The Late Quaternary Glaciations as the Response of a Three-Component Feedback System to Earth-Orbital Forcing

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

“…This is one distinguished property of our present model. Other models, e.g., ones by Pollard (1982) and by Saltzman et al (1984), do not seem to succeed better than ours, in reproduction of these small peaks and phase of each "small" ice age. Comparatively speaking, over all of the calculated duration, Fig.…”

“…One opinion for the origin of 100kyr peak in the climate spectrum is that it would be a free oscillation occurring in the earth's climate system (e.g., Saltzman and Sutera, 1984;Saltzman et al, 1984). The other suggests that it may be a non-linear combination tone of forcing primarily at the precessional periods of 19kyr and 23kyr due to modulation by eccentricity at approximately 100kyr (Imbrie and Imbrie, 1980;Le Treut and Ghil, 1983;Snieder, 1985). Although the latter opinion is possible from a mathematical point of view, it would be difficult to realize a 100kyr period oscillation in the actual earth's climate system which has complex forcing amplitudes and spectra.…”

“…The oscillator with 100kyr period seems to exist in the earth's climate system. Saltzman et al (1984) and Saltzman and Sutera (1984) indicate that some 100kyr period oscillation can exist in the earth's climate system even if in the absence of any external forcing. Moreover, the models of Kallen et al (1979) and Ghil and Le Treut (1981) indicate an existence of 10kyr free, self-sustained oscillation in the earth's climate system [from now on, we will call their model as KCG model].…”

“…So, it may not be improper to assume here that CT and CL have the values of about 10kyr or so. With use of 10kyr as the value of the relaxation time for the bulk ocean temperature, the solution of the model by Saltzman and Sutera (1984) also exhibits a periodicity of 90kyr. They explain the value as the time constant for thermal equilibrium that would prevail in the absence of any thermohaline overturnings.…”

“…If the ocean mixing and/or biological cycling change substantially, redistribution of nutrients and C in the sea can occur (Broecker and Takahashi,1984;Sarmiento and Toggweiler, 1984;Siegenthaler and Wenk, 1984;Knox and McElroy, 1984). This can explain why CO2 measurements on ice cores suggested links between climate and the joint operation of the atmosphere and ocean system.…”