Milankovitch Cycles and Nonlinear Response in the Quaternary Record in the Atlantic Sector of the Southern Oceans

Abstract

Previous studies of deep-sea sediment cores have found evidence for Milankovitch cycles, climatic cyclicity due to the periodicity of the Earth's orbital parameters. Many of the cores recovered on Leg 114 of the Ocean Drilling Program showed outward signs of cyclicity, especially at Site 704. We have analyzed the GRAPE density, carbonate content, and magnetic susceptibility using both standard and nonstandard spectral analysis techniques. One of the nonstandard techniques used was the Lomb-Scargle spectral estimation method, which is designed for unequally spaced data and which yields as part of the process the statistical significance of any observed spectral peaks. Pairs of spectra were compared for statistical similarity using the Kolmogorov-Smirnov method. All of the data sets contain some spectral peaks, including both the expected Milankovitch cycles as well as other peaks. Upon further investigation, we have found that the other peaks could be explained as the nonlinear climate system response to the Milankovitch orbital forcing functions, because the extra peaks appear to be simple linear combinations, harmonics and subharmonics of the Milankovitch peaks. At Site 704, there is a marked change in the response at the Brunhes/Matuyama boundary (0.73 Ma B.P.) from strong long-period cyclicity in the Brunhes to more prevalent shorter period cyclicity in the Matuyama.

Glacial variability over the last two million years: an extended depth-derived agemodel, continuous obliquity pacing, and the Pleistocene progression

“…(4) Glacial cycles vary in duration from $80 to $120 Ka during the last pleistocene (Raymo, 1997;Petit et al, 1999): This supports the obliquity pacing hypothesis which calls on glacial cycles to be quantized in multiples of the basic 40 Ka period. (5) Spectral peaks exist at frequencies other than those in the insolation forcing (Nobes et al, 1991;Bolton and Maasch, 1995;HW04): This can be explained by the obliquity cycle skipping and the asymmetry between rates of deglaciations and accumulation (see Section 4.3). Note that much of the variability resides at nonorbital periods indicating the presence of a significant stochastic contribution (Wunsch, 2004) or a significantly nonlinear response to the insolation forcing (Huybers and Curry, 2006).…”

Nonlinearities, Feedbacks and Critical Thresholds within the Earth's Climate System

“…For instance, it is well known that while the main driving frequency of the ice ages is about 100 ky (1 ky = 1,000 years) the timing between consecutive glacial periods has been steadily increasing from ∼80 ky to ∼120 ky over the last ∼500 ky (Raymo, 1997;Petit et al, 1999). This feature, plus the near absence of a large response at the strongest eccentricity forcing period (413 ky) and the presence of significant variance at frequencies not present in the orbital forcing, are strong evidence of nonlinearity in the climate's response to orbital forcing (e.g., Nobes et al, 1991;Ghil, 1994). To explain these nonlinear features, Rial (1999) introduced the idea that the climate system transforms the astronomically amplitude-modulated insolation into frequency modulated fluctuations of global ice mass.…”

250 Bin Yıl Uzunluğundaki Van Gölü Çökelleri’nin Spektral Özellikleri: Milankoviç Döngüleri ve Onların Harmonikleri

“…Therefore, the ice sheet and the crust beneath oscillate not on the exact periodic timescales of insolation and the model gives a nonlinear climatic oscillator (Ghil and Le Treut, 1981;Le Treut and Ghil, 1983;Le Treut et al, 1988). The evidences of this theory have been mentioned in some studies (Pestiaux et al, 1988;Yiou et al, 1991;Nobes et al, 1991;Yiou et al, 1994;Mommersteeg et al, 1995;Mayewski et al, 1997;Ortiz et al, 1999;Wara et al 2000). Therefore, we believe that, changes in insolation and their effects on the behavior of the ice sheet are global climate drivers in the long term.…”