The Role of Carbon Dioxide During the Onset of Antarctic Glaciation

Pagani, Mark; Huber, Matthew; Liu, Zhonghui; Bohaty, Steven M; Henderiks, Jorijntje; Sijp, Willem P.; Krishnan, Srinath; DeConto, Robert M.

doi:10.1126/science.1203909

Cited by 291 publications

(334 citation statements)

References 93 publications

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“…Higher reconstructed SST, therefore, results in higher apparent pCO 2 for a given δ 13 C value by integrating these two effects (figure 7d). The magnitude of this effect is more pronounced at higher pCO 2 and more negative alkenone δ 13 C values (figure 7d), and also as ε p approaches ε f (see the discussion in Pagani et al [27]). For example, for an alkenone δ 13 C value of −25 (which gives a representative pCO 2 of 300 ppm in this sensitivity test), the 2 • C analytical and calibration error in Mg/Ca or U K 37 SST estimates would result in an error of approximately 23 ppm in pCO 2 ; at a more negative δ 13 C value of −28 (pCO 2 = 400 ppm), the same error in SST results in an error of approximately 34 ppm in pCO 2 (figure 7d).…”

Section: (B) Cell Size and Productivity Correctionsmentioning

confidence: 84%

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High-resolution alkenone palaeobarometry indicates relatively stable p CO ₂ during the Pliocene (3.3–2.8 Ma)

Badger

Schmidt

Mackensen

et al. 2013

Phil. Trans. R. Soc. A.

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Temperature reconstructions indicate that the Pliocene was approximately 3 ° C warmer globally than today, and several recent reconstructions of Pliocene atmospheric CO 2 indicate that it was above pre-industrial levels and similar to those likely to be seen this century. However, many of these reconstructions have been of relatively low temporal resolution, meaning that these records may have failed to capture variations associated with the 41 kyr glacial–interglacial cycles thought to have operated in the Pliocene. Here we present a new, high temporal resolution alkenone carbon isotope-based record of p CO 2 spanning 3.3–2.8 Ma from Ocean Drilling Program Site 999. Our record is of high enough resolution (approx. 19 kyr) to resolve glacial–interglacial changes beyond the intrinsic uncertainty of the proxy method. The record suggests that Pliocene CO 2 levels were relatively stable, exhibiting variation less than 55 ppm. We perform sensitivity studies to investigate the possible effect of changing sea surface temperature (SST), which highlights the importance of accurate and precise SST reconstructions for alkenone palaeobarometry, but demonstrate that these uncertainties do not affect our conclusions of relatively stable p CO 2 levels during this interval.

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Section: (B) Cell Size and Productivity Correctionsmentioning

confidence: 84%

“…[6,7,23,[26][27][28] thought to have changed significantly from the Pliocene to today (see discussion in [8]). Specifically, 27 samples were freeze dried, ground by hand and solvent extracted either by Soxhlet apparatus or ultrasonically.…”

Section: (B) Analyticalmentioning

confidence: 99%

High-resolution alkenone palaeobarometry indicates relatively stable p CO ₂ during the Pliocene (3.3–2.8 Ma)

Badger

Schmidt

Mackensen

et al. 2013

Phil. Trans. R. Soc. A.

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“…It has been suggested that variations in the concentration of the greenhouse gas CO 2 were responsible for both the overall warmth of the Eocene and the subsequent cooling 17 . Recent studies have documented the importance of CO 2 decline for the final step into the icehouse across the EoceneOligocene transition 12,18 . Despite this, the few available CO 2 reconstructions vary markedly between different proxy systems, obscuring relationships with the global cooling trend 1,5,19,20 and therefore preventing a robust test of this hypothesis (Fig.…”

mentioning

confidence: 99%

“…We analysed foraminifera from five discrete time slices between 36.9 and 53.2 Myr ago recovered by the Tanzania Drilling Project (Extended Data Fig. 1), and we quantified the oxygen isotopic composition (δ 18 O) of up to 17 different foraminifera species occupying a range of depth habitats to derive the calcification temperature and hence the relative habitat depth of the taxa 25 . In each case we find a decrease of δ 11 B c with increasing depth, consistent with modern ocean δ 11 B borate profiles ( Fig.…”

