex pattern may certainly slightly vary from one approach to the other. However, this does not change too much the conclusion that the sea levels generally oscillates with multi-decadal periodicities of about 20 years and about 60 years in many locations worldwide, and these oscillations should not be sold as proof of the existence of global warming where convenient.