On the origin of the 100-kyr cycles in the astronomical forcing

Abstract

Investigations during the last 25 years have demonstrated that the astronomically related 19-, 23-, and 41-kyr quasiperiodicities actually occur in long records of the Quaternary climate. However, the same investigations also identified the largest climatic cycle as being about 100 kyr long. As the 100-kyr variations in standing insolation due to eccentricity change are too small, they cannot be the direct cause of the ice ages. This is the reason why most of the modeling studies attempting to explain the relation between the astronomical forcing and climatic change have focused on this 100-kyr cycle. In this paper, we will show the astronomical origin of the periods at about 100 kyr that characterize the long-term variations of eccentricity, of its first derivative, of the frequency modulation of obliquity, and of the inclination of the Earth's orbit on the invariable plane of reference. Five independent values are found between 95 and 107 kyr, and a wavelet signature is suggested to test the possible relationships between the astronomical and climatic variables. Proxy records from deep-sea cores and European Programme for Ice Coring in Antarctica ice core and modeling results from the Louvain-la-Neuve two-dimensional model are used for illustration. Copyright by the American Geophysical Union.