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confidence: 99%

Changing atmospheric CO2 concentration was the primary driver of early Cenozoic climate

Anagnostou

John

Edgar

et al. 2016

Nature

357

363

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The Early Eocene Climate Optimum (EECO, which occurred about 51 to 53 million years ago) 1 , was the warmest interval of the past 65 million years, with mean annual surface air temperature over ten degrees Celsius warmer than during the pre-industrial period 2-4 . Subsequent global cooling in the middle and late Eocene epoch, especially at high latitudes, eventually led to continental ice sheet development in Antarctica in the early Oligocene epoch (about 33.6 million years ago). However, existing estimates place atmospheric carbon dioxide (CO 2 ) levels during the Eocene at 500-3,000 parts per million [5][6][7] , and in the absence of tighter constraints carbon-climate interactions over this interval remain uncertain. Here we use recent analytical and methodological developments 8-11 to generate a new high-fidelity record of CO 2 concentrations using the boron isotope (δ 11 Β) composition of well preserved planktonic foraminifera from the Tanzania Drilling Project, revising previous estimates 6 . Although species-level uncertainties make absolute values difficult to constrain, CO 2 concentrations during the EECO were around 1,400 parts per million. The relative decline in DOI: 10.1038/nature17423 Page 2 of 38 CO 2 concentration through the Eocene is more robustly constrained at about fifty per cent, with a further decline into the Oligocene 12 . Provided the latitudinal dependency of sea surface temperature change for a given climate forcing in the Eocene was similar to that of the late Quaternary period 13 , this CO 2 decline was sufficient to drive the well documented high-and low-latitude cooling that occurred through the Eocene 14 . Once the change in global temperature between the pre-industrial period and the Eocene caused by the action of all known slow feedbacks (apart from those associated with the carbon cycle) is removed 2-4 , both the EECO and the late Eocene exhibit an equilibrium climate sensitivity relative to the pre-industrial period of 2.1 to 4.6 degrees Celsius per CO 2 doubling (66 per cent confidence), which is similar to the canonical range (1.5 to 4.5 degrees Celsius 15 ), indicating that a large fraction of the warmth of the early Eocene greenhouse was driven by increased CO 2 concentrations, and that climate sensitivity was relatively constant throughout this period.Over the past 540 million years, Earth's climate has oscillated between a globally warm 'greenhouse state' and an 'icehouse state' with substantial continental glaciation 16 . The most recent of these transitions occurred between the warmest time interval of the last 65 million years-the EECO (about 14 ± 3 °C warmer than preindustrial times 2 )-and the rapid growth of ice on Antarctica in the earliest icehouse state of the Oligocene (~33.6 Myr ago 1 ). It has been suggested that variations in the concentration of the greenhouse gas CO 2 were responsible for both the overall warmth of the Eocene and the subsequent cooling 17 . Recent studies have documented the importance of CO 2 decline for the final step into the icehous...

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“…2, come from three methods: (i) gas bubbles trapped in ice cores [0-550 kya (6-8)]; (ii) the carbon isotopic composition of sedimentary alkenones recovered from deep-sea sediments-the fractionation between alkenones and total dissolved carbon in seawater is largely a function of [CO 2 ] aq [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]]; and (iii) the boron isotopic composition of planktic foraminifera from deepsea sediments, which depends on pH (e.g., ref. 14), from which [CO 2 ] aq and atmospheric CO 2 can be calculated [11][12][13][14][15][16][17][33][34][35][36]]. Those methods, based on deep ocean sediments, can reproduce the ice-core CO 2 record accurately (19)(20)(21)(22), but each has several inherent uncertainties.…”

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confidence: 99%

Relationship between sea level and climate forcing by CO ₂ on geological timescales

Foster

Rohling

2013

Proc. Natl. Acad. Sci. U.S.A.

