Orbital Insolation Variations, Intrinsic Climate Variability, and Quaternary Glaciations

Riechers, Keno; Mitsui, T.; Boers, Niklas; Ghil, Michael

doi:10.5194/cp-2021-136

Cited by 6 publications

(7 citation statements)

References 88 publications

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“…In any case, a time interval of the most recent 0.8 or 1.5 Myr seems to have witnessed millennial-scale climate variability with an amplitude that exceeded the one due to the direct forcing by the orbital periodicities (Ghil and Childress, 1987;Ghil, 1994;Riechers et al, 2021). This fairly agreedupon fact lends support to the interpretation of the enhanced millennial variability during glacial times as arising from an internal oscillation of the climate system -which could well be consistent with the amended Bond cycle that we have proposed -as well as with the mechanisms proposed by several authors, such as Källèn et al (1979), Le Treut et al (1988), Saltzman (2002) and Crucifix (2012) -while Hodell and Channell (2016a) only considered it as noise superimposed on the orbital variability deduced from their wavelet analysis of the benthic δ 18 O record of U1308.…”

Section: Millennial-scale Variabilitymentioning

confidence: 95%

“…This fairly agreedupon fact lends support to the interpretation of the enhanced millennial variability during glacial times as arising from an internal oscillation of the climate system -which could well be consistent with the amended Bond cycle that we have proposed -as well as with the mechanisms proposed by several authors, such as Källèn et al (1979), Le Treut et al (1988), Saltzman (2002) and Crucifix (2012) -while Hodell and Channell (2016a) only considered it as noise superimposed on the orbital variability deduced from their wavelet analysis of the benthic δ 18 O record of U1308. Substantial, nonlinear interactions between internal oscillatory variability and orbital forcing are actively being explored by Riechers et al (2021) in this special issue.…”

Section: Millennial-scale Variabilitymentioning

confidence: 99%

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Abrupt climate changes and the astronomical theory: are they related?

2022

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Abstract. Abrupt climate changes are defined as sudden climate changes that took place over tens to hundreds of years or recurred at millennial timescales; they are thought to involve processes that are internal to the climate system. By contrast, astronomically forced climate changes involve processes that are external to the climate system and whose multi-millennial quasi-periodic variations are well known from astronomical theory. In this paper, we re-examine the main climate variations determined from the U1308 North Atlantic marine record, which yields a detailed calving history of the Northern Hemisphere ice sheets over the past 3.2 Myr. The magnitude and periodicity of the ice-rafted debris (IRD) events observed in the U1308 record allow one to determine the timing of several abrupt climate changes, the larger ones corresponding to the massive iceberg discharges labeled Heinrich events (HEs). In parallel, abrupt warmings, called Dansgaard–Oeschger (DO) events, have been identified in the Greenland records of the last glaciation cycle. Combining the HE and DO observations, we study a complex mechanism giving rise to the observed millennial-scale variability that subsumes the abrupt climate changes of last 0.9 Myr. This process is characterized by the presence of Bond cycles, which group DO events and the associated Greenland stadials into a trend of increased cooling, with IRD events embedded into every stadial, the latest of these being an HE. These Bond cycles may have occurred during the last 0.9 Ma when Northern Hemisphere ice sheets reached their maximum extent and volume, thus becoming a major player in this time interval's climate dynamics. Since the waxing and waning of ice sheets during the Quaternary period are orbitally paced, we conclude that the abrupt climate changes observed during the Middle Pleistocene and Upper Pleistocene are therewith indirectly linked to the astronomical theory of climate.

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Section: Millennial-scale Variabilitymentioning

confidence: 95%

Section: Millennial-scale Variabilitymentioning

confidence: 99%

Abrupt climate changes and the astronomical theory: are they related?

2022

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“…Stylized ice-age model Various types of stylized ice-age models have been proposed in the literature 24,38,57 .…”

Section: Resultsmentioning

confidence: 99%

Vibrational resonance in 100-kyr glacial cycles

Mitsui

Willeit

Boers

2022

Preprint

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During the last one million years, ice ages occurred with a dominant periodicity of 100 kyr (1 kyr = 1,000 years), while the solar radiation variability resulting from astronomical forcing is concentrated at higher frequencies and shows negligibly small power around this time scale. Although many promising frameworks have been introduced to solve this 100-kyr problem, a comprehensive theory of glacial cycles remains elusive. Here we show, using an Earth System Model of intermediate complexity, that the 100-kyr glacial cycles can be explained via a phenomenon called vibrational resonance. We demonstrate that the Earth system's response to the climatic precession, whose amplitude is modulated by the eccentricity with 100-kyr and 400-kyr periodicities, is amplified at the 100-kyr time scale and suppressed at the 400-kyr time scale with the help of the 41-kyr obliquity forcing. Our results also suggest that the present interglacial would not have appeared without the vibrational resonance discovered here.

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“…The FitzHugh-Nagumo (FHN) system is a prototypical model for slow-fast oscillations and excitability 45 . It is often invoked for conceptual models of DO oscillations 29,[46][47][48][49] . An FHN-type model of DO oscillations is obtained by introducing a slow variable y into the fold bifurcation model:…”

Section: Discussionmentioning

confidence: 99%

“…2. The FitzHugh-Nagumo-type (FHN-type) system is a prototypical model of slow-fast oscillators and often invoked for conceptual models of DO oscillations 29,[46][47][48][49] . The FHN-type model subjected to dynamical noise is obtained by introducing a slow variable y into the fold bifurcation model: ẋ = 1 τx (|x|(1 − x) + y + p) + ξ(t), ẏ = 1 τy (−x − y), where τ x and τ y are time-scale parameters (τ x ≪ τ y ).…”

Section: Candidatementioning

confidence: 99%

Statistical precursor signals for Dansgaard-Oeschger cooling transitions

Mitsui¹,

Boers²

2023

Preprint

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Given the likely bistability of the Atlantic Meridional Overturning Circulation (AMOC) and its recently inferred weakening, it is important to investigate the capability of identifying robust precursor signals for a possible future AMOC collapse. Dansgaard-Oeschger (DO) events, manifested most clearly as abrupt Northern-Atlantic temperature jumps during glacial conditions, likely reflect past switches between strong and weak AMOC modes. Previous studies find statistical precursor signals for the DO warming transitions associated with a strengthening AMOC. Statistical precursor signals for the abrupt DO cooling transitions, presumably associated with AMOC transitions from the strong to the weak mode, have not been identified although these would be practically much more relevant given the concern of a future AMOC collapse. Here we identify robust and statistically significant precursor signals for several DO cooling transitions from Greenland ice core records, using the concept of critical slowing down. The main source of predictability stems from so-called rebound event, humps in the temperature observed at the end of interstadial, some decades to centuries prior to the transition. Based on conceptual models, we propose several dynamical mechanisms producing such rebound events.

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Orbital Insolation Variations, Intrinsic Climate Variability, and Quaternary Glaciations

Cited by 6 publications

References 88 publications

Abrupt climate changes and the astronomical theory: are they related?

Abrupt climate changes and the astronomical theory: are they related?

Vibrational resonance in 100-kyr glacial cycles

Statistical precursor signals for Dansgaard-Oeschger cooling transitions

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