Long-Term Variations of Earth's Orbital Geometry and its Effect on the Climate System

Abstract

Chinese Loess data over the past 2.4 million years are good proxy records for understanding past climate. Maximum entropy spectrum of magnectic susceptibility data at the locality of Luochuan, which is in Shaanxi province of China, have shown periodic fluctuations of about 21 kyr, 41 kyr, 100 kyr and 400 kyr. These periodic fluctuations are related to the long-term variations of earth's orbital elements of the obliquity, the climatic precession and the eccentricity respectively. The data series was separated into two parts to examine the variations of these fluctuations. The first part is from present to 1.1 Myr B.P.(i.e. million years before present), the second part is from 1.1 Myr B.P. to 2.2 Myr B.P. The periodic fluctuation of 93.4 kyr has the maximum amplitude in the first part of the data series, while the periodic fluctuation of 413 kyr has the maximum amplitude in the second part. The fluctuation about the 400 kyr was found in both parts of the data series.