Climate Variations Connected with Earth Orbit Eccentricity

The climate variations in the past are strongly connected with the cycles of orbital forcing. The orbital forcing redistributes incoming solar energy on the Earth surface, especially over different latitudes. These cycles affect significantly seasons on millennial time scales. The most important influence on climate is provided by the variations of orbit eccentricity, obliquity and precession of Earth axis of rotation. The so-called Milankovitch cycles of eccentricity and obliquity are connected with the processes of glaciations during the last 3 Ma. Actually, all orbital cycles affect paleoclimate, where the effects of eccentricity dominate. The influence of orbital forcing on paleoclimate variations is investigated by two long time series of eccentricity from Laskar’s solution and sea level variations, reconstructed for the last 65 Ma. Common cycles of eccentricity and sea level in 18 different frequency bands are extracted by the Method of Partial Fourier Approximation. The short-periodical cycles, whose periods are below 400 kyr, have relatively good agreement for the last 3 to 7 Ma. The long-term oscillations of sea level and orbit eccentricity with periodicities between 0.8 Myr and 10.8 Myr have excellent agreement in 4 frequency bands, whose duration is 65 Myr. In other 5 frequency bands a good correlation exists for the last 35 – 40 Ma. The estimated amplitudes of sea level cycles are between 2 and 5 m with accuracy of about 0.4 m. The jumps inside of sea level time series are determined by a high-sensitive Method of Jump Detection, based on numerical integration of the time series. The detected jumps determine various data segments, whose duration is below 2.8 Myr and the rate of their linear trends is between 0.3 cm/kyr and 3 cm/kyr. The remarkable result is that all detected jumps occur during the extrema of eccentricity, while the jumps of sea level during glacial cycles in the last 3 Ma occur only in eccentricity minima. These results can help better understanding of climate response to orbital forcing.