Atmospheric CO<sub>2</sub> Concentration Based on Boron Isotopes Versus Simulations of the Global Carbon Cycle During the Plio‐Pleistocene

Köhler, Peter

doi:10.1029/2022pa004439

Cited by 4 publications

(4 citation statements)

References 99 publications

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“…Our reconstructed global cooling over the past 4 Myr is consistent with the long-term cooling trend that began ~15 Ma after the Miocene Climatic Optimum ( 61 , 62 ). This post-15 Ma cooling is commonly attributed to decreasing atmospheric CO 2 ( 61 , 63 ), which, on these geologic timescales, results from an imbalance between tectonic outgassing and chemical weathering of silicate rocks with an additional contribution from the SST-CO 2 feedback ( 64 ). The similar gradual rates of cooling of the previous 11 Myr ( 61 ) to those from 4 to 1.5 Ma indicate that this first phase of cooling in our reconstruction could have occurred as a straightforward continuation of this CO 2 forcing.…”

Section: Co2 Forcing Of Late Pliocene-pleistocene Temperature Changementioning

confidence: 99%

“…Several lines of evidence indicate that the uplift of the Southeast Asia islands beginning ~15 Ma helped meet this requirement by exposing ophiolitic rocks to chemical weathering, with the largest increase of island exposure and chemical weathering starting ~4 Ma ( 63 , 66 ). Uncertainties in CO 2 proxies over the past 15 Myr, however, prevent us from assessing whether the carbon budget based on these published source and sink terms is closed and what trajectory decreasing CO 2 followed ( 64 , 67 ) (Fig. 1B).…”

Section: Co2 Forcing Of Late Pliocene-pleistocene Temperature Changementioning

confidence: 99%

“…( B ) Proxy and ice-core CO 2 data. Magenta and green symbols are harmonized δ 11 B values on planktonic foraminifera T. sacculifer and G. ruber , respectively ( 64 ). Other CO 2 data are based on measurements on soil carbonate (brown symbols) ( 89 ), δ 13 C of leaf wax (red symbols) ( 90 ), and ice cores [blue symbols ( 91 ) and black line ( 92 )].…”

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confidence: 99%

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Global and regional temperature change over the past 4.5 million years

Clark,

Shakun,

Rosenthal

et al. 2024

Science

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Much of our understanding of Cenozoic climate is based on the record of δ 18 O measured in benthic foraminifera. However, this measurement reflects a combined signal of global temperature and sea level, thus preventing a clear understanding of the interactions and feedbacks of the climate system in causing global temperature change. Our new reconstruction of temperature change over the past 4.5 million years includes two phases of long-term cooling, with the second phase of accelerated cooling during the Middle Pleistocene Transition (1.5 to 0.9 million years ago) being accompanied by a transition from dominant 41,000-year low-amplitude periodicity to dominant 100,000-year high-amplitude periodicity. Changes in the rates of long-term cooling and variability are consistent with changes in the carbon cycle driven initially by geologic processes, followed by additional changes in the Southern Ocean carbon cycle.

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Section: Co2 Forcing Of Late Pliocene-pleistocene Temperature Changementioning

confidence: 99%

Section: Co2 Forcing Of Late Pliocene-pleistocene Temperature Changementioning

confidence: 99%

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Global and regional temperature change over the past 4.5 million years

Clark,

Shakun,

Rosenthal

et al. 2024

Science

Self Cite

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“…These fluctuations are characterized by strongly increased opal contents across the SAF and the PF and reduced opal deposition in the AZ during glacials compared with interglacials. Ultimately, the opal records imply a relocation of Southern Ocean fronts that altered nutrient supply, stratification and iron fertilization in these surface ocean regions [29][30][31][32]…”

