INFLUENCE OF THE CHANGING LUNAR ORBIT ON THE ASTRONOMICAL FREQUENCIES OF PRE-QUATERNARY INSOLATION PATTERNS

The sensitivity of the frequencies of the Earth's orbital elements, involved in the astronomical theory of paleoclimates (obliquity and climatic precession), to the Earth-Moon distance and consequently to the length of the day and to the dynamical ellipticity of the Earth is investigated for the last billions of years. But the new frequencies have been computed for the last 440 million years only, a time interval over which data and a model of the Earth were available. Moreover, we consider only the impact of the changing precessional parameter, assuming that the fundamental frequencies of the planetary motion are steady at the geological time scale. Under such hypotheses, the shortening of the Earth-Moon distance and of the length of the day back in time induces a shortening of the fundamental astronomical periods for obliquity and precession, a shortening that is larger for longer periods.