On the Effect of Ocean Tides on the Secular Retardation of the Earth's Rotation

Abstract

The classical problem of determining the secular retardation of the Earth's rotation due to the effect of tides (oceanic and bodily) has an important geophysical value in determining the possible existence of processes inside the Earth, which lead to secular variations of rotation of the whole Earth or its external layers.Using new cotidal charts of the world ocean calculated by Bogdanov for the main tidal waves M2, S2, K1 and O1 and using the method of moments of tidal forces the retarding moment was found to be 8.3 × 1023 dyn cm. This is twice the amount of previous evaluations. (This method is superior to the method of calculating the dissipation of energy or the moments of frictional forces). This amount corresponds to a retardation of 3.8 μs/century in the speed of the Earth's rotation. But the observations of the Sun give only 1.9 μs/century for the retardation. Thus, there seem to be nontidal and probably internal processes, which accelerate the Earth's rotation by about 2 μs/century. And this is without taking account of additional smaller effects of bodily tides. The search for these processes is an important problem.The full text of the paper will be published in the magazine Physics of the Earth, No. 2, 1972.

The Earth's rotation

“…The contribution by bodily tides in the solid earth is probably not more than a few percent of the whole [Munk, 1968]. More recently, Hendershott [1972] and Pariiskii et al [1972] have used cotidal charts and, taking ocean loading into ac count, estimated dissipation in the world ocean and thus obtained values roughly double Miller's (see also Brosche and Silndermann [1972]). " An overall dissipation rate of ^3-5 X 10 12 watts can be inferred from the rough estimate of average (oceanic and bodily) tidal phase lag from gravimetry [Smith and Jungels, 1970].…”

Paläogezeiten und Erdrotation

“…Die dureh die dynamische Weehselwirkung mit der festen Erde verursachte Xnderung der Gezeiten beeinflugt den Drehimpulstransfer nur unwesentlieh (ZAHEL 1980). Ffir die zus~itzlieh vonder Ss-Gezeit bewirkte Energie/inderung sind etwa 14 ~ zu addieren (PARIISKII 1972).…”

19. Rotation of the Earth

“…The directions of the axes of co-ordinates of the empirical or conditional reference system, defined by the time and latitude observations of a number of independent observatories, depends on the conditions imposed in combining the observations and research (37) has been carried out on the most suitable conditions that should be employed. By the use of tidal charts a value of 3-8 ms/ century has been deduced (38) for the retardation of the Earth's rotation.…”