One Hypothesis in Glaciation Cycles of the Earth : (I) Reproduction of the Observed δ¹⁸O-Derived Data Using Three Assumptions

Abstract

If three assumptions shown in the text are adopted, we can replicate the *18O-derived observations of ice mass evolution. Our results suggest that the large free oscillations with 100 kyr period may be governing the most predominant oscillations in the actual climate, and that the effect of variation in CO2 which would be induced by the link between biological action and the Milankovitch insolation variation would be superposed non-linearly on the free oscillation system with phase lock of the major variation, and play an important role in an apprearance of the real *18O data.

One Hypothesis in Glaciation Cycles of the Earth: (II) A Cause of Appearance of Oscillatory Climate in the Pleistocene

“…For, once a focus is established in the phasespace composed of climate parameters, the climate at the point B' moves abruptly toward the climate condition at the focus B and begins to draw a limit cycle around the focus. (Or it might be completely absorbed into a stable focus if a stable focus were to emerge under appropriate conditions for CL/CT, although the present earth's climate system seems not to have such a stable focus because the value of CL/CT on the earth seems not to allow a stable focus to exist (e.g., Kallen et al, 1979;Ghil and Le Treut,1981;Moriyama, 1986)). …”

“…We will indicate the importance of establishment of a climate system composed of the glacier-ocean-atmosphere, upon the present problem by a different way from theirs, i.e., analytically, based upon the other climate model. Our previous paper (Moriyama, 1986) indicates that the present earth's glacial cycles would be governed by the most dominant free, self-sustained oscillations with 100kyr period and that the effects of the Milankovitch insolation variation which would induce CO2 effect by way of biological action may be superposed non linearly on this most dominant free oscillations with 100kyr period, as external forces with phase lock of this major variation. In this paper, we will discuss the long-term variation of the earth's basic climate field, that is, the geological time variation of the most dominant where the two dependent variables are globally averaged temperature T which is the mass average of ocean temperature and atmospheric temperature, and latitudinal extent of the land ice-cover L. CT and CL denote the heat capacity of the atmosphere-ocean-cryosphere system and the relaxation time of the continental ice sheets, respectively.…”

“…(8). This means that if l were to be fixed by the lmax value during the epoch under consideration for *<* climatic condition always tends to the Ta in due time, because a geographical variation is thought to have certainly much longer time scale than CL which would have the value of only 103*104 years (Moriyama, 1986). In Fig.…”