Section: Pleistocene Acc Strength Changesmentioning

confidence: 99%

Five million years of Antarctic Circumpolar Current strength variability

Lamy,

Winckler,

Arz

et al. 2024

Nature

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The Antarctic Circumpolar Current (ACC) represents the world’s largest ocean-current system and affects global ocean circulation, climate and Antarctic ice-sheet stability1–3. Today, ACC dynamics are controlled by atmospheric forcing, oceanic density gradients and eddy activity4. Whereas palaeoceanographic reconstructions exhibit regional heterogeneity in ACC position and strength over Pleistocene glacial–interglacial cycles5–8, the long-term evolution of the ACC is poorly known. Here we document changes in ACC strength from sediment cores in the Pacific Southern Ocean. We find no linear long-term trend in ACC flow since 5.3 million years ago (Ma), in contrast to global cooling9 and increasing global ice volume10. Instead, we observe a reversal on a million-year timescale, from increasing ACC strength during Pliocene global cooling to a subsequent decrease with further Early Pleistocene cooling. This shift in the ACC regime coincided with a Southern Ocean reconfiguration that altered the sensitivity of the ACC to atmospheric and oceanic forcings11–13. We find ACC strength changes to be closely linked to 400,000-year eccentricity cycles, probably originating from modulation of precessional changes in the South Pacific jet stream linked to tropical Pacific temperature variability14. A persistent link between weaker ACC flow, equatorward-shifted opal deposition and reduced atmospheric CO2 during glacial periods first emerged during the Mid-Pleistocene Transition (MPT). The strongest ACC flow occurred during warmer-than-present intervals of the Plio-Pleistocene, providing evidence of potentially increasing ACC flow with future climate warming.

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Astronomical forcing shaped the timing of early Pleistocene glacial cycles

Watanabe

Abe‐Ouchi

Saito

et al. 2023

Commun Earth Environ

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Glacial cycles during the early Pleistocene are characterised by a dominant 41,000-year periodicity and amplitudes smaller than those of glacial cycles with ~100,000-year periodicity during the late Pleistocene. However, it remains unclear how the 41,000-year glacial cycles during the early Pleistocene respond to Earth’s astronomical forcings. Here we employ a three-dimensional ice-sheet model to simulate the glacial cycles at ~1.6–1.2 million years before present and analyse the phase angle of precession and obliquity at deglaciations. We show that each deglaciation occurs at every other precession minimum, and when obliquity is large. The lead-lag relationship between precession and obliquity controls the length of interglacial periods, the shape of the glacial cycle, and the glacial ice-sheet geometry. The large amplitudes of obliquity and eccentricity during this period helped to establish robust 41,000-year glacial cycles. This behaviour is explained by the threshold mechanism determined by ice-sheet size and astronomical forcings.

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Atmospheric CO₂ Concentration Based on Boron Isotopes Versus Simulations of the Global Carbon Cycle During the Plio‐Pleistocene

Abstract: Although carbon dioxide (CO 2 ) is one of the most important greenhouse gases, our knowledge of its atmospheric concentration beyond the 800 ka covered by ice cores (Bereiter et al., 2015) is highly uncertain (Figure 1a

Cited by 4 publications

References 99 publications

Global and regional temperature change over the past 4.5 million years

Global and regional temperature change over the past 4.5 million years

Five million years of Antarctic Circumpolar Current strength variability

Astronomical forcing shaped the timing of early Pleistocene glacial cycles

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Atmospheric CO2 Concentration Based on Boron Isotopes Versus Simulations of the Global Carbon Cycle During the Plio‐Pleistocene

Abstract: Although carbon dioxide (CO 2 ) is one of the most important greenhouse gases, our knowledge of its atmospheric concentration beyond the 800 ka covered by ice cores (Bereiter et al., 2015) is highly uncertain (Figure 1a

Cited by 4 publications

References 99 publications

Global and regional temperature change over the past 4.5 million years

Global and regional temperature change over the past 4.5 million years

Five million years of Antarctic Circumpolar Current strength variability

Astronomical forcing shaped the timing of early Pleistocene glacial cycles

Contact Info

Product

Resources

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Atmospheric CO₂ Concentration Based on Boron Isotopes Versus Simulations of the Global Carbon Cycle During the Plio‐Pleistocene