128

110

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On 10 3 -to 10 6 -year timescales, global sea level is determined largely by the volume of ice stored on land, which in turn largely reflects the thermal state of the Earth system. Here we use observations from five well-studied time slices covering the last 40 My to identify a well-defined and clearly sigmoidal relationship between atmospheric CO 2 and sea level on geological (near-equilibrium) timescales. This strongly supports the dominant role of CO 2 in determining Earth's climate on these timescales and suggests that other variables that influence long-term global climate (e.g., topography, ocean circulation) play a secondary role. The relationship between CO 2 and sea level we describe portrays the "likely" (68% probability) long-term sea-level response after Earth system adjustment over many centuries. Because it appears largely independent of other boundary condition changes, it also may provide useful long-range predictions of future sea level. For instance, with CO 2 stabilized at 400-450 ppm (as required for the frequently quoted "acceptable warming" of 2°C), or even at AD 2011 levels of 392 ppm, we infer a likely (68% confidence) long-term sea-level rise of more than 9 m above the present. Therefore, our results imply that to avoid significantly elevated sea level in the long term, atmospheric CO 2 should be reduced to levels similar to those of preindustrial times.S ea-level change is one of the most significant and long-lasting consequences of anthropogenic climate change (1). However, accurate forecasting of the future magnitude of sea-level change is difficult because current numerical climate models lack the capacity to accurately resolve the dynamical processes that govern size changes of continental ice sheets [e.g., total disappearance of the current continental ice sheets would raise mean sea level by about 70 m (1)]. This complicates long-range sea-level projections because the retreat of continental ice sheets will increasingly contribute to sea-level rise as the 21st century progresses (2), and because this rise will continue long into the future, even if temperatures were stabilized, according to different mitigation scenarios for greenhouse gas emissions (1). Because of the absence of adequate ice-dynamical processes in models, even the most recent estimates have to rely on assumed (linear) relationships between ice-volume reduction and global mean temperature increase (1), which as yet remain largely untested. Therefore, here we provide a natural context to projections of future long-term (multicentury) sea-level rise, by assessing key relationships in the Earth's climate system using recent high-quality data from the geological past. Because global mean temperature is hard to measure in the geological past without applying (often problematic) assumptions about polar amplification or deep-sea temperature relationships (3, 4), we instead concentrate on quantifying the "likely" [68% probability (5)] long-term relationship between two entities that can be measured more directly, namely i...

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The Role of Carbon Dioxide During the Onset of Antarctic Glaciation

Cited by 291 publications

References 93 publications

High-resolution alkenone palaeobarometry indicates relatively stable p CO ₂ during the Pliocene (3.3–2.8 Ma)

High-resolution alkenone palaeobarometry indicates relatively stable p CO ₂ during the Pliocene (3.3–2.8 Ma)

Changing atmospheric CO2 concentration was the primary driver of early Cenozoic climate

Relationship between sea level and climate forcing by CO ₂ on geological timescales

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The Role of Carbon Dioxide During the Onset of Antarctic Glaciation

Cited by 291 publications

References 93 publications

High-resolution alkenone palaeobarometry indicates relatively stable p CO 2 during the Pliocene (3.3–2.8 Ma)

High-resolution alkenone palaeobarometry indicates relatively stable p CO 2 during the Pliocene (3.3–2.8 Ma)

Changing atmospheric CO2 concentration was the primary driver of early Cenozoic climate

Relationship between sea level and climate forcing by CO 2 on geological timescales

Contact Info

Product

Resources

About

High-resolution alkenone palaeobarometry indicates relatively stable p CO ₂ during the Pliocene (3.3–2.8 Ma)

High-resolution alkenone palaeobarometry indicates relatively stable p CO ₂ during the Pliocene (3.3–2.8 Ma)

Relationship between sea level and climate forcing by CO ₂ on geological timescales