Australia: The Land Where Time Began |
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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).
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.
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Author: M.H.Monroe Email: admin@austhrutime.com Sources & Further reading |