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. 1997 Aug 5;94(16):8329-34.
doi: 10.1073/pnas.94.16.8329.

Spectrum of 100-kyr glacial cycle: orbital inclination, not eccentricity

R A Muller  1 , G J MacDonald
Affiliations

Spectrum of 100-kyr glacial cycle: orbital inclination, not eccentricity

R A Muller et al. Proc Natl Acad Sci U S A. .

Abstract

Spectral analysis of climate data shows a strong narrow peak with period approximately 100 kyr, attributed by the Milankovitch theory to changes in the eccentricity of the earth's orbit. The narrowness of the peak does suggest an astronomical origin; however the shape of the peak is incompatible with both linear and nonlinear models that attribute the cycle to eccentricity or (equivalently) to the envelope of the precession. In contrast, the orbital inclination parameter gives a good match to both the spectrum and bispectrum of the climate data. Extraterrestrial accretion from meteoroids or interplanetary dust is proposed as a mechanism that could link inclination to climate, and experimental tests are described that could prove or disprove this hypothesis.

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Figures

Figure 1
Figure 1
δ18O for past 800 kyr. (a) Data of site 607 from Ruddiman et al. (15). (b) Specmap stack of Imbrie et al. (16). (c) Spectral power of site 607. (d) Spectral power of Specmap. In the Milankovitch theory, the peak near 0.01 (100-kyr period) is attributed to eccentricity, the peak near 0.024 (41-kyr period) to obliquity, and the peak near 0.043 (23-kyr period) to precession.
Figure 2
Figure 2
Spectral fingerprints in the vicinity of the 100-kyr peak for data from site 607 (a); for data of the Specmap stack (b); for a model with linear response to eccentricity, calculated from the results of Quinn et al. (5) (c); for the nonlinear ice-sheet model of Imbrie and Imbrie (21) (d); and for a model with linear response to the inclination of the Earth’s orbit (measured with respect to the invariable plane) (e). All calculations are for the period 0–600 ka. The 100-kyr peak in the data in a and b do not fit the fingerprints from the theories c and d, but are a good match to the prediction from inclination in e.
Figure 3
Figure 3
Variations of the inclination vector of the Earth’s orbit. The inclination i is the angle between this vector and the vector of the reference frame; Ω is the azimuthal angle = the angle of the ascending node (in astronomical jargon). In A–C, the measurements are made with respect to the zodiacal (or ecliptic) frame–i.e., the frame of the current orbit of the Earth. In D–F, the motion has been transformed to the invariable frame—i.e., the frame of the total angular momentum of the solar system. Note that the primary period of oscillation in the zodiacal frame (A) is 70 kyr, but in the invariable plane (D) it is 100 kyr.
Figure 4
Figure 4
Bispectra of (a) inclination of the earth’s orbit, (b) δ18O data from Specmap, and (c) the eccentricity of the earth’s orbit. The inclination and eccentricity were taken from Quinn et al. (5) transformed to the invariable plane. Note the close match between the most significant peaks in the inclination bispectrum and δ18O bispectrum. The scale is linear, and the units arbitrary; for details of the bispectral method see MacDonald and Muller (26).
Figure 5
Figure 5
Spectrum of the accretion of extraterrestrial dust for the period 269–445 ka, determined from the helium-3 measurements of Farley and Patterson (39).
See this image and copyright information in PMC

References

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    1. Imbrie J, Imbrie K P. Ice Ages, Solving the Mystery. Cambridge, MA: Harvard Univ. Press; 1979.
    1. Milankovitch M. Canon of Insolation and the Ice-Age Problem. Belgrade, Yugoslavia: Royal Serbian Academy; 1941.
    1. Milankovitch M. Théorie Mathématique des Phénomènes Produits par la Radiation Solaire. Paris: Gauthier-Villars; 1920.
    1. Quinn T R, Tremaine S, Duncan M. Astron J. 1991;101:2287–2305.

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