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| Titel |
A very simple criterion for the orbital-scale occurrence of interglacials and glacial inceptions over the last 800 kyr |
| VerfasserIn |
Takahito Mitsui, Michel Crucifix, Eric Wolff, Chronis Tzedakis |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250146436
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| Publikation (Nr.) |
 EGU/EGU2017-10462.pdf |
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| Zusammenfassung |
| Past Interglacials Working Group of PAGES (2016) identifies eleven interglacials during the
last 800 kyr based on a sea level definition: Marine Isotope Stage (MIS) 1, 5e, 7a-7c (as a
single interglacial), 7e, 9e, 11c, 13a, 15a, 15e, 17c, and 19c. An important aspect of this
definition is the occurrence of more than one interglacial within an MIS. Recently, the authors
of this study proposed a simple rule to determine which insolation cycles lead to interglacials
(Tzedakis et al. in press). During the last 800 kyr, interglacial onsets occur when a peak of
caloric summer half-year insolation at 65oN exceeds a certain threshold which
decreases with time. On the other hand, Ganopolski et al. (2016) proposed a criterion to
diagnose the glacial inceptions over the last 800 kyr. Based on the experiments with
CLIMBER-2, they derived a critical insolation-CO2 relation curve, below which a
glacial inception occurs. It is consistent with all the glacial inceptions happened, but
incompatible with the lack of glacial inception near the insolation minimum at 209 kyr
BP (MIS 7b). While the summer solstice (or mid-June) mean daily insolation at
65oN has about 20 % of variance in obliquity band, the caloric summer half-year
insolation at at 65oN has about 50 % of variance in the obliquity band. In this study, we
show that the critical insolation-CO2 relation in terms of caloric summer-half year
insolation successfully diagnoses all the glacial inceptions over the last 800 kyr
and its lack near MIS 7b. This is due to the fact that, near MIS 7b, the effect of
precession maximum (boreal summer solstice at aphelion) is counteracted by the
effect of average-above obliquity more strongly in the caloric summer insolation
than in the summer solstice insolation. Unifying those two theories with the single
caloric summer insolation metric, we present a particularly simple criterion for
the orbital-scale occurrence of interglacials and glacial inceptions over the last
800 kyr. We also discuss how this criterion constrains the natural length of current
interglacial.
References
Past Interglacials Working Group of PAGES, Interglacials of the last 800,000 years,
Review of Geophysics, 54, 162-219 (2016).
P.C. Tzedakis, M. Crucifix, T. Mitsui, and E.W. Wolff, in press.
A. Ganopolski, R. Winkelmann, and H. J. Schellnhuber, Critical insolation-CO2
relation for diagnosing past and future glacial inception, Nature, 529, 200-203 (2017). |
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