The 100,000 year problem and the synchronisation of the climate system to eccentricity forcing

Australia: The Land Where Time Began

The 100,000 Year Problem and the Synchronisation of the Climate System to Eccentricity Forcing

There has been a period of about 100,000 years in the glacial-interglacial cycles over the past million years that is similar to the 100,000-year period of change in the eccentricity of the Earth's orbit. It has been difficult to reconcile the amplitude of the glacial cycles (Lisiecki, 2010; El Kibbi & Rial, 2001; Huybers & Wunsch, 2005; Raymo, 1997; Berger, Melice & Loutre, 2005) to the changing insolation as a result of this small timescale. Known as the 100-kyr problem, a lack of explanation for the transition of cycle length, from 41,000 to 100,000 years, 1.2 Ma at the mid-Pleistocene transition has compounded the problem (Clark et al., 2006). Interactions between other orbital frequencies, such as the obliquity and the 413,000-year eccentricity period (Huybers & Wunsch, 2005; Raymo, 1997; Berger, Melice & Loutre, 2005; Clark et al., 2006; Saltzman, 2002; Rial, 1999; Pisias & Moore, 1981; Paillard, 1998; Muller & McDonald, 2000; Oerlemans, 1984; Tziperman et al., 2006), as well as other individual discrepancies, have been explained, though there remains a lack of a unifying explanation. In this study Rial, Oh & Reischmann have shown that over the past 4 million years the oscillations of climate can be explained by a single mechanism - the synchronisation of non-linear internal climate oscillations and the eccentricity cycle of 413,000 years. Rial, Oh & Reischmann found, by the use of spectral analyses, aided by a numerical model, which about 1.2 Ma the climate system first synchronised to the 413,000-year cycle of eccentricity, which has remained the case up to the present. The amplitude of the 100,000-year cycle increases as a result of this synchronisation, the result of which is a transfer of power and frequency modulation. The conclusion reached by Rial, Oh & Reischmann is that the strong 100,000-year glacial cycles can be explained by the forced synchronisation through the alignment of changes of insolation and internal climate oscillations.

Conclusion

Rial, Oh & Reichmann concluded that the inconsisancies that were discussed in the introduction can be explained as being caused by forced synchronisation. Energy from the sun was allowed by synchronisation to flow into or out of the climate system at the same time it was being warmed or cooled by internal feedbacks, which resulted in unprecedentedly large fluctuations of the climate system that powered the great glaciations of the Pleistocene (a process that is akin to resonance of a forced linear oscillator). Forced phase synchronisation, which is still occurring, began 1.2 Ma, culminating at the time in MIS11 (about 0.4 Ma) and in a brief period of nonlinear resonance. That the 1/413 ka component of eccentricity forced the frequency modulation of the about 1/100 ky band during synchronisation, is evidenced by depleted spectral power at 1/413 ky and the frequencies of power at 1/413 ky and the presence of power at frequencies that are absent in the spectrum of the orbital forcing. At the present resonance has faded though the frequency modulation has persisted, which drives the about 1/82-1/125 ky frequency deviation that paces the timing of the major glaciations (Raymo, 1997).

Sources & Further reading

1. Rial, Jose A., Jeseung Oh, and Elizabeth Reischmann. "Synchronization of the Climate System to Eccentricity Forcing and the 100,000-Year Problem." Nature Geosci 6, no. 4 (04//print 2013): 289-93.